3-season room addition and heated floor Q?

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I'm putting on a 3-season room addition 17x17. Block frost wall, poured concrete floor. I'm having an in-floor heating system installed for the addition, which means adding a small boiler to heat the coils. If I don't want to run the boiler in winter I have to have the coils filled with an antifreeze mixture and they want another $300 for that. Is it necessary or worth it? Might it be more efficient to just heat the coils all the time, rather than trying to reheat the floor on a sporadic basis. I'm in Wisconsin so it does get cold!

The room is going to have a southern exposure and maximum windows possible facing that way. I'm tiling the floor and the south facing wall to maximize solar heat.

Any thoughts?

[m Ransley]

And what about when the boiler breaks down. Also insulate under the concrete.

[HeatMan]

Go to the Wall....

Do you already have a boiler? A room that small can share off the existing water heater, maybe.

Why don't you want to use it year around?

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That's part of the bid, two inches of foam under the coils.

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Currently have a gas water heater-40 gal. Actually within 20 feet of where the new addition will be. Wouldn't year round use require a larger heat source than just floor heat? More $$? I'm a newbie on this, so any advice is appreciated!

[m Ransley]

you mean under the concrete, right , use the 7.2r per inch. Blue and pink are 5r per inch

[nicksanspam]

Quaint. How 'bout curtains made from 80% dark shadecloth to turn the solar heat into hot air and a low-e massy ceiling instead?

That way, you can preserve views and minimize glare and not worry about shading the floor and wall and store the heat with minimal loss when it isn't needed and warm the room with a slow ceiling fan when it is.

Nick

[HeatMan]

I have installed an area about 1K sq.ft. and used the domestic water heater and a flat plate HX. You're not looking at a really huge load, especially if you use outdoor reset.

You contractor should be able to help you with this if he knows radiant. Is he one of the people listed here?

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[nicksanspam]

Direct gain (aka "direct loss") is so 80s. Lots of expensive low-temp thermal mass in the sun to make night setbacks ineffective and store and lose solar heat overnight and on cloudy days. Lots of windows over living space for a large 24-hour heat loss.

Like a dark window screen over the room side of the window. Hot air rises and warms the ceiling, which has insulation above a layer of water (eg a lay-flat poly film duct containing 2" of water) above a low-e surface (eg foil under plywood), to avoid warming the room by radiation.

You can see views through the shadecloth, as with a window screen, but it reduces the solar intensity from about 10,000 to 2,000 footcandles, vs a well-lit 100 FC room.

Those are direct gain worries. Rugs on floors and shading on walls are nonos.

In the water above the ceiling.

You might store enough heat for several cloudy days, and bring it down as needed (for 8 hours per day?) with a slow ceiling fan in series with a room temp thermostat.

Nick

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