Evaluation of a Single Family Low Energy Building in Cold Climate

In the present work a single family building with a heated living space area of 175 m2 has been monitored. The heating system has a wood pellet stove for space heating (SH) and domestic hot water (DHW) and on the roof there are solar collectors in a southerly direction contributing to SH and DHW. SH is distributed by the ventilation system and an under floor heating system which is connected to a heat storage water tank. The incoming outdoor air is pre-heated in an earth-to-air heat exchanger and the building has a measured specific energy usage of 54 kWh/m2year which is far lower than today's regulation at 130 kWh/m2year in the actual climate zone. The low energy use in the building are due to thick thermal insulation (average Um = 0.18 W/°C m2), an air tight envelope (q50 = 0.165 l/sm2), heat recovery of exhaust air (average 74 % efficiency) and free heat from the ground pre-heating of supply air which is above 2°C even for outdoor temperatures down to -27°C. An essential factor was the low rate of air changes during the heating season about 40 % of the regulated requirement. Measurements of indoor air quality like carbon dioxide occasionally indicated insufficient ventilation.