Hybrid Car – More Fun with Less Gas

Slab edge insulation

register ::  Login Password  :: Lost Password?
Posted by Bruce on June 12, 2004, 10:22 am

How effective is insulation of the edge of a concrete slab ? Or to put it
another way, how significant is the heat loss from the edges of the slab,
and how significant when compared to the loss of heat through the base of
the slab ?



Posted by cjensen on June 14, 2004, 3:07 am

My understanding is that for a slab "on grade" the edge accounts for about
80% of the slab heat loss.  Slab perimeter is often the only factor
considered in slab on grade heat loss calcs.  In colder climates the outer 4
feet under the slab is often insulated while the inner under-slab area is
not.  My workshop has a radiant floor heat system so I used 2" XPS ("blue
board") under the entire slab and 3" XPS 16" deep around the edge.

Posted by NN on June 15, 2004, 4:53 pm

Chuck, Where are you located? I am in Tucson AZ and am building a
shop, 24 ft x 32 ft with a covered work apron 24 x 15. The walls and
roof are SIP's. I also will have radiant heating, sun powered, and
have been trying to get some facts on what thickness insulation to use
and where. I am planning to use either  2" Pink or Blue foam,
extruded, not expanded on the stem walls, 18" to 32" deep, and then
only go in about 4 ft in on the slab. I want to use the slab in the
summer time to cool the building so the earth under will act as a heat

Posted by cjensen on June 15, 2004, 9:27 pm
 Rush, I'm in Durango CO at 7500 ft elevation.  I considered SIPs and foam
concrete forms for highest insulation and lowest infiltration construction,
however, I also wanted to maximize sweat equity.  The SIPs and foam forms
are also labor savers so what is saved in labor is spent on the materials
(according to the prices I got from suppliers), but they are a great way to
go.  Anyway, my shop is 24 x 26 (small due to terrain considerations) with
2nd floor.  I designed for -5 F outside temp and used 4- 135 ft loops of
1/2" pex on 12" spaced rebar (only 10 cents/ft when a got it). Put pex on
top of rebar so the response time is a little guicker.

outer 4

This Thread
Bookmark this thread:
  • Subject
  • Author
  • Date
please rate this thread