Musings of an Energy Nerd

My father was a college professor who was respected for his scholarship. Yet Dad doesn’t pay much attention to the physical world. If he were asked to define the stack effectAlso referred to as the chimney effect, this is one of three primary forces that drives air leakage in buildings. When warm air is in a column (such as a building), its buoyancy pulls colder air in low in buildings as the buoyant air exerts pressure to escape out the top. The pressure of stack effect is proportional to the height of the column of air and the temperature difference between the air in the column and ambient air. Stack effect is much stronger in cold climates during the heating season than in hot climates during the cooling season., he’d probably guess that it was a type of exhaustion caused by walking past miles of library bookshelves. According to a family legend, the engine of our family’s Volkswagen van had to be rebuilt in 1963 because my father drove thousands of miles without checking the dipstick or changing the engine oil.

Back in the 1980s, Canadian energy experts urged builders to use interior polyethylene as an 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. material. If the poly was installed conscientiously, and all seams were sealed with Tremco acoustical sealant, the approach worked well — at least in cold climates.

Exterior wall insulation? That usually means rigid foam and furring strips — although occasionally, it means mineral wool insulation and furring strips.

But there are other options. Two new products offer builders new ways to keep their wall 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. warm.

Many different appliances can be used to heat a house, including boilers, water heaters, heat pumps, and wood stoves. However, most homes in the U.S. are heated by a forced-air furnace.

These devices are connected to ducts that deliver heated air to registers throughout the house. Different types of furnaces are manufactured to burn a variety of fuels, including natural gas, propane, oil, and firewood. The most common furnace fuel in the U.S. is natural gas.

I've been paying attention to energy-efficiency and air-sealing tips for many years, but I still learn something new every week. This week, I learned a very useful tip from my fellow Fine Homebuilding editor, Justin Fink.

Justin wrote a great article on canned spray foam, “You Don't Know Foam,” that appeared in the current issue of Fine Homebuilding.

In a recent blog, Allison Bailes did a great job defining heat and explaining heat flow. It’s important to remember, though, that Allison Bailes lives in Atlanta. When the temperature drops to 6°F in Atlanta, the story makes national news. But when the temperature hits -20°F in Vermont, we just tell our kids to remember to wear a hat when they walk to school.

Now that insulation contractors have been installing spray foam insulation on the underside of roof 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. for several years, we’re beginning to accumulate anecdotes and data on successful installations and failed installations. The anecdotes and data are enough to provide a few rules of thumb for designers and builders who want to install spray foam on the underside of roof sheathing.

Just for fun, I recently Googled the phrase “energy-saving tips.” I dove deep — all the way to page 7 of the Google results. My research was profoundly discouraging.

Back in 2011, I wrote two articles about bad energy-savings tips. (See More Energy Myths and A Plague of Bad Energy-Saving Tips.)

Since then, is there any possibility that the quality of online advice improved? Not a chance.

(With apologies to Ernest Lawrence Thayer)

Bob Casey's business worries made him grumble, whine, and moan;
His solar thermal enterprise was dropping like a stone.
While certain clients wanted water heated by the sun,
The calls and jobs were rare these days, which wasn’t very fun.
The contractor regretted his decision long ago
To be a solar plumber; now his life was full of woe.

Researchers have known for years that most types of insulation — including fiberglass batts, extruded polystyrene (XPSExtruded polystyrene. Highly insulating, water-resistant rigid foam insulation that is widely used above and below grade, such as on exterior walls and underneath concrete floor slabs. In North America, XPS is made with ozone-depleting HCFC-142b. XPS has higher density and R-value and lower vapor permeability than EPS rigid insulation.), and expanded polystyrene (EPSExpanded polystyrene. Type of rigid foam insulation that, unlike extruded polystyrene (XPS), does not contain ozone-depleting HCFCs. EPS frequently has a high recycled content. Its vapor permeability is higher and its R-value lower than XPS insulation. EPS insulation is classified by type: Type I is lowest in density and strength and Type X is highest.) — perform better at low temperatures than high temperatures. The phenomenon was described by Chris Schumacher, an engineer and researcher at Building Science Corporation, at a conference in 2011: “If you measure the R-value of an R-13 fiberglass batt, you’ll get different results at different outdoor temperatures. If the outdoor temperature rises, the R-value goes down.