# Insulating Basement



## prairiewind (Jan 26, 2019)

When I moved into my house, the basement had a rodent problem. I did an attic inspection, duct inspection, etc., and was able to confirm that it was, for the most part, isolated to the basement because of entry points and food source (dog food).


My tolerance for ick is very low, so my spring cleaning was basement insulation removal (fiberglass batts) and TOTAL basement sanitizing. :sweatdrop:



Now I have the full view of basement to do hole filling, etc., which I will do with foam, copper mesh, caulking.


Then, the big thing, is to re-insulate the basement....


I am very hesitant to use fiberglass again, because the ease of rodent occupation is high, and when it gets contaminated it is hard to clean.


The basement is framed, so foam board would be hard because I would have to remove the current framing.


I am tempted to use closed cell spray foam, despite the cost, because it would discourage nesting (although I am confident I can exclude rodents through addressing holes, I still have PTSD and fear of recurrence). Other benefits are ease of cleaning, that it kind of further seals the basement over top of the holes I fill, and is moisture resistant (some of the batts were discolored from moisture from condensation).


Is the foam going to cause me grief. Should I stick to fiberglass batts?


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## Nealtw (Jun 22, 2017)

prairiewind said:


> When I moved into my house, the basement had a rodent problem. I did an attic inspection, duct inspection, etc., and was able to confirm that it was, for the most part, isolated to the basement because of entry points and food source (dog food).
> 
> 
> My tolerance for ick is very low, so my spring cleaning was basement insulation removal (fiberglass batts) and TOTAL basement sanitizing. :sweatdrop:
> ...


 It sounds like you are in good shape, no water leaks or anything. Condensation happens when warm moist air get to a cold surface so air getting around outlets and any others and insulation that didn't fit nice and tight. So the key is taking the time with fitting insulation like you have OCD and then make sure there are no holes for air to get in there. 

Is the wall built tight to the foundation or did they leave a little space.
Is there a space at the top where air can get to the foundation from the ceiling joist cavity?


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## chandler48 (Jun 5, 2017)

Based on your fears, consider using Roxul insulation in batts. It fits snugly between 16" oc studs, does not sag, is water proof, vermin proof, fireproof, and mold proof. It also requires no vapor barrier, but it is a good practice to install one. $pray foam is good, but expen$ive.


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## Windows on Wash (Aug 30, 2011)

CC SPF will be definitively more expensive than Roxul batts. I think, as mentioned above, you air seal everything and then use batts. 



Be sure to get putty pads behind what will be holes in the finished wall and make sure the finished wall is air tight. 



Look up ADA (airtight drywall approach). 



Be sure the rims are sealed and insulated as well.


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## prairiewind (Jan 26, 2019)

The basement is unfinished, so the walls are framed and open, with about a 1" space between the framing and the concrete. The ceiling joists and rim joists are open, too.


The experience of having contaminated insulation to remove was not pleasant, so the idea of having spray foam is appealing, as I would assume that although mice can chew through it, any tunneling would be isolated and infrequent. I am doing an exterior/interior mouse-proofing exercise, but will always remain paranoid.



I will mull over using Roxul. Although it is less conducive to rodents making nests, etc., I am just worried that if mice live on it or move around through it that it will get contaminated, and that it is difficult to clean.


I was thinking about foam board, but that would involve temporarily removing the framing, and would also be a bit difficult to manage around the rim joists. Also, half the basement is a crawl space (the house is a split level), so I can't actually remove the framing there, as it holds up the floor for the walkout level.


I think that with spray foam or foam board I may have to cover it with drywall to meet fire code, so in some respects, Roxul would be better for that. Plus, it would be easier to install in the rim joist area.


Half of the wall of the non-crawl space part of the basement is above ground, so insulation in my climate area is almost a must.


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## carpdad (Oct 11, 2010)

Also from outside. Sheetmetal between siding and foundation. Around and under deck ledger. Plumbing, electrical and vents. Drier vent is often low to the ground and big gaps around it.


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## Windows on Wash (Aug 30, 2011)

You can remove a bit of the framing and slide the foam in that way if the gap is consistent. You don't want to leave an air gap in this case. 



https://www.joneakes.com/jons-fixit...aces-in-walls-myth-and-science---overview.pdf


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## prairiewind (Jan 26, 2019)

I think I will go half the basement with rigid foam, and half with Roxul.


