RADIANT FLOORS

Oney

Curious to get views on the maximum supply temperature people use in a typical radiant floor 4" concrete with 2" blueboard underneath. I have always used 125 deg max.
To prevent sprawling and other adverse effects to the concrete. Any thoughts?

klaus

And the answer is...

Depends!

On a basement floor Bill, with proper insulation (2" rigid foam) I generally limit my supply to 80 - 85 degrees. With the high mass it helps to prevent temperature overshoot and swing. And if reasonably well insulated on the outside walls, with the conditioned area below grade the sidewall and floor losses are usually pretty minimal.

For a garage floor I generally go in the 125 degree range to offset the higher heat loss with the garage door operation. Again this figures good indulation including: underfloor, sidewall, attic, garage door, etc.

These temps are for my area, Eastern Iowa. Your results may vary

Unknown

The lower the better?

Has always been my thought in terms of fuel savings. Keep cranking it down a bit ever couple days until it won't keep up to setpoint and then bring it back up a couple degrees. Reaction time is an issue as you get lower however. In my case I always (so far) have included a hydronic forced air unit to cover that issue. I figure IF you're putting A/C in anyways why not include a HW coil as well. Cost is a little more but I've been limiting my tubing to traffic areas only which offsets the added cost. Kitchen, bathrooms and foyers only. So far I have gotten great results from this "hybrid" type install.

Unknown

I have found,,,

or actually my customers have found, that as long as the concrete is warm in the garage when they open the door, even on a frigid day, once it's closed the garage warms right back up. ~15 minutes they say. On the last one I did the whole house including garage is working with the water rising and falling from 100* to 110* (10* differential) and that includes the air handlers. In this case they are using chilled water to cool and as such the coil is used for both and is sized for cool which is about 3 times the size you need for heat. Result is warm air coming out even though they're only seeing 110* water.

Unknown

Oh,

I tube the basement concrete in addition to the traffic areas and put no insulation under the floorto the first level. The basement satisfies the first floor down to like 20* ODT before any air handlers come in.