Building Science

Air Flow Pathways in a Leaky Exterior Wall

Posted on June 1, 2016 by Allison A. Bailes III, PhD, GBA Advisor

This spring I spent a lot of hours in my bathroom. I was sick. Really. I was sick and tired of having an outdated bathroom that was falling apart. So when my wife hit the road one Monday in late April to drive across the country, I got out my wrecking bar. The lead photo shows what it looked like at the end of my first full day of demolition.

I opened up the plumbing wall first. Lots of fun stuff, there. But the real fun came when I opened up the exterior wall. The four termite-damaged studs were part of that fun, but something else was even better.

Five Types of R-Value

Posted on May 18, 2016 by Allison A. Bailes III, PhD, GBA Advisor

We talk about R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. all the time. "I've got an R-19 wall," or "Code requires R-38 in my ceiling." But what are those numbers? As it turns out, when we talk about R-value we usually give the R-value of the insulation material itself. That's the case with both of those statements above. But what's the real R-value of the wall or the ceiling? Insulation makes up only a part of each. There's also wood and drywall and 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. and claddingMaterials used on the roof and walls to enclose a house, providing protection against weather. and...

The Water Efficiency Rating Score (WERS)

Posted on May 4, 2016 by Allison A. Bailes III, PhD, GBA Advisor

The Green Builder Coalition has been working hard on their Water Efficiency Rating Score — the WERS — for homes. The inaugural WERS training happened in Santa Fe, New Mexico, in March. I was in that class, and I learned a lot.

The program has been in development for the past couple of years. Now it's ready for prime time.

More About Global Warming and Insulation

Posted on April 20, 2016 by Allison A. Bailes III, PhD, GBA Advisor

Well, I really stirred things up with my last article on insulation and global warming. My intention was to explain why Alex Wilson's results could be doing a disservice to the green building community. In the end, I was rightly accused of have done a disservice myself.

So, here goes with Part Three of my take on the global warming impact of insulation. Let's see if I can get closer to the truth this time.

Can Your Water-Resistive Barrier Take UV Exposure?

Posted on April 6, 2016 by Allison A. Bailes III, PhD, GBA Advisor

A water-resistive barrierSometimes also called the weather-resistive barrier, this layer of any wall assembly is the material interior to the wall cladding that forms a secondary drainage plane for liquid water that makes it past the cladding. This layer can be building paper, housewrap, or even a fluid-applied material. (WRB) provides protection against water damage for water that gets behind the claddingMaterials used on the roof and walls to enclose a house, providing protection against weather. of a building. But what if it doesn't really resist water? I've written a lot about installation problems that can lead to compromised water resistance. (See the article I wrote last week, for example.) But other factors can make them leaky, too. Too much exposure to ultraviolet (UV) light is one of them.

The BTU-tiful History of the BTU

Posted on March 23, 2016 by Allison A. Bailes III, PhD, GBA Advisor

Every year on New Year's Eve, I head over to some friends' house here in the Atlanta area. They have the best party around — Possum Drop — and I've been going for nearly a decade now. As midnight approaches, the newly-crowned Possum Queen leads the countdown. The possum is lowered slowly onto the fire and then erupts in an explosion flames and sparks.

Don't worry. It’s not a real live possum. It's a giant possum made of chicken wire, papier-mâché, fabric, and other scavenged materials... and it's stuffed full of fireworks!

The Misleading Numbers Behind the Global Warming Impact of Insulation

Posted on March 9, 2016 by Allison A. Bailes III, PhD, GBA Advisor

I've been reading a lot of BS lately. No, I'm not talking about blood sugar. It's brain science that's captured my attention: understanding how the human brain works, why we do the things we do, and what common illusions often lead us astray.

What I want to talk to you about today, though, is foam insulation and global warming. But first, we have to talk about calamari.

What Is the Ideal Relative Humidity in Winter?

Posted on February 24, 2016 by Allison A. Bailes III, PhD, GBA Advisor

It was a little crackly around here recently. We had a cold spell in Atlanta, with high temperatures right around the freezing point. As a result, the indoor relative humidity dropped and we got some static electricity.

Even better, what I call the Southern Lights were visible at night, too. (I've never called it that before, but hey, a man named Allison is entitled to make things up on the spot.) That's when the microfiber blanket on the bed lights up every time I move.

Unvented Gas Appliance Industry Fails to Impress ASHRAE

Posted on February 10, 2016 by Allison A. Bailes III, PhD, GBA Advisor

Unvented combustion appliances were added to the scope of ASHRAEAmerican Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). International organization dedicated to the advancement of heating, ventilation, air conditioning, and refrigeration through research, standards writing, publishing, and continuing education. Membership is open to anyone in the HVAC&R field; the organization has about 50,000 members. 's residential ventilation and IAQIndoor air quality. Healthfulness of an interior environment; IAQ is affected by such factors as moisture and mold, emissions of volatile organic compounds from paints and finishes, formaldehyde emissions from cabinets, and ventilation effectiveness. standard (standard 62.2) recently. The committee has begun their deliberations on the issue, and at ASHRAE's winter meeting in Orlando last month, the unvented gas appliance industry folks attempted a defense of their products. Based on the results they presented and the reaction from most committee members, I'd say they failed.

Don’t Let Your Garage Make You Sick

Posted on January 27, 2016 by Allison A. Bailes III, PhD, GBA Advisor

The odds are high that the indoor air quality is worse in a home with an attached garage than in a home without one. Just take a look at the photo here to see some of the potential sources of pollutants that can get into your home's air. How many do you see?

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