Radiant ceiling heating &cooling. Insulate under floor slab?

mercedes

Building a garage (28'x32'x10') in central Florida. Planning to do a radiant ceiling with heating and cooling. My question before I pour the new garage floor slab, should I place 2" foam insulation under the slab and edge perimeter or vapor barrier only? I will have the walls and ceiling insulated. Thank you again.

Dave Carpentier

In Northern Ontario, heating is the bigger challenge, so insulation under is a good idea.
My completely uneducated thought wrt Florida, cooling would be the bigger challenge, so leave the slab able to 'connect' to mother nature underneath and not insulate it.

The question I have is.. if you chill the ceiling in a Florida enviro, would it not just rain condensation inside the garage ? I've never lived anywhere that hot, so Im just guessing..

pedmec

You have to run the chilled water above the dew point of the air, whatever that is. That's how they do it with chilled beam cooling

Tim_D

Underslab insulation has no benefit in your area and with your application but a vapor barrier is advised. Radiant cooling is a challenge unless you can control the latent load through another means. The radiant cooled ceiling will only handle the sensible load. You can get 2btu/sqft per degree of difference between the surface temperature and the ambient temperature provided that you dew point is low enough, usually under 40% rh.

mercedes

Thank you all for the advice will make sure I have the dew point controlled and the vapor barrier under the slab.

Alan (California Radiant) Forbes

Can't you take care of dew point condensation with a dehumidifier?

pedmec

now what do you do with the latent heat that you just removed and is being converting to sensible heat? got to be able to dump it outdoors

hot_rod

Desiccant wheels can remove moisture also.

When the slab gets warmer or cooler than the ground below, energy will transfer, hot to cold. Insulation is used to slow the transfer, save energy costs