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

Rainscreen and exterior foam?

Quinton Bryant | Posted in Energy Efficiency and Durability on

We meet with draftsman again today,we told him we would like to do 3/4or1 inch polyiso and also a rainscreen,he didn’t know much about the rainscreen and wanted to know how we will handle windows and trim with the extra depth,I have mentioned before but this is not normal practice in Oklahoma(zone3) so we are kind of questioning is it worth it to put these behind our hardie lap siding or just do one and not the other?
Sence it’s not normal practice I’m sure the builder will charge a lot more than would be charged in an area that it is normal practice.

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. GBA Editor
    Martin Holladay | | #1

    Here is an article on rainscreen details. After you read the article, you might want to show it to your builder: All About Rainscreens.

  2. Dan Burgoyne | | #2

    I tried a rainscreen for the first time, and it wasn't too difficult. I went through 3" of exterior rigid polyiso, so 1" would be pretty easy to attach battens into studs. Attaching a stucco finish was challenging at first for stucco paper and lathers who had never seen anything like this before, but this should be much easier for Hardie lap siding. Great materials in the many articles Martin and others have posted on this site.

  3. Bob Irving | | #3

    Quentin: Yes, it is important, and it's not all that expensive; especially when compared to dealing with siding problems and replacement. material cost for wood strapping should be at/under $.20/SF. Installation should run about .50/SF, plus 3-1/2" - 4" screws (we use GRK or Fastenall)

  4. Quinton Bryant | | #4

    Thanks for the links.if you had to do one or the other,would the rainscreen be more of a benifit than the foam in zone 3.
    Just thinkin of all options because I know the builder will ask.

  5. GBA Editor
    Martin Holladay | | #5

    Your question, "What would be more of a benefit, exterior foam or a rainscreen?" is a little like asking, "What is more useful, a sink or a refrigerator?"

    Exterior foam and a rainscreen serve different purposes. Exterior foam adds R-value to your wall and limits thermal bridging through the studs. A rainscreen can't do that.

    A rainscreen gap encourages your siding to dry quickly after a rain storm. Exterior foam can't do that.

    You need to detail your house according to your goals. I think that exterior rigid foam and a rainscreen gap are both useful.

  6. Charlie Sullivan | | #6

    Martin, I vote for the sink. I tried to wash my dishes in the refrigerator once, and it made a mess. But in a pinch, you can fill the sink with cool water and keep some food cool in it.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |