Building Science

The Ventilation Omission That Can Make You Sweat

Posted on October 23, 2013 by Allison A. Bailes III, PhD, GBA Advisor

If you're designing a ventilation system, first you have to determine how much outdoor air the house needs. You can use the ASHRAE 62.2A standard for residential mechanical ventilation systems established by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. Among other requirements, the standard requires a home to have a mechanical ventilation system capable of ventilating at a rate of 1 cfm for every 100 square feet of occupiable space plus 7.5 cfm per occupant. standard or the new BSC-01 standard for that task. Then you have to decide what type of ventilation system to use: positive pressure, negative pressure, or balanced. In many green homes, the balanced system is becoming a popular choice.

The Lipstick-on-a-Pig Million-Dollar Home Syndrome

Posted on October 16, 2013 by Allison A. Bailes III, PhD, GBA Advisor

I wonder about a lot of things. I wonder what life would be like if gravity were stronger. I wonder why Americans don't dance more. I wonder why so many people who can afford million-dollar homes get cheapo HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. systems. That last one bugs me more more than the first two, by the way. It weighs on my mind because cheapo HVAC seems so out of step with the rest of a million-dollar home.

When You’re Financing a Green Home, Payback Is Irrelevant

Posted on October 9, 2013 by Allison A. Bailes III, PhD, GBA Advisor

If you're buying a green home or investing in energy efficiency improvements for your existing home, calculating the simple payback for your investment is at best incomplete and at worst, completely irrelevant. Before I get to the reasons why payback isn't the right way to look at home energy efficiency improvements, let's define simple payback.

Five Ways to Deal with Crawl Space Air

Posted on October 2, 2013 by Allison A. Bailes III, PhD, GBA Advisor

If you have a home with a crawl space — or are building or buying one — you have several options on what to do with that particular foundation type. Most crawl spaces are vented to the outdoors, but over the past decade, encapsulating the crawl space (as shown in the photo here) has gained favor among builders of green and energy efficient homes. It's often seen as the best way to eliminate the moisture problems that often result from vented crawl spaces. But what do you do about the air down there?

Is the Passivhaus Program Truly Innovative?

Posted on September 25, 2013 by Allison A. Bailes III, PhD, GBA Advisor

Last month, Joe Lstiburek gave the fifth annual Twitterview from his crawl space. (Peter Troast of Energy Circle has published the transcript of this year’s event.) One of the pearls of wisdom dispensed by Joe was that, “Passivhaus is the only place where real innovation is happening.”

Spray Foam Insulation Does Not Work with All HVAC Systems

Posted on September 18, 2013 by Allison A. Bailes III, PhD, GBA Advisor

Earlier this year I got a question about a home that had spray foam insulation in the attic. There's nothing unusual about that. A lot of builders and homeowners are going with spray foam insulation because of the airtightness benefits.

But then the questioner mentioned that the spray foam contractor had intentionally left big holes to the outside by not sealing the gable vents.

Thou Shalt Commission Thy Ducts!

Posted on September 11, 2013 by Allison A. Bailes III, PhD, GBA Advisor

The typical new home gets a heating and air conditioning system that's about two times too large. I've  discussed oversized air conditioners many times before.

Patent Troll Wins First Case Over Use of Infrared Cameras

Posted on September 4, 2013 by Allison A. Bailes III, PhD, GBA Advisor

A year or two ago, I remember getting trapped in my car one evening listening to Ira Glass's show This American Life. It was an episode titled When Patents Attack, and I was riveted. The show described how a seemingly small change in the U.S. patent office's protocol led to the growth of an industry that siphons money from tech companies through legal, but sketchy, license fees and lawsuits.

A Failure That Stalls the Certification of Many Energy Star Homes

Posted on August 28, 2013 by Allison A. Bailes III, PhD, GBA Advisor

Let me tell you a little story about the day that Jeffrey went to test several Habitat for Humanity houses that are going for certification in the Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. new homes program (the one in the photo here was not one of them). This was a couple of weeks ago, but I wrote down the numbers he told me because I think you may be somewhat surprised.

Solving Comfort Problems Caused by Attic Kneewalls

Posted on August 21, 2013 by Allison A. Bailes III, PhD, GBA Advisor

In Texas, they call them “hot walls.” My friend Mike Barcik likes to say they’re what separate you from the blast furnace. Down here in the warmer climate zones, where attics get up to 8,000°F (well, that may be a slight exaggeration), many people call them a liability. (Sadly, architects haven't gotten the message.)

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