Looking for a good detail for using 1" rigid on exterior

Anyone used 1" rigid in a new exterior wall assembly before?  What are the pros & cons, which rigid product did you use, which weather membrane (some are integral to the foam too).  Any experiences good or bad are welcome.

Views: 100

Reply to This

Replies to This Discussion

I've used XPS rigid foam on both new construction and retro-fit applications, the amount of rigid foam ( R value) will depend on the climate zone you live in, colder climate zones require a higher percentage of the balance between exterior insulation and interior insulation to be on the exterior, for example I live and build in a maritime climate in Alaska, in our area we use a 1/3 - 2/3 rule for exterior insulation with a minimum of 1/3 of the total R value of the wall assembly being on the exterior side. I have used several different types of moisture barriers or house wraps, but usually rely on Tyvek Stucco wrap at the wall sheathing and cover the foam with Tyvek or Typar house wrap. Some will say this not neccessary but I know I sleep well at night knowing that there are several layers of protection between the elements and the wood of the structure.



Possibly overkill, but the Building Science Corp white paper might help:



Interesting Conclusions in the "White Paper".

In Central NY we use 2" of XPS to keep the dew point at heating design temperature (-2°F) outside the wall assembly.  These homes are quite comfortable, get excellent blower numbers, and are well prepared to fend off the universal solvent.


Still, my general policy and universal recommendation is always the same:  "foam is good, more foam is better, and a s***load of foam is best of all."  In my opinion, the concept of "overkill" does not apply until the building achieves passivhaus -level performance.  Anything less is a compromise.  Energy consumed now to save energy indefinitely into the future is a wise investment, although it is one tough sell to a nation that likes to buy lottery tickets.


By the way . . . speaking of dew point, I understand that there is an app available for psychrometric calculations for the iPhone and one on the way for Droid. 

I discovered this comprehensive answer to the design question here:


thanks for all your suggestions!

Yes, the dew point is the issue but also has to do with cold air leakage through cracks around the foam panel joints and windows that ends up creating cold spots inside the wall for potential small spots of condensation inside the wall if inside moisture gets through gaps in the inside vapor barrier. If these are small, I suspect they can completely dry seasonally.

Leo K. PE

I just finished a deep retrofit and used 2" polyisocyurate interiorly firectly over old rock, strapping, new rock.


This site has the best free articles around. 




Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.  Home Energy Pros is sponsored by the Better Buildings Residential Network.

Latest Activity

Robyn Smith replied to Chris Woods's discussion Looking to purchase Minneapolis Blower door system- Model 3 with DG-700 in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Hi Chris, I replied to you via email yesterday. I have what you are looking for!! Minneapolis…"
2 hours ago
Profile IconJohn Gillis, William C Gilbert, Brian Breckin and 4 more joined Home Energy Pros
5 hours ago
Paul Scheckel posted a blog post

Energy Ambassadors: Cuba and Vermont

Last winter i had the pleasure of hosting a Cuban colleague for a week in Vermont. We toured the…See More
7 hours ago
Linda Wigington commented on David Eggleton's group 1000 Home Challenge
"Two more projects have recently been approved as 1000 Home CHallenge candidates. We welcome Eric…"
22 hours ago
Colin Genge posted events
23 hours ago
Craig McManus replied to Timothy Renz's discussion Vinyl batt to metal frame ware house
"How can I air seal a metal building in the south to keep out humid air which is causing mold? Will…"
Tom White posted a video
Profile IconJeshurun and Chris Woods joined allen p tanner's group

Energy Auditing Equipment for Sale, Trade or to Purchase

Discuss the pros and cons of the equipment you are interested in prior to purchase. Post equipment…See More

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service