Our Home Insulation Decision: Based on R-Value

| 8/16/2015 8:01:00 PM

Tags: home insulation, spray foam insulation, r-value, small home big decisions, build a home, Jennifer Kongs, Tyler Gill, Kansas, ,

Spray Foam Insulation

The Small Home, Big Decisions series follows Jennifer and her husband, Tyler, as they build a self-reliant homestead on a piece of country property in northeastern Kansas. The series will delve into questions that arise during their building process and the decisions they make along the way. The posts are a work in progress, written as their homestead-building adventure unfolds.

In addition to high-quality windows and thoughtful design, insulation plays a major role in a home’s efficiency.  When choosing which type of insulation we would use, we wanted to be sure we picked a type that has a good R-value (the capacity of an insulation material to resist heat flow), fit into our budget, and is something our contractor is familiar with and comfortable installing.

We decided to go with spray foam insulation for the walls (R-15; shown above) and batt insulation for the attic (R-50). Our contractor recommended this route, and we agreed after reading about the R-value we’d need in the DOE’s Guide to Home Insulation.

The insulation level on the walls, coupled with double-pane windows and house wrap, will create a solid seal around the house. While spray foam costs more than batts, it has a higher R-value and forms an air barrier. The seal is stronger because the foam expands after its sprayed, and fills in any air gaps in the cavity between the wall beams. For installation purposes, it was fast (completed in two days for the whole house) and required a certified installer. As a bonus, because the spray foam fills the wall cavities, it doubles as a house support.

When comparing R-values between different insulation types, one point to consider is where exactly that R-value applies. For example, with spray foam, the entire wall cavity (from board to board) will perform at the determined R-value. With batt insulation, often only the center of the batt actually has the full R-value; the edges of the batt do not likely fill in the cavity thoroughly and provide an insulation barrier as high as the given R-value.

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