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Old 08-13-15, 02:19 PM   #1
Geo NR Gee
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Default Adding more Blown in Insulation

I have been considering installing more blown-in insulation onto the existing blown-in already in the attic space. Its been in the 80's outside here and hotter in the attic, but I want that extra insulation benefit inside the living space for the winter also. I have help now from the boys before they get back to college, so we have to get it done in the next week.

There is a local insulation installer that has retired and is clearing out his inventory. He has bags of 30# for $11.99 each. The local box stores have 15# bags for $18.99 a bag. So a pretty good savings I figure.

I have about 950 Sq. Ft. of attic space to cover. Some of the existing insulation has been pushed aside where I navigated to add boxed covers to can lighting boxes and bath fans, etc.

I was thinking of spreading out the existing insulation to fill in those areas and then use a piece of plywood to flatten it sorta making it more of a dense pack, then blow in the new insulation on top of it. Maybe that's too much work? I don't know. Will that cause problems?

According to his ad, for 1000 sq. ft, one would need
11 bags = R13
17 bags = R19
19 bags = R21
24 bags = R25
29 bags = R30
39 bags = R38
54 bags = R49
69 bags = R60

I estimated that I have about 12 to 15 inches of cellulose insulation in there already. Wouldn't it be be a waste of money to have R60?

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Old 08-13-15, 03:20 PM   #2
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I have ~R60 in my attic. Going from your ~R40ish to R60 will reduce your heat loss / gain through the ceiling by about 30%.
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Old 08-13-15, 08:13 PM   #3
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Default

Quote:
I was thinking of spreading out the existing insulation to fill in those areas and then use a piece of plywood to flatten it sorta making it more of a dense pack, then blow in the new insulation on top of it. Maybe that's too much work? I don't know. Will that cause problems?

According to his ad, for 1000 sq. ft, one would need
11 bags = R13
17 bags = R19
19 bags = R21
24 bags = R25
29 bags = R30
39 bags = R38
54 bags = R49
69 bags = R60

I estimated that I have about 12 to 15 inches of cellulose insulation in there already. Wouldn't it be be a waste of money to have R60?
I did much the same thing.
When we moved in there was no attic insulation at all, and as we just bought the house we were broke so the cheapest insulation was the recycled newspaper bales, plus they let us use the machine to blow it in for free.
Horrible mistake because every time I went into the attic I returned with at least half a pound of the insulation stuck to my clothes, even more if I was sweating. The insulation would then find it's way into everything.
When money improved I bought enough sheets of OSB to cover the attic floor, sealing in the insulation but leaving the electrical boxes uncovered. I then bought rolls of R-30 fiberglass insulation and put 2 layers in the attic to give about R-60.
Best move ever
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Old 08-13-15, 09:23 PM   #4
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Quote:
Originally Posted by NeilTheCop View Post
...so the cheapest insulation was the recycled newspaper bales, plus they let us use the machine to blow it in for free.
Horrible mistake because every time I went into the attic I returned with at least half a pound of the insulation stuck to my clothes, even more if I was sweating. The insulation would then find it's way into everything.
I've heard this very same complaint before.

I know that in Germany, and other European countries, dense packed cellulose is all the rage because it is effective, provides some degree of thermal mass, to mediate not only humidity changes but also temperature changes, and very importantly, it sequesters carbon, while having a very low amount of embodied energy when converting from newspaper to insulation.

Maybe their secret is that they seal the built structure well enough that there is extremely low air leakage, so it follows that there would be extremely low cellulose leakage also.

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Old 08-14-15, 01:30 PM   #5
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I hear people say they have this issue, but my attic is not dusty at all. I don't know if its because I built a platform (not huge) where I store a few things or what. I don't have a problem with the cellulose blowing around making any mess.
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Old 08-17-15, 02:13 PM   #6
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We have 3.5" of open cell foam over our ceiling sheetrock for insulation from where we built the house. After Katrina spiked our natural gas bill, I bought 40 bales {to cover 1520 s.f. +/-} of cellulose and borrowed the blower from Lowes. The hose was in lousy condition and I made a mess in the garage and the attic, but I got all the bales blown in. Oh yea, don't forget a filter mask, and one that covers your eyes too would be better than goggles. That was worth about 5" in the attic.

After going solar, I decided to get rid of our central unit. It was a 3.5 ton 12 SEER AC unit and 77% efficient natural gas furnace. Our home energy auditor said that if I added 5" more insulation in my attic, it would be exactly right for a 2.0 ton unit. This time I hired it out and added 10" of cellulose. {After all, if 5" is good, 10" must be better.} I am of the opinion that you aren't wasting money adding insulation. There are charts that say how much your house needs as a minimum. You can pay for more insulation, or you can pay for more energy. I believe more insulation makes our house more comfortable.
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Old 08-17-15, 02:35 PM   #7
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Thanks for the information everybody. I am not yet convinced it's a bad idea...so I'm back to the question on if I should pack the existing blown-in to the top of the rafters to get a dense pack. They are only 2x4 trusses and I may not be able to get that much compression anyway? Not sure. Good vs. Bad?

I plan on buying 60 - 30# bails. It will be interesting to see how much it will cover.
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Old 08-17-15, 03:04 PM   #8
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I wouldn't bother compacting it. I'd just blow more on top.
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Old 08-17-15, 08:22 PM   #9
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No need to compress just blow more up there. I find it hard to put too much in any attic.

As for the dust in the attic while getting up there. My solution is that we don't store anything up there. We have just an attic hatch and I won't be putting in a ladder unless I decide to put the hvac up there. (Not a fan of them in the attic but it makes returns way easier and saves room in the house and quieter)
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Old 08-17-15, 09:05 PM   #10
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Compressing lowers the R value considerably. It is the air, trapped in the insulation, that gives the resistance to heat flow. Compressing the insulation reduces the amount of air and the R value.

By a lot.

bottom line - don't compress!


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