Radiant over existing 4 inch slab

Chris_82

Do you have a basment, or a space that you can crawl into? pictures? Are you talking staple up or building up the floor?

John P

Want to go radiant infloor on kitchen remodel. New kitchen area will include 12x18 area that has 4 inch concrete slab over crawl space. Any thoughts on how to best proceed?

Brad White_167

Can you unsulate under the slab?

Even better, can you tube-up under the slab and insulate beneath that in a tight manner? Thinking is to capture the mass and use it as your emitter. The edges may be the biggest issue though.

Otherwise, can you insulate below the slab? Thinking in this case to use a lay-on system like Climate Panel and use the slab as an anvil which eventually will be heated. At least with a slab-top system you might be able to insulate the edges where the panels will go. I assume you do not have the height to pour another slab on top. That is yet another scenario.

Paul_11

a few options

The best way is to put a new slab floor down on top of the old slab. I did a 26,000 square foot job a few years ago over a 6" slab. I first put a sheet of some kind of 1/4" or 3/8" bubble wrap with aluminum to isolate the old slab from the new slab. I highly reccomend doing some kind of insulation. You don't want to try and heat both the new and old slabs as you will have a huge mass to try and heat which will slow down response time and make sure you need to insulate under the slab big time. On my job, I was over another heated floor so this was plenty of insulation for me. In your case I might use 1" or 2" of blue styrofoam insulation as you are dealing with a slab on grade, I assume. If you don't have enough head room for this, I might demo the whole old slab out and start new with a 2" to 4" blue foam insulation base to start with.

I used 1.5" of gypcrete, but you could use 2" of cement if you were putting tiles or marble on top.
Please don't even think about putting the tubing under the slab. I would not even want to think about the inefficieny of heating the air to heat the old 4" concrete slab to heat the room. And imagine how much insulation you would have to put underneath the tubing. I would put a nice steel radiator in first, before I would do that.


Respectfully,

Paul B. Shay
pshay@arealgoodplumber.com
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jp_2

don't get it either?

you have a 4 inch slab 12x18ft over a crawl space? how is this slab being supported? can you remove it?

ALH_4

Radiant wall or ceilings

Depending on the layout, you might skip the radiant floor and use a wall (if one is available) or the ceiling to minimize complications. Roth panels might be another option for the floor.

Unknown

If you don't have an existing hydronic system to tie this into, and maybe even if you do, for an area that small I would consider just using electric mats.

the trick will be in how to insulate, if the existing slab is not insulated.

John P

The house iis a 1863 brick victorian. The area with the slab is the very back of the house. The actual measurements are 15x14 and the slab is 4.5 inhes thick. there is crawl space underneath all except a few feet on one side. on the other 3 sides the slab sits on stone or brick. We are taking out a wall to incorporate this area into the new kitchen. The other area is twice that iize and has easily accessable basement below.

John P

The house iis a 1863 brick victorian. The area with the slab is the very back of the house. The actual measurements are 15x14 and the slab is 4.5 inhes thick. there is crawl space underneath all except a few feet on one side. on the other 3 sides the slab sits on stone or brick. We are taking out a wall to incorporate this area into the new kitchen. The other area is twice that iize and has easily accessable basement below.

Rich Kontny_3

radiant over slab

I would consider Uponor's (Wirsbo) Quik Trak if the floor is level and especially if you are going with a wood or laminate floor covering.Otherwise I would indeed cap it with ligtweight concrete(gypcrete) with inbedded radiant piping.

Insulation from below if accesible would increase efficiency.

Good Luck!

R. Kontny