# Help me out with my crawlspace insulation please



## Chris74 (Dec 5, 2011)

I have a 1906 model victorian home in the Arkansas Ozark mountains. We have cold winters and hot humid summers. My crawlspace is a vented, dirt floored mess. There are probably 15 or so stone piers and screw jacks. There is zero insulation in the floor joists. The attic is insulated very well, and there are nice windows in the house, but the floors are totally uninsulated. I have spent lots of money fixing the house up the way I wanted to, and honestly I don't have thousands to pour at insulating and conditioning the crawlspace. 

I think putting down a vapor barrier would be a hugely labor/$$ intensive project. There are lots of rocks, debris, trash, in the space that would have to be cleaned out. Then I would have to overcome the issues of getting a good seal with all of the stone piers and and screw jacks in place. 

What is the easiest, most cost effective way for me to insulate my floors??? I really would appreciate any help you can offer here.


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## Windows on Wash (Aug 30, 2011)

Easiest and cost effective don't usually occupy the same reality.

Depending on where you are that is a climate zone 3.

Easiest would be to put 3-4" of 2lb foam on the underside of the floor, thus equaling a vapor retarded on the warm side. After that, you can spray some sort of an ignition barrier either via an applied paint of something like a spider fiberglass.

http://publicecodes.citation.com/st/fl/st/b400v04/st_fl_st_b400v04_3_sec014_par009.htm


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## cbaur88 (Jan 25, 2011)

Windows on Wash said:


> Easiest and cost effective don't usually occupy the same reality.
> 
> Depending on where you are that is a climate zone 3.
> 
> ...


I agree with Windows. The easiest would be using spray foam but for most it's not cost effective as hiring a contractor or even DIY is costly. Using other options such as rigid foam, fiberglass, Roxul is allot more work. I am in a similar boat.


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## Chris74 (Dec 5, 2011)

Thanks for the advice guys. I really do appreciate it. I spoke to a spray foam contractor yesterday. He quoted me $3000 to spray the joist cavities with 2 inches of closed cell and splash the joists with closed cell. I told him my main concern was the air flow from the crawlspace into the house and from the house into the crawlspace. He told me he could apply one inch of closed cell to all exposed wood and around the floor/foundation joint (seal I think??) for $2000. My major concern is the airflow, but what do I know?? Would stopping the airflow with the one inch of closed cell be very beneficial, or do you guys think I should go ahead and pay the extra money for the 2 inches of closed cell?? I really do appreciate any advice you guys can give me here. I apologize for my ignorance.


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## justincase123 (Oct 24, 2010)

I had fiberglass insulation that was moldy and falling down under my crawlspace. A couple years ago I got aggravated with it and yanked it all out. I put down 6 mil plastic on the dirt(after raking out all the debris), Then I put 2" extruded polystyrene (eps) that comes in 4'x8' sheets around the foundation walls, cutting out the vents. I also doubled the 2" and put 2 pieces in between the joists back to the band on top of the plate. I close the vents in winter and open them in summer. They make a special adhesive for adhering to the block or concrete walls for easy installation. I have been very pleased with this. I now have a clean moldfree crawlspace and having the insulation around the walls instead of between the joists keeps it from falling down and gives more headroom. My heating bills have went down and the air quality is much better in the house.


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## cbaur88 (Jan 25, 2011)

guest said:


> I had fiberglass insulation that was moldy and falling down under my crawlspace. A couple years ago I got aggravated with it and yanked it all out. I put down 6 mil plastic on the dirt(after raking out all the debris), Then I put 2" extruded polystyrene (eps) that comes in 4'x8' sheets around the foundation walls, cutting out the vents. I also doubled the 2" and put 2 pieces in between the joists back to the band on top of the plate. I close the vents in winter and open them in summer. They make a special adhesive for adhering to the block or concrete walls for easy installation. I have been very pleased with this. I now have a clean moldfree crawlspace and having the insulation around the walls instead of between the joists keeps it from falling down and gives more headroom. My heating bills have went down and the air quality is much better in the house.


Thanks for sharing your project! Do you have any insulation between the floor joists? Also can you open and close your vents from the outside?


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## iminaquagmire (Jul 10, 2010)

Insulating the crawlspace walls instead of the joists makes the crawlspace a conditioned space. This is the now preferred method for crawlspaces. No more vents to open and close and its a generally cleaner method. However you must have an effective vapor barrier on the floor and if you have foam insulation, it must be covered with an ignition barrier as it will produce toxic gasses during combustion.


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## cbaur88 (Jan 25, 2011)

iminaquagmire said:


> Insulating the crawlspace walls instead of the joists makes the crawlspace a conditioned space. This is the now preferred method for crawlspaces. No more vents to open and close and its a generally cleaner method. However you must have an effective vapor barrier on the floor and if you have foam insulation, it must be covered with an ignition barrier as it will produce toxic gasses during combustion.


Insulating the walls AND closing/sealing off the vents would make the crawlspace conditioned from what I've read but I am confused as to how just doing these two tasks makes it conditioned? What about the rim joists? Sil ledge? Air is getting in from those places as well (at least in my house) so wouldn't these be sealed off in addition? Just a thought...


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## Windows on Wash (Aug 30, 2011)

They need to be sealed as well to create the proper envelope/air tightness.

If the crawl is truly conditioned, it should have some supply side air pumped into it.


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## CrawlSpaceMoist (Nov 24, 2011)

cbaur88 said:


> Insulating the walls AND closing/sealing off the vents would make the crawlspace conditioned from what I've read but I am confused as to how just doing these two tasks makes it conditioned? What about the rim joists? Sil ledge? Air is getting in from those places as well (at least in my house) so wouldn't these be sealed off in addition? Just a thought...


Let's be careful of being too specific. Your state likely has code requirements, but here's some industry standards (i'm in NC, so humid south!)
1. Encapsulated or Sealed Crawl - typically poly on floor, up walls and vents sealed; mechanically dehumidified; can have wall or joist insulation
2. Conditioned Crawl - Encapsulated but with insulation on walls and HVAC air used to 'condition' the space.

The concern with the insulation on the walls, especially if you leave it vented, but also if you seal up the vents and don't condition or dehumidify, that the dew point can occur in or behind the wall insulation and cause mold/rot.

And, Yes, there are multiple other areas for air to leak in - along the sill, etc. Those all need to be caulked or sealed up as well. Get in the crawl during the day, turn off all lights, and move along the foundation wall caulking anywhere you see light. (use your flashlight as necessary to get around safely! )


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## cbaur88 (Jan 25, 2011)

CrawlSpaceMoist said:


> And, Yes, there are multiple other areas for air to leak in - along the sill, etc. Those all need to be caulked or sealed up as well. Get in the crawl during the day, turn off all lights, and move along the foundation wall caulking anywhere you see light. (use your flashlight as necessary to get around safely! )


Thanks CSM, that's exactly what I am doing. I've found so many spots where I can see daylight around the sil ledge it's amazing. I've been slowly sealing up the rim joists and sealing the sil ledge as best I can with a good sealant and spray foam (GSF). I've like to eventually make it conditioned since I've already go the duct work running in there. I'll eventually need some HVAC advice once I get there. Thanks for you help! :thumbsup:


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## cbaur88 (Jan 25, 2011)

Hey gang one more quick question about using Roxul around ducting. What the best or recommended way to get the Roxul insulation in and round the ductwork. I do I want to get the insulation above the duct work flush to the floor or below the ductwork? For me the latter wouldn't work simply because the ductwork comes down to far. Only way for me I think I could do is to go up and behind the duct flush to the floor, is that ok? Thanks again for all your advice :thumbup:


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