Insulation between garage and living space above

[jamesgangnc]

I've been working on my garage project and I'm about to the point of installing insulation on the garage ceiling. The joists between the living space above and the garage are 22" inches tall and manufactured from 2x4's. Inside them is the plumbing, electrical and most of the hvac flex ducts for the room above. I also plan on insulating the garage walls. I have insulated garage doors on the front and back but the front one is big, 20x9. The subfloor above is tongued osb.

Does it really matter which way I put the facing on the insulation between the garage ceiling and the floor above? I know the vapor barrier is supposed to be against the floor but i's going to be a whole lot easier to install it with the paper on the garage side as that will let me staple the paper to the bottom of the joists. Otherwise I have to figure a way to hold the insulation up while I install wallboard on the ceiling.

[Ed Pawlowski]

Easier is not always better, or even acceptable. Vapor barrier to the heated side or potential problems Thee are metal supports made for holding insulation in place between joists. .

Better applications is to have someone come in and do spray foam.

[bambam]

What Ed said.

Ken in Calgary

[Hank]

The insulation can be held up by stiff springy metal wires that are sold at various supply stores. They are about the size of a coat hanger and come in different lenghts. These wires will hold up the insulation by being inserted between the floor joists. Easy to do, no tools, inexpensive.

Hank

[jamesgangnc]

.

Yes, I know about insulation wire supports. These are open web trusses centered on 24". That makes the open space between trusses 20

1/2". I'll have to cut 24" wires down a bit. And carefully place them on the lower edge of the truss. I'm wondering if there might not be a better solution than the wires. For what it's worth the insulation is in 4' batts.

[hrhofmann]

...

You could put some nails into the sides of the joists just above the bottom of the joists, and then use string to hold the batts in place. Maybe someone has a bunch of old metal clothes hangers you could cut. How much is your time worth?

[aemeijers]

Or just use foam board attached to the bottom of the joists. Don't forget, if you have living space above, you need 5/8 firestop rock or similar fire-rated material as a fire break.

[jamesgangnc]

..

Holding the insulation up while attaching foam board presents the same problem as holding it up while installing wallboard.

I'm thinking maybe I'll use string and staple the string across the joists after I put a batt up. Not any different amount of work from stapling the batt paper. If I cut a couple dozen pieces of string the width of the space I can just let them hang as I install batts and staple the string to the next joist.

[Jeff Thies]

I have an old house with uneven joist spacing. What I do is temporarily push up the insulation and zig zag (sort of, I run across and zag) staple fence wire to keep up the insulation. You can staple the wire to the inside of the joist. You can cut insulation to fit the gap. It's a pain cutting it and I usually use a large paper cutter and chop my way through.

Vapor barrier is supposed to go to the heated side. In a hot climate that may change how it is installed.

Jeff

[Jim Elbrecht]

-snip-

I never did that- but it sounds like a good idea. My technique would be to keep a ball of string in my tool pouch- stapler in a holster. Push the bat in- then staple a zig-zag pattern with the string as I walk down the line.

Jim

[Jeff Thies]

Use fence wire. String is hard to staple and have it hold. See my other post.

Jeff

[jamesgangnc]

m...

I like the zigzag idea. I can work down one joist bay and then back up the next.

My other hassle is my ceiling height is 10' so I'll be going up and down the ladder a lot. No avoidng that though. At least I have a pneumatic 3/8 stapler so I can staple from most angles with out having to be under the stapler enough to push hard.

[EXT]

I have used fiberglass tape, self adhesive and about 1/2" wide. Use a stapler to attach to the joist, don't rely on the tape except to hold it in place until you can fire a staple into it. Strong, flexible and easy to use.

Putting insulation bats between truss joists made from 2x4s will leave lots of spaces within the truss joists allowing cold air to penetrate and will still provide no vapor barrier at the floor level to prevent water vapor condensing on the cold side of the drywall. It is still better to pay the cost and have spray foam installed on the underside of the floor, it will insulate and provide the vapor barrier without interference with duct anchors and other obstructions. The ducts can also be encapsulated to keep heat and/or cool from being lost. One could add some bat insulation afterwards to boost the insulation value if wanted.

[Jim Elbrecht]

-snip-

My latest 'why-in-hell-didn't-I-get-one-of-these-25-years-ago' purchase was a $200 Werner aluminum 'plank' that extends from 8-13'. Lowes had them by the ladders.

Jim

[jamesgangnc]

om...

This job has a budget and hiring someone to spray foam is not in it. The location is on the NC/VA border so I don't expect serious extremes and I'm trying to insulate the garage space as well as I can too.

[aemeijers]

I meant foam board in lieu of insulation batts. A few dabs of construction adhesive on the bottom of the joists will hold them in place long enough to get the screwed-up rock up under it to hold it in place long-term.

-- aem sends...

[jamesgangnc]

m...

I'd still need to hold the insulation batts up while putting up the foamboard. You are just making the job more complicated.

[Ed Pawlowski]

"jamesgangnc" wrote >>

How is it making more work if you no longer need the insulation batts? I think you misunderstand him. You can cut the foam board for a snug fit and have it stay in place with no mechanical fasteners at all. You can us it alone or you can use it in addition to the batts and hold them with the board.

I think you are looking for a simple solution but fail to see it when offered. You have a pre-conceived notion that it it going to be difficult unless it is done the incorrect way you asked about the first time. Sorry, we will not give the "seal of approval" to the wrong methods.

[aemeijers]

You're not hearing me- forget about the insulation batts entirely, and JUST use the (thick) foamboard, with the fire-rock cover. Not like this is an exterior wall- 2" foam panel is plenty of insulation for a sealed insulated garage with heated space above. No cold stripes where there is no insulation under the bottom of the trusses, and no cold little holes to freeze pipes and such if somebody accidentally leaves garage door open. A nice tight insulating barrier.