Low energy and passive building are a trend nowadays. Herrala Houses has built low energy houses for some time and is now constructing it’s first passive house..The frame was erected in Hyvinkää during the cold weather of December.
A passive house is a building that consumes very little energy. The greatest difference between a passive house and a standard building is that, apart from the few coldest months, the passive house does not need conventional heating systems. In general terms, the passive house warms up from the heat generated by people, domestic appliances, electronic equipment and lighting.
The owner of a passive house benefits in many different ways: the energy bills, and especially those for heating, are small because a passive house consumes only a quarter of the energy of a conventional one. The inside temperature also remains constant, there are no draughts and the air is clean and healthy to breathe.
According to Janne Inkinen, who works at Koskisen Timber Construction unit as a Development Engineer, the house belonging to Mike Holopainen and Maija Koivuneva is a house from the Herrala collection called ”Kaunomäki”. It’s inner spaces were altered to suit the builder’s family giving a nett floor area of 190 m2 and altogether 740 m3 of heatable space.
The changes in the frame structure were relatively small and easily implemented by the manufacturer, their influence on the total price of the house was only a few percent.
- The passive features of the house were taken into consideration when planning the size and placement of windows on the south side of the house. A few of the smaller windows were removed altogether and the bigger windows in the living spaces were enlarged, Inkinen recaps the planning project that took place last summer.
The frame of this traditional looking wooden house, which sits nicely in the landscape, is 25 mm thicker than that of a conventional house. Massive thicknesses of insulation have been used in the outside walls and upstairs in the open plan truss construction. Altogether the thickness of the outside walls is an impressive 440 mm.
According to Janne Inkinen, this trend is familiar to Herrala Houses.
- During recent years our customers have, of their own initiative, tended to favour better insulation than is required by the building regulations. The outside walls have mainly been constructed with 48x198 mm framing and either with 9 or 25 mm draughtproof panels. This way the U-value has been as many as five points better than the 0,24 W/m2K U-value required by the regulations, says Inkinen.
The building of the passive house is proceeding well and it should be completed by the end of June. The phases of the build can be seen on Herrala Houses’ website atwww.herrala-talot.fi (only in Finnish).
The basic requirements for the construction of the passive house are:
Good heat insulation by the outer shell (below the maximum values of the coefficients of thermal transmittance)
Exterior walls U < 0,15 W/m²K
Roof U < 0,08 W/m²K
Base floor: ground U < 0,15 W/m²K
- Windows U < 0,80 W/m²K
- External doors U < 0,40 W/m²K
- Hermeticity: air leak value n50 below 0,6 1/h
- yearly coefficient of efficiency of ventilation heat recovery > 70 %
In practice the target levels for the coefficients of thermal transfer are 0,10 W/m²K for the outside walls of the Finnish passive house, 0,06-0,07 W/m²K for the roof and 0,10-0,12 W/m²K for the base floor.