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  • 1.
    Ameen, Arman
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Boström, Hanna
    Lindelöw, Hanna
    Assessment of Thermal Comfort and Air Quality in Office Rooms of a Historic Building: A Case Study in Springtime in Continental Climate2023In: Buildings, E-ISSN 2075-5309, Vol. 13, no 1, article id 156Article in journal (Refereed)
    Abstract [en]

    One of the most important aspects of working in an office environment is ensuring that the space has optimal thermal comfort and an indoor environment. The aim of this research is to investigate the thermal comfort and indoor climate in three office rooms located at one of the campus buildings at the University of Gävle, Sweden. The evaluated period is in the month of April during springtime. During this period, parameters such as temperature, relative humidity, CO2, supply air flow rate, and room air velocities are measured on site. The results of the measurement show that the indoor temperature is on average lower in the rooms facing north, at 21–23.5 °C, compared to the rooms facing south, which reach high temperatures during sunny days, up to 26 °C. The results also show that the ventilation air supply rate is lower than the requirement for offices in two of the office rooms. The ACH rate is also low, at ≈ 1 h−1 for all the rooms, compared to the required levels of 2–4 h−1. The CO2 levels are within the recommended values; on average, the highest is in one of the south-facing rooms, with 768 ppm, and the maximum measured value is also in the same room, with 1273 ppm for a short period of time.

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  • 2.
    Björling, Mikael
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Environmental engineering.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Akander, Jan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Infiltration of Air into two World Heritage Farmhouses in Sweden during Winter Conditions2018In: Roomvent & Ventilation 2018: Excellent Indoor Climate and High Performing Ventilation / [ed] Risto Kosonen, Mervi Ahola, Jarkko Narvanne, Helsinki, Finland, 2018, p. 1079-1084Conference paper (Refereed)
    Abstract [en]

    As a part of an ongoing study, we report measurements of air infiltration during winter conditions into two Decorated Farmhouses of Hälsingland designated as UNESCO World Heritage Sites. In winter these two-storied farmhouses are rarely heated, except for special occasions. In this measurement one farmhouse  was  unheated,  whereas  one  room  was  heated  for  a  brief  period  in  the  other  one.  The observed local mean ages of air measured with tracer gas techniques generally increase with height, both  locally  within  each  room  and  between  floors.  The  average  temperature  and  humidity  also increases from the first to the second floor. The indoor temperature follows the outdoor temperature with a time lag. The differences in water content between inside and outside air correlate with changes of the indoor relative humidity. The correlation is stronger for humidity increase than for humidity decrease, possibly due to moisture absorption by interior text.

  • 3.
    Björling, Mikael
    et al.
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för naturvetenskap.
    Stymne, Hans
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Mattsson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Blomqvist, Claes
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Ventilation measurements combined with pollutant concentration measurements discriminates between high emission rates and insufficient ventilation2007In: IAQVEC 2007 Indoor Air Quality Ventilation and Energy Conservation: sustainable Buildings. P. 2, 2007, Vol. 2, p. 393-400Conference paper (Refereed)
    Abstract [en]

    High local concentrations of a pollutant can be the result of high local emission rates of the pollutant or insufficient ventilation. Using tracer gases to map the ventilation in multi-zone buildings combined with measurements of the local pollutant concentration provide the means to discriminate between these causes. In a similar manner, the propagation rate of pollutants from a source to a target zone and the emission rate of the pollutants at the source may be determined quantitatively.

    The paper presents both the theoretical framework for the techniques and experimental examples of the proposed methods.

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  • 4.
    Broström, Tor
    et al.
    Gotland University, Department of Building Conservation.
    Linden, Elisabet
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Lindström, Svante
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Mattsson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Convective heating in a medieval church: Effects of air-to-air heat pumps on air movements, particle deposition and temperature distribution2009Conference paper (Refereed)
    Abstract [en]

    In Europe many historic buildings use direct electric heating. Air-to-air heat pumps are an interesting alternative, in particular for conservation heating.  However, the convective heating may accelerate soiling of walls and artefacts by increasing the velocity and turbulence.

     

    The objective of the present paper is to discuss the general problem, the methodology for studying air motions and temperature distribution, and to present the results from a case study where air-to-air heat pumps and bench heaters were used for heating in a medieval church. The temperatures, velocities and humidity in the church have been measured for four different heating modes.

     

    The present study does not indicate any major disadvantages of using heat pumps for background heating in stone churches of the studied kind. More detailed long term studies are needed to ascertain the effects over time.

  • 5.
    Chen, L.
    et al.
    Sun Yat-sen University, China; Ministry of Education, China; The Hong Kong Polytechnic University, Hong Kong.
    Hang, J.
    Sun Yat-sen University, China; Ministry of Education, China; Guangdong Provincial Field Observation and Research Station for Climate Environment, China.
    Chen, G.
    Sun Yat-sen University, China; Ministry of Education, China; Guangdong Provincial Field Observation and Research Station for Climate Environment, China.
    Liu, S.
    Sun Yat-sen University, China; Ministry of Education, China.
    Lin, Y.
    Sun Yat-sen University, China; Ministry of Education, China.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Ling, H.
    Sun Yat-sen University, China; Ministry of Education, China; Guangdong Provincial Field Observation and Research Station for Climate Environment, China.
    Numerical investigations of wind and thermal environment in 2D scaled street canyons with various aspect ratios and solar wall heating2021In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 190, article id 107525Article in journal (Refereed)
    Abstract [en]

    Optimizing urban ventilation is an effective way to improve urban air quality and thermal environment. For this purpose, under the validation of wind-tunnel experiments, flow regimes and micro thermal environment in typical reduced-canyon models with aspect ratios (AR) of 1.1, 2.4, 4 and 5.67 were investigated by CFD simulations using periodic boundary condition. ANSYS Fluent 15.0 with a solar ray tracing model and radiation model was performed to numerically study turbulence characteristics with wind-driven force and solar-heating conditions. Results revealed that, with wind-driven condition, a clockwise vortex existed in normal and deep street canyon (AR = 1.1 and 2.4) while two counter-rotating vortices appeared in extremely deep canyon (AR = 4 and 5.67). Moreover, different turbulence structures and air temperature distribution existed in canyons with different solar-heating conditions. When the leeward wall or ground was heated, the pedestrian-level velocity increased and street ventilation was strengthened compared to wind-driven condition for all AR values. Particularly, the single main vortex was strengthened (AR = 1.1 and 2.4), and the two-vortex structure in extremely deep canyons (AR = 4 and 5.67) changed to single-vortex structure. When the windward wall was heated, the clockwise main vortex at AR = 1.1 and 2.4 was deformed, and a new sub vortex gradually appeared near street bottom. Furthermore, at AR = 4 and 5.67, windward solar heating destroyed the two-vortex structure and slightly improved pollutant dilution capacity. This work implied that extremely deep street design with weak pedestrian-level ventilation should be avoided. It also provides a meaningful reference for urban planning.

  • 6. Cooper, Ed
    et al.
    Etheridge, David
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Pressure Pulse Technique – A New Method for Measuring the Leakage of the Building Envelope of Churches2011Conference paper (Refereed)
    Abstract [en]

    The University of Gävle is currently involved in a project on saving energy in historic buildings (churches). An important factor in the determination of the natural ventilation rate is the adventitious leakage of the envelope. Measurement of leakage is therefore a key feature of the investigations. It was decided to adopt a new technique developed at the University of Nottingham (UNott). It is a pulse technique compared to the conventional steady technique.The conventional technique consists of generating a steady and high pressure difference (50 Pa) across the envelope by means of a fan. Such pressures are rarely encountered in ventilation and this leads to errors in the low-pressure leakage. Furthermore the use of the conventional blower door technique in churches is difficult due to their large volume and the need to replace the doors.The underlying principle of the UNott technique is described and examples of results are given. The most important advantage of the Unott technique is that the leakage is determined at the low pressure differences that are encountered with ventilation e.g. 4 Pa. This is made possible primarily by the fact that the effects of wind and buoyancy at the time of the test are eliminated by taking account of the pressure variation before and after the pulse.For measurements in large buildings, a number of identical piston/cylinder units have to be operated simultaneously. The University of Gavle has developed a system whereby up to seven units can be used. Such a number is required for a leaky church and this is the first time this has been done.

