The difference between air barriers and vapour barriers / Guides

The difference between air barriers and vapour barriers
Air and vapour barriers

The Difference between air barriers and vapor barriers

...Air leakage is due to air pressure differences between indoors and out, which forces air through any holes in your air barrier. Where the problem arises: The dewpoint in a wall is the point where the drop in temperature causes air to contract, and water vapor turns to liquid. Since the warmer the air is the more mo...

Exterior air barrier membrane © Ecohome
Air and vapour barriers

How to install an air barrier for reduced air leakage

...therwise. The difference between air barriers and vapour barriers: The job of a vapour barrier is to prevent vapour diffusion and the job of an air barrier is to stop air leakage through differences in air pressure between inside and out. A wall system should have one vapour barrier, but can have many air barriers....

Air barriers are essential to a properly functioning wall system
Air and vapour barriers

What is an air barrier?

...there are few aspects to building enclosures that are less forgiving than the air barrier. Where to install an air barrier: A building envelope should only ever have one vapour barrier, and it goes on the warm side of the insulation. Air barriers on the other hand, can be anywhere in the wall assembly and as plenti...

Vapor retarder latex primer instead of polyethylene sheet
Air and vapour barriers

Replacing polyethylene vapour barriers with latex paint vapor control

...andbook The problem is largely because the 6 mil poly that gets installed as a vapour barrier is mistaken for, and almost entirely relied upon to act as the air barrier. The purpose of the two barriers should not be confused - the job of the vapour barrier is to control vapour diffusion, the job of the air barrier ...

Tyvek home wrap left exposed to wind and UV rays
Air and vapour barriers

Choosing the right house wrap / weather barrier, which is best?

...anding the role weather barriers and rainscreens play in a wall, choosing the right products and installation tips for optimum performance. They're officially known as water-resistive barriers or WRBs, sometimes weather-resistive barriers, but in practical terms they are more commonly called housewraps and weather ba...

Problem areas of air leakage in a home and blower door test being cond
Air and vapour barriers

Airtight Construction of Homes is Essential: "Your house sucks." "Oh yeah? your house blows!"

...and negative air pressure: Neither positive nor negative air pressure in a home is good, as either puts pressure on the building envelope that promotes air leakage and they will each have different effects and impacts depending on the season, the temperatures and the humidity levels. Pressure differences in warm mont...

Choosing between OSB or Plywood for house sheathing for Roofs, Walls & Floors.
Wood and organic materials

Which is better, OSB or Plywood for Roofs, Walls & Floors?

...vapour barrier' on a work site, the standard 6 mil polyethylene. And remember - a vapour barrier goes on the inside of a wall, NOT the outside. Since we intentionally contain water vapour on the interior of a building with a vapour retarder, the more vapour-permeable the exterior of your wall is, the less likely you wi...

Building science for LEED v4 wall design made easy
Concept and design

Building science for LEED v4 wall design made easy - video

...thermal protection and energy efficiency, better drying capabilities and protects the air barrier from the assault it would normally receive from wiring and other penetrations when we rely on an interior polyethylene as an air and vapour barrier. See our pages on vapour and air movement & the difference between air & v...

What is Interstitial Condensation? (And how to stop it!)
Walls and Roofs

What is Interstitial Condensation in Walls or Roofs? (And how to stop it!)

...the warm side of insulation, however, these layers must be carefully sealed and penetrations avoided to prevent air leaking. (See here to understand the difference between air barriers and vapor barriers .) Materials with low vapour resistance should be positioned on the cooler side of the construction (although this...

Correctly installed Triple pane south facing windows on Ecohome's Demo House
Windows and doors

Installing doors & windows for the best performance in high efficiency homes, LEED & Passive House

...ther barrier/drainage plane. Don't attach windows by putting screws through the shims. Put the screw either just above or below, then remove the shims when the window is secured. Shims will offer little insulation value, and are most likely wet when purchased and installed, so as they dry they will shrink and allow a...

Better Basement Design on basement walls prevents mold and midlew
Healthy indoor air quality

Basement renovations: How to prevent mold when finishing basements

...and a vapour barrier. Notice the difference between the studs against the foundation and the studs that formed an interior division wall; the vapour barrier did not protect the exterior wall from damage and mold growth. It caused the damage by prevented the wall from drying to the interior and instead sealed the moistu...