I was recently a weekend guest at the house of some friends who live in Climate Zone 5 (a zone which includes Nebraska and Massachusetts). Since I have no interest in embarrassing anyone, I won’t mention any names or the home’s precise location. The story, however, is true.
The weather was hot. The two-story house was built in the 1980s; it included a single-zone split-system air conditioner that delivered cool air through ductwork to every room in the house.
My hosts complained that the second floor was always hot, even when the air conditioner was running full blast. Curious, I poked around a bit. There was an access door to a kneewall area upstairs, and I saw that the house had a crazy, chopped-up roofline with several distinct attic areas. The second floor had varying ceiling heights, and the first floor included a “great room” with a double-height ceiling. Most of the second-floor ceilings were sloping ceilings that followed the roof plane.
Houses with these features have complicated thermal boundaries, and rarely have an uninterrupted air barrier. Snooping around in the attic, I saw blown-in fiberglass installed above horizontal ceilings, blown-in fiberglass installed above sloping ceilings, and fiberglass batts installed in vertical kneewalls. Although the insulation job was neat and the insulation was undisturbed, none of the sloping or vertical insulation was protected by an attic-side air barrier.
What else? The second-floor ceiling was peppered with recessed can lights. And there were two skylights upstairs.
Typical 1980s construction
Needless to say, I wasn’t traveling with a Duct Blaster or a blower door, so I didn’t have a chance to test the home’s duct system or envelope leakage. But anyone familiar with homes built in the 1980s probably has a pretty good idea of what was wrong with this house:…
Get building science and energy efficiency advice, plus special offers, in your inbox.