Musings of an Energy Nerd

UPDATED and CORRECTED on 9/22/2011

Are you ready for the 2012 code? Each revision of the International codes tends to ratchet up energy performance requirements, and the 2012 revision is no exception.

Although its adoption may be a long ways off in some jurisdictions — after all, many rural areas of the U.S. still have no building codes at all — the 2012 International codes may become law in some areas as soon as next year.

About every six months, I report on new products that catch my eye. This round-up features products from both sides of the Atlantic Ocean: high-performance windows from Maine, Ontario, and Lithuania; high-performance doors from Poland; and high-performance tapes from Switzerland.

Should spray polyurethane foam be installed in an occupied house? Hundreds of spray foam contractors around the country are happy to answer “Yes!” In almost all cases, these jobs end successfully: the spray foam improves the home’s thermal performance and the homeowner is happy.

A subset of green builders have always been grumpy about foam. Such builders look at rigid foam panels and spray foam as suspect products: they are made from petroleum, laced with mysterious chemicals, and impermeable to vapor flow.

R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. is the poor stepchild of building science metrics. Although it is often essential for builders, designers, and engineers to know a material’s R-value, this useful metric is regularly abused, derided, and ridiculed for its shortcomings. “R-value doesn’t measure assembly effects: thermal bridges, air movement, thermal massHeavy, high-heat-capacity material that can absorb and store a significant amount of heat; used in passive solar heating to keep the house warm at night. , moisture content — all of which can all affect thermal properties,” explained Chris Schumacher, an engineer and researcher at Building Science Corporation, at a summer symposium in 2009. “R-value doesn’t do a good job describing the entire system.”

Older buildings with load-bearing brick walls are common in many northern U.S. cities. While these thick (muti-wythe) brick walls were often plastered on the interior, they were rarely insulated.

I live in Wheelock, Vermont, a town with 598 residents. Our town is so small that we have neither a post office nor a zip code. To get my mail, I have to travel two miles to the post office in Sheffield, our larger neighbor. (Sheffield has a population of 704.)

There’s a $90 million construction project underway in Sheffield this summer. In its entire 200-year history, the sleepy town has never seen anything like this.

Do you want to build your home out of natural materials? If so, you can build your walls with adobe, cob, cordwood, rammed earth, or wattle-and-daub. Although all of these walls have a long history, their thermal performance is poor. If you want a well-insulated wall, one natural material is the clear winner: straw bales.

A 23-inch-thick straw-bale wall has an R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. of about R-33. Moreover, since virtually all straw-bale walls are plastered on both sides, these walls are relatively airtight.

A Larsen truss is a type of wall truss used to build a thick wall — thick enough to provide room for above-average amounts of insulation. It was developed in 1981 by John Larsen, a builder in Edmonton, Alberta.

In honor of the 30th anniversary of the Larsen truss, the time has come for a definitive article on the invention. This report includes an interview with the inventor of the Larsen truss, a history of its use, and a discussion of its advantages and disadvantages.

To end my three-part report on my trip to Maine, I’ll describe my visits to two new energy-efficient homes — an elegant home in Freeport, and a compact 1,000-square-foot home in Bath.

The Freeport home was designed by architect Chris Briley and built by Dan Kolbert. Since the owners of the home haven’t moved in yet, the rooms are still empty of furniture.