Heat With Water, Cool With Air

In cold-weather regions where temperatures are below 70 degrees for more than half the year, Richard Trethewey recommends a single, fuel-stingy boiler to supply both heat and hot water for maximum comfort and efficiency. "Water conveys heat much better than air does," he says. Lower floors use hot water for radiant heat; it delivers heat to a forced-air system above. To keep the house cool, Richard specifies a traditional air-conditioning system, also shown here, which employs the same ducts used for upper-floor heating.

25th HVAC diagram
Illustration: Ian Worpole

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