Daniel McKinney is reaching four decades into the past for two important features of a new house he plans to build. Both notions were mostly discarded after early attempts at energy efficiency led builders in new directions, but McKinney thinks they may still have some merit.
“OK, here’s the basic idea,” he writes at Green Building Advisor’s Q&A forum. “I would like to use an earth tube system to bring fresh air into a very tightly sealed home. I’m also designing the home with a ‘solar stairwell,’ a stairwell that’s exposed to the sun with big windows, with the back wall of the stairwell being made of dark-colored cast concrete.
“During cold months,” McKinney continues, “the concrete wall acts as thermal mass, gathering heat during the day and shedding it during the night. Exterior louvered shades above the big windows would keep this wall from getting direct sunlight during the summer. So, the question is this: Would it make sense to duct the earth tube air vertically through the concrete wall?”
An earth tube, which is simply a pipe buried in the ground, alters the temperature of incoming air because soil temperatures well below grade don’t change much seasonally. Incoming air is warmed in winter and cooled during the summer. The other part of McKinney’s plan, a heat absorbing, high-mass Trombe wall, was a common feature of many early passive solar homes. The appeal of both of these ideas lies in their simplicity, but many builders and designers now think their flaws outweigh any potential benefit.
Who’s right? That’s the topic for this Q&A Spotlight.
No, this is the wrong approach
Earth tubes and Trombe walls are dated concepts, says GBA senior editor Martin Holladay. Don’t bother.