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Old 11-29-2010, 08:11 PM   #1
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Radiant heated floor over old conc.slab

I have several question in regards to a project I am planning.

I am converting a garage built in 1974 to a living space. Heres the plan unless someone has a better method to insure a warm floor. I plan on on adding a raised floor over the concrete slab (which I assume is not insulated beneath) First I was going to apply rosin paper over slab. Then shoot pressure treated 2x4 wood sleepers into slab and build 2x8 wood framed floor on top of sleepers. I was then planning on insulating between framing with 5"-6" of closed cell spray foam. Top the floor deck with 3/4" plywood. I think the finish floor will be carpeting but portions may be tile or engineered wood.

Conc. slab barrier questions;
Should I use rosin paper or roof felt on top of existing slab on grade? I assume spray foam will act as vapor barrier? What if I use cheaper rigid insulation vs spray foam will this change whether or not I use rosin paper or roof felt? I also assume batt insulation is not a good choice for this installation due to moisture concerns of slab on grade?

Radiant heat questions;
If I were to use radiant heating to heat space is this typically applied on top of plywood deck? Is carpet then applied over this? Does anywone have an idea of the cost for a 700 Sf space?

Is this the most cost effective way to heat the space? Heating system in home is hot water radiant heat, however garage is 10 feet away from house. Electric baseboard I assume is the easiest solution but perhaps the most expensive?

Thanks for your help and advice in advance.


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Old 11-30-2010, 04:52 PM   #2
Electric Radiant Heating
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Speakingt to teh radiant question; is your decision for heat based on a budget or preference? If it's budget, baseboard is the cheapest upfront, the most costly over the long run. If preference, you can use low voltage Zmesh on the plywood, under the carpet (but protected by a 1/4" leuon over the Zmesh) then the padding and the carpet.

Since it's primary heat, in all cases, you will want to get a heat loss calculation performed so you know how much heat you'll need. Once you have the loads, you can quote both systems.


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