# roxul exposes



## tro876 (Dec 10, 2013)

Hi there. This is my first post. I did search earlier threads but couldn't find anything on this. I live in an older split level house. The bottom level is half concrete crawl space exposed to the other half which is full living space. I need to seal and insulate the crawl space to keep it dryer and warmer. I plan to do rigid foam on concrete, then frame, then roxul Batts. Can I leave roxul exposed in a crawl space? Thanks.


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## Windows on Wash (Aug 30, 2011)

If you condition it, yes.

If you are insulating the crawlspace wall, you will be sealing it up and treating it as part of the conditioned space.

No reason that it shouldn't do fine in that application. Not sure it is needed unless you are going to be finish it with drywall as it seems a bit reverse engineered.

Why not another layer of rigid foam with a foil layer for ignition barrier.

Be sure to check with local code on application and compliance.


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## tro876 (Dec 10, 2013)

Thank for the reply. I was thinking more R value with the roxul but I see your point about having the VB on the exterior then exposed Batts being sort of backwards. If I double up rigid could I skip framing it all together? I want to use it for storage so I had planned on using Dmx subfloor, then taping it to the rigid on the wall to create the seal then OSB on floor. So 2 questions, can I get away without framing and what type of foil should I use to cover the rigid? I will double check code here but I'm sure that is acceptable.


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## Windows on Wash (Aug 30, 2011)

Double check local code.

If you use the rigid insulation, you can skip the framing.


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## Gary in WA (Mar 11, 2009)

This doesn't usually require the ignition barrier; http://building.dow.com/na/en/products/insulation/thermaxsheathing.htm

Your Dmx sub floor is $0.72 per sq.ft. PLUS shipping.... this is from local HD at $0.05 http://www.homedepot.com/p/Scotts-4...e-Fabric-204133/203074617?N=bx4q#.UqeViScbHAW plus Delta fl with free shipping; http://www.spycor.com/Cosella_Dorken_DELTA_FL_Subfloor_p/dlfl.htm

Be sure to air seal all floor penetrations- wiring/plumbing, etc.--- first- to stop sending air to attic; http://www.wag-aic.org/1999/WAG_99_baker.pdf

while pulling conditioned air out of house through the walls; http://www.homeenergy.org/show/article/nav/troubleshooting/page/2/id/1360

No frame wall required unless running electrical boxes (as in a basement). Use foil-faced foam board on the rims and on the top of concrete wall next to the mudsill; http://www.buildingscience.com/documents/information-sheets/crawlspace-insulation/ Foil tape the seams, canned foam the joints at top/bottoms. Glue and possibly mechanical fasteners required per local code. 

Find your Zone; http://energycode.pnl.gov/EnergyCodeReqs/index.jsp

Use Zone to find fb thickness; http://www.buildingscience.com/docu...ulating-sheathing-vapor-retarder-requirements

If in a cold climate and you are unsure if foam board is under rat slab perimeter at exterior walls, lay some foil-faced on first 2-4', depends on location- to stop vapor transmission to your items--- or elevate on boards with air movement under them (though they will still be a heat loss area this way; http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CC4QFjAB&url=http%3A%2F%2Fwww.engr.psu.edu%2Fphrc%2Ftraining%2FWebinar_Slab%2520Insulation.pdf&ei=b52nUtjNFdbZoATNyIGgDA&usg=AFQjCNF2aFYOL3tTe2J5ZE3_BCHzrqGZkg&bvm=bv.57799294,d.cGU&cad=rja

Gary
PS Welcome to the forums!


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## jklingel (Dec 21, 2008)

on leaving roxul exposed, if you end up using it. imo, no. it is quite dusty. good insulation, but very dusty. cover it.


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## gma2rjc (Nov 21, 2008)

Here is a good thread you may be interested in looking at. Not because of the Roxul, but it looks like it may be similar to the project you're doing.

http://www.diychatroom.com/f49/basement-redo-2013-a-174357/


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## tro876 (Dec 10, 2013)

Thanks alot for you input on this. Very Helpful


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