Air Barriers vs Vapor Barriers | You NEED To Know The Difference

Air barriers and vapor barriers are often used interchangeably in the building industry, but understanding the differences between the two is crucial to prevent future issues. Air leakage in and out of a building is the second leading cause of moisture-related problems such as condensation and mold growth, following bulk water intrusion. In this video, we will discuss the importance of air barriers in controlling moisture, the need for a vapor permeable or impermeable air barrier, or a regular vapor barrier, and how to apply these principles to your project to ensure a long-lasting and durable building for future generations.

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[thenexthobby]

2 things are needed for success:

1) simple recipes builders can follow based on temperate zone

2) simple recipes owners of all other homes can follow based on temperate zone.

And adjustments for truly older, pre-drywall homes too. If anyone treats old homes as a lost cause, i.e., nothing can be done, you lose, we all lose.

These needs are so basic, so fundamental, any design agency (ahem) could afford to “give these secrets away” as packages while still running a profitable business. There’s that level of need!

Thanks for this, and all such videos.

[earlmcgill]

Thank You for discussing mixed climates! It's always hard to find good discussions about how to apply advanced building techniques in Zone 4A.

[misterlyle.]

Your videos are excellent; thank you for posting them here! Information flow is focused and concise with useful graphics and descriptions. I usually play each video a few times. Your accuracy rating seems to be very high, as well. Less accurate construction videos regularly have obvious issues, like a host's failure to use eye protection, or some essential step being left out, or problems visible in the background that go unexplained. I am looking forward to reviewing all of the content you have shared!

[EsilyProd]

A video on interstitial space condensation would be interesting.
Thank you, this was very informative.

[pauld]

Your videos are top-notch. Thank you.

At the end of the day, aren't the best wall systems the ones that don't need any vapor barrier ?

Hempcrete walls for exemple don't need any vapor barrier because hempcrete is vapor permeable. The hempcrete wall just needs a lime plaster on the outside for airtightness. No worries about potential air leakage...

[thewoodworkersnook]

amazing video. made it clear what system to use in a given climate.

[daichimax]

Your videos are excellent; thank you for sharing your knowledge. 👍👍👍👍👍 & Subscribed!!!

[mikegrok]

I have a 1000sqft home in mobile alabama built in 1954. The condensate for my air conditioner went out a few years ago. After no AC overnight, starting it up in the morning made 2 5 gallon buckets of water in 2 hours.

[СергейШ-чт]

Great explanation of such important topic

[machickman]

Awesome video! Great content. Thank you for the educational content!

[bethfioritto]

Just found your channel; super informative, thank you! I noticed most of the resources on your site seem to be aimed at professionals: would you consider creating something for homeowners? I am looking to insulate the attic (and maybe walls?) of my circa-1919 house in the upper midwest but I am worried about someone coming in and doing it wrong and causing some of these mold and condensation issues (and also realizing I already have those issues from summer AC use causing condensation in my walls most likely). I want to be able to understand what the best practice solution looks like so I can be confident I'm hiring someone who knows what they're doing. Thanks so much for all the great info!

[timarmstrong]

I'd be interested in your thoughts on how to manage vapor for a house at 800m elevation where it's hot in summer 40c, but not exceptionally humid, and cold in winter often 0c and getting as low as -5c.

You mentioned high desert but what might a composite, i.e. layered, wall look like?
Some possbile materials. I'm sure as an architect you have a number of other products for things like thermal bridging

Outer layer: AAC or sheetrock
Possible Layer: semi permeable wrap
Possible Layer: Air gap or rockwool batts
Possible Layer: Foil backed polyiso or other rigid insulation. Which way does the foil face
Possible Layer: Air gap or rockwool batts
Inner wall: corefilled concrete blocks or sheet rock wall

Or any other combination of layers

[alinosan]

Thank you for the clear explainations. Air leakage is such an underestimated problem. The "buildings need to breathe" mantra continues the damage. What is your solution for humid air present at the roof ridge while maintaining the air barrier?

[richdobbs]

I want to use exterior ISO insulation on top of OSB sheathing. There are various techniques for getting a good air barrier on top of the OSB sheathing, such as roll on Cat 5 or peel and stick roofing underlayment. How would you recommend detailing this for Zone 5 B? Am I being excessively paranoid for wanting to have a vapor permeable route out from the outer surface of the OSB? Or should I just assume that the sheathing will dry to the inside and that it doesn't matter what the vapor pressure and moisture content is of the ISO? I've been thinking that a band of mineral wool board at the top of and the bottom would provide a vapor bridging path relatively easily, but I haven't come up with a suitably cheap vapor transport layer beneath the ISO to the top and bottom of the roof or wall.

[xokissmekatexo]

@asiridesigns this was very informative, but you do mention climate a lot. Can you please do some videos (flat roof, stucco, “perfect” hot dry climate wall) on hot dry desert climate (Vegas). Construction here is pretty “basic” but the homes are not “comfortable.” Thanks!

[SteveV]

This is nice information but I live in Middle of Pennsylvania where we get humid 90 F days in the summer months and zero F in the winter . So what side do I put my vapor retarder on? I'm planning on building this summer with 1.5" XPS on exterior 2x6 framing with 6-in fiberglass in wall cavity. Should the fiberglass be on faced or faced?

[chrissmithz]

Cold humid climate, coastal maine. Can I still use a smart vapor retarder if I can't put furring strips on the interior side of the wall for a service cavity/air gap? Can it directly sit up against the back of the drywall? Renovating an old house on the inside and there's an existing window on the wall, so I can't just make the wall come out more

[salanselmo]

Asking advice. Plan on building a house with double stud 2×4 walls with 3 1/2" in between. R15 mineral wool for a total r45 with ziga majrex on the inside of the exterior framing as a smart vapor retarder. Should I use zip sheathing or cdx on the exterior? There will be a rain screen behind the siding. This is in 6a zone with humid summers. Thanks for any advice

[thormatteson]

Curious why there is no filter fabric on the soil side of the dimple mats? Without that, you are not creating a space for the water to flow downward to a drain.

[tonyman]

What if you have spray foam insulation instead of fibrous?