Heat Recovery Ventilators are special equipment that is designed to save energy. Homes require a specific range of temperature and humidity for occupant comfort and building health.
Historically, homes were not well sealed, so drafty air movement helped to balance moisture levels, which tend to be higher indoors than outdoor air. It also brought in fresh air and replaced stale air. In recent decades, we have focused on sealing homes to prevent energy loss. But we also need SOME air movement for proper breathing and building conditions, so we added exhaust fans to pull out stale air. We also have furnaces, water heaters, and stoves that burn gas and must be vented outside due to the byproducts of combustion which replace clean air.
All of these factors mean some loss of heat as we are now pumping warm air from inside the home to outside air. Because those appliances are exhausting air from inside the home to outside, the same amount of air must seep in through gaps around doors, windows, and utility penetrations to maintain balance. A heat recovery ventilator comes into play at that realization – it recaptures some energy loss! In simple terms, warm air exits the home through a special ductwork and box – but cool outdoor air is brought in through another duct instead of gaps around the home. The ductwork for incoming and outgoing air are overlapped so that the heat from one duct will conduct across the metal and warm up the incoming air before it reaches the home.
The air does not mix, so fresh air is not diluted, but they just pass each other in special chambers that allow the exchange of heat energy. This means instead of venting stale air outside at 75 degrees and pulling fresh air in at 55 degrees – they will balance each other out to some extent – maybe the outdoor air will warm up to 60 before mixing with indoor air. By pre-warming outdoor air, the energy required to heat the home is reduced!
While most information (even the name) indicates these systems are designed to work only in winter months while you are heating your home – they also work in the summer with no changes needed. The system automatically handles the inverse: cold air that is being vented outside will cool down the incoming warm air from outside, thus reducing the effort needed to cool the new air!
Too long, didn’t read version: heat recovery ventilators warm up the makeup air brought into your home to reduce the effort needed to heat your home back up.
-Marshall Tramp, CPI, RMP
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