FHB Logo Facebook LinkedIn Email Pinterest Twitter Instagram Plus Icon Close Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Main Menu
Subscribe

In every issue you'll find...

  • Expert insights on techniques and principles
  • Unbiased tool reviews
  • Step-by-step details to master the job
  • Field-tested advice and know-how
Subscribe Now!
Subscribe
  • How-To
  • Design
  • Tools & Materials
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
  • Join
  • Log In
Main Menu Subscribe

Fine Homebuilding Project Guides

Insulation

Guide Home
Chapter
  • Energy Efficiency
  • Air-Sealing
  • Choosing Insulation
  • Installing Insulation
  • Water Management
Home-Building Cyclopedia

Air Barriers Are Essential for a Modern, High-Performance Home

Controlling air movement through the walls and ceilings is a key step toward comfort, energy efficiency, and building durability.

By Fine Homebuilding Editors
Article Image

Nothing gets a building scientist or energy geek going quite like this old chestnut in the house-building business: “Your house needs to breathe.” “No,” they will tell you; your house does not need to breathe.

Far from making houses happy, a free exchange of air between the inside and the outside induces many problems. Drafty houses (houses that breathe) are less comfortable, more susceptible to moisture damage, and use more energy than houses that are airtight. Plus, drafty houses will not meet the requirements of certification programs such as Passive House, and they will increasingly run afoul of tightening building codes.

As a result, many builders are devoting more time and energy to sealing the building envelope as carefully as they can to create an effective air barrier. Pros sometimes call this an “air-control layer.”

Many materials can be used as part of an air barrier. Concrete, drywall, glass, self-adhering membranes, flashing tapes, caulk, and plywood all are good at stopping the flow of air (oriented strand board—OSB—may not be as effective). A newly developed technology called AeroBarrier uses an atomized latex sealant dispersed by aerosol nozzles to plug gaps and holes.

Air barriers are not the same thing as vapor barriers, and building scientists generally think air barriers are the more important of the two in most climates.

The edges are a major challenge

The trick is in assembling these materials into a continuous seal at the boundary of the conditioned space. The key word is “continuous.” The most difficult spots to seal are not in the field but at the edges of the field, and the transitions from one material to another.

For example, plywood and rigid-foam insulation make good air barriers, but only when the seams between sheets have been sealed with a high-quality flashing tape.

One of the earliest approaches to air-sealing—a technique called the Airtight Drywall Approach—relies principally on sheets of gypsum drywall for the air barrier. Taping the seams creates a good air-seal in the field. Yet this system also relies on sealing the edges with beads of caulk at the top and bottom plates and around door and window openings.

Penetrations through this barrier at electric boxes and recessed fixtures also must be sealed with caulk or special gaskets. Similarly, potential gaps between the bottom plate and the subfloor should be sealed with caulk or with a gasket. In other words, when two dissimilar materials meet, the potential for a leak is higher.

One material that is rarely used these days as an air barrier is polyethylene sheeting, the stuff that once was routinely promoted as a vapor barrier. One reason is that it’s difficult to seal polyethylene at penetrations, between sheets, and around electric boxes.

Hidden problem areas also include utility chases, fireplace surrounds, recessed light fixtures, holes for plumbing under tubs and behind showers, and scuttles for attic access. An air barrier has to be continuous in order for it to be effective, so overlooking these spots can undo a lot of hard work elsewhere.

A good resource for making sure all of these potential trouble spots are managed is the Energy Star Thermal Bypass Checklist Guide (https://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/TBC_Guide_062507.pdf).

Include the air barrier in plans for the house

Including air-sealing details in your construction documents will ensure that they get done properly.
Including air-sealing details in your construction documents will ensure that they get done properly.

Designers who know the value of an air barrier will make sure it’s noted clearly on the construction drawings that builders will use. Here’s a test: Can you trace the air barrier around the perimeter of the conditioned space without lifting your pencil off the paper? That’s a sign of thorough planning.

Next is to make sure that everyone working on the house knows the importance of maintaining the air barrier. Prebuilding confabs involving everyone on the team are an excellent way of making sure all the subs get it. Architects sometimes call these get-togethers “charrettes.”

