The higher the number, the more efficient the heating equipment. Backdrafting Potentially hazardous condition in which the exhaust from combustion appliances does not properly exit the building. Backdrafting can result from several factors including a blocked flue or a pressure difference within the home. A large fan placed in an exterior doorway to pressurize or depressurize a building to determine its air leakage rate, expressed in air changes per hour or cubic feet per minute. The result is better insulation and use of fewer resources, in addition to cost savings.
Several variations are possible.
Can also refer to gas-fired systems. Combination System Heating system that uses the domestic water heater for both water and space heating. Conditioned space is separated from unconditioned space by a thermal envelope. Desuperheater Device that takes waste heat extracted by heat pumps or air conditioners and uses it to heat domestic hot water. E Seal E Seal is the electric utility industry's energy efficiency and environmental housing initiative.