  • 7.
    Cooper, Ed W
    et al.
    University of Nottingham, UK.
    Etheridge, David W
    University of Nottingham, UK.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Measurement of the adventitious leakage of churches with a novel pulse technique2011In: Proc. Roomvent 2011: 12th International conference on air distribution in rooms / [ed] Hans Martin Mathisen, Trondheim, Norge: Tapir Akademisk Forlag , 2011Conference paper (Refereed)
    Abstract [en]

    The University of Gavle is currently involved in a project on saving energy in historic buildings (churches). An important factor in the determination of the natural ventilation rate is the adventitious leakage of the envelope. Measurement of leakage is therefore a key feature of the investigations. It was decided to adopt a new technique developed at the University of Nottingham (UNott). It is a pulse technique compared to the conventional steady technique.

    The conventional technique consists of generating a steady and high pressure difference (50 Pa) across the envelope by means of a fan. Such pressures are rarely encountered in ventilation and this leads to errors in the low-pressure leakage. Furthermore the use of the conventional blower door technique in churches is difficult due to their large volume and the need to replace the doors.

    The underlying principle of the UNott technique is described and examples of results are given. The most important advantage of the Unott technique is that the leakage is determined at the low pressure differences that are encountered with ventilation e.g. 4 Pa. This is made possible primarily by the fact that the effects of wind and buoyancy at the time of the test are eliminated by taking account of the pressure variation before and after the pulse.

    For measurements in large buildings, a number of identical piston/cylinder units have to be operated simultaneously. The University of Gävle has developed a system whereby up to seven units can be used. Such a number is required for a leaky church and this is the first time this has been done.

  • 8.
    Falk, Anders B.
    et al.
    SLU.
    Lindström, Svante
    University of Gävle, Central University Administration.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Wright, Sandra A. I.
    University of Gävle, Faculty of Health and Occupational Studies, Department of Occupational and Public Health Sciences, Biology.
    Influence of some weather parameters on the susceptibility of apple fruit to postharvest grey mould attack2018In: Proceedings 2018, 2018, p. 124-127Conference paper (Refereed)
    Abstract [en]

    Several cultural and weather factors during the season influence the susceptibility of apple fruit to post-harvest pathogens. In the present study, the effect of different weather parameters on postharvest susceptibility of apples of the cv. ‘Ingrid Marie’ to grey mould was investigated. In 2015, apple fruit were collected from orchards in Southern Sweden, where local weather stations monitored different parameters. After harvest, the fruit were tested for susceptibility to grey mould by artificially inoculating them with%FLQHUHD. Lesion development was monitored over a 10-day-period. Analysis of results for a few orchards showed that cold weather for over a month preceding harvest and a low total number of growth degree days gave apples that were more susceptible to grey mould. This study was carried out in conventional orchards, but the conclusions can be important also for organic production, since they deal with the general effect of sunshine, temperature and rain, factors that may strengthen fruit during cultivation, regardless of production type. Future studies may focus on organic production to investigate whether these effects are general and also apply to organic production.

  • 9.
    Garman, Ian
    et al.
    Building Technology, Dalarna University, Borlänge, Sweden;Faculty of Engineering and Sustainable Development, University of Gävle, Gävle, Sweden.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Myhren, John Are
    Building Technology, Dalarna University, Borlänge, Sweden.
    Persson, Tomas
    Building Technology, Dalarna University, Borlänge, Sweden.
    Demand control and constant flow ventilation compared in an exhaust ventilated bedroom in a cold-climate single-family house2023In: Intelligent Buildings International, ISSN 1750-8975, E-ISSN 1756-6932Article in journal (Refereed)
    Abstract [en]

    A convertible, zoned ventilation system was field-tested in a modern, airtight Swedish home when occupied either by an experimental team or by a family. Indoor air quality in the master bedroom was monitored under four ventilation strategies. Relative to constant air volume strategies (CAV), demand-controlled ventilation (DCV) that was responding to CO2 concentration extracted more air when people were present, but less in total over 24 h. This elevated the indoor air humidity, beneficial in climates with dry winter air. Multiple monitors within the bedroom indicated that vertical CO2 stratification occurred routinely, presumably due to low mixing of supply air from a wall-mounted diffuse vent, spreading the air radially over the wall. This seemingly improved air quality in the breathing zone under local (ceiling) extract ventilation but worsened it during more typical, centralised extract ventilation, where air escapes the room via an inner doorway. The local extract arrangement thus seemed to yield both improved ventilation efficiency and reduced contaminant spread to other rooms. The noted air quality variations within the room highlight the importance of sensor placement in demand-control ventilated spaces, even in small rooms such as bedrooms.

  • 10.
    Garman, Ian
    et al.
    Högskolan Dalarna.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Persson, Thomas
    Högskolan Dalarna.
    Ventilation alone fails to prevent overheating in a Nordic home field study2022In: 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022, International Society of Indoor Air Quality and Climate , 2022Conference paper (Refereed)
    Abstract [en]

    A field study conducted in a modern Nordic single-family house with high airtightness and insulation levels, attempted to control summer indoor overheating using night-time cooling strategies. Exhaust air flow rates were manually scheduled by the researchers (based on weather forecasts), analogous to what an engaged occupant - or a predictive system - might do. Air temperatures at a nearby meteorological station peaked at 30 °C during 6 days in June that saw only 44 hours below 18 °C. Temperatures recorded indoors at the test house reached 32 °C, due also to very large solar gains, and never fell below 26 °C over 8 continuous days. It appears that under extended heat conditions that are exceptional now, but foreseen to become more frequent, some modern Nordic homes cannot be temperature controlled by ambient ventilation alone.

  • 11.
    Hayati, Abolfazl
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Akander, Jan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Development of a Numerical Air Infiltration Model Based On Pressurization Test Applied On a Church2016In: ASHRAE and AIVC IAQ 2016 — Defining Indoor Air Quality: Policy, Standards and Best Practices, 2016, ASHRAE, 2016, p. 224-231, article id C030Conference paper (Refereed)
    Abstract [en]

    Pressurization (blower door) test is a well-established standardized method, performed in order to quantify the total leakage in a building envelope. However, blower door results are not adequate to use when air leakage through the building envelope during natural conditions (non-pressurized) is to be estimated. A common assumption made when estimating air leakage during natural conditions, is that air leakage paths are evenly distributed in the areas of the building envelope. This assumption gives quite poor calculation results since different leakage configurations are often situated unevenly in the envelope. In order to improve the correspondence between Blower door and air leakage model results, more information on the types and locations of the leakage paths are required as input to simulation models. 

    This paper investigates if additional information from visual inspection and IR-thermography observations at site can increase the precision when simulating air change rates due to air leakage in natural conditions.  A numerical model is developed in this study by allocating leakage in various parts of the building envelope. The leakage allocation is based on visual inspection and IR-thermography observations at the site during the blower door test.

    This procedure is tested in the case study of a large single zone church. Blower door, neutral pressure level measurement and leakage allocation results are used as input in the numerical model. Model results are compared with tracer gas measurements and result accuracy is compared with results from the Lawrence Berkeley Laboratory model (LBL) and the Alberta Air Infiltration Model (AIM-2) for the same church. 

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  • 12.
    Hayati, Abolfazl
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Akander, Jan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Simulation of Ventilation Rates and Heat Losses during Airing in Large Single Zone Buildings in Cold Climates2019In: Cold Climate HVAC 2018: Sustainable Buildings in Cold Climates / [ed] Johansson, D., Bagge, H., Wahlström, Å., Springer, 2019Conference paper (Refereed)
    Abstract [en]

    Airing can be a solution to introduce extra ventilation in large single zone buildings, especially where there are large aggregations of people such as churches or atriums. In naturally ventilated domestic and ancient buildings, opening of a window or door can introduce extra fresh air and remove particles and other contaminants emitted from people and other sources such as lit candles in churches. However, the energy use might be an issue in cold climates, where airing might lead to waste of heated air, at the same time as indoor air temperatures can be uncomfortably low. In the present study, the energy loss and ventilation rate due to airing in a large single zone (church) building is investigated via IDA-ICE simulation on annual basis in cold weather conditions. The results can be used in order to prepare airing guidelines for large single zone buildings such as atriums, churches, industry halls and large sport halls. According to the results, one-hour of airing in the studied church building resulted in 40-50 % of exchanged room air and, if practiced once a week, an increase of around 1 % in heating energy.

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  • 13.
    Hayati, Abolfazl
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    A Study on Airing Through the Porches of a Historical Church – Measurements and IDA-ICE Modelling2016In: ASHRAE and AIVC IAQ 2016 - Defining Indoor Air Quality: Policy, Standards and Best Practices, 2016, ASHRAE, 2016, p. 216-223, article id C029Conference paper (Refereed)
    Abstract [en]

    In churches, intentional airing may be a measure to evacuate temporarily high levels of contaminants that are emitted during services and other occasions. Crucial contaminants include moisture and other emissions that may deteriorate and/or soil painted surfaces and other precious artefacts. Most old churches do not have any mechanical ventilation system or any purpose provided openings for natural ventilation, but the ventilation is governed by air infiltration. Enhanced airing may be achieved by opening external windows or doors. Thus, models provided in energy simulation programs should predict this kind of air flows correctly, also in order to get a proper estimation of the total energy use. IDA-ICE is examined here and the model for air flow through a large vertical opening used in the program is investigated. In the present study, field measurements were performed for airing rate in a historical church. In comparison with measured air flow rates, the simulated results were of the same magnitude, but the effect of wind direction was less considered by the simulation program.

