Is Radiant-Floor Heating a Good Choice?

| 10/1/2010 3:56:48 PM

Tags: heating, floor,

Radiant floors are touted as saving energy, although they're fairly expensive. A 2002 article, “Radiant-Floor Heating:
When It Does—and Doesn’t—Make Sense
” suggests that radiant floors aren't necessarily a good option in passive solar or superinsulated homes. Is that still accurate today or have there been recent developments we should know about?

Radiant-floor heating is a great heat-distribution option ... for lousy houses. In new construction, I argue that it makes a lot more sense to take the $10,000 or more you would spend on a radiant floor slab and put it into the house envelope (R-40 walls, R-60 roof, R-20 foundation, triple-glazed, double-low-e windows, etc.). Get the heating load so small that just a small woodstove or electric mini-split heat pump would provide all the heat that's needed; in a compact house you won't even need distributed central heat. It's not only a matter of economics, but in a superinsulated house, a radiant slab isn't a good thermodynamic fit, because to avoid overheating the space the slab temperature has to be kept so low (just a degree or two above the air temperature) that it won't even be warm to the touch.

Alex Wilson, green building expert

Christopher Haley
10/2/2010 8:50:54 AM

I agree investment into the envelope makes sense but would disagree with the idea of trying to use a wood stove to try to heat a super-insulated building. If you think it is hard to control temperature in a super-insulated building with a radiant slab, a wood stove is near impossible without either choking down the fire (thus creating cresote and inefficiency)or experiencing large changes in temperature. I believe radiant is perfect for an super insulated house for several reasons. If using conventional fuels like natural gas, a high efficiency boiler can reach 98% efficiency with radiant in a slab (not to mention provide hot water). Include a storage tank in the system (like an electric water heater), one could hook in solar to supplement the conventional fuel. There is also comfort. Radiant is so stable in its temperature you never get the 80F ceiling and 60F floor you do with wood or hot air heating appliances.

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