Worth a Look

Fresh Air Without Energy Loss
When a house is built so tightly that it can't "breathe," it can suffer from high indoor moisture levels (which encourage mold growth), elevated levels of carbon dioxide and other toxins (from offgassing finishes, fabrics, and glues), and plain old bad smells (from cooking and smoking).

A hybrid air exchanger (below) solves these problems by sucking in fresh outside air as it expels stale indoor air. In winter, it uses the expelled air to warm and humidify the incoming cold air. In summer, it cools and dehumidifies sticky outdoor air. And as it operates, it filters out airborne contaminants and odors.

"Sooner or later, every house will need one of these units," says Richard. He recommends connecting it to a separate duct system serving bathrooms, bedrooms, and the kitchen.

traditional air-conditioning system
Illustration: Ian Worpole

Outdoor Reset Control
These simple devices save energy by regulating the boiler or furnace temperature in response to changes in outdoor temperature. On a zero-degree day, for example, the water in a boiler might need to be 180 degrees to heat the house. But on a 35-degree day, 125-degree water might be enough. The outdoor reset control makes the adjustments, saving a heating unit from excessive on-and-off cycles and smoothing out the uncomfortable fluctuations in interior temperature that result when a thermostat is in total control. Just make sure that your heating unit works with this kind of device. "A reset control can easily improve system efficiency by at least 10 to 15 percent," Richard says.

hybrid air exchanger diagram
Illustration: Ian Worpole

Condensing Gas Boiler
One by-product of burning natural gas is hot-water vapor, which until recently went up the stack with the rest of the exhaust gases. The loss of this heat prevented boilers from becoming more than 85 percent efficient. Condensing boilers employ a heat exchanger that wrings the heat out of the vapor before it can escape. "It's a quantum leap," says Richard. "Some of these units are achieving efficiencies of 96 percent."

Out-door reset control diagram
Illustration: Ian Worpole

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