Question: Is infloor radiant heat a good backup system for a strong passive solar design that is aiming toward Net Zero Energy?    Radiant works best when run constantly at low temperature and maintaining constant temperature.  If I use fossil fuel to keep house at constant temperature, where is upside for passive solar?   I am ok with temperature swings from 60-75 deg.  And I am ok with letting house cool off at night knowing that tomorrow will be sunny (Boulder, Colorado).  If two plus days of cloudy and  cold is predicted I can turn on radiant.   NG use will be off set by extra PV capacity for Net Zero.

 

Thanks,

 PS: was not able to edit subject (solar not soalr)

Rich,

I have been told that radiant floor is not so good for a passive solar house, but I can't see the logic.

If you are OK with a minimum temp of 60deg.F. then simply set your radiant floor control thermostat at 60 so it will maintain that as you minimum.

You wrote: "Radiant works best when run constantly at low temperature and maintaining constant temperature." What is true is that heating a concrete mass from 30degF to 65 takes a long time and is inconvenient, but you will be keeping the constant temp of the slab(assuming this is your main storage mass) using the sun as the heat source. The radiant heat will work fine to hold the slab at your desired minimum temp. It is not important where the constant temp comes from, just so that the radiant heat will not need to recover some big heat difference.

I am in Sundance, NE Wyoming with similar solar conditions as you have in Boulder, and I am planning to do exactly what we are talking about here. I say do the math and install the radiant heating as the backup system.

My 2 cents.

Dave