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myzx
Crawlspace insulation

I recently had an addition built on my home. The addition was built on a concrete slab so there is about a 30” of headroom in the crawlspace. There is only one vent on the north side of the addition. The only access to the crawlspace is through the floor so this is the last time(I hope) I will have access to the crawlspace. I will be insulating the space and wanted to know if:
1. I should add a vapor barrier to the concrete slab?
2. Is Spray foam a no-brainer for this type of insulation?
3. Should I add a vent opposite to the current vent to increase airflow? Is it needed?
I live in the Northeast and any advice is very much appreciated.

Timothy Miller
Re: Crawlspace insulation

Howdy, was there a vapor barrier installed under the slab? Or was gravel installed under the slab? a 30" crawl space tight but workable. Cheapest is to install fiberglass batt insulation R-19 in the floor joist bays a stapler and a razor knife and a dust mask is all that is needed to install it.

myzx
Re: Crawlspace insulation

Hi Timothy
thanks for the response
Just gravel. It never crossed my mind to ask the contractor to add a vapor barrier.
Is there a need to make the space airtight or will that work against me?

Fencepost
Re: Crawlspace insulation
myzx wrote:

Hi Timothy
thanks for the response
Just gravel. It never crossed my mind to ask the contractor to add a vapor barrier.
Is there a need to make the space airtight or will that work against me?

Remember that concrete is naturally porous. Without a vapor barrier under the concrete, you will probably have infiltration of moisture and possibly radon gas, so you would need to provide ventilation.

A few years ago, as a demonstration and experiment, in cooperation with Washington State University and the EPA's Energy Star program, a local builder built a few houses with sealed crawlspaces. They were built as yours, with a concrete slab in the crawlspace. Vapor barrier was installed under the concrete, there was no ventilation provided, and no insulation was installed under the floor. The result was that it did result in some energy savings, but the added cost of building this way took a long time to pencil out in energy savings.

Timothy Miller
Re: Crawlspace insulation

Howdy good time to contact your local building department and inquire about the code requirements in your area for venting and crawl spaces. The gravels main purpose is to reduce moisture from wicking threw the concrete and reduce freeze/ heaving issues.

Fencepost
Re: Crawlspace insulation

If you're curious, I found an article on the sealed crawlspace issue:

http://www.vbjusa.com/stories/2007-03-02/cracking_the_code.html

Timothy Miller
Re: Crawlspace insulation

Howdy
Thank you "Fencepost
Re: Crawlspace insulation
If you're curious, I found an article on the sealed crawlspace issue:"

The information is very enlightening.

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