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Building Science

How to Become a Building Enclosure Control Freak

The fundamentals of controlling heat, air, and moisture

Frank Lloyd Wright was a control freak, and not always in a good way. To become a building enclosure control freak, you need to understand how to control the flows of heat, air, and moisture.
Image Credit: Wikimedia Commons

Frank Lloyd Wright was a control freak. This was a guy who not only designed houses but also all of the trim details and even the furniture.

No, you’re right. That’s not really enough evidence to convict him. The really damning part is that he also placed the furniture exactly where he wanted it in the homes he designed… and expected you to keep it there! If you owned one of his homes, you better hope he never visited and found the furniture out of place. If so, you’d get a good scolding. Then he’d put the furniture back where it was supposed to go. Control freak!

Sadly, his personal life was a mess, and his control didn’t extend to some areas where it would have helped more than in the placement of furniture, but let’s focus simply on the idea of control for now. If you design, build, inspect, rate, or verify buildings, I want you to be a control freak, too. Not about furniture — about control layers.

One of the biggest knowledge gaps I see in the world of building is the understanding of the properties and uses of the various materials used in building homes. For example, I ask this question a lot in our classes and when I speak: What is the purpose of housewrap?

I usually get told that it’s an air barrier or a vapor barrier. I rarely get told what it’s really for. It’s one material you can use as a really important control layer in the building enclosure. But what’s it supposed to control?

Become a control freak.

Here’s what you want to control in a building:

Understand also that controlling doesn’t necessarily mean stopping. Let’s take a look at…

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One Comment

  1. User avater
    Dana Dorsett | | #1

    But SOME housewraps are class-III vapor retarders...
    "A lot of people think housewrap is a vapor barrier. Guess what? It's not even close! It's got a permeance well outside the range of even a Class III vapor retarder."

    An exception to prove the rule: DOW Weathermate Plus, which only guarantees a minimum permeance of above 5 perms (comparable to #15 felt), well within the Class-III vapor retarder definition. It's potentially as vapor tight as interior latex paint.

    http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_08f1/0901b803808f1e34.pdf

    Typar is 11.7 perms nominal (not min), just above the arbitrary 10 perm definition of Class-III vapor retardency. (I'm sure there are real-world samples that would test a hair under 10 perms.) That's almost a Class-III vapor retarder even at the nominal number.

    http://www.typar.com/assets/downloads/pdf/TYPAR_Housewrap_Typical_Char-PGI.pdf

    Most others are well north of 20 perms, and well outside the Class-III range.

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