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New case study building added! Högåsskolan in Knivsta!
Case studies
August 13, 2015

New case study building added! Högåsskolan in Knivsta!

A new passive house school was built in Knivsta (link to the case study Högåsskolan in Knivsta), about 50 km from Stockholm. The architect´s company designing the school was the Archus Architects, Margareta Löfgren and Anna Kovács. The high school was built as passive in order to minimize the cost of school from a life cycle perspective. Högåsskolan is built using passive house technology including requirements that the building is optimally positioned on the plot, it has a thermal bridge free structure, optimum day lighting, solar shading around the window and get the entrances to reduce drafts.The school has an integrated gymnasium that meets curriculum requirements up to grade 6, as well as a preparation kitchen. The building is relatively square with three floors, which provide very good conditions for achieving passive house standards in a cost effective manner.  The heat requirement for the school is below 15 kWh/(m2.a). The school cam accommodate up to 450-500 children. The heated temperature (Atemp) is about 5,000 m2. The building frame consists of concrete slabs and I-joists with cellulose insulation. Passive House windows were installed with inst.U-value of 0.64 W/(m2.K).

During much of the year warms the school only by solar radiation and the heat generated from people, lighting and appliances. In the winter additional heat is supplied via a hydronic heating systems that are supplied by means of so-called passive geothermal heat. In the school building plot there are 28 boreholes in 250 meters. The drill holes also help cool the building on hot summer days.

In June 2015 the school was awarded the International Passive House certification.

Air tightness test report, or Lufttäthestprovningsrapport (link here). February 2015. Report by IG Passivhus is in Swedish. A passive house school in Knivsta needs to have a good air tightness (n50<0.6 h-1) to be certified as a passive house according the Passive House Institute and German definition of a passive house. Blower door equipment is used to test the air leakage. The results show that air leakage at 50 pa is q50 = 0,06 l/(s.m2) and air permeability is n50 = 0,07 oms/h. The report shows locally occurring small air leaks at the provisional seals at the unfinished details. The shortcomings should be addressed through adjusting the frame / sash and seal between the frame and the wall. The assessment for the building as a whole is that it is very tight and no air leakage is expected to cause defects in the thermal climate.

Thermography test report, or Termograferingsrapport (link here). February 2015. Report by IG Passivhus is in Swedish. Report describes the procedure how to test the house with thermographic camera including the evaluation of results and images, and the floor plans of school where the images were taken. In the three lower floors the exterior walls are made of the concrete which means there is a temperature inert material. No leakage of air or cooled surfaces could be noted for this type of wall. On the 4th floor is exterior walls of lightweight construction with a stud frame and mineral wool insulation, air and vapor-proof barrier on interior and wind shield on outside. Exterior walls are then lined with sheet material. No leakage of air or cooled surfaces could be noted for this type of wall. Roof images are generally satisfactory surface temperature and temperature distribution. No air leakage was observed onto adjacent walls. Windows are generally well sealed and no abnormal air leaks between the sash and frame or between the frame and the adjacent walls. On the single window are local minor shortcomings, that should be addressed. In summary, the building as a whole performed well regarding air tightness and insulation.

Check our other interesting building case studies (link here).

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Images by IG Passivhus.