Heat Recovery

A residential heat-recovery ventilator uses separate blowers to move incoming fresh and outgoing stale air. The heat-exchange core transfers heat to fresh air without mixing the airstreams. The damper automatically stops cold air for defrosting.

While necessity may be the mother of invention, it's increasing costs that spawn efficiency. Before the '70s, we happily cranked up the thermostat when the house felt chilly. Once heating costs went through the roof, though, we all put on sweaters and started looking for ways to save. And, with up to 40 percent of our heating dollar going to air infiltration--otherwise known as drafts--sealing the place up began to seem like the best defense against high heating bills.

Over a period of time, older homes began to sport new, tight windows and doors, insulation and vapor-barrier improvements, modern siding, and caulk for every crack through which air might pass. New homes left the drawing board designed to be tight, and builders became familiar with the new materials and skills needed to meet market demand and updated regulations. Homes were finally becoming thermally efficient. What some began to wonder, though, was whether they were habitable.

It turns out that those heat-robbing drafts had a role in the ecosystem of the home--they provided fresh air to breathe. Without realizing it, builders before the energy crisis had been installing an effective, albeit haphazard, ventilation system. If you could afford the heating bills, it worked.

Life inside today's tight home generates both moisture and pollutants. The moisture comes from cooking, washing, showers and breathing. At excessive levels, moisture condenses on windows and can cause structural deterioration. Areas of excessive moisture are also breeding grounds for mold, mildew, fungi, dust mites and bacteria. You know you have a problem if you find moisture collecting on your windows, or if you notice black spots on walls. These unsightly spots indicate mildew growth. Mold spores and dust easily become airborne and circulate freely throughout the house, possibly causing a range of symptoms and allergic reactions.

In addition to excessive moisture and biological contaminants, appliances that utilize combustion have the potential for allowing gases, including carbon monoxide, and other pollutants to escape into the air. Some common sources may include gas ranges and water heaters, unvented space heaters, leaky chimneys and wood-burning appliances. Even breathing can add to the problem when carbon dioxide reaches excessive levels, creating stale air.

And that's not all that gets into the air. If your home is new, the very products it's made of can give off gases that are less than agreeable to your comfort and good health, and in many areas of the country there's a concern about radon seeping from the ground.