Insulating between ceiling and attic floor?

[Graham08]

I'm getting ready to insulate my garage, which has storage trusses with a 2 x 6 bottom chord. I am planning to put a floor 8' wide down the center for storage. My question is: How do I best insulate between the ceiling and the attic floor and end up with good R-value?

The attic is vented, so I would like to get as much R-value as possible (probably going R-38 for the rest of the attic) because the shop will be heated, and I'm in NE Ohio. The way I see it, my options are either R-19 fiberglass batts or rigid foam (R-27.5 for 5-1/2" thick). I figured I would ask the board for ideas, to see if there are any better options out there.

 

[boiler7904]

I have a similar situation but my bottom chords are 2x4s if I remember right with drywall on the ceiling below and OSB already installed on the attic floor. I think my solution is going to be to blow cellulose into the voids and then add some pink rigid foam on top of the existing floor with a second layer of OSB as a new floor.

 

[hansen1]

I wanted to get R60 everywhere I could. I put poly iso foam board in the bottom chord. Mine at 2x10's so I put 8" of foam board. I then blew cellulose on both sides of the attic. Seems to work pretty well so far.

My attic floor is made up of 2x4's laying on their sides and the T&G 3/4" OSB on top of that. Very solid.

 

[MichMan517]

I've got the same configuration. I just rolled fiberglass down the bays, then in the none storage area, rolled another unfaced layer perpendicular to the first. Foamed all electrical boxes, openings, etc. Insulate the drop down door, and make sure there is a tight seal when up. Seams to do the trick in my 24x24x10. I really didn't want the dust associated with blown in cellulose.

 

[71flh]

I borrowed the blower thing from the home store and blew in many bales of cellulose. I also did a few areas that were thin above the house.

Strangely, I did this in July which is the hottest month around here. I'm convinced I have some form of brain damage since I also sodded half my yard in July.

My garage is much cooler now. I'm in Texas so heat is more of a problem than cold.

 

[kartracer23]

What about if you weren't planning to use the attic for storage? Because of the roof line I'll have in my new garage, putting storage up there would be about worthless so I'll just have an access hole. Is the easiest / cheapest thing to do just put some of those baffles between the joists down to the soffit vents and then fill it with blown? It's unattached, and I don't plan on heating or cooling it except just to keep it above freezing in the winter. But even my current garage (no insulation at all, open walls) / ceiling) stays 10 * warmer than outside in the winter so I'm thinkin' some insulation in the new place would help a bunch.

 

[dirttracker18]

My thought would be to use spray foam where you plan on putting your floor in. You get about R 6 per inch with foam so you can get about R 34 in that area and use batts or blow in everywhere else. It is a little more costly but it will get you your best R value in this case.

 

[Graham08]

Thanks for the input everyone. I found an ad on the local Craigslist for Poly Iso board at a really reasonable price. The ad states R-17 for 2.5" thick boards, so I could get R-34 in my space by doubling up.

 

[Reg1952]

This is what I did.I layed 2x8 on top of the trusses and screwed on 2x4 on the sides to hold them there.Insulated between the tussess. Then layed plywood on top of the 2x8 and then had lots of room for insulation under this raised platform.