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  • 14.
    Hayati, Abolfazl
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    A wind tunnel study of wind-driven airing through open doors2019In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 18, no 2, p. 113-135Article in journal (Refereed)
    Abstract [en]

    Temporarily enhanced natural ventilation of indoor environments can be achieved by opening windows and/or doors, i.e. airing. In this study, wind driven airing rate through doors was measured by tracer gas at a building model in a wind tunnel. Both single opening and cross flow airing was investigated, with doors placed in centrally on the long side of an elongated building model. It was found that cross flow airing yielded 4–20 times higher airing rate than single opening airing; lowest value occurring with opening surfaces perpendicular to wind direction. At single opening airing, windward positioned door yielded about 53% higher airing rate than leeward positioned. Inclusion of a draught lobby (extended entrance space) lowered airing rate by 27%, while higher wind turbulence increased it by 38%. Advection through turbulence appeared a more important airing mechanism than pumping. At cross flow, however, turbulence and draught lobby had practically no effect.

  • 15.
    Hayati, Abolfazl
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Evaluation of the LBL and AIM-2 air infiltration models on large single zones: three historical churches2014In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 81, p. 365-379Article in journal (Refereed)
    Abstract [en]

    Air infiltration in ancient churches and other historical and monumental buildings is of great importance considering moisture transfer, energy consumption, thermal comfort and air pollutants that induce surface soiling. Two of the most established models for predicting air infiltration rate in buildings are the Lawrence Berkeley Laboratory (LBL) model and the Alberta air Infiltration Model (AIM-2). Being originally developed mainly for dwellings, their applicability to large single zone buildings is evaluated in this study by comparing model predictions with field measurements in three historical stone churches that are naturally ventilated only through infiltration. The somewhat more developed AIM-2 model yielded slightly better predictions than the LBL model. However, an LBL version that allows inclusion of the Neutral Pressure Level (NPL) of the building envelope produced even better predictions and also proved less sensitive to assumptions on air leakage distribution at the building envelopes. All models yielded however significant overpredictions of the air infiltration rate. Since NPL may be difficult to attain in practice, the AIM-2 model was chosen for model modification to improve predictions. Tuning of this model by varying its original coefficients yielded however unrealistic model behaviors and the eventually suggested modification implied introducing a correction factor of 0.8. This reduced the median absolute prediction error from 25% to 11%. Thus, especially when the NPL is not at hand, this modification of the AIM-2 model may suit better for air infiltration assessment of churches and other buildings similar to the tested kind.

  • 16.
    Hayati, Abolfazl
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Single-sided ventilation through external doors: measurements and model evaluation in five historical churches2017In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 141, p. 114-124Article in journal (Refereed)
    Abstract [en]

    Ventilation through open doors is a simple way to temporarily enhance ventilation of indoor spaces, with the purpose to evacuate indoor air pollutants or to adjust the indoor temperature. In churches and other historical buildings, which otherwise are ventilated only through air infiltration, temporarily enhanced ventilation through open doors or windows may be a prudent deed after e.g. services involving large congregations and burning of candles or incense. In the present study, the air exchange occurring at single-sided ventilation through the external doors of five historical churches is measured by tracer gas decay method. Further, air velocity measurements and smoke visualization in a doorway are performed. Measurement results are compared with predictions attained from four previously developed models for single‐sided ventilation. Models that include terms for wind turbulence yielded somewhat better predictions. According to the performed measurements, the magnitude of one hour single-sided open-door airing in a church is typically around 50% air exchange, indicating that this is a workable ventilation method, also for such large building volumes. A practical diagram to facilitate estimation of a suitable airing period is also presented. The study adds particularly knowledge to the issue of airing through doors, in large single zones.

  • 17.
    Hayati, Abolfazl
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Evaluation of two air infiltration models on a church2013In: Conference proceedings: Cultural heritage preservation – 3rd European Workshop on Cultural Heritage Preservation, 2013, p. 47-53Conference paper (Refereed)
    Abstract [en]

    Air infiltration in ancient churches and other historical and monumental buildings is of great importance considering moisture transfer, energy consumption, thermal comfort and indoor surface soiling. Two of the most established models for simulatingand predicting air infiltration in buildings are the Lawrence BerkeleyLaboratory (LBL) model and the Alberta air Infiltration Model (AIM-2). The applicability of these models in superimposing wind and buoyancy driven infiltration in large single zone buildings such as churches are evaluated in this study by comparing model predictions with field measurements in a 19thcentury stone church. Both tested air infiltration models yielded significant positive correlations between measured and predicted data, and it is concludedthat the AIM-2 model works better than the LBL model for the studied church. Both models tend however to over-predict the air infiltration rate significantly. The over‑predictions were larger in cases with high wind speed and it seems that the models are more fragile in wind dominating conditions. Inclusion of crawl space coefficients in the AIM-2 model improved however the predictions, especially at high wind speeds. It seems that models of the tested kind can be useful in predicting air infiltration in churches and similar buildings, but that some empirically attained model coefficients might need some adjustment to suit this kind of buildings better.

  • 18. Holmberg, Sture
    et al.
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Mattsson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Nilsson, Håkan
    Holmér, Ingvar
    Indoor Air Quality and climate control parameters in office environment – CFD calculations and measurements2000In: Roomvent 2000 Conference, 2000Conference paper (Refereed)
  • 19.
    Lundström, Hans
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Modified thermocouple sensor and external reference junction enhance accuracy in indoor air temperature measurements2021In: Sensors, E-ISSN 1424-8220, Vol. 21, no 19, article id 6577Article in journal (Refereed)
    Abstract [en]

    Indoor air temperature belongs to the most important climatic variables in indoor climate research, affecting thermal comfort, energy balance, and air movement in buildings. This paper focuses on measurement errors when using thermocouples in indoor temperature measurements, with special attention on measurements of air temperature. We briefly discuss errors in thermocouple measurements, noting that, for temperatures restricted to indoor temperature ranges, a thermocouple Type T performs much better than stated in “standards”. When thermocouples are described in the literature, industrial applications are primarily considered, involving temperatures up to several hundred degrees and with moderate demands on accuracy. In indoor applications, the temperature difference between the measuring and the reference junction is often only a few degrees. Thus, the error contribution from the thermocouple itself is almost immeasurable, while the dominant error source is in the internal reference temperature compensation in the measuring instrument. It was shown that using an external reference junction can decrease the measurement error substantially (i.e., down to a few hundredths of a degree) in room temperature measurements. One example of how such a device may be assembled is provided. A special application of room temperature measurements involves measuring indoor air temperature. Here, errors, due to radiation influence on the sensor from surrounding surfaces, were surprisingly high. The means to estimate the radiative influence on typical thermocouples are presented, along with suggestions for modification of thermocouple sensors to lower the radiation impact and thereby improve the measurement accuracy.

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  • 20.
    Lundström, Hans
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Radiation influence on indoor air temperature sensors: Experimental evaluation of measurement errors and improvement methods2020In: Experimental Thermal and Fluid Science, ISSN 0894-1777, E-ISSN 1879-2286, Vol. 115, article id 110082Article in journal (Refereed)
    Abstract [en]

    Radiation influence on commonly used temperature sensors for measuring indoor air temperatures can be significant, especially at the typically low air velocities occurring indoors. Conceptually, a physical sensor may not read the true air temperature, it only reads its own temperature, and, being a solid body, it will exchange energy with the surrounding surfaces (walls, windows etc.) through radiation. In the present study, radiation influence on indoor air temperature measurements was investigated experimentally and errors were quantified in simple terms. Measures to reduce the impact on some common temperature sensors were explored. A special test rig was built to simulate typical airflow and radiation environments indoors. It is suggested that the radiation impact on a temperature sensor is quantified by a radiation sensitivity factor defined as RSF = hrad/hconv, where hrad and hconv are heat transfer coefficients for radiation and convection, respectively. As this definition infers, the radiation sensitivity is dependent on size, geometry and emissivity of the temperature sensor. The radiation sensitivity factor, thus being unique for each type of sensor, was measured for some common types of thermistors and thermocouples. It is demonstrated that radiation errors may be reduced by 60 – 80 % on thermistors by reducing their emissivity through gold sputtering, and on thermocouples by stripping the insulation at the outermost part of their sensor leads.