Plumbers and electricians are often blamed for boring holes haphazardly and creating a leaky building envelope. The chances of this happening are much lower when the GC explains how important the air barrier is.

This is not a problem exclusive to snow country

It may be tempting to skip all these details if you live in a part of the country where heating bills are low. In a leaky house in the humid south, however, the cool, conditioned air that’s leaking out of the house will be replaced by hot, humid air from outside. That’s a comfort and energy-loss issue.

Moreover, the moisture that the incoming air brings with it may condense on cool surfaces inside walls and ceilings. That may result in moisture problems, such as mold.

Don’t forget the ventilation

One important caveat to building an airtight home: It will need a whole-house ventilation system. All that trapped air needs steady mixing with outdoor air in order to stay healthy for people to breathe. In an airtight house, builders typically do this with energy-recovery or heat-recovery ventilators. Both of these similar devices draw in fresh air and expel stale air through a core that exchanges either heat (an HRV) or heat and humidity (an ERV).

More on air barriers:

  • The California FHB House Air-Sealing and Insulation in Pictures
  • Foundation Air and Vapor Strategy
  • Air-Sealing a High-Performance House
  • What Makes the ‘Best’ Air Barrier?

 

Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers.

Sign Up
X
X
Previous: Air-Sealing 101 Next: A Practical Air-Sealing Sequence

Guide

Insulation

Chapter

Air-Sealing

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Insulation

Insulation

Trusted, comprehensive guidance from the pros for a home that is healthy, comfortable, and energy efficient

View Project Guide

View All Project Guides »

Become a member and get unlimited site access, including the Insulation Project Guide.

Start Free Trial

Energy Efficiency
  • Understanding Energy and Houses
  • Building Energy-Efficient Homes
Air-Sealing
  • Air-Sealing Basics
  • Air-Sealing Tools and Materials
  • Foundations and Floors
  • Walls, Windows, and Doors
  • Attics and Roofs
Choosing Insulation
  • Insulation Basics
  • Material Choices
Installing Insulation
  • Insulating Attics and Roofs
  • Insulating Walls
  • Insulating Floors, Footings, and Slabs
  • Insulating Foundation Walls
Water Management
  • Water-Management Principles
  • Materials
  • Installation Methods

Fine Homebuilding

Follow

Newsletter

Get home building tips, offers, and expert advice in your inbox

Sign Up See all newsletters

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Manage Preferences

Taunton Network

  • Green Building Advisor
  • Fine Woodworking
  • Fine Gardening
  • Threads
  • About
  • Contact
  • Advertise
  • Privacy Policy
  • Careers
  • Copyright
  • Terms of Use
  • Accessibility
  • California Privacy Rights

© 2021 The Taunton Press, Inc. All rights reserved.

    Main Menu

  • How-To
  • Design
  • Tools & Materials
  • Video
  • Blogs
  • Forum
  • Reader Projects
  • Magazine
  • Members
  • FHB House
  • Podcasts

  • FHB Podcast
  • ProTalk
  • Account

  • Log In
  • Join

    Podcasts

  • FHB Podcast
  • ProTalk
  • Popular Topics

  • Kitchens
  • Business
  • Bedrooms
  • Roofs
  • Architecture and Design
  • Green Building
  • Decks
  • Framing
  • Safety
  • Remodeling
  • Bathrooms
  • Windows
  • Tilework
  • Ceilings
  • HVAC

    Magazine

  • Current Issue
  • Past Issues
  • Magazine Index
  • Subscribe
  • Online Archive
  • Author Guidelines

    All Access

  • Member Home
  • Start Free Trial
  • Gift Membership

    Shop the Store

  • Books
  • DVDs
  • Taunton Workshops

    More

  • FHB Ambassadors
  • Reader Projects
  • Podcast
  • Customer Support

    Account

  • Log In
  • Join

Newsletter

Get home building tips, offers, and expert advice in your inbox

Sign Up See all newsletters

Follow

Join All Access

Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

Start Your Free Trial

Subscribe

FHB Magazine

Start your subscription today and save up to 52%

Subscribe

We hope you’ve enjoyed your free articles. To keep reading, become a member today.

Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

Start your FREE trial

Already a member? Log in