Building Science

Air Leaks Happen at the Surface, Not in the Volume

Posted on December 5, 2012 by Allison A. Bailes III, PhD, GBA Advisor

During the Westford Symposium on Building Science in 2010,* I was watching the tweets from the people who were there. At one point, I saw this one: “@EFL_Guy: ‘Air leaks through surfaces, not volume’ Joe Lstiburek.” I'd been meaning to blog about this issue for a while, so I wrote an article about it. Now, a couple of years later, it's time for a little update.

Should Flex Duct Be Banned?

Posted on November 28, 2012 by Allison A. Bailes III, PhD, GBA Advisor

Ah, flex duct. That bane of home performance contractors and green builders everywhere. If you’ve seen only one forced-air duct system that uses flex, you’ve most likely seen a bad installation.

‘Building Enclosure,’ Not ‘Building Envelope’

Posted on November 21, 2012 by Allison A. Bailes III, PhD, GBA Advisor

When I wrote about the debate over the terms “building envelope” vs. “building enclosure” recently, I favored the former but overall felt agnostic on whether we should choose one over the other. I didn't think I'd change my mind.

Location Efficiency Trumps Home Energy Efficiency

Posted on November 5, 2012 by Allison A. Bailes III, PhD, GBA Advisor

My last article here at Green Building Advisor was about my perception that the USGBC is out of touch. Apparently, quite a few others feel similarly, including many who work in the program.

Why Is the U.S. Green Building Council So Out of Touch?

Posted on October 29, 2012 by Allison A. Bailes III, PhD, GBA Advisor

Yesterday I read a short interview with Rick Fedrizzi,* the CEO of the U.S. Green Building Council (USGBC), and it got me to thinking about that organization. They're probably the largest, most well known green building organization in the world.

Why Don’t More HVAC Contractors Own Duct Leakage Testers?

Posted on October 22, 2012 by Allison A. Bailes III, PhD, GBA Advisor

HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. contractors own a lot of equipment. Of course, they have pressure gauges to test refrigerant charge in air conditioners and heat pumps, and many more pieces of technical equipment. One piece that few contractors own, however, is a duct leakage tester.

With more and more state energy codes requiring duct leakage tests, doesn't it seem obvious that HVAC contractors need to be like plumbers and test their own work before passing it off?

Joseph Lstiburek Surprises Passive House Conference Attendees

Posted on October 4, 2012 by Allison A. Bailes III, PhD, GBA Advisor

At the 2012 Passive HouseA 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. Conference in Denver, Dr. Joseph Lstiburek gave the keynote address for the opening plenary (or plenum, as Henry Gifford would say) session. His words, clever as always, added some nice historical perspective to what the Passive House folks are doing but also caught some people off guard.

Read on, and I'll tell you more about that.

Raining, Dripping, Crying Duct Boots

Posted on September 25, 2012 by Allison A. Bailes III, PhD, GBA Advisor

I've seen it over and over: The central air conditioner's ceiling registers raining down onto the floor. The insulation liner on the duct in the crawl space holding a gallon or two of water. The office that has spots appearing on the ceiling. Such problems are not at all uncommon, although they should be.

The Loophole and the Ozone Hole

Posted on September 5, 2012 by Allison A. Bailes III, PhD, GBA Advisor

Holes are generally bad things. Those of us who teach building science spend a lot of time showing people how to measure the effects of holes, how to seal them up, and why they’re bad in the first place. That’s not universally true, of course. Some holes we do want, but we also want to be able to control what happens in those holes, as with a door or window.

Grading the Installation Quality of Insulation

Posted on August 27, 2012 by Allison A. Bailes III, PhD, GBA Advisor

Six years ago, RESNET published a major revision of the HERSIndex or scoring system for energy efficiency established by the Residential Energy Services Network (RESNET) that compares a given home to a Home Energy Rating System (HERS) Reference Home based on the 2006 International Energy Conservation Code. A home matching the reference home has a HERS Index of 100. The lower a home’s HERS Index, the more energy efficient it is. A typical existing home has a HERS Index of 130; a net zero energy home has a HERS Index of 0. Older versions of the HERS index were based on a scale that was largely just the opposite in structure--a HERS rating of 100 represented a net zero energy home, while the reference home had a score of 80. There are issues that complicate converting old to new or new to old scores, but the basic formula is: New HERS index = (100 - Old HERS score) * 5. Standards, officially named the 2006 Mortgage Industry National Home Energy Rating Systems Standards. One important new feature in the standards was the grading of insulation installation quality. Before this change, R-13 insulation installed poorly (as shown in the second photo, below) was equivalent to any other R-13 insulation, including insulation with impeccable installation quality (as shown at the top of this article).

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