Passive houses for a cold climate

Passive house refers to a specific construction standard for residential buildings with good comfort conditions during winter and summer, without traditional heating systems and without active cooling. Typically this includes very good insulation levels, very good airtightness of the building, whilst a good indoor air quality is guaranteed by a mechanical ventilation system with highly efficient heat recovery. The properties of the Finnish passive house were defined by VTT in the European research project Promotion of European Passive Houses (PEP) funded by Intelligent Energy Europe program in FP6: • the total primary energy use for appliances, domestic hot water and space heating and cooling is limited to 130 – 140 kWh/m2, • the total energy demand for space heating and cooling is limited to 20 - 30 kWh/m2 floor area; • the airtightness of the building envelope n50 ≤ 0,6 1/h The energy demand is defined to be higher than the corresponding demand in Central Europe. Energy simulations have shown that a Passive house in the climate of Central Finland would require insulation thicknesses of 50 - 60 cm in exterior walls, 70 - 80 cm in the roof, and roughly 40 cm in the floor to fulfill the Central European requirement. At the same time window area should be minimized, and the window U-value should be less than 0,5 W/m2K. The economic viability of such a building is rather low, and thus the Central European definition is not justified. Thick insulation layers necessitate special attention to be paid to the performance of the structures. frost protection of foundations, drying capacity of insulated structures, avoidance of thermal bridge effects, and long term performance of the airtight layers need to be considered. The concept development and construction of the first Finnish Passive houses tackled these challenges. Experiences on ventilation heating systems show that simple heating systems are viable also in the cold climates. The increased heating power demand compared to climates in Central Europe does not reduce the indoor air quality. Room based control enables varying room temperatures according to specific needs of the users.