Heated concrete slab?

[2zwudz]

  Who here has a hydronic radiant heat system in the concrete floor of their cabin?  What do you think of it and was it worth it?
Thanks Mark

[rdzone]

I installed radiant tubing in my basement slab, but haven't gotten to the point I can use it.  It was cheaper to install before the slab was pored than trying to retrofit.  My neighbor use it and loves it.  I must say it is nice to be able to walk around on a warm floor. 

[tc-vt]

I installed it in my slab and am very close, finally, to using it for the first time since I built in 2005.

With radiant, it seems like if you ask five people the best way to install it, you'll get ten answers.

I have recently come across some information on design of a radiant system which I haven't seen before.  These concern the depth of the tubing in the slab and how that will effect efficiency, and the use of plates and insulation in an underfloor installation.

www.inspect-ny.com/heat/Radiant-Slab-Heat-Mistakes.htm

http://findarticles.com/p/articles/mi_m0BPR/is_6_20/ai_102862289/pg_1

From
http://www.radiantmax.com/r-underfloor.htm
l I found this "data" concerning the use of aluminum plates and insulation in an installation under a wood subfloor:
Floor Output at 140°F Inlet Temperature: Output in Btu/hr/sq. ft
No plates, 5/8" air gap   
   23.5
No plates, 2" air gap      26.2
Plates, 2" air gap      42.0
Plates, 5/8" air gap      46.3
Average test results at steady state with a 140°F inlet water temperature

From the theories of design I heard when I built, a radiant in a slab could be designed either as a (relatively) fast reacting source of heat (a well insulated slab) *or* as a storage form of heat (less insulated slab).  If you want storage capabilities so that the house will stay above freezing for a few days to a week without keeping automated sources of heat running, then a slab with less insulation under it will do this because heat is supposed to be stored in the earth under the slab.  I figured on using the radiant as a secondary heat source with wood heat as the primary, and wanted a way to keep the house a bit warmer if I am gone for a few days, so built  it without insulation underneath.  The perimeter of the building is well insulated to a depth of 4 feet and the slab is isolated from the perimeter wall by being floated with insulation separating the two.  When I start it up, I'll post back after I see how long it takes to reach a steady state.  I'm guessing I'll see it stabilize over one to two weeks.

Tom

[okie-guy]

Mother Earth News has a extensive article on solar heating using radiant heat this month. Their idea is to contruct a shed that has one side facing south and having a solar collection system incorperated in the contruction of the shed. The heated water is held in a tank and then circulated thru the coil in the slab or wood floor. I think that you can look up their articles on line for more info.