Musings of an Energy Nerd

With apologies to Edgar Allan Poe

Once upon a midnight dreary,
    while I pondered, weak and weary,
Many unpaid bills and letters
    from my local big-box store —
While I nodded, nearly napping,
    suddenly there came a tapping,
As of someone gently rapping,
    rapping at my office door.
“’Tis some visitor,” I muttered,
    “tapping at my office door —
        Only this and nothing more.”

UPDATED on December 16, 2014

Most builders assume — and GBAGreenBuildingAdvisor.com has long reported — that oriented strand board (OSB) is a good air barrierBuilding assembly components that work as a system to restrict air flow through the building envelope. Air barriers may or may not act as a vapor barrier. The air barrier can be on the exterior, the interior of the assembly, or both.. If a builder uses a high quality tape like Siga Wigluv, Zip System tape, or 3M All Weather flashing tape to seal sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. seams, OSB wall and roof sheathing can act as a building’s primary air barrier.

When you drive a borrowed car, it takes a few moments to figure out how to operate the windshield wipers and the headlights. But in your own car, your hand reaches for these switches without thinking.

Using the psychrometric chart is a little like driving a car. If you use the psychrometric chart every day, you don’t have to orient yourself. But if you are like me, and you only consult the psychrometric chart two or three times a year, it’s useful to refer to a cheat sheet every time you use it.

Rummaging through the shelves of a used book store, my son Noah came across an old paperback called Energy Saving Handbook. Written by James W. Morrison, the book was published by Harper & Row in 1979.

A brief web search failed to reveal any biographical information about the author. However, I discovered that the book was published under several different titles, and was distributed by at least four state energy offices. Morrison’s book may have been funded by the U.S. Department of Energy; some of its chapters seem to have been repurposed from government brochures.

Recently I decided to research heat transfer during turkey roasting. It turns out that this issue has been extensively studied by physicists and engineers.

As with houses, there are two basic camps: those who use computer modeling and those who make measurements. Some researchers feel more comfortable at a desk with a laptop; others feel more comfortable in a kitchen with a thermometer.

Foundation discussions can get heated. For some reason, builders often dig in their heels when the topic of slabs versus crawl spaces versus basements comes up. It’s time to declare a truce.

It’s perfectly possible to build a great house on any one of these three foundation types, as long as everything is properly detailed. Each type of foundation has advantages as well as disadvantages. If you have a foundation type that you prefer, that’s great. I’m not going to try to change your mind.

Back in the early 1990s, I worked for a nonprofit agency, overseeing renovation work at several old wood-framed buildings in St. Johnsbury, Vermont. Each of these century-old buildings had between two and five apartments; after renovation, they were rented to low-income families at subsidized rents.

One of the presentations I attended at the Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. conference in Portland, Maine, on September 22, 2014 was a session called “Passive House certifiers’ roundtable.” The first speaker on the panel, Tomas O’Leary, explained that he usually charges about $2,200 to certify a residential Passivhaus project. He warned the audience that certification is “quite an effort; don’t underestimate it.”

I’ve lived in an off-grid house for the past 39 years. Since I make my own electricity, my electricity costs are much higher than those of most Americans. Because of my off-grid lifestyle, I often lack perspective when I try to help people who ask questions about ordinary energy choices. (I’ve had to compensate for my lack of relevant experience by undertaking anthropological studies of my grid-connected neighbors.)

Does the exterior sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. on a double-stud wallConstruction system in which two layers of studs are used to provide a thicker-than-normal wall system so that a lot of insulation can be installed; the two walls are often separated by several inches to reduce thermal bridging through the studs and to provide additional space for insulation. accumulate worrisome quantities of moisture in late winter? Several researchers are now looking into this question, and Green Building Advisor has been sharing the researchers' findings as the information becomes available.