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Hey Guys, I am in the process of adding insulation in my garage. As you can see, I have done the walls using R-13. For the attic, I bought R-30 and I am not sure where the batts are suppose to be installed. I did some research under Google and found that the insulation for the attic was installed horizontally between the joists. In the images below, you will notice two batts of R-30 insulation that has been tacked on top. One runs along the 2x4's up in an angle (left one) and the other simply between the joists (right). If you can point me to the right direction with some advice, I'd appreciate it! Thanks.


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Lost in the 60's
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OK...those going at an angle are your roof rafters.....those going straight across the room are your ceiling joists. The insulation goes between the ceiling joists paper side down or facing the heated area. It would be easier to do if your ceiling was already installed....all you would have to do then would be to lay the bats in between the ceiling joists paper side down. Just have to crawl or knee walk on the joists....thats how I did my house.
 

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Discussion Starter #3
Henry Highrise said:
OK...those going at an angle are your roof rafters.....those going straight across the room are your ceiling joists. The insulation goes between the ceiling joists paper side down or facing the heated area. It would be easier to do if your ceiling was already installed....all you would have to do then would be to lay the bats in between the ceiling joists paper side down. Just have to crawl or knee walk on the joists....thats how I did my house.

Excellent! Thanks for the terminology and advice! So you recommend that I install the sheetrock in the ceiling first and just lay the insulation batts between the joists, resting on the sheetrock?
 

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djjc76 said:
Excellent! Thanks for the terminology and advice! So you recommend that I install the sheetrock in the ceiling first and just lay the insulation batts between the joists, resting on the sheetrock?
Thats what I would do....if your up there be sure to stay on top of the 2 by 6's or you will come through the sheetrock. You could put a piece of sheet rock up, then place batts on top of it paper side down and just work your insulation one or two sheets of sheet rock at a time...that way you would not have to crawl around on the 2 bys...except for when you put up the last piece of sheetrock.
 

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djjc76 said:
Excellent! Thanks for the terminology and advice! So you recommend that I install the sheetrock in the ceiling first and just lay the insulation batts between the joists, resting on the sheetrock?

Only if you have good balance !...LOL

Personally... I'd hang the sheetrock and then go to the local Home Depot or similar...buy several bags of blow in type insulation...stop by the local rent-it-all type center on the way home and pick up an insulation blower for about 2 hours and fill the attic area...... way easier....way less itchy.... no stapling the insulation up before rocking, and no doing the 2-step from joist to joist praying you don't miss a step rolling the itchy **** out and falling through your freshly rocked ceiling. Almost all this stuff now already comes pre-soaked with fire retardant and some type of insect guarding stuff. I put it in my house recently when I did some remodeling.... super easy and energy efficiant.

Whichever you choose be sure to leave space at the ends near the walls, so the air can circulate up from your eve vents into your attic..... otherwise you're gonna have mold issues later on.
 

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If you decide to go with the blown in insulation....then you wiill need to staple up a moisture barrier before you put the sheetrock up.
 

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If it was me I would put up a vapor barrier. (A roll of plastic is cheap) When installing start at one end and work to the other. Put the plastic up between joist 1 & 2 then stand on your ladder between 2 and 3 and lay in your isolation. And work across from one side to the other. Even tho you have the bats with the plastic on them I would still seal everything with plastic and tuck tape. It helps on keep the cold out and makes heating simple.

John
 

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I imagine that living in Escondido, CA you are not worried about keeping the cold out but keeping the heat out. You use different materials there then we do. Our insulation does not come with a vapor barrier. It did when fiberglass was first introduced in about 1950 around here. I just threw away a small roll of it that my father had left over when he built his house in 1951. We now use six mil poly for a vapor barrier and seal all joints with acoustical sealant and more recently tuck tape. In your case stapling the paper to the truss bottoms (ceiling joists) first is the way to go. You want to do this as you will create a continuous vapor barrier that way. The size of the insulation will give a friction fit into the trusses and it won't fall down before you put up your sheet rock (we call it drywall). Try to get someone to give you a hand or get a scaffold as getting up and down off of a ladder to do that kind of work is a pain. Good luck with your project.

