Musings of an Energy Nerd

If you’re interested in residential energy efficiency, you’re probably familiar with the marketing pitch of the EPA’s Energy Star HomesA U.S. Environmental Protection Agency (EPA) program to promote the construction of new homes that are at least 15% more energy-efficient than homes that minimally comply with the 2004 International Residential Code. Energy Star Home requirements vary by climate. program.

Among the program’s claims:

Let’s say you’re building a house with plywood or OSB 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. . You plan to install 2 or 4 inches of rigid foam on the exterior of the wall sheathing, followed by vertical rainscreenConstruction detail appropriate for all but the driest climates to prevent moisture entry and to extend the life of siding and sheathing materials; most commonly produced by installing thin strapping to hold the siding away from the sheathing by a quarter-inch to three-quarters of an inch. strapping and siding. Where does the housewrap go?

Depending on who you talk to, you get two different answers:

• It goes between the rigid foam and the vertical strapping, or
• It goes between the sheathing and the rigid foam.

Designing a superinsulated house can be tough. How much insulation should you install under a slab? Should your walls be sheathed with rigid foam, or should you go with double-stud walls? Could SIP(SIP) Building panel usually made of oriented strand board (OSB) skins surrounding a core of expanded polystyrene (EPS) foam insulation. SIPs can be erected very quickly with a crane to create an energy-efficient, sturdy home. walls save you money? Does the added cost of triple glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill. make sense?

Residential energy codes have evolved rapidly over the last two decades. The origin of many of our current energy codes can be traced back to the Model Energy Code (MEC), which was first introduced in 1992. The MEC eventually evolved into the International Energy Conservation Code (IECC International Energy Conservation Code.).

When I published my first Energy Quiz over a year ago, a reader posted the comment: “I want another quiz.” Okay — we aim to please.

Remember, using Google for research is cheating. Answers are at the bottom of the page.

1. Evaporative coolers:
a. Perform better in a dry climate than a humid climate.
b. Perform better in a humid climate than a dry climate.
c. Don’t work very well anywhere in the U.S.

UPDATED on September 18, 2013

By now, almost all builders know the importance of installing a water-resistive barrierSometimes also called the weather-resistive barrier, this layer of any wall assembly is the material interior to the wall cladding that forms a secondary drainage plane for liquid water that makes it past the cladding. This layer can be building paper, housewrap, or even a fluid-applied material. (WRB) behind siding. Most types of siding leak, so it’s a good idea (and a code requirement) to install a WRB to protect your 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. from any wind-driven rain that gets past the siding.

A WRB can be vapor-permeable, like Tyvek, or vapor-impermeable, like foil-faced polyisocyanurate. As long as the wall assembly is designed to dry out when it gets wet, either vapor-permeable or vapor-impermeable WRBs work well.

UPDATED on December 12, 2014

Builders of a certain age — say, those older than about 55 or 60 — started their careers at a time when no one talked about air leakage or air barriers. Back in the early 1970s, even engineers were ignorant about air leakage in buildings, because the basic research hadn’t been done yet.

Times have changed, and most residential building codes now require builders to include details designed to reduce air leakage. Today’s young carpenters are working on job sites where air barriers matter.

In Europe, builders interested in energy efficiency are gravitating to the PassivhausA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. standard. Meanwhile, American researchers — and a few American builders — have developed a fascination with the idea of the net-zero-energy house. The U.S. Department of Energy has established as a goal that new buildings in the U.S. will be built to a net-zero-energy standard by 2030.

UPDATED April 22, 2014

Millions of Americans live in states where residential HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. contractors routinely install ductwork in unconditioned attics. In many cases, these attics also contain a variety of appliances, including air handlers, furnaces, or water heaters.

Advanced framingHouse-framing techniques in which lumber use is optimized, saving material and improving the energy performance of the building envelope., also called optimum value engineering (OVE), is a framing system that aims to pare the amount of lumber used to frame buildings to the bare minimum. Advanced framing was developed in the 1960s by the Department of Housing and Urban Development as a way for builders to reduce costs.

In recent years, the decades-old framing system has been adopted by many green builders. These new advanced framing devotees are focused less on the cost-cutting aspects of the framing system than on its other virtues, including energy and materials savings.