# To insulate or not to insulate a basement bathroom??



## mrmichaeljmoore (Mar 30, 2010)

I am in the process of doing a basement bathroom.
It will be connected to an already existing finished basement.

I have a question regarding what to do for insulation for the bathroom wall on the poured foundation wall. The wall is completely below grade. The sink and toilet will be on the foundation wall. Shower is completely interior. And the pex warer supply pipes that are on that wall are near the bottom third of the concrete wall.

Originally, I was going to do fiberglass batts in the stud wall cavities.
Then I did a little research on this topic and found a better way to go is the rigid foam board insulation.....

Unfortunately, though, I have no way of doing the rigid foam insulation. The stud walls are already up, and are completely fire blocked. So, I can’t even slide the 1/2" Dow Styrofoam behind the studs....

For what it is worth, the bathroom will have radiant floor heat (Warm Up brand) and a Panasonic Whisper Warm 110 CFM vent fan....so the bathroom will be heated and vented sufficiently, I would assume to remove any dampness....

Plus, I always run dehumidifiers on both the unfinished and finished parts of the basement in the summer. And my pellet stove is always running in the finished basement in the winter. So the basement is usually around 40-55% humidity.

Also, I have never got any water through the poured foundation wall that will now be part of the bathroom (knocking on wood right now). Also, one of the previous homeowners put a coat of what appears to be Dry Lock on the wall as well.

So, this is my question....
Should I just put some batts in the stud cavities? Or should I just leave it uninsulated?
If I do fiberglass batts, should I do faced batts toward the warm in winter side? Or unfaced batts?


thanks.
mm


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## vvvv (Mar 30, 2010)

Can you get a sheet of poly installed behind the studs?


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## gzecc (Mar 30, 2010)

Use unfaced. Fill it loosely. I don't think it pertains to your situation, but put it 6-8" off the ground.  I suggest this for when the basement floods- washer, hotwater heater malfunction etc.


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## op_man1 (Mar 30, 2010)

Roxul is probably better than fibreglass insulation for basement application (better resistance to elements, i.e. moisture, and can have R14 for stud applications). I would definitely insulate.


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## dave11 (Mar 30, 2010)

I definitely would insulate. It's still so easy at this point, with the stud bays open. 

Rigid foam is preferable IMO. It fits tighter, never falls down, and won't be bothered by any moisture that might accumulate. You're more likely to get the "advertised" R value out of rigid than you are out of batts.

The foam cuts pretty easy, easier than drywall in fact. If you have access to a table saw, it cuts like a dream, using a plywood blade. If you are using the 0.5 inch or 1 inch panels, they cut easily with a sharp knife and a straight edge. You could measure the bays and cut the foam to fit. Then caulk any wide seams. 

At the very least, put in unfaced batts, if you can find them. An unfaced 3.5 inch thick batt is made, but you can hardly ever find it, as everyone wants faced. But below grade, it's now the rec that you use no vapor barrier or retarder, so unfaced is the way to go (and it's cheaper than faced too). Use faced if that's all you can find.


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## gzecc (Mar 30, 2010)

If you have to use faced, cut slits it the paper all over.


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## mrmichaeljmoore (Mar 30, 2010)

Thanks to everyone for ther help thus far.....
still researching....

I found this at Lowes:

http://www.reflectixinc.com/basepage.asp?Page=DIY+Wall+-+Masonry&pageIndex=562

I can staple it right to the studs, which would leave an air pocket between concrete wall and studs, then go over it with sheetrock.

Anybody have an opinion on that product?  Anybody forsee any problems with it?


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## vvvv (Mar 30, 2010)

lolololo...! r=3.7 from how thick?
Moisture can come from the bathroom or the cement wall which if painted with sealcoat may minimize the moisture penetration. If you cant get poly behind the studs, install fiberglass with vaporface facing@ concrete  wall & finish the interior wall with poly also before hanging sheetrock


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## dave11 (Mar 31, 2010)

gzecc said:
			
		

> If you have to use faced, cut slits it the paper all over.