  • 21.
    Mahaki, Mohammadbagher
    et al.
    Shahid Bahonar University of Kerman, Kerman, Iran.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Salmanzadeh, Mazyar
    Shahid Bahonar University of Kerman, Kerman, Iran.
    Hayati, Abolfazl
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Comparing objects for human movement simulation regarding its air flow disturbance at local exhaust ventilation2021In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 247, article id 111117Article in journal (Refereed)
    Abstract [en]

    The movement of people and other objects indoors may affect airflow patterns and velocities near local exhaust ventilation hoods, and consequently has influence on the hoods’ ability to remove locally emitted contaminants and on ventilation energy requirements. In this study, such disturbance effects have been studied experimentally and numerically, with the movements consisting of a human-sized plate, cylinder and detailed manikin, respectively, making back-and-forth movements near an exhaust hood. In the experimental part of the study, a 3-D sonic anemometer was used to measure air velocity in front of the hood opening. The numerical simulations used dynamic mesh to handle object movements. The numerical results were validated against the experimental ones and yielded supplementary results on the air flow field. The results show that the turbulence produced by the objects movements included marked air velocity peaks – both assisting and impeding the suction flow – in the near field of the exhaust hood. The generated turbulence, and particularly those peaks, proved substantially larger in the case of plate movement than with cylinder and manikin movement. Overall the results indicate that a moving cylinder represents human movement better than a moving plate, and thus that it’s better to use a cylinder in some test standards that now stipulate a plate as moving object. A Percentage of Negative Velocity (PNV) parameter was introduced for assessing the capture efficiency of the local exhaust system. The PNV represents the percentage of time that the air flow is directed away from the exhaust hood in an imagined point of contaminant release. The study includes test cases where the PNV values were significantly above zero, suggesting a strong effect on the capture efficiency of the exhaust hood. Human induced turbulence that cause such reverse air flows and overall impedes hood suction may be counteracted by enhanced exhaust flow rate, but then at higher energy consumption.

  • 22.
    Mahaki, Mohammadbagher
    et al.
    Shahid Bahonar University of Kerman, Kerman, Iran.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Salmanzadeh, Mazyar
    Shahid Bahonar University of Kerman, Kerman, Iran.
    Hayati, Abolfazl
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Experimental and numerical simulations of human movement effect on the capture efficiency of a local exhaust ventilation system2022In: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 52, article id 104444Article in journal (Refereed)
    Abstract [en]

    In local exhaust ventilation systems, external turbulence from e.g. human movements can affect the capture efficiency of the system considerably. In this study, experimental and numerical (CFD) approaches were utilized to evaluate the effect of human movement on the capture efficiency of a local exhaust ventilation system with an exterior circular hood. Human movements were simulated by back-and-forth movements of three human-sized moving objects: a flat plate (CFD + experimental), a cylinder (CFD) and a human-shaped manikin (CFD), respectively. The experiments consisted of tracer gas measurements in a full-scale test room. The numerical simulations included dynamic mesh methods to handle object movements. The results showed reasonable agreement between numerical and experimental results regarding the capture efficiency at different movement frequencies and exhaust flow rates, indicating that CFD is a feasible method for investigating complex flows of the studied kind. In comparison with the moving manikin, the moving plate caused significantly lower capture efficiency, whereas the moving cylinder yielded higher values. Overall, the results with the cylinder as moving object proved more similar to those of the manikin than the results with the flat plate. These findings have particular relevance towards existing test standards that stipulate the use of a moving flat plate in similar test situations. Further, some parameter variations verified that local exhaust capture efficiency increases by increasing the exhaust air flow rate and movement time interval, and also by decreasing the distance between contaminant source and exhaust hood opening. Also increasing the distance between the movable object and the contaminant source, as well as decreasing the diameter of the exhaust hood opening increased the capture efficiency.

  • 23.
    Mattsson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    A Note on the Thermal Comfort in Displacement Ventilated Classrooms2000In: Air distribution in rooms (Roomvent 2000): Proceedings of the 7th international conference on air distribution in rooms, 2000, p. 1129-1134Conference paper (Refereed)
    Abstract [en]

    Nineteen university students were asked about their thermal comfort while attending ordinary lessons in a displacement ventilated test room of typical classroom size. Two different ceiling heights were tested. Both the general temperature level and the strength of the vertical temperature stratification in the room increased continuously during the lessons due to the presence of the students, however slower with the higher ceiling. The temperature stratification of the air eventually reached a strength of 3.1°C/m, which, according to international standards, should cause some complaints about the thermal comfort. There was however no indication of that the students could feel this stratification. The fact that the vertical radiative temperature asymmetry was comparatively small in the room – due to radiative heat exchange between the interior surfaces – is believed to be a major reason for this insensitivity of the students to the vertical air temperature stratification.

  • 24.
    Mattsson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Displacement Ventilation in a Classroom: Influence of Contaminant Position and Physical Activity1998In: Proc. 19th AIVC Conference, Oslo, Norway., 1998Conference paper (Refereed)
    Abstract [en]

    This study describes how the air quality in a displacement ventilated classroom can be influenced by the position of a contaminating person, and by the activity of a person who walks around in the room. Tracer gas measurements have been performed in a full scale mock-up of a classroom, with person simulators at the student’s desks.

    The spreading of contaminants from a person seems to be strongly dependent on the position of the person. The closer the contaminating person sits to the outlet terminal(s), the less of his/hers contaminants are spread in the room. Paradoxically, people sitting furthest away from the air supply were found to be provided with the least contaminated air. Physical activity, produced by a walking person, tends to increase the concentration of contaminants emitted from people in the room, whereas the air exchange efficiency actually can benefit from it. At all levels of activity tested in this study the displacement ventilation system provided significantly better air quality than a mixing system would. The temperature gradient in the occupied zone was rather high during these steady-state experiments, and it was only marginally affected by the movements of a person.

  • 25.
    Mattsson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Removal of airborne particles of different sizes in classrooms using portable air cleaners2007In: Roomvent 2007, 13-15 June 2007 Helsinki, Finland: Scanvac Conference : proceedings, abstract book, 2007Conference paper (Refereed)
    Abstract [en]

    Portable electrostatic air cleaners (precipitators) were tested in six different classrooms during ordinary lessons. The number concentration of airborne particles in the classrooms was measured using optical particle counters, which separated the particle recordings into six different size fractions in the range 0.3 μm to >25 μm. It was found that the effectiveness of the air cleaners in cleaning the classroom air was decreasing significantly with increasing particle size. For the smallest particles measured, 0.3-0.5 μm, the measured effectiveness was 76 %, whereas for the particle size fraction 10-25 μm it was only 33 %. This reduced effectiveness for the large particles can be explained by the removal process of particle deposition onto room surfaces. The removal rate due to deposition seems to be competitive with the removal rate of the air cleaners as regards large particles. It appears that the deposition effect often needs to be taken into account in effectiveness assessments for particulate air cleaners.

  • 26.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Testing local exhaust ventilation at controlled turbulence generation by using tracer gas and a 3-D anemometer2014Report (Other academic)
    Abstract [en]

    Local exhaust (LE) ventilation is a ventilation technique where contaminated air is locally extracted close to the contaminant source, usually with the purpose to reduce the exposure of a person doing work which involves the contaminant. There is a need for well-defined and appropriate methods to test the performance of LE constructions. The present study aims at contributing to the establishment of such tests. The study entails full scale experimental measurements that include 3-D air velocity measurements, tracer gas tests and controlled generation of air turbulence through physical movements of a vertical, human-sized plate. The tested exhaust hood (EH) was of circular, flat plate flanged type.

    One part of the study concerned the task of determining the 0.4 m/s distance, x0.4, at the EH; i.e. the distance from the EH opening to a point where the air velocity has declined to 0.4 m/s. This is a currently used measure of “safe zone” at an EH. It was found that practicable measurements of good accuracy seem to be attained by using the following fairly simple correction equation:

    x0.4=xm*rot(Vm/0.4)

    where Vm is a provisionally measured air velocity, preferably within the zone where Vis within 0.35-0.45 m/s in front of the EH, and xm is the measured distance from the EH opening to the measuring point of Vm.

    The tracer gas tests implied injection of a neutrally buoyant tracer gas through a perforated sphere placed in front of the EH. The amount of tracer gas that escaped from the suction flow was measured in the room air, thus yielding a sensitive method for measuring the capture efficiency (CE) of the EH. The CE is the percentage of injected tracer gas that is directly captured by the EH. Measurements of CE was performed at several test cases, were exhaust flow rate, gas release distance, turbulence level and EH arrangement were varied. The recorded CE values varied between 75 to 100% and the response to the different test cases appeared trustworthy.

