Cold floating Slab in 1/2 of Living room.

[larrylwill]

I'm remolding a 1962 ranch house. The living room is approx 32 x 22, with 12x32 being a plywood floor over a crawl space of 2ft to 3ft. Bat insulation between the joists. The other 32x10 is a 4" cement slab with 1.5" of mortar and 4" ceramic tiles on top. That half used to be a porch that was closed in and made part of the LR 20 or more years ago.
The slab is held up at the perimeter by 4" blocks with a 4ft crawl space with a dirt floor, there are 2 vents and one 2x3' opening. Last year I had the slab stabilized, it was only held up with 3 - 8" block columns and the perimeter walls were blowing out. They added 24 double 8" block piers to hold it up.
I just finished tearing up the wall to wall carpet and installed a vapor barrier and laminate floor over the entire space, getting the plywood and slab level at the seam is another story.

Right now the outside its 60 and inside its 75 and the plywood floor is 74 and the slab portion is 69. I need a way to warm up the slab. I couldn't use under floor heat because of the hight. So I will have to work from the bottom of the slab.

My ideas are:
1. Spray foam 2"
2. Suspend foam board and fill the cavity between it and the slab with bat insulation, seal around the columns.
3. Install metal clips and pex to the bottom and heat with a hot water heater.
4. Suspend foam board with foil on top and force hot air through a 3" duct from my heat pump on one end and the other end duct back to the return air.

I'm looking for the cheapest solution of course.
Do you think any will work to keep the slab less than 2 or so degrees different from the rest of the floor?

Any help or advice?

One thing I'm worried about is 2 years ago I built a metal building with 2x4 of 16" centers. I insulated it roof, sides and floor. The floor has 3/4 plywood with R21 bats and the entire building is covered with a bubble wrap blanket with silver on each side. Its heated with a heat pump but the floor is really cold compared to the inside temp. Its sitting on concrete with a 8" to 2ft crawl space the metal is down to within 1/2 of the ground. Although it is not heated 24/7 like the house. Its only heated when I'm working in it.
If that floor cant be room temp how can the slab? I'm in North Alabama.

[flange]

i would have used a radiant tubing product on top of the slab, it will take much less heat that way. to keep your whole slab warm enough to get rid of the cold floor using staple up will be tough. sealing it will be another tough problem. with a product like viega climate panel, it would have been much easier, and added only 1/2" to total floor height. it would have alos allowed you to level out the floors rather easily.

[larrylwill]

i would have used a radiant tubing product on top of the slab, it will take much less heat that way. to keep your whole slab warm enough to get rid of the cold floor using staple up will be tough. sealing it will be another tough problem. with a product like viega climate panel, it would have been much easier, and added only 1/2" to total floor height. it would have alos allowed you to level out the floors rather easily.

I got that but I'm already 1/2 inch up, that would have been 1" higher than the 5 exits from the LR not counting the porch door would have to be raised.
I should have done what I wanted when we bought the house before after the footing broke and jack hammered out the slab and put in a real floor.
I'm still curious how they even built it 4ft off the ground.


thanks