Spray Foam and Vapor Barrier in Crawlspace?

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  #1  
Old 01-13-15, 01:34 PM
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Spray Foam and Vapor Barrier in Crawlspace?

I am looking into getting the walls of my crawlspace insulated with spray foam, and I have a few questions:

1. Is open-cell or closed-cell best? (do I even have a choice?)
2. Are there any concerns with off-gassing (I think that's what its called, i.e., the foam giving off toxic fumes)
3. Is there a rule of thumb for cost (e.g., X dollars per square foot, or whatever)?
4. There is no reason to spray foam the joists, is there? That would just defeat the purpose of making the crawlspace conditioned, I think?
5. As this would make the crawlspace conditioned, do I need to put any kind of vent leading to the house so that the air can be freely exchanged?
6. Is a vapor barrier needed over a crawlspace's cement floor? A company I called for an estimate told me that it would be a waste of time/money because cement floors are all built with a vapor barrier included.

Is there anything else I should be aware of? I have two companies coming later this week to give me estimates, and I'm wondering if there is anything else I should ask them.

Any and all info is greatly appreciated!
 
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Old 01-13-15, 01:41 PM
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1. Closed cell has vapor retarding qualities which open cell does not. Closed cell is also more expensive.
2. I don't know.
3. Not that I'm aware of but a general rule of hiring contractors is to get three or more bids so you can compare.
4. Nope, leave the ceiling alone/
5. Yes.
6. If there's a concrete floor already poured, you can stop. No guarantee there's a vapor barrier beneath it but it's fine regardless.
 
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Old 01-13-15, 01:46 PM
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Thank you for the info. Looks like I should go for closed cell, unless its much more expensive.

Regarding the vapor barrier - what type of floor would need a vapor barrier? Is there any real difference between a concrete floor and a cement floor? By "already poured", what do you mean? Do you mean that its not a dirt floor, or something else/ We have either concrete or cement (I don't know how to tell the difference...is there a third thing it could be), so I assume as long as i have that then I don't need a vapor barrier?

Why does the same not hold true for the walls of the crawlspace? I think they are made of the same stuff as the floor, so if the floor is fine then why are the walls helped by spray foam? Would it make sense to spray foam the floor?

(I am not doubting you at all, I'm just not sure of why I should do something to the walls but not the floor.)

Thanks again.
 
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Old 01-13-15, 01:50 PM
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Cement is an ingredient in concrete - think of it as the glue. You have a concrete floor and it is installed by being poured in wet, hence my reference to you already having a concrete floor poured.

Make sense?

A dirt floor would need a vapor barrier.

The spray foam is for temperature insulation and, while it would help on the floor, it does not make for a good surface upon which to walk or set things. It is not uncommon for people to put a vapor barrier or insulation like spray foam down before pouring concrete, I'm just saying you shouldn't need to worry about it since your concrete is already in place as it would be way more work than benefit to do anything about it now.
 
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Old 01-13-15, 02:00 PM
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Yep, make sense re: cement vs. concrete.

Our crawlspace is only about 3' tall at its tallest, so actually crawling on hands-and-knees is required. Therefore, we don't store anything down there at all, and I only ever go down there to check the dehumidifiers (which we shouldn't need anymore after spray foaming!) and the sump pump.

Still, it seems like it would be a waste of money to do something to the floor. I'm guessing/hoping that the un-foamed/un-barriered concrete floor would not add much moisture to the air. That being said, if the concrete floor won't add much moisture, would the concrete walls add much moisture? That is, should I go for the cheaper open-celled foam instead of close-celled foam?

Thanks again for all your help.

Also, does anyone have any info on off-gassing as well as average price-per-foot?

Thanks again.
 
  #6  
Old 01-13-15, 04:21 PM
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What is the age of the house? Newer homes would be most likey to have a vapor barrier installed, older homes would not. Do not spray foam the floor for a VB barrier. Lay 6 mil plastci and tape all the seams. That's all you need.
 
  #7  
Old 01-13-15, 06:37 PM
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The foundation is from the 1950s, I don't know the exact year. A second floor was added in 1999-2000 by the previous owners, but I highly doubt that the foundation was touched.

When did vapor barriers begin to be installed in the concrete foundation? How bad is it if the foundation is old enough to probably not have a vapor barrier installed? Laying down plastic and taping the seams is a lot easier said than done. It is extremely dirty in the crawlspace, so that would need to be cleaned up before the plastic could be laid down. Its also only accessed through the floor of a closet, and its only tall enough to move around on hands-and-knees only. Not easy at all to put the plastic down (or to lean the floors first). So, I might look into doing it if it would help a lot, but if it wouldn't really matter then I'll forget about it.

Thanks again for all the help.
 
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