Figure 18 Oil boiler with an outside air kit installed on the burner.
The DER work required reworking the houses’ HVAC systems. Most fossil fuel heating systems use air from the basement for combustion. Air sealing the basements removed the source of combustion air. One house replaced the oil boiler and window air conditioners with a geothermal heat pump. One house replaced the worn out oil furnace with a condensing sealed combustion propane boiler. The third house kept the oil steam boiler and we installed a fresh air vent directly onto the burner housing. The house with the geothermal heat pump saved the most heating energy. The house where the oil boiler was kept saved the least.
Figure 19 Heat recovery balanced ventilation system.
Because the house had been air sealed, a heat recovery balanced ventilation system needed to be installed. It removes the stale air from the kitchen and bathroom and provides fresh air to the bedrooms. There is a heat exchanger that transfers the heat from the outgoing air stream to the incoming air stream. This preheats the fresh air with the heat being dumped with the stale air. The balanced ventilation system brings in the same amount of fresh air as is exhausted, keeping the house pressure balanced. The heat exchanger recovers most of the heat energy from the exhaust air, making the process very energy efficient.