    The use of a 3-D sonic anemometer, that yielded both magnitude and direction of the air movement, proved very useful in analyzing the generated air turbulence. Its measurement data was also used to construct another measure of the local exhaust performance: Percentage Negative Velocities, PNV. This measure represents the percentage of the time when the air flow at the measuring point in front of the EH is directed away from the EH nozzle, i.e. when the velocity component in the direction towards the EH opening is negative. The recorded PNV values correlated well with the corresponding CE values, attained at the tracer gas tests. Thus, measuring PNV might be a convenient alternative or complement to tracer gas measurements.

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  • 27.
    Mattsson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Vertical distribution of occupant-generated particles in a room with displacement ventilation2002In: Indoor Air 2002: 9th international conference on indoor air quality and climate, 2002, p. 509-514Conference paper (Refereed)
    Abstract [en]

    The vertical distribution of airborne particles in a room ventilated according to the displacement principle was measured using a vertically conveyed particle counter. The supply air was absolute-filtered and the particles generated through office-like activity of people. In general, particle concentrations increased with height, indicating a displacement effect. This effect improved with ventilation rate. A threshold-size of the particles could be discerned, above which the displacement effect started declining. The measured threshold-size agreed well with calculations based on the settling velocity of the particles and the hypothetical vertical piston-flow velocity of the room air (ventilation rate divided by floor area). At the ventilation rates tested (normal to high), the threshold-size was in the range 5-10 µm. Slightly negative concentration gradients were observed for large particles at the lowest ventilation rate. Hence, if hazardous substances are known to be associated with fairly large particles, the use of displacement ventilation is questionable.

  • 28.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Akander, Jan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Ameen, Arman
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Karlsson, Björn O.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Fältstudie av två metoder för energieffektivisering av äldre fönster – fönsterfilmer testade med hotbox-teknik2020Report (Other academic)
    Abstract [en]

    The present study has examined two kinds of window films that aim to improve windows regarding energy and comfort aspects. The films consist of thin self-adhesive plastic with high-tech radiation-reflective coating. Main focus has been on a new kind of heat insulating film ("Energy Film"), which primarily intends to reduce heat loss through the window towards a colder outdoor climate. In this project, the energy film has been tested in the field with the so-called hotbox method, with which the heat loss through a 2-pane window could be measured on site in a real historical building: the Town Hall in Gävle, Sweden. The hotbox method is normally used in a laboratory environments, and an important purpose of the project was to evaluate the method in the field. In addition to the energy film, solar reflective film ("Solar Film") was also tested, which mainly aims to reduce the transmission of radiant heat from direct sunlight. The study also includes subjective assessments by building anti-quarians regarding aesthetic and antiquarian aspects of the application of the window films.

    The results indicate that the hotbox method is useful in the field, although rather laborious to get in place practically. The measurement results indicate that mounting Energy Film reduces the heat transfer (U-value) through the glazed part of the window by about 31% if the film is placed on one of the pane surfaces in the gap between the panes, while the reduction becomes about 19% when placed on the inside of the inner pane. Placement in the gap thus seems most effective, if practicable; it also reduces the risk of condensation and convective down draught along the inside of the window. However, from an economical point of view, it seems difficult to reckon any profit by investing in either Energy Film or Solar Film. On the contrary, mounting Solar Film tends to increase energy costs. Thermal buffering in the heavy city hall building helps reduce the heat increase that occur from much solar radiation; Solar Film is likely to be more effective in lighter buildings. The town hall building was also equipped with mechanical demand controlled ventilation, with the possibility of quite high ventilation rates for cooling; in buildings without such a system, Solar Film will benefit more. However, both Energy and Solar Films improve thermal comfort, both in terms of chilliness and warmth, especially for people being close to the windows. So, rather than reduced costs, it seems to be comfort and/or environmental reasons that can motivate investment in the window films.

    The window films resulted in reduced light transmittance (-16% for Energy Film; -22% for Solar Film) and some (moderate) color change at certain lighting conditions and viewing angles. Overall, however, the studied window films received fairly high acceptance by the building antiquarians, but it was noted that professional care is needed during installation. The installation of the films was however demonstrated to be done relatively quickly and cause little disruption to the activities in the premises. The films can also be cut to fit e.g. curved frames, and they do not add any extra load (weight) to the window, as compared to other methods that involve addition of an extra pane on the frame. Tests of removal of a 3-year-old Energy Film showed that this could be done without damaging the window glass, but it seems doubtful to mount the films on really thin, fragile glass, since those may break if removing the film, which nonetheless was noted to stick fairly hard to the glass surface.

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    Slutrapport Fönsterfilmer testade i hotbox
  • 29.
    Mattsson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Andersson, Lars T
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för naturvetenskap.
    Birch and grass pollen allergens in filtered office indoor air2008In: Indoor air 2008: proceedings of the 11. International Conference on Indoor Air Quality and Climate, Technical University of Denmark, Kongens Lyngby 2008, Kgs Lyngby: Technical university of Denmark , 2008Conference paper (Refereed)
    Abstract [en]

    In an experimental field study, airborne particulate birch and grass pollen allergens were sampled with a cascade impactor on the roof of an office building in the centre of a middle-sized town in Sweden. The impactor separated particles into eight size fractions. Simultaneously, inhalable pollen allergens in the indoor air were sampled in offices of the building. Significant amounts of the outdoor pollen allergens were found on particles much smaller than the pollen grains. These small particles could penetrate the fine filters (quality F6) of the building’s ventilation system. By taking into account the effectiveness of the installed ventilation filters, the pollen allergen concentration indoors could be well predicted, thus pointing out the supply air as the main source of indoor pollen allergens. Comparison of data from workdays with those from weekends indicated that secondary emissions of pollen allergens brought indoors by people (on clothes, hair, shoes etc.) were insignificant.

  • 30.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Andersson, Lars T
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Chemistry.
    Alm Kübler, Kerstin
    Swedish Museum of Natural History, Laboratory of Palynology.
    Ekebom, Agneta
    Swedish Museum of Natural History, Laboratory of Palynology.
    Jansson, Anders
    Stockholm University, ITM.
    Holmquist, Leif
    Consultant at University of Gävle.
    Vesterberg, Olof
    Consultant at University of Gävle.
    Ventilation filter efficiency for birch pollen allergens: experimental data from one pollen season2011In: Proceedings from Roomvent 2011 / [ed] Hans Martin Mathisen, Trondheim: Tapir Akademisk Forlag , 2011Conference paper (Refereed)
    Abstract [en]

    In an experimental study, ventilation filters of high quality (F7 & F9) were tested regarding their efficiency in collecting birch pollen allergens in outdoor air. The birch pollen grain concentration in outdoor air was measured at the same time as pollen allergen and particle number concentrations were measured before and after the tested ventilation filters, thus enabling collection efficiency calculations. Simultaneously, the size distribution of birch pollen allergens was measured in outdoor air using a cascade impactor. The study confirms previous indications that pollen allergens may occur in outdoor air in particles much smaller than pollen grains, and can penetrate ventilation filters to a larger extent than might be expected. This entails that although the high quality filters collect most of outdoor air pollen allergens, a significant exposure dose to these allergens can occur in the indoor environment, especially when considering the fact most people stay much more indoors than outdoors. The study also confirms previous similar indications attained with grass pollen allergens, in that the allergenic particles tend to penetrate ventilation filters to a greater extent than other airborne particles.

  • 31.
    Mattsson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Andersson, Lars T
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för naturvetenskap.
    Jansson, Anders
    Stockholms Universitet, ITM.
    Holmquist, Leif
    Timanställd vid HiG.
    Vesterberg, Olof
    Timanställd vid HiG.
    Alm Kübler, Kerstin
    Naturhistoriska riksmuséet, Palynologiska laboratoriet.
    Ekebom, Agneta
    Naturhistoriska riksmuséet, Palynologiska laboratoriet.
    Ventilation filter efficiency for particles and grass pollen allergens2009In: Proceedings of the 9th International Healthy Buildings Conference and Exhibition: HEALTHY BUILDINGS 2009, Paper No: 460. / [ed] Santanam, S., Bogucz, E.A., Peters, C., Benson, T., 2009Conference paper (Refereed)
    Abstract [en]

    In an experimental study, commonly used ventilation fine filters were tested regarding their efficiency in collecting airborne particles and grass pollen allergens from outdoor air. Grass pollen allergen and particle number concentrations were measured before and after the filters, enabling collection efficiency calculations. Simultaneously, the size distribution of grass pollen allergens was measured in outdoor air using a cascade impactor. The study confirms previous indications that pollen allergens occur in the outdoor air as particles much smaller than pollen grains, and can penetrate ventilation filters to a larger extent than might be expected. The initially high collection efficiency of synthetic, electrostatically charged filters declined significantly with time of use (dust load), whereas glass fiber filters showed steady performance. A slight tendency for pollen allergenic matter to penetrate ventilation filters more than other airborne particles was noted, but no difference in the response to electrostatic charge of filters could be seen.

