Musings of an Energy Nerd

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

Posted on December 13, 2013 by Martin Holladay

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

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

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

Here at, 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?”

All About Embodied Energy

Posted on November 15, 2013 by Martin Holladay

What’s embodied energyEnergy that goes into making a product; includes energy required for growth, extraction, and transportation of the raw material as well as manufacture, packaging, and transportation of the finished product. Embodied energy is often used to measure ecological cost., and is there any reason to pay attention to it? Embodied energy is the energy it takes to manufacture building materials. Until recently, it was safe to advise builders that it wasn’t worth worrying about embodied energy, because the amount of energy (especially heating energy and cooling energy) used to operate a building over the building’s lifetime dwarfed the relatively small amount of energy embodied in the building materials.

Can Solar Power Solve the Coal Problem?

Posted on November 8, 2013 by Martin Holladay

I recently read a New York Times article on the coal problem. In the future, the article notes, we won’t be able to burn coal at our current rate, so there is an obvious need to make a transition to alternative sources of energy. According to the Times article, the most likely replacement for coal is solar energy.

Monitoring Moisture Levels in Double-Stud Walls

Posted on November 1, 2013 by Martin Holladay

Most wood-framed buildings have no insulation on the exterior side of the 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. . That means that the wall sheathing gets cold and wet during the winter.

Low-Road Buildings Are Homeowner-Friendly

Posted on October 25, 2013 by Martin Holladay

There are at least two recognizable camps in the green building community. The older camp includes hippies, owner/builders, and those in the natural building movement. These builders prefer to scrounge materials from the woods or demolition sites rather than purchase new materials from a lumberyard. Their homes might be made of adobe, logs, or straw bales.

Martin’s Energy Quiz — Third Edition

Posted on October 18, 2013 by Martin Holladay published an energy quiz in 2009, and another one in 2011. It looks like we're overdue for another installment.

Answers are provided at the bottom of this column; don't peek until you've finished the quiz.

1. True or false: In freezing climates, a drainback solar hot water system circulates ordinary water (without any antifreeze) through its solar collectors.
(a) True.
(b) False.

All About Radon

Posted on October 11, 2013 by Martin Holladay

Several colorless, odorless gases can injure your health. For example, carbon monoxide can kill you in minutes. RadonColorless, odorless, short-lived radioactive gas that can seep into homes and result in lung cancer risk. Radon and its decay products emit cancer-causing alpha, beta, and gamma particles. takes longer — usually decades — to kill you, and (fortunately) death is less certain.

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