Long term monitoring of residential heat recovery ventilation with ground heat exchange

The monitoring of a demand controlled heat recovery ventilation system with ground heat exchange in a zero-energy building in Groenlo, The Netherlands, revealed interesting practical insights.
A healthy indoor climate can be obtained with a high comfort in terms of CO2 levels and supply air temperatures. The CO2 level stays well within the comfortable range in the living room and three bed rooms (parents, child, and guests), thanks to the demand controlled ventilation. Supply air temperatures are in the comfortable range thanks to the heat recovery in combination with the ground heat exchange by an earth pipe. This is shown for ambient temperatures between -8°C and +33°C.
The energy efficient behaviour is proven by the avoided heating load of 3465 kWh and free cooling of 1052 kWh during a full year. The observed seasonal performance factor SPF is 17 for the avoided heating and 8 for the free cooling. The thermal efficiency based on the supply air temperature is observed to be as high as 91% for a slightly unbalanced air flow. When this is mathematically corrected, the thermal efficiency would have been 97% for a perfect balance between supply and return air flow.