The most recent blogs at Green Building Advisor

Setting Roof Trusses at the Potwine Passivhaus

Posted on October 27, 2014 by Alexi Arango in Guest Blogs

As they set out to build a single-family 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. on Potwine Lane in Amherst, Massachusetts, Alexi Arango and LeeAnn Kim asked themselves, “Is it possible to live without burning fossil fuels?” One measure of success would be meeting their goal of net-zero energyProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. performance. This is the sixth blog in a series.

A New Ground-Mounted Solar Array

Posted on October 24, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

I’ve lived in an off-grid house for the past 39 years. Since I make my own electricity, my electricity costs are much higher than those of most Americans. Because of my off-grid lifestyle, I often lack perspective when I try to help people who ask questions about ordinary energy choices. (I’ve had to compensate for my lack of relevant experience by undertaking anthropological studies of my grid-connected neighbors.)

Hard Truths of Home Performance

Posted on October 23, 2014 by Nate Adams in Guest Blogs

If you've been reading my blogs, you know that I have learned some hard truths. You read the warts-and-all implosion story of my Century Club company in How an Efficiency Program Killed My Business.

Spray Foam Insulated Homes Need Ventilation

Posted on October 22, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Most installations of spray foam insulation, when properly installed, act 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.. When you use it instead of the fluffy stuff (fiberglass, cellulose, cotton), a house will be more airtight. That's good.

When a house is airtight, the nasties in the indoor air tend to stick around. Volatile organic compounds (VOCsVolatile organic compound. An organic compound that evaporates readily into the atmosphere; as defined by the U.S. Environmental Protection Agency, VOCs are organic compounds that volatize and then become involved in photochemical smog production.), water vapor, odors, 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., and other stuff you don't want to immerse yourself in make the home's indoor air quality worse.

Presumptive European Superiority Syndrome

Posted on October 21, 2014 by Stephen Thwaites in Guest Blogs

UPDATED on October 22, 2014 with an Addendum.

[Editor's note: The author of this article, Stephen Thwaites, is a window manufacturer. His company, Thermotech Fiberglass FenestrationTechnically, any transparent or translucent material plus any sash, frame, mullion, or divider attached to it, including windows, skylights, glass doors, and curtain walls., is located in Ottawa, Ontario.]

Most of the world, especially the green building community, assumes that “European” implies “more energy-efficient.” When it comes to windows, this automatic presumption of superior energy efficiency is both so common and so misplaced that it deserves a name: the Presumptive European Superiority Syndrome.

Determining the Best Attic Option

Posted on October 20, 2014 by Scott Gibson in Q&A Spotlight

Attics come in many shapes and sizes, but they are either conditioned or unconditioned. That is, they are insulated and heated like the rest of the house and can be considered conditioned spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort. , or they are designed to allow the free circulation of outdoor air and become unconditioned spaces.

Is one option better than the other? That's what Rus Pearson would like to know.

Dense-Packed Cellulose and a Wrong-Side Vapor Barrier

Posted on October 17, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Does the exterior 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. on a double-stud wallConstruction system in which two layers of studs are used to provide a thicker-than-normal wall system so that a lot of insulation can be installed; the two walls are often separated by several inches to reduce thermal bridging through the studs and to provide additional space for insulation. accumulate worrisome quantities of moisture in late winter? Several researchers are now looking into this question, and Green Building Advisor has been sharing the researchers' findings as the information becomes available.

An Affordable Zero-Energy House in Massachusetts

Posted on October 16, 2014 by David Posluszny in Guest Blogs

Recently I designed and built my home in Shirley, Massachusetts. The design goal was to build a net-zero-energy house. However, it had to be comfortable to live in, easy to build with low-skilled labor, and very affordable.

I had to keep it simple because I had my family for laborers, and they do not have construction skills. The home also had to be comfortable to live in, with adequate daylightingUse of sunlight for daytime lighting needs. Daylighting strategies include solar orientation of windows as well as the use of skylights, clerestory windows, solar tubes, reflective surfaces, and interior glazing to allow light to move through a structure. and easy circulation. The budget demanded that the house be kept small, but several design tricks involving lines of sight were used to make the space feel much larger than it actually is.

The Diminishing Returns of Adding Insulation

Posted on October 15, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

If you're building a house and want to have a really good building enclosure, you need it to be airtight, handle moisture properly, and have a good amount of insulation. Ideally, you'd also consider the effects of solar radiation on the home, but for now let's just focus on the insulation. What exactly is "a good amount" anyway?

Living in a Passivhaus

Posted on October 14, 2014 by Daniel Roy in Guest Blogs

[Editor's note: Daniel Roy is one of the owners of a recently completed 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. in Falmouth, Massachusetts. Designed by architect Steve Baczek, the house was featured in a series of GBA videos. For more information on the home's energy specifications, see the attached Excel spreadsheet.]

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