Musings of an Energy Nerd

All About Furnaces and Duct Systems

Posted on January 24, 2014 by Martin Holladay, GBA Advisor

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.

Justin Fink’s Canned Spray Foam Tip

Posted on January 21, 2014 by Martin Holladay, GBA Advisor

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.

Twenty Below and Off the Grid

Posted on January 10, 2014 by Martin Holladay, GBA Advisor

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.

Open-Cell Spray Foam and Damp Roof Sheathing

Posted on January 3, 2014 by Martin Holladay, GBA Advisor

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.

Stupid Energy-Saving Tips

Posted on December 27, 2013 by Martin Holladay, GBA Advisor

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.

Casey Makes a Bet

Posted on December 20, 2013 by Martin Holladay, GBA Advisor

(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.

In Cold Climates, R-5 Foam Beats R-6

Posted on December 13, 2013 by Martin Holladay, GBA Advisor

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.

All About Attic Venting

Posted on December 6, 2013 by Martin Holladay, GBA Advisor

Most homeowners and builders believe that attics should be vented. If you walk down to your local lumberyard and lean on the counter, the employees and nearby customers will offer a variety of opinions about why attics need to be vented. Unfortunately, it’s highly unlikely that the statements you hear will be true.

The Klingenberg Wall

Posted on November 29, 2013 by Martin Holladay, GBA Advisor

When Katrin Klingenberg designed the first single-family Passivhaus in the U.S. in 2003, she used 12-inch-deep I-joists (TJIs) as wall studs. Located in Urbana, Illinois, the house was sheathed on the exterior side of the vertical I-joists with vapor-permeable fiberboard and on the interior with OSB, which acted as an interior 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., an interior vapor retarder, and structural bracing. The bays of the engineered studs were filled with blown-in fiberglass insulation.

Cut-and-Cobble Insulation

Posted on November 22, 2013 by Martin Holladay, GBA Advisor

Here at GBAGreenBuildingAdvisor.com, readers regularly ask about the best way to install rigid foam insulation between studs or rafters. A typical question might go like this: “I’d like to insulate between my studs with strips of 2-inch-thick polyisoPolyisocyanurate foam is usually sold with aluminum foil facings. With an R-value of 6 to 6.5 per inch, it is the best insulator and most expensive of the three types of rigid foam. Foil-faced polyisocyanurate is almost impermeable to water vapor; a 1-in.-thick foil-faced board has a permeance of 0.05 perm. While polyisocyanurate was formerly manufactured using HCFCs as blowing agents, U.S. manufacturers have now switched to pentane. Pentane does not damage the earth’s ozone layer, although it may contribute to smog. . I plan to cut the rigid foam pieces a little bit loose, and seal the edges of the polyiso with canned spray foam. Will this work?”

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