The most recent blogs at Green Building Advisor

Battling Condensation on Attic Ducts

Posted on September 28, 2015 by Scott Gibson in Q&A Spotlight

Jimmy Miller is trying to solve a condensation mystery in a Florida ranch-style home that is being renovated. Even though the air conditioning equipment appears to be operating normally, humidity inside the house is between 60% and 65%, and return ducts located in the attic show significant condensation.

Air Leakage Through Spray Polyurethane Foam

Posted on September 25, 2015 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Many builders use spray polyurethane foam 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., raising the question: How thick does the spray foam layer have to be to stop air flow? There's a follow-up question, of course: Is the answer different for open-cell spray foam than for closed-cell spray foam?

As with most building science questions, there is a short answer and a long answer. The short answer is that closed-cell spray foam needs to be at least 1 or 1.5 inch thick to act as an air barrier, while open-cell spray foam needs to be between 3.0 and 5.5 inches thick to act as an air barrier.

In Clash of Greens, a Case for Large-Scale Solar

Posted on September 24, 2015 by Philip Warburg in Guest Blogs

If the United States and the world community hope to avoid the worst effects of climate change, solar power will have to play a pivotal role in electricity production. The technology is quickly maturing, and the price of solar panels has plummeted to the point where new utility-scale solar installations are a sound investment, cheaper than new coal plants and frequently competitive with natural gas.

How to Become a Building Enclosure Control Freak

Posted on September 23, 2015 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Frank Lloyd Wright was a control freak. This was a guy who not only designed houses but also all of the trim details and even the furniture.

Undamming Rivers Could Make Room for PV

Posted on September 22, 2015 by Karin Limburg and John Waldman in Guest Blogs

Hydroelectric power is often touted as clean energy, but this claim is true only in the narrow sense of not causing air pollution. In many places, such as the U.S. East Coast, hydroelectric dams have damaged the ecological integrity of nearly every major river and have decimated runs of migratory fish.

Solar Decathlon: The Search for the Best Carbon-Neutral House

Posted on September 21, 2015 by Crystal Gammon in Guest Blogs

What’s the latest in well-designed, energy-efficient solar homes? The U.S. Department of Energy (DOEUnited States Department of Energy.) has invited teams from colleges across the country to design and build solar-powered houses that are cost-effective, energy-efficient, and attractive.

Quality Issues With Brick Buildings

Posted on September 18, 2015 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

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.

Ventilation for Your Tight House — Part 2

Posted on September 17, 2015 by Christopher Briley in Green Architects' Lounge

Our conversation with Sonia Barrantes continues. (If you missed it, here is a link to Ventilation for Your Tight House — Part 1.)

We've come to realize that we all want simple rules of thumb to guide our design process. Unfortunately, there isn't a rule of thumb for everything and we're going to have to rely on some common sense, good advice, and good old-fashioned engineering to get this balanced ventilationMechanical ventilation system in which separate, balanced fans exhaust stale indoor air and bring in fresh outdoor air in equal amounts; often includes heat recovery or heat and moisture recovery (see heat-recovery ventilator and energy-recovery ventilator). system right.

Our cocktails are refreshed and we're ready to go.

The Science of Air Flow in Flex Duct

Posted on September 16, 2015 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Sagging flex duct is bad for air flow. We all know it. We all talk about it. It turns out there's research data to prove it, too. Texas A&M did a study a few years ago to look at the pressure drop that occurs for different levels of compression. If you're not familiar with this study, the results may astound you.

Building a Small House in the White Mountains

Posted on September 15, 2015 by Brian Post in Guest Blogs

Editor's note: This is the first in a series of blogs chronicling the design and construction of a house owned by Brian Post and Kyra Salancy.

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