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engineered floors on concrete slab - radiant heat or no?

Posted by kopellimonster (My Page) on
Tue, Jan 18, 11 at 13:30

Hi All -
i have been searching a lot and have not found answers to my questions. i am planning on putting in engineered wood floors in my family room. it is a large (17'x21') addition to my 1930's house. hence it is on its own concrete slab. i live in Denver, CO so we have hot and cold/snowy weather but no humidity. i am worried that the floor is going to be very cold (the room itself has a seperate heater that isnt the best) and had thought about putting the electric radiant heat mats underneath the flooring. this will almost double my costs so i really want to know if this is worth while. my goal would really be to have it as the primary heat source for the room. i have concerns that it will just heat the slab and not do much else.

is there anyone out there that has had a similair experience? is there another product that might be a better compromise - i.e. a mat that would reflect the heat that is already in the room?

thank you so much in advance!

Follow-Up Postings:

RE: engineered floors on concrete slab - radiant heat or no?

Are you talking about glue down flooring or floating? I will not install floating floors but the glue down is great for slabs and below grade areas, as long as there are no moisture issues. I have only put the heating mats under tile though. It does a great job.
When a client wants a warm hardwood floor on a slab I often times lay 6 mil. plastic, sleepers, ridged insulation between the sleepers, 3/4 inch plywood and then the hardwood. It takes you up 1 1/2" which is not always possible but it does give you a warm floor. You could incorporate the mats into this system.

RE: engineered floors on concrete slab - radiant heat or no?

Do you have a boiler for heat? If so, use a roth panel over the slab with pex tubing (hydronic radiant). Do not expect the mat to be primary heat for the room.

The slab needs to have a vapor barrier laid done and then insulation, then floor.

RE: engineered floors on concrete slab - radiant heat or no?

thank you both for your responses. i am not able to raise the floors in the room due to existing exterior doors, ceiling height, ect. my furnace is forced hot air so the hydronic radiant heat is out as well.

RE: engineered floors on concrete slab - radiant heat or no?

Electric floor warming systems are for floor warming only. They do not heat the room. If your slab is uninsulated, then in your cold environment your floors won't even really get warm as the heat will be sucked out through that slab into the outdoors. It'll be a waste of money. I'm really surprised that you actually have slab construction in such a cold climate. Slab requires footings to be dug down below the frost level so it won't heave, and in your area, that's down low enough that it's not that much further to do a basement. And to do a slab without insulating it is also strange.

I would not put hard surface flooring in such a situation where you cannot install the sleepers and additional insulation. Your best bet for comfortable flooring will be for carpet. The padding will give a small amount of insulation between you and that freezing cold slab.

RE: engineered floors on concrete slab - radiant heat or no?

You are probably living on a floating slab which would require about 18" footers with a monolithic pour. There should also be 2" ridged insulation extending 24" into the room and under the slab. I install many radiant electric pads under tile and I assure you Those clients toes appreciate it. If you put enough of the product in it can help heat the room but would not be the primary heat, although it would sure knock down the need for primary.

RE: engineered floors on concrete slab - radiant heat or no?

This is older discussion but, hopefully, the participants still will be reachable. Don92, may I ask how high sleepers do you use and how high is rigid insulation? Only 1 1/2" floor raising sounds good. Is it with insulation, panels, plywood and hard floor or only insulation?
Wianno, do you think Roth panels provide enough of insulation? I think it has R value of 4.5. I would think it should be at least 10. On another hand, Roth panels don't allow additional insulation underneath. What are your thoughts and experience with them?
We would like to install radiant heat with maximum insulation and minimum floor raising. Though, we will need to change doors yet so raising around 2" would be ok.
Thanks in advance for you opinion.

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