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  • 1.
    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 discriminate between high emission rates and insufficient ventilation2007In: IAQVEC 2007 Indoor Air Quality Ventilation and Energy Conservation: sustainable Buildings. P. 2, 2007, 402-409 p.Conference 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.

  • 2.
    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.

  • 3. Cooper, Ed
    et al.
    Etheridge, David
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Pressure Pulse Technique – A New Method for Measuring the Leakage of the Building Envelope of Churchesmms2011Conference paper (Refereed)
  • 4.
    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.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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.

  • 5.
    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, 224-231 p., 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. 

  • 6.
    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, 216-223 p., 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.

  • 7.
    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 wind tunnel study of wind driven airing through doors2017In: Article in journal (Other academic)
  • 8.
    Hayati, Abolfazl
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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, 365-379 p.Article 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.

  • 9.
    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, 114-124 p.Article 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.

  • 10.
    Hayati, Abolfazl
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Evaluation of two air infiltration models on a church2013In: Conference proceedings: Cultural heritage preservation – 3rd European Workshop on Cultural Heritage Preservation, 2013, 47-53 p.Conference 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.

  • 11. 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 calculaions and measurements2000In: Roomvent 2000 Conference, 2000Conference paper (Refereed)
  • 12.
    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, 1129-1134 p.Conference 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.

  • 13.
    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.

  • 14.
    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.

  • 15.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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.

  • 16.
    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, 509-514 p.Conference 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.

  • 17.
    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, Kgs.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.

  • 18.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Andersson, Lars T
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Electronics, Mathematics and Natural Sciences.
    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 Univeristy of Gävle.
    Vesterberg, Olof
    Consultant at Univeristy 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.

  • 19.
    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.

  • 20.
    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.

  • 21.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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.

  • 22.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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.

  • 23.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development.
    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.

  • 24.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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.

  • 25.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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.

  • 26.
    Mattsson, Magnus
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Lindström, Svante
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Hayati, Abolfazl
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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, 63-68 p.Conference 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.

  • 27.
    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, 458-464 p.Conference 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.

  • 28.
    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.

  • 29.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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.
    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.

  • 30.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development.
    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.
    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.

  • 31.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Hayati, Abolfazl
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Claesson, Leif
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Khan, Mubashar
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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, 504-517 p.Article 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.

  • 32.
    Sandberg, Mats
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Sattari, Amir
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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, 69-75 p.Conference 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.

  • 33.
    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.
    Blomquist, 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.))
    Abstract [sv]

    Med begreppet luftkvalitet som utgångspunkt beskrivs översiktligt de olika ventilationssystemen som förekommer samt de viktigaste principerna för luftströmning. Vidare behandlas ingående hur luftflöden och ventilationens effektivitet kan analyseras och mätas med spårgasteknik. Metodavsnitten innehåller tillämpningsexempel från både modellförsök och fullskaleprov.

  • 34.
    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.

  • 35.
    Smedje, Greta
    et al.
    Uppsala University.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    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, 454-461 p.Article 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.

  • 36.
    Widström, Torun
    et al.
    Department of Civil and Architectural Engineering, The Royal Institute of Technology, Stockholm, Sweden.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Multifunctional whole building simulation as a method in assessing retrofitting strategies in historical buildings2011In: Proceedings of Building Simulation 2011: 12th Conference of International Building Performance Simulation Association, Sydney, 14-16 November, 2011, 2943-2949 p.Conference paper (Refereed)
    Abstract [en]

    The design of retrofitting strategies for historical buildings involves various challenges. The aim is often not only to save energy while providing acceptable indoor conditions for its users, but also to preserve the building and potential cultural artifacts, making it a multi-criteria issue, with multiple demands on the simulation tools and methods. This paper describes one way to fulfill on these demands through a serial, stepwise simulation process and a special tool, designed for that process. A case study, performed with the use of the method and tool, is presented. The results show that the method is workable and provides good agreement between simulated results and measured data.

  • 37.
    Widström, Torun
    et al.
    The Royal Institute of Technology, Stockholm, Sweden.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Simulation of the energy performance of historic buildings.2011In: EEHB 2011: Conference on Energy Efficiency in Historic Buildings. / [ed] Tor Broström & Lisa Nilsen, 2011Conference paper (Refereed)
    Abstract [en]

    In historical buildings, to an even greater extent than in modern buildings, the energy performance is connected to other aspects, such as moisture performance and damage risks. Here building simulation is of value, but it also faces some challenges in the form of complexity, flexibility and stability that need to be overcome in order to render useful results. This paper suggests a new, serial approach to the simulation process and presents a new simulation tool that makes it possible.

  • 38.
    Widström, Torun
    et al.
    The Royal Institute of Technology, Stockholm, Sweden.
    Mattsson, Magnus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Whole building simulation and damage risk assessment in historical buildings2011In: Energy Management in Cultural Heritage / [ed] Vlasta Zanki, UNDP Croatia , 2011Conference paper (Refereed)
    Abstract [en]

    When simulating historical buildings, available tools tend to be intended for simulations of either of two kinds: whole building simulations of energy-/moisture performance, from which we can determine general conditions that may give an indication of potential damage risks, though unspecific, or detailed simulations that look into what takes place at specific points/materials, which provides us with knowledge about the specifics but without much context. Both are efficient scientific methods, but when dealing with reality we need both perspectives simultaneously. This paper describes multi-criteria simulations that take this into account, using a new tool integrating display of specific moisture-connected risk-factors into whole building simulations, providing a coherent basis for decision-making when retro-fitting, and compares the results to case-study measurements.

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