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check out how they do new homes. staple up the insulation then put up the sheetrock .as far as blowing it in you might want to check with your utility company . when i went to insulate the attic in my home i priced out the blow in stuff and home depot would loan me the blower for free but with the rebate from the utility company it was cheaper ,faster and less itchy to have someone else do the work.plus if you sheetrock first it would be difficult to properly lay out the insulation between the joist. insulation performs best when it is not crushed into place but allowed to fill out the joist cavity
 

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Discussion Starter #11
Thank you very much for all of your replies! Yes, I will add the drywall one 4' x 8' at a time and install the batts of insulation. I like your idea of plastic sheeting and will consider it. Yes, Southern California during the summer gets very hot at times. Right now, its the opposite being cold right now (cold for us in So. California is ~ 55ºF)! I'll take images as I work through this and show you all.

:welcome:
 

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Discussion Starter #12
59 wagon man said:
check out how they do new homes. staple up the insulation then put up the sheetrock .as far as blowing it in you might want to check with your utility company . when i went to insulate the attic in my home i priced out the blow in stuff and home depot would loan me the blower for free but with the rebate from the utility company it was cheaper ,faster and less itchy to have someone else do the work.plus if you sheetrock first it would be difficult to properly lay out the insulation between the joist. insulation performs best when it is not crushed into place but allowed to fill out the joist cavity

Ah, ok....so maybe install R-30 insulation batts first by stapling, then a plastic sheeting, and then drywalling....
 

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Discussion Starter #13
do you think that 1/2" thick drywall will be fine for the ceiling? The joists are 23 or 24" apart. Thanks.
 

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1/2 inch drywall will be fine. There is virtually no weight from the insulation and it will hold up and not sag over that span. Is your garage attached to your home? In some places they require 5/8 inch drywall as a fire barrier if your garage is attached to your home. Check it out with your local building department, fire department or insurance agent.

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Run your rock perpendicular to the joist not parallel to reduce the tendency to sag. Half inch will sag over time on 24" centers, it may not be noticeable for 20 years but it will happen.
 

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home brew said:
1/2 inch drywall will be fine. There is virtually no weight from the insulation and it will hold up and not sag over that span. Is your garage attached to your home? In some places they require 5/8 inch drywall as a fire barrier if your garage is attached to your home. Check it out with your local building department, fire department or insurance agent.

Yep, the garage is attached to the house. The wall is already drywalled when I bought it and it is my understanding that it has some fire resistance to it.
 

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Kinda tough to tell from the pics, but it looks like the garage is attached to living space (your house).

Not sure what the building and safety codes are where you are, but around here "code" is 5/8" Fire Code sheetrock/drywall and fire stops in any abutting framing to living space, in any garage attached to living space.

Even if it's not "code"... it still might be a requirement by your insurance company to cover you against any future loss.

Either way, it's WELL WORTH the small extra expense.
 

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sorry I guess HOME BREW was typing the same exact point as I was at the same time.... or I never scrolled far enough down to see his post before I started replying
 

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We use 5/8 on the lids because of the sag..You can rent what we call a sheetrock jack from a local rental place..just think of a really big scissors jack tall enough to jack the rock up to the ceiling..makes for a real back saver and is real helpful for the guy that does not hang rock for a living..

The guys have you well sorted out on the insulation deal..I put mine up then hang the rock..getting too old to be crawling around in the rafters..that can even be a bit of a zoo for the young guys..

Sam
 

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You could strip it with 1 X 4 furring strips put up perpendicular to the ceiling joists and put the strips on 16 in. centers....it would never sag then. Thats the way I did all of the ceilings in my house.
 
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