Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

basement vapor barrier

basement vapor barrier

basement vapor barrier



I'm about to finish my basement. I have a french drain in my basement. So I was thinking about putting up a 6mm poly vapor barrier that would extend to the bottom of the wall to the top to help direct any moisture that collects into the french drain. I've pretty much resolved all the water coming through the wall by installing a french drain in my yard, but I thought I would be prudent and install a vapor barrier. A portion of the wall has a french drain and the other portion does not.

If I install a vapor barrier my only question is do I need to worry about ventilation in the wall? Should I install vents on the drywall side from the living space to the wall cavity? Or will that be asking for trouble? I read in some articles people are suggesting a product made by CertainTeed MemBrain that would act as a vapor barrier in the winter and allow moisture to escape in the summer time. I saw some people would install 6mm at the bottom 4 feet of the wall and then install this CertainTeed MemBrain on the top 4 feet. Is CertainTeed's product any good? Is it worth getting or should I just stick to 6mm poly?


I'm an airframe engineer, so I thought I would ask my fellow engineers who specialize in HVAC for any advice. I've drawn up a picture of concept in Visio for feedback that I've converted into a PDF. I will be using 3.1" thick R-21 foam board that I've already purchased.

Many thanks. It is always good to get feedback.


Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close