I am planning out my footing insulation job. Right now it's a pretty standard floating slab-on-grade with footings extending down a few feet, and the footings are uninsulated. A ring of concrete was, at some later point, poured around the original slab to ring the house with a walkway type thing. It's annoying me because it let termites enter the house unseen at some point. A "snow test" revealed that the house leaks a lot of energy from the original slab through the external one. So it's going to be history!
Here's a cross-section of the current state of affairs:
My plan is to remove the exterior concrete and dig a trench around the house to expose the footings. Then I'll attach 6" of EPS insulation foam boards right up against it, and metal flashing for drainage and termite control/tube visibility will be attached over that:
This leaves the question of what to do about the trench. I don't want to create any drainage or water control issues as a part of this project, because right now the house has none. I assume that simply filling it back in with dirt would be safe, but I want to fill it with other things instead, for the following reasons:
1. Scoria (lava rock)
Pros: extra insulation, looks pretty
Cons: Would having a trench filled with a gravel-like rock right up against footing insulation create drainage issues?
Pros: 16-grit sand creates a permanent termite barrier (16-grit sand is exactly the right size to impede their movement)
Cons: Would having a trench filled with sand right up against footing insulation create drainage issues?
I should mention that this house is in the Albuquerque, NM area and receives less than 12" of rain a year. So this isn't as important as if the house were in Seattle, but I still want to get it right.
P.S. I know that EPS foam is white, not blue, but white didn't look right in the diagram!