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-   -   Adding more fiberglass insulation on top of R19 in attic (http://www.diychatroom.com/f103/adding-more-fiberglass-insulation-top-r19-attic-126750/)

aminus21 12-15-2011 10:48 PM

Adding more fiberglass insulation on top of R19 in attic
 
Hello all,

Last year we rolled on some faced fiberglass R19 between the studs in the attic. It didn't seem to quite insulate enough, still cold inside the house. I was told that R19 is not quite enough and I should add on another roll of R19. Do I just roll it on top, perpendicularly?

titanoman 12-15-2011 11:55 PM

Yes.

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cbaur88 12-16-2011 07:57 AM

Quote:

Originally Posted by aminus21 (Post 795097)
Hello all,

Last year we rolled on some faced fiberglass R19 between the studs in the attic. It didn't seem to quite insulate enough, still cold inside the house. I was told that R19 is not quite enough and I should add on another roll of R19. Do I just roll it on top, perpendicularly?

See the below link to find which zone you are in. R19 is really not much R-Value for your attic. That's usually recommended in a crawlspace or basement (at least in my zone). In fact all the zones I think except for zone 1 recommend R38 - R60 so I would for sure add another layer of R19 or more to bring you closer to recommended R-Value.

http://www.energystar.gov/index.cfm?c=home_sealing.hm_improvement_insulation _table



Yes, you would roll it on top perpendicular to your studs and try to avoid creating big gaps or seems where are can pass through. Make sure they are snugged up against each other. If you add another layer make sure it's unfaced (paperless) fiberglass as you don't want create a double vapor barrier. Also if possible air seal up any holes that might be visable up there to keep the warm air from passing through. Check out the helpful link below! Good luck :thumbsup:

http://www.youtube.com/watch?v=FRsOvW59V9I

Rewound98 12-16-2011 01:45 PM

Your best value for the $ is usually R30.

Just be sure to put in unfaced insulation over the existing R19.

If you haven't already air seal underneath that existing R19 or at least at the penetrations you can find.

Once you put any insulation over it perpendicularly it will be more difficult to do any air sealing.

AGWhitehouse 12-19-2011 03:10 PM

I would recommend a layer of R-30 with a cover of Tyvek. The air barrier will eliminate convective currents that greatly reduce the effective R-value.

Paul.le 12-20-2011 04:29 AM

AGWhitehouse, can we tyvek on the attic? Should we use radiant barrier instead?

Windows on Wash 12-20-2011 08:10 AM

Quote:

Originally Posted by AGWhitehouse (Post 797718)
I would recommend a layer of R-30 with a cover of Tyvek. The air barrier will eliminate convective currents that greatly reduce the effective R-value.

Better yet, blow cellulose. It will accomplish both.

It will settle out and form a good enough cap to prevent convective looping.

To the original poster, do not use a radiant barrier. You need proper insulation depth and an R-38 is the minimum.

AGWhitehouse 12-20-2011 09:46 AM

Yes you can use Tyvek in the attic. A radiant barrier is not necessary.

Blown cellulose is not considered an approved air barrier though it is much less resistant to air flor than standard fiberglass batts.

http://www.greenbuildingadvisor.com/...se-air-barrier

Windows on Wash 12-20-2011 10:36 AM

Quote:

Originally Posted by AGWhitehouse (Post 798413)
Yes you can use Tyvek in the attic. A radiant barrier is not necessary.

Blown cellulose is not considered an approved air barrier though it is much less resistant to air flor than standard fiberglass batts.

http://www.greenbuildingadvisor.com/...se-air-barrier

Blowing cellulose is so much easier at the end of the day.

It settles out better, more complete coverage, healthier and safer to work with (borate only stabilized option), does not allow the convective looping issues of blown in fiberglass or to a lesser extent, batts, recycled content, etc.

Putting tyvek, while effective and works well on kneewalls and similar, is just another step.

I 100% agree with you AGW, I just think it is another step and complicates the matter a bit.

aminus21 12-21-2011 10:38 PM

Wonderful, thanks for the advice everyone.

I don't want to go with cellulose or blown in fiberglass in the attic because it gets too messy.

Currently, the R19 that is up there between the joists is unfaced, but the "comfort touch" (plastic wrapped) insulation. I'd like to add another layer of the same stuff (R19 comfort touch), because I don't like to get itchy when I go in the attic for plumbing or storage. Is it okay to have two layers of unfaced comfort touch? Would it trap in moisture?

AGWhitehouse 12-21-2011 10:49 PM

Quote:

Originally Posted by aminus21 (Post 800026)
Would it trap in moisture?

Yep...it's wrapped in plastic...

For the amount of times you have to get up in the attic to deal with things you can stand a little scratching...If you wear long sleeves and gloves you won't get much at all. Plus when you're done touching it, rinse off with cold water first before washing with warm water. The cold water keeps your pores closed and allows the fibers to wash off easier.

Paul.le 12-21-2011 11:27 PM

I currently have close to 1foot of the white like cotton blow insulation but it is not condensed. I would like to add some batt to it. How should I do it? Above or under what I have?

AGWhitehouse 12-21-2011 11:43 PM

Quote:

Originally Posted by Paul.le (Post 800061)
I currently have close to 1foot of the white like cotton blow insulation but it is not condensed. I would like to add some batt to it. How should I do it? Above or under what I have?

You're better off just blowing in more on top. The pain-in-the-rear-end factor of trying to get around your attic to lay in batts with all that is pretty large. Unless, of course, you want it all gone anyways...then it can vaccumed out...

Paul.le 12-21-2011 11:46 PM

Quote:

Originally Posted by AGWhitehouse (Post 800065)
You're better off just blowing in more on top. The pain-in-the-rear-end factor of trying to get around your attic to lay in batts with all that is pretty large. Unless, of course, you want it all gone anyways...then it can vaccumed out...

Can I just push it down and cover with vitek before putting batt across ?

AGWhitehouse 12-21-2011 11:51 PM

Pushing it down will only reduce the R-value of the system. So in effect you will reduce your existing system and add more to compensate for what you just removed. The end result will be the same insulative value but you spent a few hundred bucks and alot of time sweating in an ichy attic. And what is vitek? If you meant Tyvek, then I would look into the blown cellulose that WOW spoke about to cover over the stuff you have. It will reduce air movement, add more insulation, and allow you to not have to mess with what you already have.


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