Building Science

The RESNET Standard Becomes the New Ventilation Battleground

Posted on July 27, 2016 by Allison A. Bailes III, PhD

Just because I haven't written about the jockeying over ventilation rates and strategies with 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. committee doesn't mean nothing's going on. If you've been following the battle over this issue, you know that Joe Lstiburek, PhD, PE, got fed up with 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. and introduced his own ventilation "standard" in 2013. Then the "Great Ventilation Debate" happened in Detroit, and he got back on the ASHRAE 62.2 committee.

Stuff happened and now RESNET just put an interesting amendment out for public comment. Follow that?

From Superinsulation to Passive House, With a Trip Across the Pond

Posted on July 13, 2016 by Allison A. Bailes III, PhD

In 2002, Katrin Klingenberg introduced 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. program to North America when she built the Smith House in Urbana, Illinois. She had come to the U.S. from Germany, where she studied architecture and got involved with Passivhaus. But is this really where it all began?

Complex Three-Dimensional Air Flow Networks

Posted on June 29, 2016 by Allison A. Bailes III, PhD

A lot of discoveries and research work over the past four decades have ledLight-emitting diode. Illumination technology that produces light by running electrical current through a semiconductor diode. LED lamps are much longer lasting and much more energy efficient than incandescent lamps; unlike fluorescent lamps, LED lamps do not contain mercury and can be readily dimmed. to our current understanding of air leakage in buildings. I’ll mention a few here, but I want to focus on one: the MAD AIR paper by John Tooley and Neil Moyer. The full title of the paper was, Mechanical Air Distribution And Interacting Relationships. The first letters of those words spell out MAD AIR.

How I Fixed My Leaky, Underinsulated Exterior Wall

Posted on June 15, 2016 by Allison A. Bailes III, PhD

When I began remodeling my master bathroom last month, I found the exterior wall ripe for some serious improvement. It had a number of problems, and I was excited to find them.

It was worse than I imagined in some ways. The photo at right shows the wall partially opened up.

Air Flow Pathways in a Leaky Exterior Wall

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

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

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

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

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

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

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!

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