# How Should I Insulate Basement Walls that Were Studded Out?



## Windows on Wash (Aug 30, 2011)

Are the studs tight to the walls?

Are you opposed to Spray Foam or are you wanting a Homeowner/DIY application only?


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## vcollaco (Mar 11, 2016)

Half of the basement has the studs tight to the wall, the other side is about 4 inches out, due to plumbing. Never thought about spray foam. How expensive is it? I'm going to spend about $1500 on R21. What are the benefits of spray foam? Thanks for the advice!


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## Windows on Wash (Aug 30, 2011)

Spray foam will be more. 

Benefits are that it will serve as an air barrier, typically performs better in harsher climates, and it easier to get it done behind a wall that is already there.

I am not typically a fan of the SPF, but in a case like this, it seems to make sense.


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## mikegp (Jul 17, 2011)

Can you detach the walls and slide them forward enough to get rigid foam back there? Well, you definitely can, but are you willing to? Just knock out a stud or two to get the rigid foam in there depending on what size you can get and then slide it down the wall and repeat. Use tape and spray foam to seal seams and top/bottom.

If there's pipe or tight wiring in the wall already it might take a little extra effort, but still doable.


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## spaceman spif (Jul 28, 2009)

XPS behind the studs and then unfaced batt between the studs will get you a good R rating, plus it's a great choice to reduce any moisture or mildew concerns. Make sure you don't put in any plastic sheeting behind the walls!


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## vcollaco (Mar 11, 2016)

There is subflooring up to the studs, and the previous owner/contractor bolted the base of the studs to the concrete slab, so if I move the studs, I am basically starting all over. There is zero space behind the studs in half the basement. What is XPS? Also, I should avoid faced insulation with a vapor barrier no matter what? 

Do I want a gap between the insulation and the wall, or do I want to fill the entire space? keeping in mind how I waterproofed the foundation. Thanks everyone!


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## vcollaco (Mar 11, 2016)

Another question. Can I use faced batts without the vapor barrier, or is unfaced the only way to go?


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## spaceman spif (Jul 28, 2009)

XPS is extruded polystyrene, a type of foam board insulation that's better suited for an environment like a basement. You can buy it at any of the big box stores.

You are probably okay with faced batt insulation, but I would recommend unfaced. Using a vapor barrier is a no-no. Moisture will always find a way in and out of your basement, there's no way to make it 100% waterproof. So the trick is to minimize moisture intrusion, which you did. But what moisture does get through you should allow it a way to migrate. If you put up a vapor barrier, that will trap the moisture, and trapped moisture is where mold and mildew grow. I suggested unfaced batt cuz mold grows on organic surfaces like the paper facing on the batt. I actually bought faced batt that was on sale and gently peeled off the paper.


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## Fix'n it (Mar 12, 2012)

lets see pics. perhaps you could use a recip saw to trim the studs back from the wall.
but that would be a bit of work.


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## vcollaco (Mar 11, 2016)

Fix'nit, that sounds like a good idea. I might do that, since I'll still have 4 inch studs to support sheetrock... If I go that route, 2 inch xps and then unfaced R13 on top of it?


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## Gary in WA (Mar 11, 2009)

Welcome to the forums!

Seems like a LOT of work, since you have the membrane/drainage on the exterior to stop any water/moisture from going to the inside. That is why one uses XPS, most don't have the water stopped outside or CMU walls with a lot of area exposed above grade. Foam board is the safest way, but have you looked at other options?

Gary


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## vcollaco (Mar 11, 2016)

Gary, what else would you recommend? Should I just go with R-21 unfaced batts?


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## Windows on Wash (Aug 30, 2011)

Try PM'ing him directly. He will probably get notification of that communication more quickly.


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## Olcrazy1 (May 28, 2013)

Spray foam would be the best option in my opinion but it is not cheap, you get what you pay for. No gaps, no leaks, great to seal up rim joists, and adds rigidity to studs along with moister barrier. Expect to pay at least a $1 per square board foot. That's 12"x12" by 1" thick and you want at least 2" thick so $2 per sq ft. That's cheap imo but that's what I paid, had quoted as high as $6. Best of you I didn't do anything but cut a check, was done in a few hours.


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## Gary in WA (Mar 11, 2009)

IMHO, use some tar paper and fibrous cavity fill; http://www.diychatroom.com/f103/using-fiberglass-batts-basement-362354/index2/

An interesting read, click on the blue colored printings; https://foursevenfive.com/foam-fails/

Gary


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## vcollaco (Mar 11, 2016)

Ok, thanks for all of the suggestions. I had a spray foam guy give me an estimate. Not an option. It is about $1,000 more than what I'll spend on buying foam boards and installing it all myself. What about if I go with 2in. XPS, secured to the concrete block, which would be R-10 I believe, and then put back the R-13 fiberglass that is already existing on top of that? 

Can I leave the curled insulation the way it is along the sill plate, or should I rip it out and add rigid foam there as well?

I've attached photos of two different spots in my basement. Thank you!


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## vcollaco (Mar 11, 2016)

What will the tar paper do? On both sides as the article stated, or just against the concrete?


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## Fix'n it (Mar 12, 2012)

take out the top stuff and put EPS in there, save $$$.

idk, but i think you would be creating multiple vapor barriers = not good.


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## Gary in WA (Mar 11, 2009)

Good reads; https://www.cmhc-schl.gc.ca/publications/en/rh-pr/tech/95-207.pdf

http://www.diychatroom.com/f103/using-fiberglass-batts-basement-362354/index2/

https://www.google.com/url?sa=t&rct...sg=AFQjCNEWg58rFw5esA2hqHIyI2pYnsob9w&cad=rja

Gary


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## Olcrazy1 (May 28, 2013)

I would spend the grand and get spray foam. No way to 100% seal all gaps and leak paths with board, caulk and tape. I'm my opinion spray foam is money well spent. Quick, best seal and most of all someone else does it. Your time is worth something as well. Just my 2 cents


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## vcollaco (Mar 11, 2016)

Is friction fitting the xps between the studs enough, or do I need to use adhesive? If so, which do you recommend? Thanks!


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## ddsrph (Nov 23, 2013)

I would remove a few of the two by sixes at a time put in a sheet of XPS then replace with cut studs or substitute two by fours. The studs can be easily removed with saws all by cutting the nails. You could reattach the new studs by toenailing or use short pieces at top and bottom to nail to. Proceed down the wall removing and replacing the studs and adding the XPS sheets as you go.


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