# Crawlspace Insulation?



## Spencer (Jul 6, 2005)

How would you insulate a new construction Indiana crawlspace?

My insulator has this thing against fiberglass. He is saying to spray foam the exterior walls and box sill area and do nothing for the floor. That don't seem right.??? Even to meet code surely something has to go in the joist cavities. Am I crazy?


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## tgeb (Feb 9, 2006)

Is it a vented or conditioned crawl space?


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## Spencer (Jul 6, 2005)

tgeb said:


> Is it a vented or conditioned crawl space?


No vents.


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## Dan_Watson (Mar 1, 2008)

Foam around the perimeter under the slab and against the foundation. 6 mil under the entire slab, and spray as he said. As long as all of the proper steps have been taken to inhibit water infiltration I prefer his recommendation.


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## bob hutson (Mar 16, 2013)

what dan^ said, I wouldn't put fiberglass under the floor, if there is ever a leak it will hold water. Im in central Indiana.


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## Rio (Oct 13, 2009)

If you have a crawlspace why wouldn't you insulate between the floor joists?


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## ScipioAfricanus (Sep 13, 2008)

Now wait a minute...is there is or is there ain't a design on this thing by an archy or designer?

This was not thought out before building?

Andy.


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## muskoka guy (Nov 16, 2013)

I believe he is talking about a crawl space below the floor area. Don't know how cold it is there, but my old house had a crawl space under it. The perimeter walls were insulated but the floor was not. The crawl space was heated as all the plumbing was under the floor. This kept the floor warm in winter. I also am not a fan of batt insulation in crawl spaces and if you can afford the spray foam or ridgid, I would go that route. Either way cover up the insulation with sheetrock or some type of cover. It is code here to cover foam with fire protection. Regular insulation I wouild cover because critters love to make nests in the stuff.


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## overanalyze (Dec 28, 2010)

Spencer your insulator sounds correct. Closed cell foam at a minimum of 1-1/2" to meet the R-10 requirements. No fiberglass. No vents is good also. Make sure there is a vapor barrier over the soil. 6 mil is minimum, thicker is better. We like to have the foam crew spray after the vapor barrier is installed so the edge gets sealed. 

Of course proper drainage and grade on the exterior are necessary as well to keep a dry crawl.

I would check about covering the foam like said above. Some places require it period, others only require it if there is a fuel fed appliance in that space like a furnace or water heater.


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## Spencer (Jul 6, 2005)

overanalyze said:


> Spencer your insulator sounds correct. Closed cell foam at a minimum of 1-1/2" to meet the R-10 requirements. No fiberglass. No vents is good also. Make sure there is a vapor barrier over the soil. 6 mil is minimum, thicker is better. We like to have the foam crew spray after the vapor barrier is installed so the edge gets sealed.
> 
> Of course proper drainage and grade on the exterior are necessary as well to keep a dry crawl.
> 
> I would check about covering the foam like said above. Some places require it period, others only require it if there is a fuel fed appliance in that space like a furnace or water heater.


I haven't done much with crawl spaces so I'm learning.

Before framing I installed inside perimeter tile and inside sump in crawlspace.

I put a couple inches of stone on. Then added 6 mil plastic. Then more stone.

I left the plastic long and was planning on taping it to the cement crawlspace wall and then spray foaming over that to create a seal. 

I had heard of it before but it just seemed foreign to me to condition that space but I guess there really isn't much difference between that and concrete floor when I really think about it.


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## Mark122 (Sep 27, 2014)

Yes sounds right for a unvented crawl space.

Insulating the bottom side of your floor would be appropriate if the space was vented.


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## overanalyze (Dec 28, 2010)

Spencer said:


> I haven't done much with crawl spaces so I'm learning.
> 
> Before framing I installed inside perimeter tile and inside sump in crawlspace.
> 
> ...


Sounds like we do them all the time. Nicely done. I will even have a supply put in the crawl space off the furncace. It keeps some conditioned air moving down there. No return air though.


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## saynever (Jan 6, 2009)

A closed crawl should be treated like a basement. 
If it is indeed new construction, It would be beneficial to have the customer pony up for a concrete slab ( even a rat or thin service slab). The mechanical trades and any future service people will appreciate it.
With proper foundation water management it can be used as storage for items you'd store in a basement. 
It keeps your mechanicals protected and in the thermal envelope. 
The slab and vapor barrier is a good step to prevent radon from entering the structure. 


I personally would prefer a smooth finished slab down there poured over sub slab insulation and vapor barrier. 

Keep a cheap floor creeper down there for service or retro work. Customer we worked on last year had a rat slab and the creeper down in the section of the house with the crawlspace and was a pleasent surprise. As an electrician I love it. Beats throwing the tyvek suit on and going commando in prone position. 

If its a closed crawl space it has to meet certain requirements for ventilation and conditioning. 


Using an energy modeling software package can help determine open vs closed crawlspace for a particular site. 

Plenty of wall details around online showing acceptable insulation details of closed crawls/basements.


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## muskoka guy (Nov 16, 2013)

Agreed on the concrete floor. My old house had a dirt floor, and I poured the floor after I bought the house. I pulled one of the kids wagons with pails of concrete on it, hand troweled my way out. The house had vents that I would open in the summer and close in the winter.


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## Spencer (Jul 6, 2005)

Thanks for all the advice. Sounds like we are moving in the right direction. I dug the inside dirt down to the top of the footer so I've got a 3' crawl space under the joist. Its pretty easy to move around. I like to make it as easy as possible on my mechanical trades/insulators.


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## CarpenterSFO (Dec 12, 2012)

Spencer said:


> Thanks for all the advice. Sounds like we are moving in the right direction. I dug the inside dirt down to the top of the footer so I've got a 3' crawl space under the joist. Its pretty easy to move around. I like to make it as easy as possible on my mechanical trades/insulators.


It's just a thought for the future, but you need to be careful about digging fill away from a foundation wall, and turning it into a retaining wall if it wasn't designed to be one. Maybe not an issue with a wall that short, probably you were just scooping out a few inches of dirt. Something to be aware of, especially in places where the ground freezes.


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## Spencer (Jul 6, 2005)

CarpenterSFO said:


> It's just a thought for the future, but you need to be careful about digging fill away from a foundation wall, and turning it into a retaining wall if it wasn't designed to be one. Maybe not an issue with a wall that short, probably you were just scooping out a few inches of dirt. Something to be aware of, especially in places where the ground freezes.



Could you explain what could go wrong further?


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## CarpenterSFO (Dec 12, 2012)

Spencer said:


> Could you explain what could go wrong further?


If you remove the fill from one side of a wall that wasn't designed as a retaining wall, the wall can crack, topple, get shoved in, because the fill isn't holding it there. It does occasionally happen where people have excavated out basements or crawlspaces, and freeze/thaw topples the wall.

If you removed a significant amount of fill, you want to ask why it was put back in after the wall was poured and forms removed. I don't know your situation - it might be nothing, but you might want to check before winter settles in. The designer or the foundation guy could tell you.


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## pappagor (Jan 29, 2008)

it is a basement wall that is 3 ft tall.
most are cord every 32 inches in this area with 42 inch frost footing.
poly the drit foam the walls heat the space like the rest of the home.:whistling


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