  • 32.
    Mattsson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Bjørn, Erik
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Nielsen, Peter
    Simulating People Moving in Displacement Ventilated Rooms1997In: Proc. Healthy Buildings/AIQ ‘97, Washington DC, USA. / [ed] Wood JE, Grimsrud DT, Boschi N, 1997Conference paper (Refereed)
    Abstract [en]

    A displacement ventilation system works better the more uni-directional the air flow through the ventilated room is: from floor to ceiling. Thus, from an air quality point of view, there should be as little vertical mixing of the room air as possible. It is therefore comprehensible that physical activity in the room – like peoples movements – in previous studies has been shown to influence the effectiveness of the ventilation. In this study we have compared results from previous tests, where a cylindrical person simulator was used, to results obtained when using a person simulator of more human-like shape. The main results verify previous findings: if the movements are not very slow, they have a detrimental effect on ventilation effectiveness and on the air quality in the breathing zone of the inhabitants. Some quantitative differences were found between using the simple and the detailed person simulator, although the qualitative results were about the same.

  • 33.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Broström, Tor
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Fan Convectors vs. Bench heaters in Churches – impact on air velocities2011In: EEHB 2011: Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström & Lisa Nilsen, Visby: Gotland University Press, 2011Conference paper (Refereed)
    Abstract [en]

    Air movements in churches affect the deposition rate of airborne particles on surfaces, and hence influence soiling of valuable artifacts of different kinds. Sooting from candles and the thermal comfort of people is also affected by indoor air velocities. In an experimental field study, two different heating systems were compared regarding their effect on room air velocities in a church: air-to-air heat pumps with indoor fan convectors vs. a combination of bench heaters and radiators. Hot-sphere and 3-D sonic anemometers were used to record air velocities in the church. Strong buoyant air flows were found both in the supply air flow path of the heat pumps and above the bench heaters, but the air velocities were rather low outside of these air currents. A ~25 cm thick downdraught air flow was found along walls and windows, with a magnitude that was similar at both heating systems and much larger than the outdoor air infiltration rate.

  • 34.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Broström, Tor
    Högskolan på Gotland, Institutionen för kultur, energi och miljö.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Impact of heating system on air velocities in a medieval stone church2011In: Roomvent 2011: 12th International conference on air distribution in rooms, Trondheim, Norge: Tapir Akademisk Forlag , 2011Conference paper (Refereed)
    Abstract [en]

    The air flow pattern and magnitude of air velocities in churches and other historic buildings are of interest since they influence the deposition rate of airborne particles on surfaces, and hence affect soiling of valuable artifacts of different kinds. Increased air movements might also cause enhanced sooting from candles and it has an influence on the thermal comfort of people. The type of installed indoor heating units is likely to be important here since these usually induce substantial air movements through natural or forced convection. In an experimental field study, two different heating systems were compared regarding their effect on room air velocities in a medieval stone church: air-to-air heat pumps with indoor fan convectors vs. a combination of bench heaters and radiators. Hot-sphere anemometers were used to record air velocities in the near-zone of the heat pumps and their surroundings, and 3-D sonic anemometers were used to measure downdraught air velocities at the surfaces of a wall and a window. Smoke was used to visualize air flow patterns.

    It was found that the heat pumps caused strong buoyant air jets that rose to the ceiling, but that the air velocities were rather low outside of these jets. The bench heaters caused buoyant plumes, which also seemed to attain rather high air velocities and reach the ceiling. As regards downdraught along wall and window, no significant difference between the two heating systems could be seen, although there was a tendency towards slightly higher air velocities at these surfaces when the heat pumps were in use. Since the air flow pattern at the surfaces appeared similar, also the particle deposition mechanisms and soiling rate can be expected to be similar.

  • 35.
    Mattsson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Hygge, Staffan
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Effect of Particulate Air Cleaning on Perceived Health and Cognitive Performance in School Children During Pollen Season2005In: Indoor Air 2005: Proceedings of the 10th international conference on indoor air quality and climate, 2005, p. 1111-1115Conference paper (Refereed)
    Abstract [en]

    Cleaning of room air from particulate contaminants was performed using electrostatic air cleaners (precipitators) in four classrooms of 12-year old pupils. The air cleaners were active/inactive according to a cross-over design for 2 + 3 weeks during pollen season. Health questionnaires and cognitive tests were used to investigate the impact of air cleaning on perceived health and on cognitive skills that relate to schoolwork and learning (semantic and episodic memory, logical reasoning, attention, reading comprehension). Pupils stating themselves as being sensitive to airborne particulate contaminants, such as pollen and pet allergens, experienced somewhat less irritation in airways and eyes when the air cleaners were active (p=0.02). The most sensitive pupils also scored about 25% higher on the cognitive test relating to semantic memory when the air cleaners were active (p=0.015). No significant effects were however found for the four other cognitive skills.

  • 36.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, BMG laboratory.
    Test av luftrenare i Visby domkyrka2016Report (Other academic)
    Abstract [sv]

    Efter den senaste renoveringen av Visby domkyrka, som bl a innefattade rengöring av innerväggar (våren 2014), noterades en oväntat snabb försmutsning av rengjorda väggytor, orsakad av avsättning av partiklar i inneluften. Med syfte att minska försmutsningstakten installerades två fristående luftrenare av elektrostatisk modell i kyrkan i oktober 2015. Föreliggande studie har haft som främsta syfta att utvärdera dessa luftrenares effektivitet i att rena inneluften på luftburna partiklar, framför allt från levande ljus. Utvärderingen har gjorts genom att mäta hur partikelhalten i kyrksalen förändrades vid olika driftfall på luftrenarna. Två olika flödesinställningar på luftrenarna provades: maxflöde resp. lågflöde, där maxflödet provades med både horisontellt och vertikalt riktat utblås av den renade luften. Anledningen till att även ett lägre luftreningsflöde provades var att luftrenarna bullrade så mycket vid maxflöde att detta driftförhållande endast torde bli aktuellt utanför besökstid. Studien har även inkluderat luftomsättningsmätning med spårgasteknik, luft- och yttemperaturmätningar, samt kallrasmätning vid vägg. Även ett vädringstest via portöppning har ingått. 

    Resultaten tyder på att luftrenarna har en klart renande effekt avseende luftburna partiklar i kyrksalen. Den minskning i antalet partiklar som luftrenarna åstadkom (partikelrenings-effektiviteten) varierade emellertid med partikelstorleken. I lågflödesfallet erhölls en reduktion av de minsta partiklarna (ultrafina, 0,02-0,3 µm) med ca 31 %, medan den för större partiklar (0,3-10 µm) var av storleksordningen 65‑75 %. I maxflödesfallet blev motsvarande siffror ca 58 % för de minsta partiklarna och 80‑90 % för de större. I välbesökta kyrkor där levande ljus ofta tänds – som i Visby domkyrka – utgör emissionerna från ljusen förmodligen den största partikelkällan. För dessa tycks de minsta partiklarna dominera avseende partikelyta (som kan tänkas täcka/försmutsa invändiga ytor), varför den sammantagna partikelreningseffektiviteten avseende försmutsning hamnar närmare den för de minsta partiklarna. Det är dock troligt att partikelreningseffektivitet blir något högre sommartid, då de riktigt stora besökarskarorna kommer i fallet Visby domkyrka.

    Riktningen på utblåset på luftrenarna hade ingen nämnvärd inverkan på partikelrenings-effektiviteten. Dock indikerade mätningarna av kallras (nedfallande luft) längs yttervägg i kyrkan att detta blir något större vid uppåtriktat utblås på luftrenarna, vilket riskerar att öka partikelavsättningstakten vid ytan. Detta fenomen behöver dock studeras närmare. Testet med vädring genom portöppning indikerade att ett avsevärt luftutbyte erhölls med denna metod, och att tillfällig vädring därför kan vara en lämplig åtgärd (även som komplement till luftrenare) vid tillfällen med många besökare och/eller mycket ljusbränning. Både partikel- och spårgasmätningarna påvisade god luftomblandning i kyrksalen, vilket är positivt för spridningen av den renade luften, och detta bidrar till att placeringen av luftrenarna är mindre kritisk. Sommartid kan dock luftomblandningen bli sämre; detta kan behöva undersökas närmare. Förutom minskad försmutsning kan luftrenarna förväntas bidra till en hälsosammare innemiljö ett minskat städbehov i kyrkan.

