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Rafalski 03-16-2011 11:47 AM

Putting up additional insulation in the attic
 
Hello to all, my first post here so please be gentle :) We are closing on our first home end of March and one of the inspection items that came up was that the inspector suggested we add some additional R-19 insulation in the attic to what is already there. I am pretty sure I will be going with fiberglass insulation as its what's already there but am not sure if it is faced or not. If it is then I would like to purchas unfaced insulation in order to add but found it hard to find an R-19 insulation that is unfaced. Do you guys know if it would be ok to purchase lets say faced R-19 insulation and rip off the vapour barrier from what I have in the attic now or the new one in order to eliminate one of the vapour barriers? I do know that it needs to face towards the living space. If there is no current barrier I imagine I would just need to lift current insulation and put the new one on the bottom. I live in northern NJ. Thanks for the help.

thehvacguy 03-16-2011 11:50 AM

If it were my home i would blow insulation right on top of what is already there. The cool thing with blown insulation is you can control what the r value is based upon how much you blow in

Rafalski 03-16-2011 04:10 PM

Quote:

Originally Posted by thehvacguy (Post 610578)
If it were my home i would blow insulation right on top of what is already there. The cool thing with blown insulation is you can control what the r value is based upon how much you blow in

I did think of that but I would rather stay away from blow in insulation, for one thing I heard its heavier and actually compresses the batted insulation losing on R value, second thing I might want to make some storage space in the attic one day and just dont want to deal with the mess of little cornwebs everywhere. Also the house has an attic vent so I need to worry about not insulating everything.

Marty S. 03-16-2011 07:25 PM

Certainteed makes R25 unfaced fiberglass batts. Bought a bunch,enough for 2 small homes, last summer when one of the big box stores had a real good sale going on, 15"x 18' was $6. Our attic is very short so rolling back batt instead of belly crawling though blown was the only way it was getting done. It made a noticable difference in the heating.

HomeSealed 03-16-2011 10:42 PM

If you blow fiberglass over the existing batts, it will not affect the r-value due to compression... For storage, the r-value per inch will be the same, so it wont make any difference that way either. If you insist on making it more difficult, then go with the batting, but find unfaced. I'd also HIGHLY recommend air sealing prior to adding insulation.

Rafalski 03-17-2011 04:59 PM

Quote:

Originally Posted by HomeSealed (Post 611028)
If you blow fiberglass over the existing batts, it will not affect the r-value due to compression... For storage, the r-value per inch will be the same, so it wont make any difference that way either. If you insist on making it more difficult, then go with the batting, but find unfaced. I'd also HIGHLY recommend air sealing prior to adding insulation.

Could you provide a bit more info on ait sealing, do you suggest somewhere I could read up on it ? not really familiar with this idea.
update. Ok I did google some info on it and I guess I know what you are talking about, great idea by the way. Perhaps you can enlighten me on another subject. The attic in the house is ventilated and in one spot there is a big vent that I guess opens to circulate the hot air out of the house at certain times. Is there a way to insulate that if I was to keep it off ? I assume I can not insulate otherwise as I would not be able to move air, but uninsulated isnt that a big air leak ? there is really not much there to stop air from traveling up or down.

cschwehr 03-18-2011 10:29 AM

I totally agree with HomeSealed...

Air seal all penetrations, chases, electrical boxes, fans, recessed lighting, wall joints, etc. properly using acoustical sealant, foam, fire caulk, EPS inserts, drywall and the right items.

There are lots of articles and read lots about it. Install vent channels and fill the space under the vent channel carefully with EPS to prevent circumvention of the channel through your additional insulation.

Once all your air sealing is done, verify your b-vent (if you have it) shielding is high enough to protect the additional insulation from contact.

I'd then blow in extra. I've never heard complaints of additional compression, that sounds like something a guy at a hardware store would come up with and tell you. :D

Batts have holes no matter how well you try to get it right. Blow in, cellulose or fiberglass, both reduce that issue.

I guess it depends where you live, but here in Canada - few people use the unconditioned attic for storage as a commonplace thing, but I wouldn't recommend it all the same anywhere. Every item you put in there will be subject to the hard ends of the spectrum of winter's chill and summers heat - along with variations in moisture. I know there is a price on space though in today's world - so I understand your interest also.

HomeSealed 03-18-2011 09:07 PM

Quote:

Originally Posted by Rafalski (Post 611458)
Could you provide a bit more info on ait sealing, do you suggest somewhere I could read up on it ? not really familiar with this idea.
update. Ok I did google some info on it and I guess I know what you are talking about, great idea by the way. Perhaps you can enlighten me on another subject. The attic in the house is ventilated and in one spot there is a big vent that I guess opens to circulate the hot air out of the house at certain times. Is there a way to insulate that if I was to keep it off ? I assume I can not insulate otherwise as I would not be able to move air, but uninsulated isnt that a big air leak ? there is really not much there to stop air from traveling up or down.

I'm unsure what you are speaking of as a "big vent", but put it this way: Ventilation from attic to exterior= good. Ventilation from conditioned airspace to attic= very bad... Seal all of those up.

AllanJ 03-19-2011 09:27 AM

Quote:

Originally Posted by HomeSealed (Post 612233)
I'm unsure what you are speaking of as a "big vent",.

For a whole-house fan that vents into the attic.
Quote:

Originally Posted by HomeSealed
If you blow fiberglass over the existing batts...

Is blown fiberglass intended for attics? Wouldn't fiberglass dust be stirred up everytime someone went up into the attic and then be inhaled? (I think rock wool is heavier and not likely to float in the air.)

HomeSealed 03-19-2011 10:19 AM

Personally, I prefer cellulose, but either will work in your application. I only suggested fg because you were concerned about the weight. Blown FG is intended almost exclusively for attics (although there are some new products that can be dense-packed) . FG is actually not very dusty at all. There is less dust than cellulose during installation, and afterward, neither produces much... You probably are not going to want to roll around in it very often anyway. If you need attic storage, build a platform so that you are not disturbing it everytime you go up there.
On the fan, if you have an exhaust fan venting the conditioned air of your home into the attic, that is bad. That needs to be ducted to the exterior.

gma2rjc 04-16-2011 11:58 PM

A few years ago my neighbor added a lot of fiberglass blow-in insulation to his attic. The reason I know this is because there is a small window in their attic that faces my driveway. After he added it, there was about 10"-12" of it up against the lower half of that window. Every year it settled and I saw less and less of it. Now I don't see any of it.


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