Musings of an Energy Nerd

Quality Issues With Brick Buildings

Posted on September 18, 2015 by Martin Holladay, GBA Advisor

The design of brick buildings and the quality of brick construction have declined dramatically in the last 100 years. While this statement is debatable, I'll try to defend it with evidence. If my evidence is compelling, it raises questions about why certain technologies advance in sophistication while other technologies decline.

Before I return to the topic of brick buildings, I'd like to take a detour to look at an example of technological evolution.

Flash-and-Batt Insulation

Posted on September 11, 2015 by Martin Holladay, GBA Advisor

Closed-cell spray polyurethane foam insulation has several desirable characteristics. It’s an excellent 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 excellent vapor retarder, and it has a high insulating value per inch (about R-6 to R-6.5). Unfortunately, it’s also expensive.

Cold-Weather Performance of Polyisocyanurate

Posted on September 4, 2015 by Martin Holladay, GBA Advisor

The ability of insulation products to resist the flow of heat changes with temperature. Most insulation products — 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. At lower temperatures, there is less conductionMovement of heat through a material as kinetic energy is transferred from molecule to molecule; the handle of an iron skillet on the stove gets hot due to heat conduction. R-value is a measure of resistance to conductive heat flow., less convection, and less radiation — so insulation materials usually work better than they do at warmer temperatures.

Hygrothermal Software Sometimes Yields False Results

Posted on August 28, 2015 by Martin Holladay, GBA Advisor

Building designers and researchers have begun to realize that computer modeling programs, including WUFI, sometimes falsely predict that certain common wall assemblies — wall assemblies that have been used successfully for years — should be failing. (WUFI is a so-called “hygrothermal” modeling program — that is, a program that calculates heat and moisture flows through building assemblies. For more information on WUFI, see “WUFI IS Driving Me Crazy.”)

Yet experienced builders know that these wall assemblies aren’t failing. So what’s going on?

Can Unvented Roof Assemblies Be Insulated With Fiberglass?

Posted on August 21, 2015 by Martin Holladay, GBA Advisor

Experts usually advise builders that you can’t install fiberglass insulation directly against 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. . If you want to install fiberglass between your rafters, you have two basic choices: either include a ventilation channel between the top of the fiberglass insulation and the underside of the roof sheathing, or install enough rigid foam above the roof sheathing to keep the roof sheathing above the dew point during the winter. These rules were developed to prevent damp roof sheathing.

Nuggets From the 2015 Westford Symposium

Posted on August 14, 2015 by Martin Holladay, GBA Advisor

Building science experts, architects, engineers, and builders from across the U.S., Canada, and Europe gathered in early August in Westford, Massachusetts, for the 19th annual Westford Building Science Symposium, a conference sometimes known as “Summer Camp.”

Over three lively days filled with education, networking, and drinking, experts gave ten presentations on a variety of building science topics.

Exterior Rigid Foam on Double-Stud Walls Is a No-No

Posted on August 7, 2015 by Martin Holladay, GBA Advisor

Many green builders like double-stud walls. Double-stud walls use affordable and environmentally appropriate materials to achieve a high R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. .

The classic double-stud wall is made up of two parallel 2x4 walls with a space between them. If the framers leave a 5-inch space between the two rows of studs, this type of wall provides room for 12 inches of insulation — for example, dense-packed cellulose, blown-in fiberglass, or mineral wool.

Liquid-Applied Flashing

Posted on July 31, 2015 by Martin Holladay, GBA Advisor

By now, most conscientious builders know that window rough openings need to be carefully flashed before a window is installed. For residential builders, the most common way, by far, to flash window rough openings is with peel-and-stick flashing.

However, an increasing number of builders are taking a closer look at something different: liquid-applied flashing.

Misconceptions About HRVs and ERVs

Posted on July 24, 2015 by Martin Holladay, GBA Advisor

Since refrigerators have been around for almost a hundred years, most Americans know what a refrigerator is used for. But heat-recovery ventilators (HRVs) and energy-recovery ventilators (ERVs) have only been around for about 30 years, and many Americans still don’t know much about these appliances. regularly receives questions that show that some homeowners are confused about the purpose of these appliances, so it’s worth examining and debunking common misconceptions about HRVs and ERVs.

Saving Energy With an Evaporative Cooler

Posted on July 17, 2015 by Martin Holladay, GBA Advisor

Evaporative coolers are appliances used to cool indoor air. Evaporative coolers use much less energy than air conditioners, but they can’t cool indoor air effectively in all weather conditions.

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