Airtight homes like the BC&E units need fresh air to ensure good air quality and avoid moisture issues. In cold climates, heat-recovery ventilator (HRV) systems are an energy-efficient solution for high-performance houses.
At BC&E, the Zehnder America HRV system continuously brings in outside air, filters and heats it with a heat exchanger, and supplies fresh air to the bedrooms. It draws stale air out of the kitchen and bathroom and transfers up to 90% of the heat to the incoming outside air before the stale air leaves the home. The ComfoAir 160 was installed in the one- and two-bedroom units; the ComfoAir 200 was installed in the three-bedroom homes. An integrated electric preheater was necessary on these units due to low winter temperatures and the potential for condensate freezing.
The HRV system helps maintain cool indoor air temperatures in the summer by working in reverse to cool the incoming air when outdoor temperatures are higher than indoor temperatures. When outdoor temperatures are lower than indoor temperatures (like at night), the intake air bypasses the heat exchanger to maintain pleasantly cool indoor temperatures.
The ecovillage homes contain no exhaust fans or vented hoods, to avoid exhausting hot air out of the home without recovering the heat. Manual switches in the kitchens and bathrooms allow residents to boost the system by increasing the air intake and exhaust speed on the HRV system after taking a shower, while cooking, or to remove odors more quickly than the HRV’s default mode.
Each home has a heat recovery ventilator to supply fresh air while reducing thermal losses.