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Building Science

My Top 10 Building Science and Energy Efficiency Ideas of 2015

A year-end review of the articles and ideas that made me think

This duct monster was one of the highlights of my year. I get to see a lot of spectacularly bad duct systems in my work, and this was one of the worst.
Image Credit: Energy Vanguard

The year 2015 is almost finished. I’ve written 70 articles in the Energy Vanguard Blog and this one makes 49 here at GBA. I’ve been to a bunch of conferences and talked to a lot of people. A lot of thoughts about building science, energy efficiency, indoor air quality, and more have gone through my head. (Not to mention all the thoughts about skiing, Little Baby’s Ice Cream, and those things that I never let out of the confines of my skull!)

As I sit here at the end of the year looking back on all of it, here’s what I see as the best and most interesting stuff I’ve written and thought about.

10. My New Favorite Duct Disaster

Of course, there’s always the fun stuff like this absolute monster of a duct system. And I don’t mean that in a good way. The photo above shows part of it, but if you click the link above, you’ll see a bit more.

9. The Layers and Pathways of Heat Flow

I’ve been teaching this stuff in classes for years, and this year I finally wrote it up for public consumption. Combine this with some of my other articles—like the one about the mind-blowing hole in your building enclosure and the one about flat vs. lumpy insulation — and you’ll have a good understanding of insulation and heat flow.

8. California Mistakes Put Spray Foam Insulation on the ‘Bad List’

Oh, California. There may be good reasons to be cautious about spray foam, but you sure didn’t get this one right. The official recommendation was to include spray polyurethane foam (SPF) insulation in the first three Priority Products in the Safer Consumer Products Program.

7. Introduction to the Physics of Water in Porous Materials

Joe Lstiburek teaches this stuff in his two-day Building Science Fundamentals classes, and I’ve seen versions of it in some of his presentations. It’s also really important stuff that can help you understand how to protect buildings from those three things that cause the most problems in buildings: water, water, and water. (That’s from the late Gus Handegord, a Canadian building scientist.)

6. Green Builder Coalition’s WERS – Water Efficiency Rating Score

And speaking of water, it’s kind of important to everything we do. In fact, it’s right up there with energy. The Green Builder Coalition has been working for nearly two years to put together a program similar to home energy ratings but based on water efficiency. (RESNET’s working on a similar program, but GBC’s program is already out there and getting some traction.) New Mexico is already implementing the program, and you can read about it in this article.

5. Nest Thermostat Data Unveiled at ACI Conference

Michael Blasnik got permission to share some of the data that all those Nest thermostats have been collecting for the past few years. The room was packed. Blasnik had a multitude of charts. The data did not disappoint. Click above to read all about it.

4. Winterizing Your Home? Don’t Caulk the Windows!

Every fall I have to write about this topic, it seems, as the media trot out their silly advice about caulking your windows and weatherstripping your doors. This article, I believe, is the best one I’ve written on the topic. Be sure to read the followup article I wrote, too: Winterizing Tips That Work.

3. Is This the End of the Double-Wall, Cold Sheathing Scare?

Vapor diffusion is, Martin Holladay says, the bogeyman of building science. It’s been the source of a lot of confusion and misinformation and is rarely the source of moisture problems. With thick walls packed with vapor permeable insulation, however, it can be a problem. In a study from Building Science Corporation, the exterior sheathing of a home with double-stud walls got wet because of vapor diffusion. This was my article explaining their study, in case you don’t want to read the whole 72 page paper yourself.

2. Electricity Demand and the Duck Curve

I ate duck a couple of nights ago. The “duck curve” has nothing to do with real ducks. It has to do with electricity production and use and the shape of a utility company’s load profile throughout the day. It has to do with the increasing amounts of solar electricity in the mix. It has to do with problems that occur when utilities have to ramp up more quickly than is possible as the sun goes down.

And it could be hitting your state already.

1. The evolution of “smart”

What’s happening with the electricity grid is part of this, but the thing that really captured my attention this year was self-driving cars. It started when I listened to an episode of my favorite podcast, 99 Percent Invisible, called Johnnycab (Automation Paradox, pt. 2).

In that podcast, Roman Mars talked about cars that would do the driving for us, of course, but the bigger idea was getting to the point where we don’t need to own cars anymore. We just call for a self-driving car when we need one. And when all the cars on the road are self-driving, we’ll be able to reduce lane size because they’ll be programmed with great precision to avoid each other. The name of that episode also hints to a darker side. Johnnycab was the name of the robot-driven taxis in the Arnold Schwarzenegger movie Total Recall — but hey, let’s focus on the positive here.

I heard of a similar idea on another podcast, The Unconventionals. There’s a company named Bridj in Boston, and they’re somewhere between a taxi and a bus, but optimized with big data on traffic patterns and the movement of people from one place to another. You should check it out. There’s some really cool stuff happening out there that’s changing the world.

Allison Bailes of Decatur, Georgia, is a speaker, writer, energy consultant, RESNET-certified trainer, and the author of the Energy Vanguard Blog. Check out his in-depth course, Mastering Building Science at Heatspring Learning Institute, and follow him on Twitter at @EnergyVanguard.


  1. James Morgan | | #1

    Duct disaster - Carolina style
    Come across this in a first floor closet yesterday. That's the supply duct to the 2nd floor on the right, the return on the left. Homeowners were telling me their 2nd floor heating and air was not delivering the goods, and they'd never needed to change the filter on the 2nd floor return. I wonder why.

  2. GBA Editor
    Martin Holladay | | #2

    Response to James Morgan
    Don't you just love those tiny utility closets!

  3. John Semmelhack | | #3

    About #7...
    ...the list I've heard of the things that cause the most problems in buildings is a little different...

    1) Water
    2) Rain

    3) Moisture

    Merry New Year!

  4. Dan Kolbert | | #4

    As a fierce advocate of double wall construction, I have a similar take on the cold sheathing "problem." I call it the Yeti of building science - much discussed, rarely seen.

  5. Aj Builder, Upstate NY Zone 6a | | #5

    I'm leaning toward using
    I'm leaning toward using pressure treated (PT) plates in future wall framing. that and Iinsulated Zip sheathing would make a wall framing very resistant to seasonal moisture. All the old decks and docks rot at wood junctures. But rot much less when one of the touching components is PT. And why not PT exterior studs?

    Joe L. experiment with my ideas... Dan.... moist foam doesn't ror nor does PT...

    Martin, cell browser opened this blog... any Prime member deals this year?

  6. James Morgan | | #6

    The ultimate head scratchers about this arrangement are 1) as the closet doors were solid and fairly tight fitting the auxiliary return register which causes the congestion at the bottom of the closet was pretty much nonfunctional, and 2) if this useless item were not in the way there would actually be ample room for two properly sized hard ducts. Good news is the whole mess is coming out as part of a remodel.

  7. GBA Editor
    Martin Holladay | | #7

    Response to AJ Builder
    Q. "Any Prime member deals this year?"

    A. Not that I know of. GBA Prime membership costs $14.95 per month or $149.95 per year. Here is the link to sign up: GBA sign up page.

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