Even Exchange: Heat Recovery Ventilators

Heat recovery ventilators let you have your cake and heat it, too.


| September/October 2002



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Illustrations by Gayle Ford

Only a few years back, a “tight” house still lost 40 percent of every heating dollar to air infiltration. Plenty of fresh air found its way in through small cracks in the foundation and walls and around doors and windows, replacing the warm air that escaped through cracks and gaps in the ceiling and roof. Because of this constant exchange, older homes are notoriously drafty and expensive to heat. But from a clean air standpoint, they’re a healthier place to live.

Opening a window is the simplest solution, although doing so defeats the purpose of a tight house and provides only temporary relief. Local exhaust fans can be used to remove moisture and other pollutants from high-use rooms, such as kitchens and baths, but the negative pressure created by these systems draws in outside air from every crack and crevice. A negatively pressurized home can potentially draw in carbon monoxide from an attached garage or radon gas from the surrounding soil. The biggest problem with both solutions is that they sacrifice the heat your home was designed to save.

A heat recovery ventilator (HRV) is a better option. HRVs work much like an open window, but they can recover up to 85 percent of the outgoing heat. In addition, HRVs (unlike windows) can filter out pollens and dust before they enter your home.

HRVs aren’t new. They’ve been used throughout Europe—where super-efficient homes first encountered air quality and humidity problems during the winter—for more than a decade. Consumers and builders in the United States have quickly adopted the new technology. Today, many local building codes require mechanical ventilation systems in new construction.

How HRVs work





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