Building Science

What Happens When You Put a Plastic Vapor Barrier in Your Wall?

Posted on April 30, 2014 by Allison A. Bailes III, PhD, GBA Advisor

A lot of people have heard advice about vapor barriers and vapor retarders. Many of them have walked away confused. A big part of the problem, I think, is that they've been told what to do — "Put it on the warm-in-winter side," or "Never use one" — but they haven't had the physics of what happens explained to them.

Does Open-Cell Spray Foam Really Rot Roofs?

Posted on April 23, 2014 by Allison A. Bailes III, PhD, GBA Advisor

Murmurs and hearsay about open-cell spray foam insulation have been gaining traction for a while. It rots roofs, people have told me. Not long ago, someone even told me that in Florida, roofing companies won't let their workers go up on roofs with open-cell spray foam because the roofs are so spongy, the guys fall right through.

Open-cell spray foam is getting a bad reputation among some people in the construction industry. But is it deserved?

How to Detect an Internet Solar Energy Scam

Posted on April 16, 2014 by Allison A. Bailes III, PhD, GBA Advisor

All I was trying to do was find some sports scores on Yahoo the other day when I saw it. I don't go looking for this stuff, and when I do see it, I try to ignore it. But this one clotheslined me with an unfair term.

That's the ad in question to the right. Have you seen it? I probably shouldn't tell you the name of the website (, but the kryptonite term that made my fingers go apoplectic was “free energy.” Seeing it capitalized intensified the effect. And the photo! Is that a diseased wireless router robot surrendering its secrets to me?

Four Ways Bad Duct Systems Can Lead to Poor Indoor Air Quality

Posted on April 9, 2014 by Allison A. Bailes III, PhD, GBA Advisor

Indoor air quality (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.) is a big deal. It doesn't get nearly as much attention as energy efficiency or green building programs, but it should be one of the highest priorities for anyone who breathes air and spends time indoors.

It's actually part of an even bigger deal called indoor environmental quality (IEQ), but I'm just going to focus on IAQ here as I show you four ways your ducts might be hurting your indoor air quality.

A Classic 1970s Home Goes from Solar-Heated to Net Zero Energy

Posted on April 2, 2014 by Allison A. Bailes III, PhD, GBA Advisor

Last week I was in Lexington, Kentucky speaking at the Midwest Residential Energy Conference. It was a great regional conference, and the folks there are making things happen. (I even played nice. With all those Kentucky Wildcat fans there, I held back and didn't mention in any of my talks that I'm a Florida Gator.) One of the many highlights for me was getting to visit Richard Levine’s 1970s active solar house. It stands out like no other house I've seen, and I've seen other solar houses.

An Interview with Dr. Iain Walker on Ventilation

Posted on March 26, 2014 by Allison A. Bailes III, PhD, GBA Advisor

The debate over how much to ventilate a home has been going on a long time. Last year, Building Science Corporation introduced its own standard to compete against 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. because (according to Dr. Joseph Lstiburek) of problems that weren't adequately addressed in the 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. standard. I've written about the standard and interviewed Lstiburek and ASHRAE 62.2 committee chair Paul Francisco. (See links at bottom.)

Induction Cooktops, Steve Jobs, and a Lone Nut Dancing

Posted on March 19, 2014 by Allison A. Bailes III, PhD, GBA Advisor

Last Friday was Pi Day, named for that special number, 3.14159265358979323846264338327950288...

The three dots at the end mean that I've exhausted my memory of the digits of pi, but pi doesn't care. It just goes on and on. Anyway, Pi Day is a perfect day for a physics lesson because so many physics equations (and solutions) use that special number. And what better physics lesson for Pi Day than one about a device that cooks yummy things for us!

New Englanders Love Heat Pumps

Posted on March 12, 2014 by Allison A. Bailes III, PhD, GBA Advisor

Last week I went to NESEA's Building Energy conference, and I think I heard three terms more than any others: heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump., net zeroProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. Calculating net-zero energy can be difficult, particularly in grid-tied renewable energy systems, because of transmission losses in power lines and other considerations., and 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.. (The second most popular trio was beer, wine, and whisky, but that may have something to do with the folks I was hanging out with.)

So let's get right to the important question here: Why do these people in the cold climate of New England love heat pumps so much?

How to Make Your Dumb Heat Pump Defrost Intelligent

Posted on March 5, 2014 by Allison A. Bailes III, PhD, GBA Advisor

Heat pumps can get frosty when they run in heating mode. It doesn't happen all that often, but it's a fact of life when you're trying to extract heat from cold, outdoor air.

Do Combustion Safety Testing Protocols Need Fixing?

Posted on February 26, 2014 by Allison A. Bailes III, PhD, GBA Advisor

Burning fuels inside a house can lead to serious health and safety problems. That's why energy auditors perform a variety of combustion safety tests to find potential hazards and recommend fixes.

A couple of weeks ago at the Dry Climate Forum, I heard Vi Rapp, PhD, from Lawrence Berkeley National Lab (LBNL) make an argument for changing the way we do combustion safety testing. It turns out that one of the tests we do may not be as helpful as many people think it is.

Register for a free account and join the conversation

Get a free account and join the conversation!
Become a GBA PRO!

Syndicate content