I think I can remove a lot of the framing either temporarily, or permanently if I get foam that I can attach drywall to directly. Reinstalling the framing should be easy, I just have to learn how to put nails into concrete floor.


Being diligent with air sealing and vapor barrier will be my goal, especially at the foam board and Roxul interfaces. The foam board is ideal, just not suitable for the whole basement.


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## chandler48 (Jun 5, 2017)

I'm not following your "removing" the framing, putting in Rigid foam and sticking sheetrock to it, then putting up framing. What is that? Your foam will be much more expensive than Roxul, so why not frame it properly, install Roxul and be done with it?


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## user_12345a (Nov 23, 2014)

batt insulation with vapour barrier on warm side is common in basements but lousy in cold climates.

a vapour barrier on warm side only works well when you have drying potential on the other side. Exterior house wrap is specially made to allow moisture to escape, in a basement you have soil on the other side of the concrete wall and water-proofing membrane.

No barrier is perfect and air/moisture always leak in and move through the wall. No foundation water proofing is perfect either.

So in a basement, you have moisture coming from the concrete and moisture coming from the house even when the barrier is used. Moisture that gets in can get trapped by the barrier and condense on the foundation, especially above ground.

Water reduces insulation r-value and can rot out wood framing if there's enough condensation.

It's best to have a complete thermal break directly on the wall that's unaffected by moisture (like 2" of foam or roxul board) to prevent condensation from ever forming. Roxul batt insulation can be put between the studs for extra r-value* with no vapour barrier *so moisture does not get trapped in the wall assembly.

The thermal break stops the condensation so you don't need the vapour barrier and the wall assembly has drying potential.

Code may still require a vapour barrier when batts are used even with a thermal break, so if you're getting permits and have the thermal break it's best to put just to pass inspection, then slash many holes in it just before hanging the drywall.

People starting doing fiberglass with plastic vapour barrier in basements before there was a good understanding of building science. 

It's still done this way due to a lack of education and out of date codes.

Problem is it's too labour intensive - the framing has to be removed to put the thermal break.

Another good method is just using sprayfoam which is impermeable and has fantastic air sealing properties, but it's expensive and can potentially off-gas toxins if the foam doesn't cure properly on site.

This is only my opinion.


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## prairiewind (Jan 26, 2019)

chandler48 said:


> I'm not following your "removing" the framing, putting in Rigid foam and sticking sheetrock to it, then putting up framing. What is that? Your foam will be much more expensive than Roxul, so why not frame it properly, install Roxul and be done with it?



Yeah, I could have been a bit clearer. There is currently framing, but I can't fit rigid foam behind it. So, I would have to remove the framing. I saw some rigid foam that can have drywall screwed into it directly. Not sure if that is an option, though. In any event, I could put the framing back up if I needed to after putting the rigid foam in. Then I would have something to hang the drywall on.



I would rather use rigid foam than Roxul, because cleaning after previous owners' mice when the fiberglass batts were there was horrible, and because I'm paranoid about mice now, I think cleaning rigid foam would be easier, and it would be more mouse proof. However, part of the basement I will need to use Roxul anyway (the crawlspace), because the framing holds up the floor above it. I don't think it is possible to put rigid foam between the studs.


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## chandler48 (Jun 5, 2017)

Just so you are clear, you will not have any XPS to "clean" after you install it as it must be covered with a wall covering like sheetrock, paneling, etc. Roxul is waterproof, fireproof, mold proof and vermin proof, so mice won't eat any of it.


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## user_12345a (Nov 23, 2014)

> I don't think it is possible to put rigid foam between the studs.


You can cut it to size and seal it to the studs with canned foam.

*

Yes, foam must be covered with something non-combustible.

For roxul keep in mind there's also the board - made from the same stuff but solid. It's a good substitute for foam in some applications.

Roxul in general is good stuff.


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## prairiewind (Jan 26, 2019)

I will keep the thread up to date with progress. This is still a couple of months down the road. 



I really appreciate the help! Youtube videos tend to promote a single way of doing something, and miss all the nuances of what to do for the case-by-case scenarios of a real homeowner.


