On November 22 in 2013 the Swegon Air Academy seminar on Modern and energy-saving concept in a small residential buildings took a place in Tallinn, Estonia. The first speaker was Karin Adalberth, consultant and owner of the Prime Project in Sweden, and she talked about the proper building technique to build an energy-efficient house.
When Karin as an expert on a passive house started to think about building her own house, she had always imagined to build a passive house for herself. But one day she talked this idea over a coffee with her friends and one friend has asked her why to build just a passive house if she could get a zero energy house. At the end of a conversation the decision was to build a plus energy house.
Karin said: “We wanted to build a normal house, not a UFO house. And we were set on using renewable energy sources such as solar panels producing electricity and heat. And today as a result, we buy 1,100 kWh/year in pellets and sell 1,700 kWh of electricity. At that time it would have been cheaper to have a windmill than solar panels, but that would look odd. Photovoltaic panels of 32 m2 were more expensive and produce 4,200 kWh/a of electricity, and the heat comes from solar panels of 18 m2 with main production of 1,900 kWh/a in April – September. And for the rest of the year the heat is produced by pellets, surplus of 1,700 kWh/a is sold to the power company but they don’t like it is sold at a very low rate.”
The layout of the house has a cold entryway with traditional Swedish room from old times (so not to lose energy) and pellet stove is located in a living room next to the storage tank to lower the thermal loss in piping.
Karen stated: “The three important things to get the passive house are: insulation, air tightness and ventilation (heat recovery).”
The floor construction (resulting in U-value of 0.07 W/(m²·K)) is made of a slab on ground with 400 mm of polystyrene, with special construction of 250 mm made of polystyrene under the edge of bearing walls (tricky to get build) to create a beam from polystyrene plus added polystyrene, and the floor is finished with iron bars and layer of 100 mm of a concrete slab. The proper care was taken when a sewage system was installed along with electricity installation in a concrete slab floor and as extra measure the special system for exchanging the heat from sewage system was installed.
The external wall (U-value of 0.07 W/(m²·K)) is made of 3 layers of mineral wool, 250 mm stone wool with no main beams in it, followed with 230 mm consisting of wooden studs with insulation and ventilation air gap as in a typical Swedish structure, and followed with 70 mm of insulation attached via wires.
Karin joked: “The wooden structure of a house was built under a tent which made the workers happy because they would not get wet and they could leave equipment lying out freely without being worried about ruining them.”
The good-quality and high-performance windows from a Swedish producer were a challenge to purchase in 2008. So in order to get windows with U-value of 0.8 W/m2.K the filling had to be changed from argon to krypton which improved the original U-value of 0.9 to 0.8. The windows have 3 layers of glass, with one low emission coating and a plastic distance in-between glazing. To block the solar radiation in the house, the windows have g-value of 0.35.
To get the best air tightness possible, the motives were: energy (warm air needs to leave through heat exchanger), moisture (prevent mold problem) and thermal comfort (no draft next to windows). The requirements in Sweden are 0.3 l/s per m2 at 50 Pa (and with the normal pressure in house is 2-5 Pa), and the leaks are typically between wall and intermediate floor, penetrations (plumbing, electricity, etc.) and windows, etc. To secure the best results Karin has used 0.2 mm polyethylene foil which has a good resistance of aging and was installed along with non-aging tape. Karin has shown an example on how to install the airtight layer around the windows using cut-outs in a shape of X. She also joked about builders who nowadays can wrap a nice Christmas gift as they have done a good airtight layer on a Karin´s house.
Karin has showed the Swedish Guinness of record in air tightness which started in 2003 with 0.098 l/s m2 and ended with 0.040 l/s m2 in her house. Karin said: “There went a joke around from the experts who never tested a house with such a low air tightness, so they said that there must be something wrong with their equipment.”