Insulate at rafters or overhead ceiling beams?

[Totohydra]

My detatched garage is pretty much uninhabitable during the winter months so I would like to start putting in some ceiling insulation.

I can access either the rafter (?) area where the actual roof is. There's also the horizontal beams at the ceiling level however there is no actual ceiling.

My question is which of these two levels is best to install insulation? If possible I'd like to put it against the roof - especially if a ceiling install means having to put drywall or other covering on.

This is in Kentucky so in addition to the cold it gets extremely hot in the summer as well.

Thanks for any advice on this.

 

[jimbbski]

It the ceiling joists are either 16 or 24 inch on center then you can buy paper or foil faced fiberglass insulation that you can then just staple to the joists from below. Install the faced side down toward the floor and just tack it up. You don't need to cover it but I would then tack up a sheet of plastic over the fiberglass. It will keep the fiberglass fibers away from where you're working and keep the warm air where you need it.

 

[theoldwizard1]

What Jim said, but I would add sheetrock underneath.

 

[randomtwinkie]

make it white plastic to brighten the place up

 

[Totohydra]

To confirm: So the (I'm assuming Kraft faced) insulation is facing the floor, stapled to the underside of the joists, the plastic needs to be on top to keep the loose-facing fiberglass from blowing around?

Doesn't sound like the color of the plastic would matter if it's on top and not visible.


Will the facing material alone support the fiberglass? Sounds like some kind of sheetrock is needed. If so the kraft paper would be permantly nailed in.

 

[rburke65]

I would insulate between the ceiling joist and not the rafters. You can use the kraft faced insulation and staple it to the joists. The paper will support the weight of the insulation. The addition of the plastic sheeting would, as stated, probably help keep a lot of "kucka" from your hair. This is a great forum that you have joined here......tons of info., untold number of minds to pick....hundreds of talented people. Welcome to Garage Journal.

 

[kngelv]

If using Kraft-faced you need to vent from soffits to ridge. If you put it directly against the underside you will have shingle de-lamination. No plastic with Kraft-faced. Double vapor barriers can cause problems.

James

 

[kerr]

You might consider the bubble wrap roll insulation too . One side can be bright white or silver . Pretty desent r value and great vapor barrier and it comes 4' wide . Just staple up . I ever get the extra $ thats what I want to do.

 

[Spudland_Dave]

To confirm: So the (I'm assuming Kraft faced) insulation is facing the floor, stapled to the underside of the joists, the plastic needs to be on top to keep the loose-facing fiberglass from blowing around? .

NEVER do this...it will be nothing but moisture/mold/future problems. Vapor Barrier always goes facing the living side.

Will the facing material alone support the fiberglass? Sounds like some kind of sheetrock is needed. If so the kraft paper would be permantly nailed in.

Yes it will support it no problem. Heck just the tension of the batts themselves will keep em up there...Just staple it up with a stapler...1/4" or 3/8" Staples.....IF your worried, you can then strap the cieling, I'd probably strap the ceiling at 32" OC for now...if you ever decide to hang sheetrock up just come back and strap inbetween, giving you 16" OC...I am strapping AND sheetrocking the ceiling. Makes for a nicer/easier/stronger cieling.

 

[Steevo]

To confirm: So the (I'm assuming Kraft faced) insulation is facing the floor, stapled to the underside of the joists, the plastic needs to be on top to keep the loose-facing fiberglass from blowing around?

Doesn't sound like the color of the plastic would matter if it's on top and not visible.


Will the facing material alone support the fiberglass? Sounds like some kind of sheetrock is needed. If so the kraft paper would be permantly nailed in.

Not quite.
The Kraft-faced insulation fits between the joists (what you referred to as the "horizontal beams", that run across the room where a ceiling would be.
The insulation has flaps along the edges, and you staple those to the sides of the joists, not the bottom. With the raw fiberglass facing up, towards the cold/hot "attic space", and the kraft-face down, there is no requirement to add plastic below, because the kraft-facing itself is a vapor barrier. You can add a plastic to the bottom side of the joists to make it more dust-proof if you want to. Just don't put anything on top of the fiberglass side.

 

[SARG]

Just one issue to mention with the methods given above ....... because I'm facing the situation right now.

The kraft paper over time will wear out and the staples will give way letting the insulation drop with gravity. You must hold it up with drywall or something else over the long haul.

My dad put up insulation in the second story of a storage building and after 25 years it is now falling down because the paper is dried out and brittle.

 

[Steevo]

. . .The kraft paper over time will wear out and the staples will give way letting the insulation drop with gravity. . . .
My dad put up insulation in the second story of a storage building and after 25 years it is now falling down because the paper is dried out and brittle.

Oh, and McDonalds coffee is hot! Don't pour it in your lap.

 

[Totohydra]

This is a great forum that you have joined here......tons of info., untold number of minds to pick....hundreds of talented people. Welcome to Garage Journal.

Thanks guys. You're right this really is a goldmine.

I've looked into using the foam baffles for insulating direct to ceiling. The garage itself gets extremely hot in the summer so if possible I'd like to insulate there and keep the area above the joists open. However I don't believe the soffits are vented correctly so I may just go ahead and keep it at joist level. I just need to make sure the ventilation is sound it seems.

Does there need to be any openings on the roof (currently none, just all shingles)?

 

[Falcon67]

Last shop used kraft faced on the ceiling with no drywall. I ran 1x2s cross ways to the joists to help hold the batts in place. No problems in 12 years.

The old place, note the ceiling

 

[Spudland_Dave]

Thanks guys. You're right this really is a goldmine.

Couldnt agree more...LOVE this place and the people on it.

I've looked into using the foam baffles for insulating direct to ceiling. The garage itself gets extremely hot in the summer so if possible I'd like to insulate there and keep the area above the joists open. However I don't believe the soffits are vented correctly so I may just go ahead and keep it at joist level. I just need to make sure the ventilation is sound it seems.

You'll need at least a "starter strip" of those foam baffles...for the first 4' under the roof...so when you put your rafter insulation, it doesnt close off and block off the soffits.

Does there need to be any openings on the roof (currently none, just all shingles)?

Yup...Either a Ridge Vent or Gable Vents. Personally I prefer Ridge vents...but thats just me and what is most common around here. It keeps the roof cool by allowing convection air flow to essentially "****" the hot air out. Supposedly it extends shingle life too.

 

[b4z]

Spray foam the underside of the roof sheathing. Then write the installer a check for big $$$.

 

[ormachine]

When I insulated my garage, I used R30 Fiberglass insulation stapled to the sides of the horizontal joists, then covered that with 1" fiberboard stiff insulation acting as my sheetrock.
Been up 3 years with no heat and NO FREEZE at all inside. Coldest temp recorded has been 38* so far.
I am giving serious thought to a wood burning stove for the winters though.

Ron

 

[Totohydra]

Thanks all. This is going to be a LOT of cash either way but I feel a lot better now going into it.

 

[NUTTSGT]

If you start to insulate,you should have something like this.

If you put in soffit vents, I believe you need a ridge vent. From what I have read and been told, soffit vents with ridge vents or gable vents with roof vents for them to work properly.

Creating an attic space with contain the cold during the winter and seperate the heat during the summer. Put up the best insulation you can, as insuation is an investment and will pay for itself time after time.