More Q&A Spotlight
As he plans a new home in western Alabama, Weldon Koehn is considering an unusual wall assembly. In an era when high-performance, superinsulated walls are becoming ever-more common, Koehn is thinking about plain old brick.
“I have been very interested in using a 12-in.-thick, triple-wythe brick wall for all structural walls in our ‘forever’ home,” he writes in this recent Q&A post. “The wall would be structural, uninsulated, and the finish surface inside and out.”
Koehn says he was inspired by an article in Fine Homebuilding magazine that led him to videos by the builder, Clay Chapman.
“The wall seems to perform much better in the summer than most models would indicate,” Koehn writes. “However, the data is incomplete, and I have reservations [around] how this type of wall would perform through our very damp, cloudy winters. The simplicity of using only one material in the wall, combined with its strength, durability, resilience, and beauty have compelled me to try to study it out.
“Any thoughts?” he adds. “Am I crazy for even considering it?”
That’s where this Q&A Spotlight begins.
Interesting, but not cheap
There are just two things that really count, says GBA reader Akos: specific heat (the amount of heat the assembly can store) and its R-value per inch.
“When it comes to certain building techniques, there are a lot of hand-wavy arguments as to why it will work better than standard construction,” Akos says.
With the wall that Koehn is mulling, the R-value would be roughly 5 (which could be stretched to R-6, if the interior finish were installed over strapping). This has a specific heat capacity similar to concrete, although it is slightly less dense. Let’s say it’s the same as a 9-in.-thick concrete wall.
“If you…
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2 Comments
A couple of these solid brick homes Clay built are walking distance from my house. They are very beautiful and well crafted, but I have always had issues with his logic. He managed to get the designs approved using spray foam rooflines and other high performance features to meet the total UA through tradeoffs, although I am not quite sure how. I have not spoken to any occupants of these homes to find out how they fare in terms of comfort and energy use, but I expect that during some of our infrequent cold snaps which can be in the 20's for days at a time, the walls turn into major heat sinks and make the homes very uncomfortable. Humidity is probably managed well with central AC which most people around here run continuously through the summer.
I met Clay and discussed his methods and his energy calculations, but I remain unconvinced that they perform as well as he claims. I would like to see energy use and comfort reports from some owners.
I have worked on all types of houses in Alabama over the past 30 years. I would strongly recommend against building this type of home. To start with, I recommend using systems that are built often and have had most of the "kinks" worked out. Second, brick in Alabama stores tons of energy from the sun. Summer rains soak the brick and the sun drives lots of moisture into the interior. I experienced this in the early days of wet spray cellulose. Many of the brick installers squeeze the excess mortar out of the backside and this mortar provides a gateway into the wall assembly when there is cellulose and wood framing. Third, warm and sunny days with cold nights turns the brick into a condensing surface. Fourth, the brick in cold, rainy weather stores a lot of moisture. Also, it doesn't pass code.
Todd Witt
Synergy Home Performance
Decatur, AL
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