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.
Thanks

Views: 87

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.

Scott

Scott

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

 

http://www.buildingscience.com/documents/reports/rr-1012-residentia...

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:

http://www.greenbuildingadvisor.com/blogs/dept/musings/calculating-...

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. 

 

http://www.buildingscience.com/documents/information-sheets/high-r-...

RSS

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.

Latest Activity

Colin Genge replied to billy g pinnick jr's discussion Blower Door Question
"I didn't take your comment as a challenge. I agree that his impression of what was occuring is…"
9 hours ago
Tom White posted a blog post

Clean Energy Works Oregon: Total Home Performance

Clean Energy Works Oregon (CEWO) is the largest nonprofit home performance provider in Oregon,…See More
12 hours ago
Tom White posted a video

Twas The Night Before a Clean Energy Christmas

From the foothills of the Rockies, RMI editorial director Pete Bronski reads 'Twas The Night Before a Clean Energy Christmas. Happy Holidays and Happy New Year!
12 hours ago
Chad Mcaulife commented on Green Jobs Training Center's photo
13 hours ago
Chie Kawahara's discussion was featured

THC Candidate Shares Energy Data

Midori Haus, a Passive House retrofit in Santa Cruz California and a Thousand Home Challenge…See More
13 hours ago
Bob Blanchette's discussion was featured

How does Cycles Per Hour affect real world AFUE?

Some claim that modern furnaces have minimized off cycle losses to the point they no longer matter.…See More
13 hours ago
Dale Stephens's blog post was featured

LED Lighting 24-month update 18,240 hours & counting

Background:In November 2012 I replaced 80% of my home's interior lighting with LEDs (35 bulbs…See More
13 hours ago
Home Energy Magazine's blog post was featured
13 hours ago

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service