air barrier

Stupid Multifamily Construction Tricks

Posted on March 29,2015 by CarlSeville in air barrier

Although I spent most of my construction career working on single-family homes, the primary subject of this great website, I find that my current work involves primarily multifamily projects — mostly low-rise and mid-rise apartments that are seeking green building certification. In these projects, my partner and I continue to see both new and recurring problems that are not resolved in the design phase, only to be pushed down to the field to be figured out — on a tight budget, in a hurry, and often in the cold or rain.

Is OSB Airtight?

Posted on March 29,2015 by user-756436 in air barrier

UPDATED on December 16, 2014 Most builders assume — and GBA has long reported — that oriented strand board (OSB) is a good air barrier. If a builder uses a high quality tape like Siga Wigluv, Zip System tape, or 3M All Weather flashing tape to seal sheathing seams, OSB wall and roof sheathing can act as a building’s primary air barrier.

The Importance of Defining the Building Enclosure

Posted on March 29,2015 by ab3 in air barrier

The photo at right shows a common problem in new homes. It's also one that can make it difficult to pass the blower door test required by many building codes these days. If I tell you that the wall pictured here separates two rooms in a basement and one of them is not conditioned, can you see the problem? If so, how many mistakes do you see here?

What Architects Need to Know About Attic Kneewalls

Posted on March 29,2015 by ab3 in air barrier

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?

Understanding Air Barriers, Vapor Barriers, and Drainage Planes

Posted on March 29,2015 by ab3 in air barrier

Is housewrap a vapor barrier? What's the purpose of building paper? Who'll stop the rain? I've covered this topic in various forms before, but the confusion about what the different building materials do is so widespread that I have to keep coming back to it. I'm going to keep it simple here so maybe we can get a few more people to use the proper terms, and especially to know when not to use the term “vapor barrier” ... and when not to use it.

A Review of Siga Wigluv Air-Sealing Tape

Posted on March 29,2015 by Matt Risinger in air barrier

Every house needs four control layers. In order of importance, these layers need to provide:

  1. 1. Water control
  2. 2. Air control
  3. 3. Vapor control
  4. 4. Thermal control
The building codes have dictated the levels of thermal control and vapor control that builders must adhere to, and nearly every builder in the U.S. knows off the top of their head the R-value of the insulation in their walls and attics.

Using Interior Poly As an Air Barrier

Posted on March 29,2015 by user-756436 in air barrier

Back in the 1980s, Canadian energy experts urged builders to use interior polyethylene as an air barrier material. If the poly was installed conscientiously, and all seams were sealed with Tremco acoustical sealant, the approach worked well — at least in cold climates.

Air Leaks in Homes Insulated With Spray Foam

Posted on March 29,2015 by user-1072052 in air barrier

If you’re retrofitting a vintage brick building without an air barrier, don’t count on the spray foam to create a perfect air seal. If you plan to use the spray foam as your air barrier, it's important to test your work before you cover it with drywall so you can seal any air leaks.

Spray Foam Insulation Is Not a Cure-All

Posted on March 29,2015 by ab3 in air barrier

Spray foam insulation is a great product. Homes insulated with it can be some of the most efficient and comfortable homes built. I've been in plenty of homes insulated with spray foam and can tell you that, when done well, those homes are airtight and comfortable. I’ve also seen homes where the spray foam was a waste of money.

Solving Comfort Problems Caused by Attic Kneewalls

Posted on March 29,2015 by ab3 in air barrier

In Texas, they call them “hot walls.” My friend Mike Barcik likes to say they’re what separate you from the blast furnace. Down here in the warmer climate zones, where attics get up to 8,000°F (well, that may be a slight exaggeration), many people call them a liability. (Sadly, architects haven't gotten the message.)

Blower Doors Have Become Essential

Posted on March 29,2015 by user-1048334 in air barrier

Blower doors are spoken of in reverential tones in energy circles. Or at least they were a few years back. Now you can’t throw a manometer without hitting a contractor setting up a blower door. Which is a very, very good thing. With the incorporation of air leakage standards into various housing codes, blower doors are becoming essential. In fact, I tell customers that a simple shorthand for whether your insulation contractors grok building science is whether they own/use/understand blower doors.

Heat Loss from Air Is No Big Deal, Right?

Posted on March 29,2015 by user-1048334 in air barrier

No, it’s a huge deal. The photo (right) is of air streaming through recessed lights in a cathedral ceiling. I often and exhaustively speak about air sealing as if it were a universal good. And it is, right up there with brown ale and Avengers movies. My audit customers often look confused when I address their insulation questions by bringing up air barriers and air leakage. I mean, “Why are you talking about air leaks when I asked about the insulation?”

Joe Lstiburek on Spray Foam

Posted on March 29,2015 by ab3 in air barrier

Spray foam insulation evokes some interesting conversation among building scientists, construction professionals, environmentalists, and homeowners who have it in their homes. Many think it solves all problems, no matter how poorly it's installed. Some think it's helping to warm the planet and compromise the health of people and pets. In the middle are those who work with it regularly and see both the warts and the beauty of the product.

Green Basics Air Barriers

Cape Cod Style Homes Are Difficult to Heat

Posted on March 29,2015 by user-1048334 in air barrier

One of the great ironies in construction (I bet you didn’t even know that construction could be ironic) is that Cape Cod style houses perform pretty poorly on Cape Cod. The year-round sea breezes wash right through a Cape building frame, making them chilly and uncomfortable in the winter months. How did Cape Cod style houses (which perform not-so-great in the winter) become popular in New England? Maybe the name was a marketing scheme? And how can we address the air leakage and heat loss issues to make Capes more comfortable?

Service Cavities for Wiring and Plumbing

Posted on March 29,2015 by user-756436 in air barrier

Conventional wood-framed walls perform many functions. Exterior walls are supposed to support the roof load, resist racking, and provide insulation. They must also provide space for routing electrical cables and (in some cases) plumbing pipes or even ductwork. If the walls are built properly, they should also include an air barrier.

Top 10 Air Leaks in Existing Homes – Part 2

Posted on March 29,2015 by Tristan Roberts in air barrier

From an energy-efficiency standpoint, the trouble with owning an old home is that you’re stuck with whatever bad decisions the previous owners made, and historical trends also tend to work against you. The trouble with building a new home is that you are the one that is going to make the bad decisions. The best opportunity to make important decisions that will deliver energy efficiency for the life of the home is during design. There is rapid diminution of these opportunities during construction and then during use of the home.

New Air Sealing Requirements in the 2009 International Residential Code

Posted on March 29,2015 by user-756436 in air barrier

One of the most cost-effective ways of lowering residential energy costs is to reduce a home’s air leakage rate, so it makes sense for energy codes to ratchet up air-sealing requirements. The latest (2009) version of the International Residential Code does exactly that.

Questions and Answers About Air Barriers

Posted on March 29,2015 by user-756436 in air barrier

UPDATED on December 12, 2014 Builders of a certain age — say, those older than about 55 or 60 — started their careers at a time when no one talked about air leakage or air barriers. Back in the early 1970s, even engineers were ignorant about air leakage in buildings, because the basic research hadn’t been done yet. Times have changed, and most residential building codes now require builders to include details designed to reduce air leakage. Today’s young carpenters are working on job sites where air barriers matter.

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