The typical residential building is located at the crossing of S. Centralgatan Street and Nedre Akargatan Street in the city of Gavle. It is a quadrangle building of six floors with a yard in the middle. There are 180 apartments of five types in total, and at the first floor there is a kindergarten. There is a District Heating in the building and heating recovery system ventilation which use heat exchanger to reheat.

Several solutions are used for reducing the heat loss. In the first step, the heat loss  and heat  in  has  been  calculated. There  are  several parameters  that involve the heat loss and heat in of whole building, so each parameter in the energy balance equation is extracted and calculated. And then the Energy Balance Sheet has been built. Among the heat loss part, the transmission is 1237MWh,  the  hot  tap  water  is  332MWh,  the  mechanical  ventilation  is 1041MWh, the natural ventilation is 325.7MWh.In the part of heat in, the DH is 1265.7MWh, the heat pump is 793MWh, the solar radiation is 562MWh, the internal heating is 315MWh.Later in the second step, after analyzing data of heat loss part, the improvements will be focused on the transmission and hot tap water parts because the heat loss in those two parts occupy the most. At the end of final step, the solutions have been discussed to optimize the heating system.

As conclusion, there are several suggested solutions. The total reduction of heat loss after adjustment is 163MWh, accounts 5.6% of originally heat loss. The  heat  loss  of  the  building  has  been  reduced  from  2935.7MWh  to 2772.7MWh.