GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

How do I prevent condensation on my new open beam ceiling?

user-7110790 | Posted in General Questions on

I am a general building contractor and built a custom single level home comprising of an open beam cathedral ceiling with 2×6 T&G sheathing under 4” Ridgid Foam insulation under 1/2” plywood sheathing under Mission Tile style roof. The air space between the T&G and the plywood is filled with rigid cellular foam insulation.
Building is located in a beach community in Southern California where temperatures are relatively mild between 65-80 degrees 80% of the year. The building has under floor duct work for both heating and A/C.
My problem is when the temperature exceeds 85 degrees the ceiling ridge beams start to sweat and drip.
I have installed a dehumidifier as part of the HVAC which consistently expels water into an outside drain.

Any suggestions to help with correcting this problem would be apppreciated.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. user-2310254 | | #1

    Where is your air barrier? Is it the foam? Did you tape the seams of the air barrier layer?

    It sounds like conditioned air from the AC is meeting unconditioned air at the roof peak.

  2. GBA Editor
    Martin Holladay | | #2

    User-7110790 (by the way, it would be a good idea if you would tell us your name),

    Wow! We're getting a lot of these reports these days!

    Here is a link to a similar thread -- read my long answer there: "How do I fix condensation between ceiling and closed cell spray foam insulation?"

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |