The most recent blogs at Green Building Advisor

High Humidity in Spray Foam Attics

Posted on October 26, 2016 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

I recently investigated an attic with spray foam insulation where we observed an interesting humidity pattern. We placed data loggers near the ridge and floor of the attic as well as in the living space and outdoors.

The graph at below shows dew point data for the four locations. The really interesting part is the big difference in dew point between the highest and lowest points in the attic, shown by the red and green curves in the graph.

Junk Science and the Heat-Island Effect

Posted on October 25, 2016 by Stuart Kaplow in Guest Blogs

Among the most interesting exhibitors at the GreenBuild International Conference and Expo, an event held in early October in Los Angeles, may have been the Asphalt Pavement Alliance, a group that challenged what we thought we knew about the urban heat-island effect with peer-reviewed research from Arizona State University (ASU).

Is a Ground-Source Heat Pump the Right Choice?

Posted on October 24, 2016 by Scott Gibson in Q&A Spotlight

Ben Rush likes the idea of a ground-source heat pumpHome heating and cooling system that relies on the mass of the earth as the heat source and heat sink. Temperatures underground are relatively constant. Using a ground-source heat pump, heat from fluid circulated through an underground loop is transferred to and/or from the home through a heat exchanger. The energy performance of ground-source heat pumps is usually better than that of air-source heat pumps; ground-source heat pumps also perform better over a wider range of above-ground temperatures., despite their reputation for higher cost than other heating and cooling alternatives.

A ground-source heat pump (GSHPs) requires heat-exchange tubing buried in the ground or inserted in a well or pond. The excavation required to bury the lines (or drill an extra well or two) helps to make GSHPs more expensive than air-source units. In addition, the equipment itself tends to be more costly. In all, GSHPs suffer a significant disadvantage when it comes to cost.

Ventilation Failures and Vocabulary Lessons

Posted on October 21, 2016 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

During the last week of September, I attended the annual conference sponsored by the Energy and Environmental Building Alliance (EEBA). This year’s conference was held in Frisco, Texas.

EEBA was founded in Minnesota in 1982; the original name of the organization was the Energy Efficient Building Association. Thirty-four years later, EEBA is still going strong.

Building Science Puzzles: The Jigsaw Approach

Posted on October 20, 2016 by Peter Yost in Building Science

Just about every week, I get a call or an email that turns into a building science puzzle. While the problems are varied, how you solve them doesn’t change.

First, you understand how heat and moisture move through building assemblies. Second, you follow the advice of your spouse.

My wife of 27 years is a real master at jigsaw puzzles, and she would laugh to learn that I think of myself as a puzzle master of any sort, since I am useless at the jigsaw ones. But she completely agrees that I should use her method of solving jigsaw puzzles in my work on building science problems.

Buildings Don’t Need to Breathe

Posted on October 19, 2016 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Breathe. It's a good thing. We need to breathe to live. Breathing consciously relaxes us. “Breathe” is also the name of a great song by Pink Floyd from the Dark Side of the Moon album.

Breathe, breathe in the air
Don't be afraid to care
Leave but don't leave me
Look around and choose your own ground.

Breathing is required of many life forms. But when it comes to buildings, all this talk of breathing is just confusing.

Relative Humidity and Makeup Air at a Tight Minnesota House

Posted on October 18, 2016 by Elden Lindamood in Guest Blogs

This is the fourth installment of a blog series by architect Elden Lindamood about the design and construction of his own home. The first installment was called A Low-Energy House for Northern Minnesota.

Our All-Renewable Energy Future

Posted on October 17, 2016 by Bronwyn Barry in Guest Blogs

If you’ve been puzzled by the proliferation of "net," "nearly" and "almost ready" zero-energy definitions and standards and have wondered just how net or nearly they truly are, take heart. 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. Institut (PHI) has introduced an equitable assessment of energy use to help guide us toward the 100% renewable energy future we must rapidly achieve.

A Superinsulated House from 1984

Posted on October 14, 2016 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Were the techniques of superinsulation well understood in the early 1980s? The answer depends on who you talk to. Back then, in most areas of the country, residential builders were slapping together leaky homes insulated with thin fiberglass batts. Yet even 35 years ago, a small subset of builders had already adopted superinsulation techniques. In the early 1980s, anyone who was interested in the topic had access to in-depth information on superinsulation details.

Banish ‘Payback’

Posted on October 13, 2016 by Bruce Sullivan in Guest Blogs

Every conversation about zero-energy homes (ZEHs) eventually comes around to the question of “cost.” The negative connotation of added cost and, even worse, “payback,” always puts ZEH advocates at a disadvantage. For years, I’ve encouraged advocates to call energy expenditures investments rather than “costs that must be recovered.” So, let’s banish the entire idea of “payback” and “payback period.”

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