  • 37.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Methods to Identify Air Leakages in the Building Envelope of Churches2011In: EEHB 2011: Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström & Lisa Nilsen, Visby, Sweden, 2011Conference paper (Refereed)
    Abstract [en]

    Frequently there is a wish to reduce the natural ventilation rate in churches in order to save energy and/or improve the thermal comfort. It is then often difficult to ascertain exactly which the dominating leaks in the building envelope are, and where tightening measures would be most effective. A number of different methods to identify these leakages are discussed here. It appears that valuable help can be attained by a combination of several measuring techniques, including IR-thermography, tracer gas and pressure measurements. These techniques can also be useful in verifying the effect of tightening measures.

  • 38.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Tracer gas techniques for quantifying the air change rate in churches – field investigation experiences2011In: Proc. Roomvent 2011: 12th International conference on air distribution in rooms / [ed] Hans Martin Mathisen, Trondheim, Norge: Tapir Akademisk Forlag , 2011Conference paper (Refereed)
    Abstract [en]

    Two different tracer gas techniques for quantifying the air change rate were tested in three naturally ventilated churches. The techniques were the decay method (or tracer gas dilution method) and a passive tracer gas method. It appeared that the room air in the studied churches tended to be fairly well mixed when the churches are heated, presumably due to strong natural convection air currents occurring at heat sources and cooler outer building surfaces. This seems to entail that both the decay and the passive method are fairly easy to apply during times of heating. It then doesn’t seem to matter much were the tracer gas is injected or where it is sampled. During non-heating periods, however, spatial differences in tracer gas concentrations were observed, making tracer gas measurements more difficult to perform.

  • 39.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Hayati, Abolfazl
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Fan pressurization method for measuring air leakage in churches – wind and stack induced uncertainties2013In: Conference proceedings: Cultural heritage preservation – 3rd European Workshop on Cultural Heritage Preservation / [ed] A. Troi and E. Luchi., 2013, p. 63-68Conference paper (Refereed)
    Abstract [en]

    The air leakage of the building envelope of ancient churches and other historical and monumental buildings has impact on energy consumption, thermal comfort, humidity and indoor surface soiling. To measure the air leakage in such large and naturally ventilated single-zone buildings is however challenging, especially due to wind and buoyancy (stack) induced disturbances. This study describes experiences in this regard, attainedat field tests where the fan pressurization technique (“Blower door”) was employed. Reference is made to the European test standard EN 13829. Also results of wind-tunnel tests are utilized. It is shown that both buoyancy and wind at commonly occurring conditions can cause significant uncertainty in fan pressurization tests, and that some of the directions in the standard might need to be strengthened or amended. While the uncertainty in measured air leakage rate at the standard (high) pressure of 50 Pa may be small, the predictions of the air leakage rate occurring at realistically (low) indoor-outdoor pressures tend to suffer from significant uncertainty. That uncertainty is then conveyed to later utilizations of the test results, e.g. building energy modeling and prediction. It is also shown that the wind induced pressure at buildings like churches extends a considerable way out into the surroundings of the building; in the order of two times the building height. This has particular importance when choosing a reference point for outdoorpressure measurement.

  • 40.
    Mattsson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Smedje, Greta
    Holmquist, Leif
    Vesterberg, Olof
    Wålinder, Robert
    Mixing and displacement ventilation compared in classrooms; distribution of particles, cat allergen and CO22003In: Proceedings from Healthy Buildings 2003: 7th International conference, 2003, p. 458-464Conference paper (Refereed)
    Abstract [en]

    Mixing ventilation and displacement ventilation were compared in an intervention study in classrooms. Particles, cat allergen and CO2, were measured in classroom air at different levels above the floor, during regular lessons. With mixing ventilation, the particle concentration tended to decrease with height, with a stronger gradient occurring for larger particles. With displacement ventilation, the particle concentration increased with height, except for particles >25 µm. The displacement system thus tended to have a slight upward displacement effect on most of the particles. Significant correlations were found between concentrations of cat allergen and particles in the size fraction 1–10 µm. The particle and cat allergen concentration at breathing height did not, however, differ significantly between the two ventilation systems. CO2 was about 10% lower with displacement ventilation. A fairly high level of physical activity of the pupils is believed to have had significant dispersing effect on the airborne contaminants.

  • 41.
    Mattsson, Magnus
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Stojanovic, Bojan
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för byggnadskvalitet.
    Elfman, Lena
    Effect of Particulate Air Cleaners on the Content of airborne Dust and Cat Allergen in Classrooms2004In: Roomvent 2004: 9th international conference on air distribution in rooms, 2004Conference paper (Refereed)
    Abstract [en]

    Electrostatic air cleaners (precipitators) were tested in four classrooms during ordinary lessons for four weeks. Airborne dust in the classrooms was collected on filters using two different kinds of samplers: IOM-sampler and a new kind of ionizing sampler. The amount of collected dust was evaluated by visual inspection (“filter blackening”) and the content of cat allergen was measured using an amplified ELISA assay. It was found that the filter blackening was 64% lower when the air cleaners were active than when they where inactive (p<0.001). This suggests that the air cleaners were effective in reducing the content of airborne particulate matter. The reduction in cat allergen appeared however to be less substantial. The variance of the allergen data was unexpectedly large, presumably due to relatively few allergen-carrying particles in the sampled air. It is believed that larger sampling volumes are needed to get more reliable data of airborne cat allergen in spaces where the allergen is emitted indirectly.

  • 42.
    Moghaddam, Saman Abolghasemi
    et al.
    University of Coimbra, Portugal.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Ameen, Arman
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Akander, Jan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Gameiro Da Silva, Manuel
    University of Coimbra, Portugal.
    Simoes, Nuno
    University of Coimbra, Portugal.
    Low‐Emissivity Window Films as an Energy Retrofit Option for a Historical Stone Building in Cold Climate2021In: Energies, E-ISSN 1996-1073, Vol. 14, no 22, article id 7584Article in journal (Refereed)
    Abstract [en]

    Low‐emissivity (low‐E) window films are designed to improve the thermal comfort andenergy performance of buildings. These films can be applied to different glazing systems withouthaving to change the whole window. This makes it possible to apply films to windows in old andhistorical buildings for which preservation regulations often require that windows should remainunchanged. This research aims to investigate the impacts of low‐E window films on the energyperformance and thermal comfort of a three‐story historical stone building in the cold climate ofSweden using the simulation software “IDA ICE”. On‐site measurements were taken to acquirethermal and optical properties of the windows. This research shows that the application of the lowemissivitywindow film on the outward‐facing surface of the inner pane of the double‐glazedwindows helped to reduce heat loss through the windows in winter and unwanted heat gains insummer by almost 36% and 35%, respectively. This resulted in a 6% reduction in the building’sannual energy consumption for heating purposes and a reduction in the percentage of totaloccupant hours with thermal dissatisfaction from 14% (without the film) to 11% (with the film).However, the relatively high price of the films and low price of district heating results in a ratherlong payback period of around 30 years. Thus, the films seem scarcely attractive from a purelyeconomic viewpoint, but may be warranted for energy/environmental and thermal comfort reasons.

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  • 43.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Etheridge, David W
    University of Nottingham, UK.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Wind tunnel measurements of pressure distribution on  the facade of a church2011In: Proc. EEHB 2011: Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström & Lisa Nilsen, Visby: Gotland University Press, 2011Conference paper (Refereed)
    Abstract [en]

    Elderly churches have a unique shape with their high towers and long naves. There seems to be few if any reported measurement of pressure distribution on churches. Churches are naturally ventilated buildings and therefore when the wind speed is high  the  wind becomes an important driving force for ventilation. A model in scale 1: 200 was built of a 19th century Swedish church provided with a crawl space.The pressure on the façade of the model was recorded in 42 points. With the aim of studying the ventilation of the church, dedicated measuring points were located on windows, doors and in the positions corresponding to the location of the openings in the crawl space.  Some field trials were undertaken with the scope of measuring the time history of the static pressure on the façade in some positions corresponding to measuring points on the wind tunnel model. Examples of these measurements are  reported in the paper. With the aim of measuring the “region of influence” on the ground caused by the church, also the static pressure on the ground was recorded in the wind tunnel tests.  The static pressure on ground was recorded with a pressure plate provided with 400 pressure taps arranged in a quadratic pattern.

