attic insulation – paper on batts
Hi again – i have another question regarding insulating my attic. I’m preparing it for the blown in cellulose that is happening next week and while looking at places to air-seal, i noticed something that didn’t seem right to me.
whoever insulated my attic previously but a cotton batt against the ceiling, with the paper side facing the lower level. That seems right to me based on what i’ve read. However, they then put another layer of insulation on top of this. the additional layer was a fiberglass batt, and it had paper on it and the paper side was against the lower cotton batt.
my reading on this (minimal at best) is that this allows for condensation between the two papers and this is not the right way to do it. The top batt should be paperless. am i right?
when i removed the cotton batt, it was very crumbly and impossible to remove cleanly. not sure if this is normal for this type of insulation after years, but i’m just checking.
Thanks,
pulper
Replies
Not ideal but don't obsess about it. Unless you live in an area where temps commonly hover near 0F the importance of a vapor barrier (and its placement) is overrated.
And in particular, in this case, there's really no (added) problem with two layers right against each other. The real issue is having insulation/barrier/insulation when the outer layer of insulation is insufficient to prevent condensation against the barrier.
Hi Dan - thanks for the reply. i'm near Detroit Michigan so the temps definately get near 0F. also, what i have here is:
barrier/insulation/barrier/insulation, with the top insulation being fiberglass so definately insufficient to prevent condensation against the barrier.
given my info above, would you think that this isn't good or still nothing to obsess over? i can remove and then have blown in cellulose if what i have, given above, is a bad situation.
thanks again.
As I understand it, you're putting the cellulose in the floor. And before you do that you will do your best to air-seal the floor (ceiling below). So I'm confused about you talking about replacing the attic ceiling insulation with cellulose. The "official" line would be to remove all insulation in the attic ceiling if the attic is "unconditioned" and the floor is insulated, but in practice there's likely no harm in having it there.
Thanks Dan for the follow up. I did some looking online and found a video that explains what i'm trying to avoid here. This should explain what my issue is with how the insulation was previously done in my house using two faced batts in insulation.
http://www.thisoldhouse.com/toh/tv/ask-toh/video/0,,20605338,00.html
If you go to this video and watch from around 18:10 to 18:50, you'll see what i'm talking about. Based on this video, it sounds like it's important to get rid of the insulation that was done in this manner in my home prior to having the cellulose blown in. the contractor wanted to simply blow on top of the current insulation but didn't look at the insulation carefully enough to see what was going on.
Thanks.
You still haven't explained how you're going to blow insulation OVER insulation in the ATTIC CEILING. That's what's got me confused.
the insulation company is blowing the celluose on top of the insulation that is already there, in my case fiberglass batts on top of cotton batts.
So the insulation is on the attic FLOOR, not the ceiling.
(In any event, if you put about 3x insulation on the cold side of a vapor barrier than what you have on the warm side of the barrier then condensation will not be a problem in normal circumstances.)