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## More Power! (Aug 2, 2011)

user_12345a said:


> It's best to have a complete thermal break directly on the wall that's unaffected by moisture (like 2" of foam or roxul board) to prevent condensation from ever forming.
> ...
> 
> The thermal break stops the condensation so you don't need the vapour barrier and the wall assembly has drying potential.
> ...


 Nailed it, in my (inexpert, but studied) opinion.

I'm doing it this way: How to Insulate a Basement

Because my local HDs and Lowes' didn't have the tongue-and-groove insulation, I'm just making sure the seams are as tight as possible and I'll tape the insides of the seams with Tyvek™ tape. I'm applying expanding foam to any gaps along the bottoms.

The rim joists, which, in some places are doubled-up, were first "seam sealed" with Great Stuff. I placed 2" Foamular where there were single thickness' of rim joist, 1" Foamular over-all, then 1" of foil-backed foam over-all for fire code. The first layer of insulation was seam-sealed *again*. The 2nd and, in some cases, 3rd layers of insulation were fitted as snugly/precisely as possible.

Part of the my reasoning for going to all that trouble was not only to reduce radiated heat, and air and moisture incursion, but to reduce the heat signature outside to make the area less attractive to critters looking for warm places come fall. We've had rodent problems, ourselves, in the past. (I had found, in the process of gutting the room in question, that there had been a gap of 1/4" or more between the top of the basement wall and the bottom of the rim joist. I'm sure that had a lot to do with it.)


Btw: If you go with rigid foamboard insulation, and choose to use Loctite PL300 adhesive, *don't* believe what you read or see about its initial tack. It has all the initial tack of toothpaste. Unless the surface to which you're applying the foamboard is nearly ruler-flat: It won't stick worth diddly, initially, and it takes a full 24 hours to cure. So ways to keep the foamboard tight against the walls for that 24 hours is de rigueur.












(Note the clamps on the floor joists at the top, as well.)


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## chandler48 (Jun 5, 2017)

Use FuzeIt by Locktite and it will stick almost immediately and hold well.


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## geenowalker (Aug 19, 2013)

Just a side note...I used 1" rigid foam directly on the concrete floor. Shaw laminate flooring right over top. I did not want to use the tiles nor wood on the concrete. 5 years later, the floor is performing and looking great. There is a light touch of sponginess in a corner due to the concrete, but I would do it all again. Wife is happy cause her feet are warm.


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## prairiewind (Jan 26, 2019)

As an update, apparently foam board will cost me a fortune, as it needs to be R12 for my building code. Spray foam would be the same cost, so I think that Roxul is going to be my choice.


Despite the PTSD from cleaning the basement before (the rodent contamination), I could replace the Roxul insulation 5 times and it would still be cheaper than spray foam. Not to mention, I spent the summer sealing the outside of the house from rodents, think I actually found where they got in and sealed that, and run a pretty decent trap line in my basement these days (and don't catch anything).


I will carefully do sealing of cracks, etc., with a can of spray foam as a way of sealing airflow prior to putting Roxul in place.


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## user_12345a (Nov 23, 2014)

Remember, you can put only like 2" (or maybe 1") of roxul or foam board and put batts between the studs. you don't need the full r-value to be rigid insulation, you only need enough to have a good thermal break.

the higher the r-value batts used, the thicker the thermal break has to be.

this is a classic example of codes being really stupid and written by people who don't understand how things work in the real world. 

R-10 rigid continuous thermal break will outperform R12+ batts in a framed wall any day, especially in a basement. You have thermal bridging through studs and reduce r-value due to moisture.


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## More Power! (Aug 2, 2011)

user_12345a said:


> R-10 rigid continuous thermal break will outperform R12+ batts in a framed wall any day, especially in a basement. You have thermal bridging through studs and reduce r-value due to moisture.


This ^^^^^

Plus rigid continuous foam will yield a continuous vapor barrier, which cannot be achieved with batts between studs.

By the time I add air space and drywall my basement wall insulation R-value will be darn close to, if not better than, R-12. (Insulation: R-10, air space: +-R-1, rock: +-R-0.5.)


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## Calson (Jan 23, 2019)

I would have had 1-2 inches of spray foam applied to the joists above the basement as that would have provided a moisture and thermal barrier for your living space. 

Something to be aware of is that many termite and pest control companies are terminating contracts where homes have spray foam applied as it makes inspections impossible to do properly.


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