[stevehull]

Memphis - to get an idea of the amount of perimeter BTU leakage, first get the peripheral area that is exposed. This might be one foot high all around the house. Assume 300 sq feet.

Then multiply that by the temperature difference between inside and outside. Lets call the interior slab 70F and the outside 50 F. That is a 20 F difference. The concrete stem wall already has an R value of 2-3.

Now go look this up in the manual J calculator and you will see that it is a very few BTU/hr. However, in the summer, you "bleed" BTUs into the soil (soil cooler than slab) and a non-insulated slap helps keep the house cool. You are in a dominant hot area and your winter load is very low. I figured that my noninsuated slab basement was about 12-15 KBTU/hr in terms of cooling. Yes, the floors were just a bit cool in winter, but we had throw rugs down there.

If I had all the money in the world, I might insulate everything - but time is also an issue and you want to build this before you die . . .

Again, you will do what "allows you to sleep at night". For some, in a moderate climate, this is R100 - for others it is R40 (just picking an example for attic insulation).

AC has some very nice tables that have cost/benefit intersecting lines on it. Study this concept.

Now look up the cost to insulate the entire periphery and see how much you lower your BTU loss in winter. Will not be much.

The entire issue is to do perimeter insulation in climates where it is a MAJOR cold area. You just are not that cold and your "frost" depth is on the order of inches.

You can do the same with sub-slab duct insulation. But remember that if using a GTHP, that the supply temp is only 100-110 F. A standard gas fired heater has very high hot air. So in the case of sub-slab, the delta T is 105-65 = 40 degrees F. If the dirt under your slab is kept dry (which is typical), then there is "insulation" around the PVC duct Now look up the cost of closed cell duct insulation and gasp. I found it was not worth it IN THE SOUTH.

The reason I am doing this in caps is that we have people from tropical areas all the way almost to the poles on this site and insulation is highly regional.

One size (or advice) does not fit all.


Steve