Musings of an Energy Nerd

Thermal Drift of Polyiso and XPS

Posted on June 3, 2016 by Martin Holladay, GBA Advisor

Most insulation materials have an R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. lower than R-5.6 per inch. As David Yarbrough, a nationally known insulation expert, explains, “At 75°F, the theoretical maximum R-value of a product is 5.6 per inch. That represents the maximum R-value if there is no convection and no radiation — it represents the pure conductivity of air. That’s as high as you can go unless you are talking about a product that incorporates encapsulated gas, or a vacuum, or nano-scale powders.”

How Much Insulation is Too Much?

Posted on May 27, 2016 by Martin Holladay, GBA Advisor

To reduce future energy bills, some builders are willing to include above-code levels of insulation. Each additional inch of insulation saves energy — but with each additional inch, the savings per inch diminishes. At some point, the cost of adding more insulation because hard to justify.

How to Order Windows

Posted on May 20, 2016 by Martin Holladay, GBA Advisor

Anyone who needs to choose windows for a new home has a lot of decisions to make. In this article, I’ll try to provide an overview of some of the factors to keep in mind when ordering windows.

Domestic Hot Water: No Perfect Solution

Posted on May 13, 2016 by Martin Holladay, GBA Advisor

Some questions are easier to answer than others. For example, there is a fairly straightforward answer to, “How should I insulate the floor of my unconditioned attic?” — namely, “With a deep layer of cellulose.” (There’s more to say on the topic, of course — but even a full answer isn’t very complicated.)

There is no easy answer, however, to, “How should I heat my domestic hot water?” Every type of water heating technology is flawed; every solution involves compromise.

Many factors affect the decision about what type of water heater to choose, including:

These Superinsulated Homes Were Delivered By Truck

Posted on May 6, 2016 by Martin Holladay, GBA Advisor

Last fall, Dartmouth College realized that it needed to build four new single-family homes, pronto. Beginning this summer, the homes will be occupied by the “house professors” assigned to new “house communities” — the term that Dartmouth uses to describe the college’s dormitory clusters.

Are New Homes Getting Better?

Posted on April 29, 2016 by Martin Holladay, GBA Advisor

A subset of North American builders has been interested in a high-performance homes for at least 40 years. You could call these people green builders, progressive builders, or energy-conscious builders; whatever you call them, they’ve been around for a while.

Vegetated Roofs

Posted on April 22, 2016 by Martin Holladay, GBA Advisor

Vegetated roofs are low-slope roofs the have enough soil (or soil-like growth medium) on top of the roofing to support the growth of grass, wildflowers, or shrubs. Although some people call this type of roof a “green roof,” the term “vegetated roof” is more accurate and less confusing.

Is Your Ventilation System Working?

Posted on April 15, 2016 by Martin Holladay, GBA Advisor

What’s a “faith-based ventilation system”? It’s a ventilation system installed by a contractor who never verifies the air flow rates after the equipment is installed.

So, will this type of ventilation system work? It’s hard to say — because no one measured anything.

Managing Lead Paint Hazards

Posted on April 8, 2016 by Martin Holladay, GBA Advisor

About 37 million American homes and apartments have some interior lead paint on walls and woodwork. Any house built before 1978 — the year when most types of lead paint were withdrawn from the market in the U.S. — may contain lead paint. If lead paint is present on friction surfaces (for example, window sash), or if any lead paint is flaking or deteriorated, any children under the age of 6 or pregnant women who live in the house are at risk.

Two Wingnuts Describe Their Backyard Tape Tests

Posted on April 1, 2016 by Martin Holladay, GBA Advisor

Regular visitors to probably know that I’m a big fan of backyard product tests. (In the past, I’ve reported on my tape tests, flexible flashing tests, and liquid-applied flashing tests.) So when I noticed that Peter Yost and Dave Gauthier would be giving a presentation titled “Sticky Business: Tape Testing, Round Two” at the BuildingEnergy 16 conference in Boston, I showed up early to make sure I got a good seat.

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