My House is Built with Styrofoam Insulation?

When we moved to Arizona recently, I knew I'd be learning more about stucco (it's everywhere) and air conditioning which is more important than heating, with temperatures over 100° for several months each year. What I wasn't prepared for was a remodeling friend visiting from New York, tapping on the walls of our house and telling me it was built with styrofoam insulation.

So on a trip to see the beautiful red rocks in Sedona, my friend pointed out a house under construction that was wrapped in styrofoam insulation. We stopped to see what this styrofoam house looked like before the stucco gets applied, so I could understand more about my own house.

Sitting here researching the different types of rigid foam insulation, I'm still surprised and a bit scared. When I think about my house built of styrofoam, it reminds me of the three little pigs. Houses can be built from straw, sticks, brick or styrofoam?

Building with Styrofoam Insulation

The most important lesson here is not how styrofoam insulation is used in home construction, or even the importance of good insulation. You want to learn about the type of construction used for your house, so you can do a better job maintaining it, and make improvements to lower utility bills.

So here are some of the questions I had regarding the use of styrofoam insulation:

• How much structural support does styrofoam add? Foam provides no support, so you need to add bracing to any foam sheathed wall according to the GreenBuildingAdvisor.com website.
• How well does styrofoam shed water that penetrates the stucco? At Green Building Advisor, they discus leaving a drainage gap in front of the foam. There's also an article on styrofoam as a water resistive barrier (WRB), a fairly new building practice that requires careful installation.
• How easy is it to seal the gaps where the styrofoam meets doors and windows? When inspecting the house shown here, the doors and windows had traditional flashing and a moisture barrier wrap.
• How does styrofoam hold up to the intense sunlight and heat in Arizona? The stucco protects the foam so the ultraviolet rays that damage everything, never reach the styrofoam.

All the exterior walls from the slab up to the roof are wrapped in styrofoam and metal lath, which will hold the stucco siding.

Notice how the same styrofoam and metal lath is applied to the deck wall, to maintain consistency across all the exterior walls.

Here you can see that the styrofoam surrounding this window is covered with a weather resistive barrier, which in turn is covered by the wire lath in preparation for the stucco.

Yes, I'm holding the styrofoam insulation boards that were lying on the ground next to the house. You'll find the most common sizes for rigid insulation are 2 ft x 8ft and 4 ft x 8ft, and the thickness will vary based on which type of foam you use.

And one of the things I'm really beginning to appreciate in Arizona, is how most houses are painted colors that allow them to blend into their environment, which in Sedona means red.