+1


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## dave11 (Mar 31, 2010)

mrmichaeljmoore said:
			
		

> Thanks to everyone for ther help thus far.....
> still researching....
> 
> I found this at Lowes:
> ...



In general, you don't want open air space in any structure you are trying to insulate, unless you can make it airtight, which is hard to do in a basement wall.


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## mrmichaeljmoore (Mar 31, 2010)

I appreciate everyone chiming in....

But what's amazing to me is that there are so many differing opinions (on this forum and other forums that I have asked the same exact question)....frustrating for a homeowner.
Yes vapor barrier, no vapor barrier....
Faced insulation, unfaced insulation.....


I am wondering though......... would the safest option to be leave it uninsulated??
That way if I do get any moisture, it can dry out on its own and I wont have to worry about any insulation retaining moisture...
Pipes will not freeze....so that's not an issue....

Like I said, the bathroom will have radiant floor heating and a Panasonic 110CFM vent fan (with the heater)....
Plus, I always have two dehumidifiers running in the basement....along with my pellet stove in the winter.
So the bathroom shouldn't be damp...

Unless someone can give me an overwhelming reason why I shouldn't leave it uninsulated, I may go that route...

Thanks again.
mm


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## vvvv (Mar 31, 2010)

mrmichaeljmoore said:
			
		

> I appreciate everyone chiming in....
> 
> But what's amazing to me is that there are so many differing opinions (on this forum and other forums that I have asked the same exact question)....frustrating for a homeowner.
> Yes vapor barrier, no vapor barrier....
> ...


R=R


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## mrmichaeljmoore (Mar 31, 2010)

BLIMP said:
			
		

> mrmichaeljmoore said:
> 
> 
> 
> ...



BLIMP --

Not sure what you mean by R=R.....


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## mrmichaeljmoore (Apr 1, 2010)

Here are a few pics of what my wall looks like now.

The gap between the back of the studs and the concrete wall is no more than 3/4".
Plus, it is all blocked off and fire foamed, so I can't slide some 1/2" rigid foam behind it.
Plus, as you can see, I have all the plumbing and wiring running through the studs...so not much room in the stud cavity.

Like I said, I think I may go the* no insulation *route......

thanks for the help....
mm


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## dave11 (Apr 1, 2010)

Any room that gets cold enough to require heating should be insulated. Otherwise, for the next 30-40 years, heat that you're paying for will be passing straight through the drywall and right into the soil around your basement. If you were to do a heat analysis (which is fairly easy to do yourself), you will see how much money you will lose by not insulating.

That said, I admit that at this point of construction, you have limited options. You have a lot of obstructions to work around in the stud bays. It would be hard to get either fiberglass or rigid foam into many of those spaces, but you could do so in the bays that are relatively clear. Blown-in FG or cellulose could be attempted after the drywall is up, but it's more expensive, and I'm not sure it's recommended for basement walls. You might want to check into that. Also it's much more expensive than FG batts. Blown-in foam is even more expensive still. 

As for poy/no-poly and faced/unfaced, it is the old opinions versus the new. It used to be thought that poly or faced insulation prevented moisture from moving through the wall and condensing on the cold concrete, or that it prevented moisture moving from the soil around your home from coming through the concrete. In fact, you can have both, and the current rec is to use unfaced batts below grade, and use no poly barrier, so that any moisture coming into the wall cavity can eventually pass through without condensing. Check out the studies and recs at buildingscience.com. The current belief is that vapor barriers in basement walls trap moisture and encourage rot.

It's even less an issue for you, since you left the small air space behind the wall structure. Any vapor passing through from either direction will be taken up by the air in the open space. Where it goes from there depends on the temps of the two surfaces, and if the air circulates at all.


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## Tony H (Apr 4, 2010)

yes insulate as much as possib;e


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## LLigetfa (Apr 4, 2010)

Even if not for saving on heating, anywhere humid air meets a cold surface has to be insulated to prevent mold and mildew.  It would be a big mistake not to insulate.


