SIERRA VISTA, ARIZ. — I read with interest Gary Klein's excellent article, "The Future of Space Heating is a Very Efficient Water Heater." He makes a good point regarding the dearth of low-capacity furnaces, and his list of impediments to hydronic heat hits the nail on the head. However, he fails to point out that mid-efficiency heat pumps are often a better choice for high performance homes in much of the southern U.S.
Klein's main premise is that conventional furnaces are often oversized in high performance homes, by necessity. This is absolutely true. However, the heat pump is an obvious solution in markets where little or no supplemental heat is required. Oversizing is simply not an issue with heat pumps. They run continuously at low temps, so air mixing is ideal.
Even with natural gas prices near decadal lows, my mid-efficiency heat pump costs 35% less to operate than would a 96% hydronic furnace. In cold climates or in markets with high electric rates (like California, where Klein lives), natural gas-fired hydronic furnaces should be given serious consideration.
David Butler, President
Optimal Building Systems LLC
http://optimalbuilding.com