Lower Utility Bills and You - Wall Insulation

As any good home owner knows utility bills are no fun. But, instead of complaining about high energy costs and melting ice caps, let's talk about how to make a change. Let's Start with wall insulation. The stuff that helps keep the heat in the winter and out in the summer. At the core of the insulation conversation is a property called Thermal Resistance, or R-value.

If you are like most people then you probably don't have the foggiest idea of what an R-value really is, but It's quite simple really. R-value is the heat transfer per unit area per unit time or R = \Delta T/\dot Q_A.

Okay, I know that is about as clear as mud for most of us. So, think about it this way:

R Values

Thermal resistance is like holes in a pipe. The bigger the holes the more water leaks out. In the case of thermal resistance the water is heat and the pipe is a wall in your house. Think of high R-values as small holes and low R-values as bigger holes.

Pretty simple right?

Now that we all have a simple understanding of thermal resistance let's start answering some of the basic questions like, "what R-values should I be looking for?" Here is a simple list to help you make heads and tails of things

Wall R-values: The Good, The Bad and The Awesome

Keep in mind that insulation types and requirements vary greatly depending on climate. These suggestions are for applications in climate zones 4 & 5 (Kansas and Missouri) Learn about Climate Zones

The Good: R-15

  • Most houses in our area are built with 2x4 construction
  • R-15 is the maximum rating a 2x4 wall can carry without adding external insulation.
  • If buying a home with 2x4 construction R-11 is low, R-13 is good and R-15 is a sign the builder has gone the extra mile!

The Bad: R-11

  • Most building codes do not even allow R-11 exterior wall insulation any more!
  • R-13 should be your minimum acceptable insulation rating

The Awesome: R-21 and up

  • 2x6 exterior walls start at R-19 and max out at R-23 without adding external insulation
  • R-19 is basic but still a step above the best 2x4
  • R-21 is a good target for 2x6 walls
  • R-23 is great
  • Even higher R-values are attainable with super insulated wall assemblies (Super Insulated Wall Detail).

Show me the Money!

Glad you stayed with us because here is the pay off. The savings on one of our reverse story and a half plans with a finished walkout basement using 2x6 walls with R-23 insulation is over 25%!

That is $6,300 of savings over the first 10 years of home ownership!

(*10 year estimate assuming 10% increase in fuel cost each year)

Cost of construction

When choosing the right insulation for your home it is important to weigh the long term savings with your up front costs. 2x6 exterior construction with R-23 insulation is standard with our homes, but when looking at insulation upgrades the long term savings should clearly out weigh the short term costs.

Want a deaper look at thermal resistance? Take a look at these sites:

Wikipedia: Thermal Resistance
Department of Energy