Weather Barrier Vs Air Barrier Vs Vapor Barrier - What's the difference?

EDIT: You can write the answers to the follow-up questions, or read what others have answered, in the forum at the link below.

When I was studying for my AREs, this was a tricky concept for me. Through the process, I realized that it's a simple concept if you take a moment to understand the difference between them. And that's exactly what I have tried to do through this short animation video.

I will be bringing more of such animation videos on basic concepts that are in a way similar but yet very different.

Personal Note:
I am starting this channel to help the ARE community. I recently passed all my exams and want to share the knowledge that I gained by studying for them. Hope it helps!

All the best for your exams! Keep it up!

Get in touch with me! Ask me Questions!

Bhawya Joshi @sallakastudio
Clubhouse: @bhawyajoshi

#areexams #airbarrier #vapourbarrier #weatherbarrier

[arebasics]

If you all have a moment, please leave a comment and give me your thoughts. You can also give a thumbs up and let me know if you like it. Thank you all for watching! :)

[ProTradeCraft]

Almost. The IRC (building code) calls it a Water Resistive Barrier, not a Weather Resistive Barrier. The WRB in the code is typically a housewrap, such as Tyvek, that protects the wall sheathing from water that gets behind the siding.

In an effort to get more value from water resistive barriers, high-performance builders began using housewrap to stop air, too, by sealing the seams and edges using tapes and caulk. This is where the term WEATHER Resistive Barrier came into use. Weather usually consists of water and wind, so a Weather Resistive Barrier is detailed to stop air and water.


You state that the air barrier is usually a similar material to the weather barrier, but this is misleading. Air barriers can be anything that stops air. It can be plywood, spray foam, drywall, housewrap, or some interior vapor-permeable membrane, like Intello. Usually, when talking about the air barrier, it makes sense to talk about an air barrier SYSTEM. There is often a primary air barrier and a lot of secondary layers that add to the primary one. A gasket on an electrical outlet is an example.

Vapor barriers are usually plastic sheeting installed before drywall, and this is usually a huge mistake -- unless you live in northern Minnesota, northern Maine, the cold parts of Canada, Alaska, or some other extremely cold climate. Vapor barriers are intended to stop vapor diffusion, as you state, but vapor diffusion is almost never the cause of moisture in building assemblies. Because moisture travels on air currents, most moisture problems from vapor are air leak problems, not vapor diffusion problems.

Your graphic is a little confusing at best and dangerous at worst as it equates the hot and cold sides of the wall to the exterior and interior, respectively—because that's how the only other wall sections are drawn. People who don't know what a WRB, air barrier, or vapor barrier is will very likely think they need a vapor barrier on the outside of the building, which will trap a ton of vapor in the wall for any cold-climate building. Adding to this confusion is an already-existing confusion among building professionals who do not keep up with the science of their craft and who think that Tyvek is a vapor barrier, which could not be further from the truth. it is a water barrier, but it is vapor-open, allowing vapor molecules to pass. I've even seen it written on blueprints from an architect.

[johnswilley]

Living in Florida, we don't have extreme cold, but we have extreme humidity all year except immediately after a cold front passage. Humidity control is paramount here. As for water; even on a concrete type structure, during a hurricane, if the exterior surface isn't properly sealed the water can pass through. In 2004 in a new subdivision North of Daytona Beach, the entire subdivision had rain driven through the block walls (painted only) where it built up within the cells and then migrated to the interior. I liked your quick simple very effective demo. Thank you very much.

[kd]

Absolutely brilliant video. Simple, short, clear. Thank you. Could i ask if you could add something? When you introduce each barrier, could you show examples with photos of each type? Just so people can understand what a typical material might look like, so people can then say "ah yes i've seen that before". Excellent video though well done.

[pariakia]

it would be better if you remove the background music, it's very loud compare to your voice!

[Ktsusna]

Thank you for making the video. I think it would’ve been more informative if you had included insulation layers and finished wall layers. That would give viewers more of an understanding of these examples in the real world.

[nicks]

Vapour barrier on warm side of insulation 😊

[rachellemckool]

Great job! I like that they are nice and short and to the point!

[echoyue]

Great Video! I wonder would you answer the question you put at the end of the video? What are the materials that can be used in a building envelope to provide weather barrier/air barrier/vapor barrier?

[kashifbajwa]

thanks you so much its cleared in very simple way really helping and thanks for making this video.

[BawzWorkz]

I'm curious how this would work in a Scottish climate.

[andreycham]

It is good but not enough . You should have clarified that air barrier for hot climates and installed outside to prevent vapor from outside to get into wall assembly. It does not make sense to have air barier in cold climate when you have vapor barrier which already do not let hot air to escape out of building

[acctsys]

I'm in the tropics. I wonder how these apply to a passively cooled home.

[gloriahague]

How about just information forget the music

[takingbackcrypto]

What's up with the gigantic pauses between sentences. Makes this video super annoying to watch.

[ubernelson]

Thanks for posting this. I think you covered the basics very well.

[trevspark]

With insulation on the plaster board not much could get up inside the cold space but I guess that a vapour barrier would stop it completely. Thank you