  • 44.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Etheridge, David W
    University of Nottingham, UK.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, BMG Laboratory.
    Wind tunnel measurements of pressure distribution on the façade and surrounding ground of a church2011In: Roomvent 2011: 12th International conference on air distribution in rooms / [ed] Hans Martin Mathisen, Trondheim, Norge: Tapir Akademisk Forlag , 2011Conference paper (Refereed)
    Abstract [en]

    Elderly churches have a unique shape with their high towers and long naves. There seems to be few if any reported measurement of pressure distribution on churches. Churches are naturally ventilated buildings and therefore when the wind speed is high  the  wind becomes an important driving force for ventilation.

    A model in scale 1:200 was built of a 19th century Swedish church provided with a crawl space. The pressure on the façade of the model was recorded in 42 points. With the aim of studying the ventilation of the church dedicated measuring points were located on windows, doors and in the positions corresponding to the location of the openings in the crawl space. 

    Some field trials were undertaken with the scope of measuring the time history of the static pressure on the façade in some positions corresponding to measuring points on the wind tunnel model. Examples of these measurements are  reported in the paper.

    With the aim of measuring the “region of influence” on the ground caused by the church, also the static pressure on the ground was recorded in the wind tunnel tests.  The static pressure on ground was recorded with a pressure plate provided with 400 pressure taps arranged in a quadratic pattern.

  • 45.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Hayati, Abolfazl
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, BMG laboratory.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, BMG laboratory.
    Khan, Mubashar
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Viewpoints on wind and air infiltration phenomena at buildings illustrated by field and model studies2015In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 92, p. 504-517Article in journal (Refereed)
    Abstract [en]

    Ventilation and infiltration caused by wind are difficult to predict because they are non-local phenomena: driving factors depend on the surrounding terrain and neighbouring buildings and on the building orientation with respect to the wind direction. Wind-driven flow through an opening is complex because wind can flow through the opening or around the building, in contrast to buoyancy driven flow. We explored wind and air infiltration phenomena in terms of pressure distributions on and around buildings, stagnation points, flow along façades, drag forces, and air flow through openings. Field trials were conducted at a 19th-century church, and wind tunnel tests were conducted using a 1:200 scale model of the church and other models with openings.

     

    The locations of stagnation points on the church model were determined using particle image velocimetry measurements. Multiple stagnation points occurred. The forces exerted on the church model by winds in various directions were measured using a load cell. The projected areas affected by winds in various directions were calculated using a CAD model of the church. The area-averaged pressure difference across the church was assessed. A fairly large region of influence on the ground, caused by blockage of the wind, was revealed by testing the scale model in the wind tunnel and recording the static pressure on the ground at many points. The findings of this study are summarized as a number of steps that we suggest to be taken to improve analysis and predictions of wind driven flow in buildings.

  • 46.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Sattari, Amir
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Plaster finishes in historical buildings: Measurements of surface structure, roughness parameters and air flow characteristics2013In: Conference proceedings: Cultural heritage preservation – 3rd European Workshop on Cultural Heritage Preservation / [ed] A. Troi and E. Luchi., 2013, p. 69-75Conference paper (Refereed)
    Abstract [en]

    Soiling of surfaces in historical buildings by deposition of particles is a common problem. Minimizing soiling is an important goal for conservation of structures and objects. The surfaces give rise to an interference with the air motions along the surfaces. Properties of surfaces may therefore influence the particle deposition. It is well known that with increasing roughness of the surfaces the particle deposition rate increases. The properties of surfaces in historical buildings are not well documented.  We have investigated samples of surfaces finished by wood float finish, steel float finish and brushed finish. As a reference we have used an MDF board. The geometrical properties of the surfaces have been documented by using the stripe projection method. The resistance to airflow along the surface and the turbulence generated by the surfaces has been investigated by recording the boundary layer flow over the surfaces in a special flow rig. The work reported is part of a project where the process of soiling is studied both in laboratory and in field studies. The air velocity adjacent to the surfaces will be recorded with both PIV (Particle Image Velocimetry) and hot-wire technique. The temperature gradient close to the walls will be recorded with cold-wire technique.

  • 47.
    Sandberg, Mats
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Stymne, Hans
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Blomqvist, Claes
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Mattsson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Ventilation i funktion: En handledning för konsulter och kontrollanter1995 (ed. 2)Book (Other (popular science, discussion, etc.))
    Download full text (pdf)
    Ventilation i funktion, del 1
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    Ventilation i funktion, del 2
  • 48.
    Sandberg, Mats
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Wigö, Hans
    University of Gävle, Department of Mathematics, Natural and Computer Sciences, Ämnesavdelningen för naturvetenskap.
    Mattsson, Magnus
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Generation of dust balls and their aerodynamic properties2008In: Indoor air 2008: Proceedings of the 11th International Conference on Indoor Air Quality and Climate, 17-22 August, Copenhagen, Denmark, Kgs Lyngby: Technical university of Denmark , 2008Conference paper (Refereed)
    Abstract [en]

    Dust balls, sometimes called dust bunnies or balls of fluff, are balls with threads of textile fibres and hair as a skeleton on which particles, dead skin and debris are attached.

    In the present study, dust balls were sampled from normal homes by the homeowners. The structure of some of the dust balls was studied in a scanning microscope. The weight of each individual dust ball was quantified. Each sample was placed on a plate of a painted particleboard, representing a floor surface, and was exposed to a velocity field generated by the outflow from a rig for calibration of velocity transducers. The velocity was gradually increased until the dust ball started to move. The majority of the dust balls had a weight less than 20 mg. A particleboard is a fairly rough surface and the velocity required to initiate a movement was beyond what usually is generated by a ventilation system. These levels of velocity can only be generated by opening windows or by people’s movements. The mechanisms by which distant textile fibres are brought together was studied by placing textile threads on the plate of particleboard and following the process by taking pictures with a digital camera. The protruding parts of the surface would sometimes catch the textile fibres.

  • 49.
    Smedje, Greta
    et al.
    Uppsala University.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Wålinder, Robert
    Uppsala University.
    Comparing mixing and displacement ventilation in classrooms: pupils' perception and health2011In: Indoor Air, ISSN 0905-6947, E-ISSN 1600-0668, Vol. 21, no 6, p. 454-461Article in journal (Refereed)
    Abstract [en]

    Several studies have found that indoor air quality (IAQ) in schools is often poor and may affect the health of the pupils. Building ventilation is a means to reduce pollutant indoors but different designs should be evaluated for their effectiveness in different environments. In a field experiment performed in four classrooms in one school building we alternately supplied the air according to the mixing and displacement mode and collected information on exposures, pupils’ perception of IAQ and climate, health symptoms and performed clinical examinations. At breathing height, room temperature, relative humidity and the concentration of CO2 and cat allergen were similar in the periods with each ventilation type. The children perceived indoor air quality as similar in the two ventilation regimes, and there were few differences in symptom reports or clinical parameters. However, the pupils reported more eye symptoms during displacement ventilation.

  • 50.
    Wahlborg, Dan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Chemistry.
    Björling, Mikael
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electrical Engineering, Mathematics and Science, Chemistry.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Evaluation of field calibration methods and performance of AQMesh, a low-cost air quality monitor.2021In: Environmental Monitoring & Assessment, ISSN 0167-6369, E-ISSN 1573-2959, Vol. 193, no 5, article id 251Article in journal (Refereed)
    Abstract [en]

    Field calibrations of NO2, NO, and PM10 from AQMesh Air Quality Monitors (AQMs) were conducted during a summer and an autumn period in a busy street in a midsize Swedish city. All the three linear calibration procedures studied (postscaled, bisquare, and orthogonal data) significantly reduced the ranges and magnitudes of the performance indicators to yield more reliable results than the raw data. The improvements were sufficient to satisfy the European Union (EU) Data Quality Objective (DQO) for indicative measurements as compared to reference data only for NO2 (above 50 µg m-3) and NO (above 30 µg m-3) during the autumn calibration period. The relatively simple bisquare procedure had the best performance overall. The bisquare procedure improved the root mean square error by the same amount as other studies using complex multivariate calibration methods. Low concentrations of pollutants were measured, far below the EU Environmental Quality Standard thresholds and even satisfying the future goals for the Environmental Quality Objectives. Cleaning the raw data by removing data points in the reference data that were below the reference station limit of detections (and the synchronous data points in the AQM prescaled data) was found to improve the performances of the calibration procedures appreciably. Many NO2 and almost all PM10 data points in this study fell below the AQM limit of detection. These low concentrations will probably be a common problem in many field studies, at least in areas with relatively low air pollution. However, the relative errors were sufficiently low for these data points that they could be interpreted as accurately representing low concentrations and did not need to be removed from the datasets. For the NO2 measurements, a slight periodic error correlated with sunlight and increased ambient temperature was noted. NO measurements correlated strongly with increased traffic.

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