Hot Topics: Installing Faced Insultion Over a Bathroom

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Original Post: Direction of faced insulation over bathroom?

SamAlex Member

I need to install insulation in the attic over a full bath that has an exterior wall. It's my understanding I should use faced insulation for a vapor barrior since there is no previous insulation laid down. Does the "faced" side go down toward the ceiling/house or up facing the roof? I heard it varies based on your region; I am in the Northeast where we do get cold winters, but it also can get fairly hot in the summer.

XSleeper Group Moderator

Faced side to the interior.

SamAlex Member

If I need more R-value, can I stack unfaced rolled insulation or blown-in insulation on top of the base layer of the faced insulation? Does it matter what type?

XSleeper Group Moderator

Yes, you can. And no, it doesn't. If you do more batts, put them perpendicular.
SamAlex Member

Thanks for your help. Eventually, I want to better insulate the rest of the attic. I have a lot of areas with blown-in insulation already there, but it's not enough. Would you still recommend laying unfaced insulation over it perpendicular even though it could probably stack on top of what's already there?

XSleeper Group Moderator

The whole point of laying it perpendicular is so that there are no gaps. If it fits between the joists you have a 1 1/2" gap everywhere. If you lay it on top of the joists, you can push it tight. If you have blown-in, I would forget the vapor barrier and blow more in.

stickshift Group Moderator

I'm with X in that I would add more blown-in rather than batts.

SamAlex Member

That makes sense. For any other area (aside from above this bathroom), I could just have more blown-in.

Unfortunately, above this bathroom I had only installed unfaced insulation (all the blown-in got lost when the ceiling got replaced). I get moisture from the shower on the ceiling all the time when it's cold, so that's why I am planning to install R-38 Faced Insulation Batts above that area. Hopefully, that will take care of the moisture issue.

XSleeper Group Moderator

A vapor barrier won't have anything to do with whether or not the ceiling gets wet. It gets wet because it's a cold surface and the dew point is highest at the ceiling. If you don't have an exhaust fan yet, now is the time.

SamAlex Member

Unfortunately, I way over-calculated insulation in a past home project so I have a lot of faced R-38 batts sitting around to use.

Here is a picture of the bathroom in question where I get moisture on the ceiling when it gets cold. It does have an exhaust fan that seems to run just fine. I removed the R-13 insulation that was there and replaced it with faced R-38 as pictured. I still don't know if this will fix the issue, but I think the insulation that was there previously wasn't enough (plus it was unfaced). I made sure to use ventilation channels as shown in the second picture.

Since I have so much of these R-38 batts, I would still like to lay them perpendicular over the blown insulation in other areas of the attic. I know you said it would be best to just blow-in more insulation, but since I have these R-38 batts I might as well use them. It's been easy to remove the paper from them so that shouldn't be an issue. Assuming I install ventilation channels, can I just lay down the batts perpendicular as shown in my third picture? The fourth picture is a reference of what my current situation is in regard to the blown in insulation.

Thanks again for all the quick replies. I sure need the help, obviously!

XSleeper Group Moderator

Yes, as long as you don't block the soffit ventilation. You should also lay a lot of insulation over your bath fan. That cold metal could drip water in the winter otherwise.

jeweler Member

Is that the bath fan vent stack in the attic? Looks like it just dumps into the attic. Or does it terminate outside?

SamAlex Member

Thanks for the tip, I will insulate over the fan. Yes, it's connected to a stack vent (?) in the roof. I did find that the flexible duct is leaking though, so maybe it got a hole in it somehow. I will have to replace it.

I did have another question on the soffit ventilation. I am trying to install plastic vent chutes, but I am finding I can't reach far enough down to staple them for the length of the chute. Even doing an army crawl, it's physically impossible to reach far enough down to staple the bottom.

Is it OK to just have 3-4 staples at the top to hold it in place or will I run into issues later? I figure the insulation batts will even further hold them in place. I wanted to ask before installing all of these though as I have at least 100 to do. See pictures for detail on what I am talking about.

XSleeper Group Moderator

Yes, stuffing insulation snugly underneath them will hold them up.

To read the rest of the thread, look here: https://www.doityourself.com/forum/insulation-radiant-vapor-barriers/602984-directon-faced-insulation-over-bathroom.html

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