06 November 2008
This study describes a field test on a low energy house built in the cold region of Japan. The floor area is about 200 m2. The building envelope consists of well-insulated walls and windows and a floor with high thermal capacity. The total Q-values and C-values are
0.96 W/(m2·K) and 0.4 cm2/m2 respectively.
Heating and cooling are provided by a ground source heat pump unit made in Japan.
Continuous heating operation means that the supply temperature for floor heating can be mostly kept low between 30 ºC and 35 ºC throughout the season. The daily average heating
output is 3.0 kW, with higher COPs being achieved due to the partial load operation. We can
also observe a high seasonal performance. The system COP including the pumping power
reaches 4.45. Acceptable indoor environment conditions are maintained by an air change
rate of 0.5 hr-1. The room temperature is kept stable above 20ºC all day. The vertical temperatures also show uniform distributions.
From the monthly electric consumption, the largest consumption occurs in January due to the heating operation. The power production by the solar photovoltaic (PV) system nearly
meets the load in the summer season. The total amount of annual electricity consumption consists of 37 % for heating, 10 % for DHW and 53 % for ventilation, lighting and other purposes. The real consumption – that is, the difference between production and consumption – is 24 kWh/m2, which is equivalent to 236 MJ/m2 in the primary energy quantities. 48 % of the electric power demand can be covered by the PV system.