Tony’s email to me began by saying, “Tim- Here’s a fun one”.
We have two projects in the works, Columbia City Green and the South Bennett Development, which together comprise a total of five single-family residences to be built in the coming year or two. As such, we’ve been working to make further advancements toward energy/resource efficiency in our house designs. Tony was asking me to compare four different types of stud-wall construction to see which had the best insulative performance for the least amount of wood. This seemed like a novel concept to me; calculate the R-value and volume of wood used in a given type of wall construction, divide the R-value by the wood used, and poof you get a number which serves to rank the wall-types by both of these criteria at once.

A fun one for me indeed, I love this kind of thing. It’s nice to be understood.

We compared:



The thermal-break stud design was refined to this optimal configuration thanks to a lively and enlightening interaction with Jonathan Heller from Ecotope.

Here are the figures:





The results show clearly the advantages of using either a Thermal-break 2X8 Stud or Advanced 2X6 + Rigid in terms of R-Value alone. They both show at least a 32% increase over Standard 2X6 (16"O.C.) framing and 27% increase over Advanced 2x6 Framing(24"O.C.). The Advanced 2X6 + Rigid system offers the most efficient usage of wood (35% less wood than Standard 2X6) while only compromising 1 point in R-Value from the Thermal-break 2X8 system.

This exercise has been useful much in the way a Swiss Army Knife may be useful when backpacking in the mountains. We just opened our can of soup and whittled a wooden bear with the same tool. The results are not an answer in and of themselves, just a glimpse at something better, more efficient. We’ll keep whittling away at it.

If you would like a closer look at these diagrams and figures here is a PDF.

In the last few weeks, a few of our colleagues and Tony have been involved in creating this brief document. We think it is a splendidly concise reference for green building/remodeling. Feel free to click on the link, download, and print at your leisure.