Ventilation
According to the EPA, indoor air is five times more contaminated than outdoor air. As a society, we’re spending more and more time indoors - as much as 90% of our time, by some estimates. That’s why indoor air quality (IAQ) is being implicated in health problems from asthma to cancer. An air filter can filter out large particles, but fumes from cleaning products, paints, furniture, and other sources can off-gas volatile organic compounds (VOCs) which can negatively affect our health. These are more difficult to filter from indoor air, so they should be vented to the outdoors.
Increasingly, mechanical ventilation is being integrated into the HVAC system to remove stale air from inside a home and bring in fresh air from outdoors. This can be as simple as a set of ducts with fans on timers which exhaust stale indoor air and bring in fresh outdoor air. A system like that, however, wastes energy. That’s why many newer homes and remodels are employing Heat Recovery Ventilators (HRVs) and Energy Recovery Ventilators (ERVs). These appliances attach to the existing duct system and add an exhaust duct and a supply duct to the outdoors. Then, the units exhaust stale air from the home and bring in fresh air from outside the home, but pass both air streams through an energy recovery medium which extracts the heating or cooling energy in the outgoing stale air. That energy is then passed into the incoming fresh air stream, reducing energy loss by up to 95% while still providing fresh air. Many mechanical ventilation units also include air filters to remove dust and allergens from incoming air.
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