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## Dune (Apr 4, 2010)

For such a small space, call a spray foam contractor. Yes, definitely insulate, and pretty much nothing beats spray foam, especialy proffesionaly applied.


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## Rustaholic (Apr 4, 2010)

mrmichaeljmoore said:
			
		

> Here are a few pics of what my wall looks like now.
> 
> The gap between the back of the studs and the concrete wall is no more than 3/4".
> Plus, it is all blocked off and fire foamed, so I can't slide some 1/2" rigid foam behind it.
> ...



That slightly busy wall is perfect for the spray in foam insulation.
You would have to know someone that does that work to get any decent price on the job though.
If you just took the total time so many folks have used 'talking" about this here you could have insulated it with unfaced fiberglass already.
It is simple to split the batt to put some behind the pipe and the rest in front of the pipe.
If the only 3 1/2" R-11 or R-13 insulation is faced just peel the paper off of it.
If you slept through the job it would all be done in two hours.
By all means insulate it.
I am a licensed builder.


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## mrmichaeljmoore (Apr 5, 2010)

Dune said:
			
		

> For such a small space, call a spray foam contractor. Yes, definitely insulate, and pretty much nothing beats spray foam, especialy proffesionaly applied.




I did call a local company to inquire about spray foam insulation......the guy said it was too small of a job for him....at least $1000. he said it was not worth it to me or him.


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## mrmichaeljmoore (Apr 5, 2010)

Well, let me ask the question this way.......
What potential problems can i possibly run into if I DO NOT insulate?
Is it merely that it will cost more to heat the bathroom?
With no insulation in there (fiberglass or foam or any other kind), there is no potential that moisture or vapors will build up in the stud wall causing mold, right?

For what it is worth, I do not plan on heating the bathroom 24/7.  The unfinished portion of the basement typically will be about 60-65 degrees year round.  The finished side is a little bit warmer.
The bathroom will have the radiant heat in the floor, on a thermostat timer.  Come on in the morning for showers, then go off for the day...then come on in the evening until bedtime.  In addition, the bathroom will have the Panasonic heated fan.  And from what I understand, that fan can throw a lot of heat in a short amount of time.....

But, it seems though base don what dave11 and Rustaholic said, that since I can't do the rigid foam panels or spray foam, then the next best thing to do would be the un-faced fiberglass batts, right?  What happens though if the fiberglass gets wet?

thanks.
mm


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## Rustaholic (Apr 5, 2010)

Do what you want to do.
You ask for advise then as it is given to you you keep questioning it.
If it was mine from the start I would have planned it differently.
There would be at least an inch of blue styro. behind the framing.

If it was handed to me as-is then I would use unfaced FG.
Like someone already mentioned.
Keep it up just a bit from the bottom.
I would keep it up six inches.
The key here is JUST do it.
I'm done here.


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## LLigetfa (Apr 5, 2010)

mrmichaeljmoore said:
			
		

> I did call a local company to inquire about spray foam insulation......the guy said it was too small of a job for him....at least $1000. he said it was not worth it to me or him.


Google for *do it yourself spray foam kits*.  They are good for small jobs.


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## mrmichaeljmoore (Apr 5, 2010)

Rustaholic said:
			
		

> Do what you want to do.
> You ask for advise then as it is given to you you keep questioning it.
> If it was mine from the start I would have planned it differently.
> There would be at least an inch of blue styro. behind the framing.
> ...



Rustaholic:

Sorry if I came across as unappreciative of everyone's advice and help....that was not my intent.
It's just that there is so much conflicting information out there regarding basement insulation, it is tough for a homeonwer like myself to make a decision he can feel comfortable with.  
Someone will say one thing, then another person will say that's wrong.
That's why I keep asking questions.

Yes, you are right, I did make a mistake in planning out the insualtion portion of this project....but unfortunately, I cant go back now.


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