Building Science

Using Rooftop Solar to Meet the Energy Code

Posted on November 9, 2016 by Allison A. Bailes III, PhD

Supply and demand are two different things. When you think of an energy code, say the International Energy Conservation Code (IECC International Energy Conservation Code.), you probably think of demand, not supply. Conserving energy, after all, means reducing demand. It's related to supply only indirectly.

As a result, you might expect an energy conservation code to have requirements that affect only the demand side of the equation. With the 2015 IECC, however, that's not true anymore.

High Humidity in Spray Foam Attics

Posted on October 26, 2016 by Allison A. Bailes III, PhD

I recently investigated an attic with spray foam insulation where we observed an interesting humidity pattern. We placed data loggers near the ridge and floor of the attic as well as in the living space and outdoors.

The graph at below shows dew point data for the four locations. The really interesting part is the big difference in dew point between the highest and lowest points in the attic, shown by the red and green curves in the graph.

Building Science Puzzles: The Jigsaw Approach

Posted on October 20, 2016 by Peter Yost

Just about every week, I get a call or an email that turns into a building science puzzle. While the problems are varied, how you solve them doesn’t change.

First, you understand how heat and moisture move through building assemblies. Second, you follow the advice of your spouse.

My wife of 27 years is a real master at jigsaw puzzles, and she would laugh to learn that I think of myself as a puzzle master of any sort, since I am useless at the jigsaw ones. But she completely agrees that I should use her method of solving jigsaw puzzles in my work on building science problems.

Buildings Don’t Need to Breathe

Posted on October 19, 2016 by Allison A. Bailes III, PhD

Breathe. It's a good thing. We need to breathe to live. Breathing consciously relaxes us. “Breathe” is also the name of a great song by Pink Floyd from the Dark Side of the Moon album.

Breathe, breathe in the air
Don't be afraid to care
Leave but don't leave me
Look around and choose your own ground.

Breathing is required of many life forms. But when it comes to buildings, all this talk of breathing is just confusing.

Does Cheaper Solar Mean We Can Forget Efficiency?

Posted on October 12, 2016 by Allison A. Bailes III, PhD

Solar energy has sex appeal. If you want to show the world you're doing something to reduce pollution, you put photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. (PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow.) panels on your roof to generate clean electricity. Even better, you drive a plug-in hybrid or an all-electric car and charge your car's batteries with your clean solar electricity.

The good news for solar enthusiasts is the cost of installing a solar electric system on your home just keeps falling and falling. Let's take a look at some data and then ask if it’s time to abandon energy efficiency.

Installing an Exhaust Fan During a Bathroom Remodel

Posted on September 28, 2016 by Allison A. Bailes III, PhD

Remember my bathroom remodeling project? I took the liberty of gutting our outdated, decaying bathroom while my wife was out of town in April. I found some interesting air leakage pathways when I opened the walls. I fixed that. I found termite damage. I fixed that.

Our 1970 condo didn't have an exhaust fan in this bathroom because, hey, who needs a bath fan when you have a window? I fixed that. Here's how.

How Dirty Is Your Electricity?

Posted on September 21, 2016 by Allison A. Bailes III, PhD

Lately I've been working on my presentation for the 10th anniversary of the North American Passive House Conference. It's on the global warming impact of insulation, a followup to my latest article about Alex Wilson's work on that subject.

Manual J Load Calculations vs. Rules of Thumb

Posted on September 7, 2016 by Allison A. Bailes III, PhD

We do a lot of heating and air conditioning system design at Energy Vanguard. Alexander Bell, who goes by Andy, is our design wizard, and I've been getting involved with the process again lately.

Seven Reasons to Gut Your Aging Bathroom

Posted on August 24, 2016 by Allison A. Bailes III, PhD

If your home is old enough for a bathroom renovation, you may want to go ahead and completely gut it. I remodeled my bathroom this year and began with a complete demolition. If I hadn't, a number of problems would have been unavailable for repair... or even undiscovered.

Here's what I found when I opened up the walls and ceiling of my 1970 condo in the Atlanta, Georgia area.

Three Reasons to Remove Attic Floor Insulation in a Sealed Attic

Posted on August 10, 2016 by Allison A. Bailes III, PhD

I get asked a lot of questions about spray foam. Do I need an ignition barrier? Should I use open-cell or closed-cell spray foam? Will open-cell spray foam really rot my roof?

But the question I get more than any other on this topic is about whether or not the insulation on the attic floor should be removed when insulating the roof deck in an existing home. As you can tell from the title of this article, my answer is to remove it. Here are my three reasons, in increasing order of importance.

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