Building Science

How Duct Leakage Steals Twice

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

Duct leakage is a big deal. It's one of the top three energy wasters in most homes (air leakage and cable TV set-top boxes being the other two). The U.S. Department of Energy did a study a few years ago and found that duct systems leak about 40% of the air they're moving. In far more homes than you might suspect, the main culprit is a disconnected duct, as shown in the photo at right, but a typical duct system has a lot of other leaks, too.

Energy Efficiency Requires More Than an App on Your Smartphone

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

When it comes to air conditioning, there are a lot of bad products and bad ideas out there. Here are a few: You can buy a cover for your condenser that could kill your compressor.

Four Ways to Find the Size of Your Air Conditioner

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

Do you know what size your air conditioner is? In the world of building science, you'll hear a lot of talk about why oversized air conditioners are a bad idea. Why? Briefly, they don't dehumidify as well, short-cycling wears them out quicker, and your home will probably be less comfortable if the air conditioner is too big. But to know if your AC is oversized, first you have to know what size it is.

A Blower Door Is the Hydraulic Jack of Building Science

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

Remember the first time you ran a blower door? OK, maybe that's not the best way to get where I'm going because most first-timers turn the pressure up like they're practicing tai chi on Jupiter. After you've done a few tests, though, you learn to crank it up to 50 Pascals of pressure difference in just a few seconds. And that's where you may have discovered the mystery that Blaise Pascal solved nearly four centuries ago when he invented the hydraulic press.

What Architects Need to Know About Attic Kneewalls

Posted on June 25, 2014 by Allison A. Bailes III, PhD, GBA Advisor

We were working on a project, so we got a set of plans to get started. It includes the attic kneewall and vaulted ceiling section you see at right. This is typical of plans that architects draw, and builders build houses this way all the time. Unfortunately, it contains several errors. Can you spot them?

Beware of This Expensive Ventilation Scam

Posted on June 18, 2014 by Allison A. Bailes III, PhD, GBA Advisor

How much does an exhaust fan cost? Search online and you can find lots of them that move 200 cubic feet per minute (cfm) for $100 to $150. But, if you put one in a semi-attractive (emphasis on the "semi") package, create some fancy marketing materials, and target people who don't know much building science, you can charge $1,200 to $1,700 for that same fan. At least that seems to be the business plan for these three companies.

The Two Main Reasons Your Ducts Don’t Move Enough Air

Posted on June 11, 2014 by Allison A. Bailes III, PhD, GBA Advisor

Two things. Just two things in your ducts are responsible for giving the blower in your furnace or air handler a hard time. They make the blower push against more pressure, thus reducing air flow or increasing energy use, depending on blower type. They cut the amount of air that gets delivered to the rooms. And they can be reduced but not eliminated. Do you know what they are?

The Top Two Reasons Powered Attic Ventilators Are a Waste of Money

Posted on June 4, 2014 by Allison A. Bailes III, PhD, GBA Advisor

Three years ago I wrote an article titled, Don’t Let Your Attic Suck: Power Attic Ventilators Are a Bad Idea. Nearly a hundred thousand page views and 93 comments later, it's still generating lots of heat. I don't know why so many people are so defensive about powered attic ventilators (PAVs), but here are a few of the things they've said to me in the comments:

This Heat Pump Problem Is a Surprisingly Common Cause for High Electricity Bills

Posted on May 28, 2014 by Allison A. Bailes III, PhD, GBA Advisor

She lives in a small, simple house in southern Mississippi. It's only 1,700 square feet. Why then, she wondered, were her summer electricity bills running more than $600?

The house didn't have any energy-hog features like a swimming pool, and she didn't do stupid things like leave all the doors and windows open while she ran the air conditioner. What could it be?

California Study Shows Big Savings in Home Energy Retrofits

Posted on May 21, 2014 by Allison A. Bailes III, PhD, GBA Advisor

At the Forum on Dry Climate Home Performance earlier this year, I got to hear three building science experts talk about a really cool research project they've been working on in Stockton, California. Bruce Wilcox, John Proctor, and Rick Chitwood (Wilcox and Proctor are shown in photo at right) filled us in on the Stockton project, which now has two years of data and shows some really impressive results.

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