# Crawlspace



## cbaur88 (Jan 25, 2011)

You may have also seen some posts on the topic in other threads "Insulation 'Great Stuff' by DOW Chem'" & "Crawlspace/Foam Insulation DIY" so in continuing to try and research as much as possible to do the right thing & use the right product, etc.. I was back down in the crawlspace doing more recon work only find some more interesting things. I understand now why some of the area above the crawl space are so drafty and very cold because the rim joists are not properly sealed and insulated

In the front of my home around the bow window there is a 2ft overhang. Same goes for the back of my home. After removing the pieces of faced insulation lightly stuffed in there I could feel the air just gushing in. More evidence of this was the black on the insulation. 

So now my question is what would be the best way to fill these rim joists and sill ledge? They are approx 24" deep, 8" high, and 14" - 15" wide (see pic's). I have something in mind but wanted to get some forum feedback as to the best way to seal this off and insulate it so it makes the room above more comfortable. I would like to do this over this winter.

Additional info: Shooting the area in question with a thermal temperature gun show temps 47.5. 53 degree's on the bottom of the above floor in that area (throws a monkey wrench into spray foaming it). Also the cinder-block foundation all around the front of the house (faces dead north) was similar in temperature. Hasn't been that cold in our area yet at all. Thanks to all in advance....


----------



## Windows on Wash (Aug 30, 2011)

Spraying it will be easiest.

Caulk the exterior box (from inside and seal up all the leaks).

Get it air tight. You can spray it if you want or once it is air tight, you can just as easily fill it with Roxul, FG, or cellulose.

Cut in some rigid blockers and be done with it.


----------



## cbaur88 (Jan 25, 2011)

Windows on Wash said:


> Spraying it will be easiest.
> 
> Caulk the exterior box (from inside and seal up all the leaks).
> 
> ...



Thanks Windows, I planned on doing exactly what you recommended by caulking and sealing it up airtight then cutting to fit some rigid blocker and back filling w/ Roxul. Thanks again for the advice!! :thumbsup:


----------



## cbaur88 (Jan 25, 2011)

Windows on Wash said:


> Spraying it will be easiest.
> 
> Caulk the exterior box (from inside and seal up all the leaks).
> 
> ...


One more quick question. If I used a product like DOW Super Tuff-R (like I in-boxed you the other day with) cut it to size to fit the rim joist and back filled the remaining space w/ the Roxul would that have any ill affect in creating moisture situation. I know the super tuff R has moisture resistant facers and Roxul says to be water repellent.


----------



## Windows on Wash (Aug 30, 2011)

Should be fine. What is the floor above?


----------



## Gary in WA (Mar 11, 2009)

To be really safe from condensation; http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces/

Pull the soffit board, flash the perimeter to cover new soffit and 1-1/2” foam board.
.
Darn radiation, a more varied explanation; http://www.buildingscience.com/documents/insights/bsi-049-confusion-about-diffusion

You have to “break” the thermal bridges. Your plywood soffit has an R-1.25 plus the 2x6 = 8.13 R-value, but worse yet is they are acting as thermal “heat sinks” tied to the outside air. Foam board on the bottoms is the only way…… then insulate in the cavities as WW correctly stated.


Gary


----------



## cbaur88 (Jan 25, 2011)

Windows on Wash said:


> Should be fine. What is the floor above?


Floor above looks like plank flooring (see attached pic's) with carpet on top.


----------



## cbaur88 (Jan 25, 2011)

GBR in WA said:


> To be really safe from condensation; http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces/
> 
> Pull the soffit board, flash the perimeter to cover new soffit and 1-1/2” foam board.
> .
> ...


Thanks Gary, I am not the sharpest tool in the shed so I need to try and wrap my head around all the info loaded into those great articles, thanks for sharing. 

I just want to make sure I am doing the right thing and using the right products. As of now I have no issues with my crawlspace and moisture. If fact I am impressed at how clean and in good shape all the wood and flooring is in. However it's very cold the living space above it and I can see why. The last thing I want to do it try fix one problem and create another problem. 

As of now my plan is tackle all the rim joists 1st and seal them up. I want to use the rigid foam (DOW S.Tuff R) cut it to fit the rim joist (see attached pic) and seal it with Great stuff. I then want to back fill the cavity with Roxul. Once these are sealed up insulated I am thinking of just using faced fiberglass batt's between the joists seal up any holes around venting or duct-work with fire great stuff. If any of this sounds like a disaster please yell out. My plan changes everyday it seems as I learn more. Like I said I just don't want to fix a problem and then create another problem, thanks for all you help


----------



## Windows on Wash (Aug 30, 2011)

cbaur88 said:


> Floor above looks like plank flooring (see attached pic's) with carpet on top.


What is the floor covering? If something like vinyl, you need to be mindful of creating a double vapor barrier.



cbaur88 said:


> As of now my plan is tackle all the rim joists 1st and seal them up. I want to use the rigid foam (DOW S.Tuff R) cut it to fit the rim joist (see attached pic) and seal it with Great stuff. I then want to back fill the cavity with Roxul. Once these are sealed up insulated I am thinking of just using faced fiberglass batt's between the joists seal up any holes around venting or duct-work with fire great stuff. If any of this sounds like a disaster please yell out. My plan changes everyday it seems as I learn more. Like I said I just don't want to fix a problem and then create another problem, thanks for all you help


Fiberglass is the worst of the insulators on the market. You would be better suited with rigid foam cut to width, sealed up and then covered with a suitable ignition barrier.


----------



## cbaur88 (Jan 25, 2011)

Windows on Wash said:


> What is the floor covering? If something like vinyl, you need to be mindful of creating a double vapor barrier.
> 
> Fiberglass is the worst of the insulators on the market. You would be better suited with rigid foam cut to width, sealed up and then covered with a suitable ignition barrier.


Just vinyl in the kitchen under the tile. I will sure to be-careful in that area. 

I am not crazy about fiberglass either I am just dreading cutting to fit rigid foam for the entire crawl space, it's a daunting task so I am trying to take an easy way out. I may go Rolux the entire route, looks easy to work with, easy to cut, and more forgiving when compressed. Thanks again!


----------



## Gary in WA (Mar 11, 2009)

Roxul is fine*, inboard of the rigid foamboard* – canned foam sealed to *stop the air*, fig.#2: http://www.buildingscience.com/documents/information-sheets/crawlspace-insulation/

http://www.buildingscience.com/documents/information-sheets/critical-seal-spray-foam-at-rim-joist/

Check locally on the ignition barrier requirement also; http://dow-styrofoam.custhelp.com/a...sion/L3RpbWUvMTMxODYwMjg4MS9zaWQvKkNueDl5R2s=


Gary


----------



## cbaur88 (Jan 25, 2011)

GBR in WA said:


> Roxul is fine*, inboard of the rigid foamboard* – canned foam sealed to *stop the air*, fig.#2: http://www.buildingscience.com/documents/information-sheets/crawlspace-insulation/
> 
> http://www.buildingscience.com/documents/information-sheets/critical-seal-spray-foam-at-rim-joist/
> 
> ...


Thanks Gary, fig#2 is exactly what I did. I sealed up the gaps w/ sealant and cut to fit foam board sealed w/ great stuff. Will eventually back fill with Roxul to give some extra insulation. I already feel a difference in that area. Thanks for the info!


----------

