House/garage insulation for attic

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Old 02-12-17, 11:43 AM
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House/garage insulation for attic

I have a ranch style home that I moved into about 4 months ago.
Over the Christmas holiday I had the chance to go into the attic, I see that there is really a minimal amount of insulation in there. Trusses are 24 wide.

I had 2 questions.

I want to insulate over the garage, there is nothing on the ceiling. I'm having a tough time finding insulation that is 24 wide and maybe 4" thick. Is it worth it to have 6 or 8" over the garage? It isn't heated, but doesn't seem like anything less than 6" is available in 24" wide pieces.

For the remainder of the house, I could justify using the 6" rolls, although I may just re-organize the shredded stuff that is in there and then roll perpendicular to what is in there now. The current part over the house is loose and pretty thin, I was thinking to kind of pile that up a bit tighter with a broom and fill in with rolls/batts.
 
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Old 02-12-17, 11:51 AM
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The garage and house should be sealed from each other, but with an access opening for fire fighters. The air in the two attics should not mix. Being unheated, there is no need for insulation, but often it will keep heat from being overbearing in the garage for when you use the area. Unless the existing insulation in the house is above the ceiling joists, I would not recommend using a roll insulation. I would continue with blown in insulation to a point of R39 plus. You would need to adhere to whatever is adequate for your part of the country. Most outlets will allow you to use their blower free of charge as long as you buy the insulation from them. Not a bad deal. That way you could go ahead and take care of the main part of the house and the garage at the same time.
 
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Old 02-12-17, 01:34 PM
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The garage is attached to the house. The attic is common space for the house and garage.
I am in Michigan.
 
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Old 02-12-17, 02:50 PM
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How old is the house? I live in a different part of the country and the garage and main house cannot share open rafters. In fact there must be 5/8" fire rated sheetrock and an access door between the two.
 
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Old 02-12-17, 03:22 PM
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https://www.energystar.gov/index.cfm...sulation_table
I agree 100% with chandler, no way would that meet modern code!
Garage needs to be fire walled off from the living space!
Not sure where your shopping but R-19 X 24 is very common.
It's used all the time in modern construction.
 
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Old 02-12-17, 09:21 PM
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Every house I have owned her in MI has had open access between house and garage attics.

The garage itself is sealed but attics are wide open.

I agree, for new install insulation go with blown in cellulose, attempting to haul up all those batts and roll out is a PITA, much easier to blow in the insulation. Make sure your soffit venting is taken care of.
 
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Old 02-13-17, 02:52 AM
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Good to know about the Michigan attics being open. We have to treat them as separate entities due to the gasses and possibilities of fire encroaching from the garage to the house. Doors entering the house from the garage must be fire rated and have self closers.
 
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Old 02-13-17, 06:49 AM
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I think 1972 or so is the build year.

I did blown in at my previous house, I'm not really sure that it did a whole lot. Although that house was much older and before I started it had nothing. We did the walls on that house, so I'm familiar on how to do this type. Having an access in the attic would be easy, and blown in would just be about the same as watering the lawn with a garden hose.
Do I just pile it up 24" or so? I know people do this, but it doesn't seem so effective to me. I'm no construction or builder type person though. I know enough to be dangerous, and that what I have isn't enough.
 
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Old 02-13-17, 06:57 AM
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I would air seal first since there isn't much insulation in the way and then I would blow in cellulose.
 
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Old 02-13-17, 08:08 AM
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Could you give more detail about what you mean? I get what is meant by air seal, but curious how to put that in perspective to the house.
Overall the house doesn't leak, it was fairly windy here this past weekend and I was watching the curtains & stuff to monitor air leaks. My previous house was pretty bad, however this one seems tons better.
 
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Old 02-13-17, 04:02 PM
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But you may have air leaks via light fixture boxes in the ceiling. Sealing them will help keep that migration down. Be sure not to occlude your soffit vents when blowing the insulation. The attic must breathe.
 
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Old 02-14-17, 05:11 AM
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Gotcha, I understand what you're saying. Thanks for clarifying.
 
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