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

Paul Raymer posted a blog post

Rocket Science?

The old expression when something is supposed to be simple is to say that, “This is not rocket…See More
2 hours ago
Sean Lintow Sr replied to Jim Gunshinan's discussion Tax Time Blues
"Well if I had to guess your credit will be 0 as it used to be up to $1500 & wasn't as hard…"
2 hours ago
Hannah Miller commented on Adam Flowers's blog post Comfort as a Selling Point
"Hello Adam! I hope you are still messages from this site. I just was forwarded your post and it…"
11 hours ago
Michael Dunseith replied to robert jones's discussion Should your local weatherization company be required to have someone BPI certified on their staff?
"Why the concern with airflow around heating and domestic pipes? Most are inside the envelope. What…"
14 hours ago
Tom White posted a video

Weatherization to Home Performance -- Tools & Tips for Developing For-profit Services

Are you a low income weatherization contractor looking to add home performance work you your services? The Home Performance Resource Center, Efficiency First, and NCAF present resources developed through expert industry engagement. While many of the…
16 hours ago
Jim Gunshinan posted a discussion

Tax Time Blues

There is a tax credit available to homeowners who have walls insulated. The credits were continued…See More
16 hours ago
Bruce Glanville replied to robert jones's discussion Should your local weatherization company be required to have someone BPI certified on their staff?
"I have been testing homes for my state utility as a baseline residential load data collection…"
16 hours ago
Stan Kuhn replied to Jim Gunshinan's discussion When your shower is in your kitchen...
"I think this is in the wrong Forum, it belongs in Hall of Shame.  One the dumbest ones…"
17 hours ago

© 2015   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service