[Editor’s note: Roger and Lynn Normand are building a Passivhaus in Maine. This is the second article in a series that will follow their project from planning through construction.]
Goodbye radiant floor. Though we never really knew you, we are sad to see you go away.
Our original vision included radiant floor heating. Though we’ve never lived in a home with radiant floors, we had read numerous articles celebrating its comfortable, silent, even heat with no blowing air currents. According to many articles we’ve read, it’s also a good match to the output temperature of a solar thermal system, which is some 30 degrees below the input temperature for baseboard radiators.
Dad’s house in southern Maine has oil-fired, cast-iron baseboard heat, and we’ve always admired how comfortable the house felt, even with the thermostat set several degrees cooler than our own home with its natural gas-fired forced-air heat. We figured radiant floors would be even better than baseboard heating. We would not miss seeing dust and pet dander (we have one dog and two cats, and frequently host other dogs as part of a vacation dog-sitting exchange) wafting in the air currents whenever the heat comes on. We would have concrete floors for both thermal mass and embedded PEX tubing for radiant floor heating.
Ductless minisplits are all the rage
Alas, it seemed most articles we read about heating/cooling a Passivhaus or other very tightly insulated homes relied on ductless minisplit systems. These systems consist of a condensing unit outside, connected via a small copper tube that circulates refrigerant to an indoor wall-mounted blower unit. The indoor component is touted as being whisper quiet. Some manufacturers claim their units can heat effectively down to a very cold -13 degrees Fahrenheit outdoor temperature.
One such article was the one by Martin Holladay in the February/March 2011 issue of Fine Homebuilding, in which the author writes that radiant floor heat is a good match to heat poorly insulated homes, but overkill and a waste of money in a small tight house that needs only a small annual heat load. At some 4,000 square feet equally divided between a main floor and a basement, our planned home isn’t small, but it will be very tight.
We’ll await to see the results of the heat load analysis. At this point, however, we’re figuring that, sadly, radiant heat probably won’t make sense. We’re still not enamored with the forced hot air approach of a minisplit system, and are dubious of its prowess when the thermometer plummets outside. On the other hand, it would provide an inexpensive way to provide air conditioning in the summer, which is something Lynn absolutely wants. I’m not a big AC fan for Maine, though I will admit there’s been more uncomfortably warm summer evenings when we’ve visited Dad, which has no air conditioning. Lynn says when the temperature and humidity get high, it’s time for AC, no matter where you live.
Just a few radiators?
We’ve started thinking that perhaps a small forced hot water system with a few carefully placed baseboard radiators would make sense for heating our new home in the winter. It would still be radiant heat, perhaps fired by a tankless water heater or very small boiler that takes preheated water from a solar thermal storage. We just hate the thought of giving up some form of radiant heat.
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