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

Using WUFI to check wall moisture

Tom_Bassett_Dilley | Posted in Energy Efficiency and Durability on

I’m doing a number of highly insulated retrofit projects, and am concerned about long-term moisture in wall and ceiling cavities. I’ve had a brief intro to WUFI, the hygrothermic analysis tool, and am using v.5.1 (non-commercial) on my projects. But there are some inputs on the Surface Transfer Coefficient page that make a big difference in performance, but aren’t intuitive or explained. They are:

-Short-wave Radiation Absorptivity (should we use “no absorption” or try to use the closest value?)
-Adhering Fraction of Rain (using “According to inclination and construction type” makes a huge difference, but sometimes seems to give wrong results when used).
Also, a lot of our projects (especially exterior insulation w/furring strips) use an airspace behind the siding. If we model “Air space 20mm” vs. “Air space 20mm without additional moisture capacity”, it also makes a huge difference but isn’t explained.

Does anyone have experience with these? I’m hoping they are simple answers so I can know I’m getting the right results…and results that are in line with the building science guides I read, like this forum and Lstiburek’s Builder’s Guide. Thanks very much for any guidance you can provide.

Attached is a sample image of a results graph.

Tom Bassett-Dilley

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. Tom_Bassett_Dilley | | #2

    Mike, thanks, I had been on the WUFI-Wiki but had missed some of this. Getting there...
    Maybe we can chat at the PH Conference if you'll be there in DC in a few weeks.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |