Treating crawl spaces (with ductwork) when the adjacent basement ceiling is insulated.

I am currently speaking with a homeowner who would like to replace the existing FG batt insulation in the ceiling above his crawl space. The crawl is connected to the basement, and the basement ceiling is insulated with FG batts as well. The crawl has ducts insulated to R-4.2 throughout it. The crawl floor is a thin layer of concrete (about 1").

I spoke to him of two options:

1. Slap R-19 un-faced FG batts in the ceiling, and then slap 1/2" to 1" of foil-faced rigid foam to the underside of the floor joists.

OR

2. (This is my preference). Lay down 6-mil poly across the floor of the crawl, and adhere the poly to the crawl walls (up a couple of feet). Then install 2" of foil-faced rigid foam to the crawl walls. 

I will also be insulating the rim\band joists throughout the basement.

Any advice?

Views: 210

Reply to This

Replies to This Discussion

I agree with your preferred option.  If the connected space is climate controlled then stopping moisture and outside air from entering is the best option.  Only putting the FG batts in the ceiling of the crawl space would still leave the influx of air to deal with and it would decrease the efficiency and comfort of the home.

Thanks Tim. I have been pushing this option, and I think the homeowner is going to bite.

I would suggest a true vapor barrier product or ASTM  E-1745

From my short education on the product you want to make sure that the product is rated for the application. It is critical that the product is mechanically fastened to the wall and sealed. If there are any piers the product should be fastened and sealed to it as well.All seams sealed with tape approved for the product

I use 1x2  and ramset for fastening and duct mastic for sealing.

It is tedious, boring and often unappreciated in a challenging space.

I would always be concerned about the walls ability to dry. If the outside stem wall is buried I would think twice before insulating it

That is some really valuable input Glen. I definitely will continue to think this one through.

Thanks.

Patrick

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

Hal Skinner replied to Hal Skinner's discussion 'YGRENE' super fund for energy upgrade financing
"Hi again John, If you could directly answer these questions and comment on anything else related,…"
8 hours ago
Gregory Homan commented on Tom White's video
Thumbnail

The Future of Housing - And How Airtightness Can Help

"This is a reposting. The original is out of date due to the URL of the source video having…"
9 hours ago
Profile IconRick Causo, Sean McLoughlin, PAUL JOHNSON and 1 more joined Home Energy Pros
9 hours ago
Chris Dorsi posted a group
Thumbnail

International Home Performance Forum

A group dedicated to international collaboration among home performance practitioners.All topics…See More
9 hours ago
Tom White commented on Tom White's video
Thumbnail

The Future of Housing - And How Airtightness Can Help

"This video link has been deleted.  You can now view and comment on the updated video at…"
9 hours ago
Tom White posted a video

The Future of Housing - And How Airtightness Can Help

http://www.houseplanninghelp.com/80 The search for a new home can be daunting; whether it’s your first purchase, you’re relocating, or your family is increas...
9 hours ago
Corbett Lunsford's 2 videos were featured
10 hours ago
Sean Lintow Sr posted a blog post

http://thehtrc.com/2015/illinois-the-eri-the-iecac-resnet-the-final-push

Monday April 6th (10 AM to noon) will decide whether the ERI aka as the HERS option will be part of…See More
11 hours ago

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service