Heat Recovery from Drainwater: About 80 to 90% of the energy used to heat water is carried down the drain after it is used. A drainwater (or greywater) heat recovery system captures this energy to preheat water going to showers, a water heater or other dedicated water storage device. Heat from any waste hot water (e.g. shower, bathtub, clothes washer) is transferred to the cold supply water without mixing. Such a system preheats the cold water thereby reducing the energy needed for heating water.
Heat Recovery with an Enthalpy Wheel: An enthalpy wheel is an energy recovery unit that captures and reuses heat from exhausted air. Enthalpy wheels function by making the exhaust air preheat the supply air when the outdoor air is cooler than the inside air. When the outside air is warmer than the inside air, the exhaust air will cool the supply air. This system saves energy depending on the season and only operates for sensible heat recovery.
