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Insulated Concrete Slab

  In Texas where I build the most common foundation type is Slab on Grade.  In effect, we pour a big rock of concrete on top of the ground (also mainly rock) then build a house on top.

My Project Manager Ryan on top of this newly poured Slab Foundation.

 I just completed my first house with Perimeter Slab Edge Insulation and I thought I’d walk you through the process.  First, let’s talk about why to insulate the slab.  As we builder tighter and better insulated houses the uninsulated slab becomes more of a heat loss in the winter time for these High Performance Homes.  Check out this Manual J energy loss chart from a house we remodeled recently. 

Check out the BTU loss through the un-insulated concrete slab on this house.

The chart above is from a house with R-19 walls, and an R-40 roof.  As we build better that slab becomes a larger % of the loss of heat! 

This is for a house with an R-11 Insulated Slab.

Now look at this chart with a house with similar specs for walls/roof but it has an R-11 Perimeter insulated slab.  Big difference!  As a percentage of heat loss the floor went way down compared to the un-insulated slab house. 
  So, let’s look at the mechanics of actually insulated the slab.  One of our first concerns for this process is Termites!  Adding foam to the outside of a slab is a big no-no in Termite country.  First, we used Borate impregnated foam from Nisus Corporation.  I’ve been using their Bora-Care on my framing lumber for about 10 years now, but I only recently realized they make a termite resistant foam aptly called Bora-Foam.  Our local Termimesh dealer sourced it for me and did the install.

I want to thank Joel Roeling from Termimesh for his help in this project.  Also want to extend a big thanks to my Energy Rater/Tester Kristof Irwin of Positive Energy here in Austin, TX.  His modeling really helps us decide what approaches will yield benefits long term for the houses I build.  Last, but certainly not least was the amazing Architect/Client on this house Scott Ginder of Dick Clark & Associates.  Scott and his wife Andrea are wonderful clients and it was such a pleasure to build this beautiful high performance home with them!  

Here’s the tall slab before insulation. 
The Termimesh guys installing Bora-Foam.
After the foam is installed we installed Termimesh to the slab/foam joint.

It really didn’t take too much foam to do the entire slab.

We basically turned the foam on the foundation into a standard STO EIFS install.
Here’s the completed house.

Architect & Client Scott Ginder had a very nice “Wrap” party for us!

Matt Risinger, Dick Clark AIA, Scott Ginder AIA

 Best,
Matt Risinger – Risinger Homes in Austin, TX

Risinger Homes is a custom builder and whole house remodeling contractor that specializes in Architect driven and fine craftsmanship work. We utilize an in-house carpentry staff and the latest building science research to build dramatically more efficient, healthy and durable homes.
Be sure to check out my video blog on YouTube.