Need to add insulation to attic

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Old 10-19-16, 11:19 AM
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Need to add insulation to attic

Hi all!

So, we bought a late 50s/early 60s era split level home back in July. Among my to-do list: improve insulation in the lower attic.

Basically, there is insulation between the rafters, but it is very thin/has settled. I need to get in there and measure, but I know that the rafters are 2x6 and there is (at most) 2" of insulation there, with a paper backing facing up (away from the ceiling below / facing to roof).

My question: I know I could remove the insulation and get faced R-19/21 that will fit in the 6" cavity. I would prefer to just add insulation on top. So, what should I be looking for? I know (I think I know, anyway) to look for unfaced insulation. Question is whether to go the R-19/21 route and extend above the rafters, OR is there a thinner option readily available at 4" thick? Then I would buy more insulation to lay across the rafters (perpendicular) to really up the R value...

My other attic has insulation to the top of the rafters, and thats it. I put a floor down up there for storage, so I dont have ability to go any higher on the R value. Hopefully that isnt a problem (ie, having the lower attic R-50ish, and upper R-19)?

Thanks in advance for any advice! I learn a lot on this site
 
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Old 10-19-16, 11:39 AM
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First thing I would do is air seal while there isn't a lot of insulation to push aside. I prefer blown in cellulose to batts in an attic myself.
 
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Old 10-19-16, 11:43 AM
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You can get unfaced R11 fiberglass that is about 3.5 inches thick. That plus your 2" will fill your 2x6 cavity. Then put the thickest unfaced insulation you can fit on top of the joists running perpendicular.

R19 isn't ideal for an attic space; one option might be to install 2x6 sleepers under your storage floor area to give you more room for insulation; but if that's not practical you will have to live with it. There's no issue with having more insulation in one area than another.

Before you do all this you should look at your attic ventilation. If you have soffit vents you won't want to block them with added insulation; you may have to install baffles. If you don't have any ventilation, this would be a good time to address that issue as well.
 
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Old 10-19-16, 01:59 PM
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#1, No way are just 2 X 6 ceiling joist suitable for anything but light weight storage.
In your area you need at least R50 insulation.
https://www.energystar.gov/index.cfm...sulation_table
What you have was installed upside down.
The way to go is blown in with baffles added so the soffit vents do not get blocked.
 
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Old 10-19-16, 02:52 PM
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How much weight? This is a bit alarming. We put a bunch of storage bins up there, nothing over 100lbs-- is expect most in the 35-50lb range
 
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Old 10-19-16, 03:34 PM
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All advice above is good.
One of the problems with creating a storage area with a limited weight capacity is others in the future will not see the load limit sign. Basically, spaces like that get filled with whatever fits.

If the storage area is over a wall or two below then it will do much better.

Bud
 
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Old 10-19-16, 04:35 PM
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There are a couple walls under it. If I have too much weight up there, how would problems manifest?
 
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Old 10-20-16, 04:08 AM
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I don't often do load calculations but from experience, some in NJ, there are a lot of 2x6 ceiling joists out there and I have walked across many. Just my opinion here, but if you keep it reasonable and the area is not in the middle of a long span you should be fine. But 400 pounds or more pounds of dead weight will cause the ceiling to sag over time.

When you step on a 2x6 rafter it will bend but return to its original position when you step off. If that weight were to stay there for a long time the bending will not return and the displacement will be permanent.

Doubtful that things will come crashing through the ceiling, but cracks in the drywall around interior doors could be expected.

Bud
 
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Old 10-20-16, 07:52 AM
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thanks so much. I think if I keep things single stacked, we should be ok. Likely each bin is sub 100 lbs, spread over two 4/8 sheets of plywood

Now, back to the insulation question:

folks seem to have recommended blown in over batt. I had heard that batt over batt is better, as blown in will settle over time.

Now I am really confused

Also, what was the recommendation about upping the insulation on the area I have the 'floor' in? basically build a higher platform? Im unfamiliar with the term 'sleeper'...Not sure if that will fly...

We have soffits. Now I need 'baffles' too? Is this only if I go blown in, or with batts as well?
 
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Old 10-20-16, 08:21 AM
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hmmm. maybe I can do something like this?

https://www.youtube.com/watch?v=ghH5un9P7zQ
 
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Old 10-20-16, 08:24 AM
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Both blown in and batts have advantages and disadvantages. Blown in can be faster to install (but is really messy) and tends to fill odd spaces easier and better. It can settle over time, and it is a royal pain to do any work in an attic (such as wiring or plumbing, etc) that has blown in insulation. You definitely need baffles to keep it out of soffit vent areas, and baffles to keep it away from things like chimneys. Since you are usually borrowing or renting the blower, you generally have to do the blowing part of the job all at once.

Batts require care to install properly, especially near obstructions where fitting is important. Batts compress over time, which reduces R value the same way settling reduces r value of blown in. Both can be fluffed up to reverse this; but no one actually ever does that You can get by without installing baffles for batts, but it is better to do so because air washing over the insulation ends reduces it's effectiveness. Batts can be installed a little at a time as you have time, but overall they take more time to install.

Pick whichever you are most comfortable with....the important thing is to improve your insulation. Personally I prefer batt, because I really, really hate working in an attic with blown in.

Sleepers are pieces of framing lumber you would run perpendicular to the floor joists to raise up your storage flooring. You would remove the flooring, fill the joist cavities with insulation. Install the sleepers, insulate between them, and reinstall the flooring. It's a good idea to leave a little air space between the insulation and flooring so you don't build up moisture on the underside of the flooring.
 
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Old 10-20-16, 10:38 AM
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this is incredibly helpful. Thank you!

One follow up question: on the attic without the floor, I had can lights installed--they can contact insulation. Do I need to / should I use baffles/shields around them to keep insulation away (even though they are contact rated)?

What about on the other attic? I have a bathroom fan there... same question (do I need a shield around it?)

If I use batts, do I just simply cut it shy of the lights?
 
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Old 10-20-16, 12:40 PM
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Insulation contact rated can lights won't catch on fire if they get too hot, but it's still a good idea to keep insulation 2 inches or so away from them to make sure you won't get blinking from the thermal cutout activating from time to time. You can just shape batts short of the cans. With blown in you need a baffle that is rated for use with can lights. Depending on type of cans and how they are wired, the baffles can be a pain to install.
 
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