Foil Insulation

[Burbman]

The new garage is built and is going to need some insulation in the ceiling. I had an earlier thread going when the build started but wanted to get specific to this topic.

The structure is 24x30 detached, 9' ceiling and 14' ridge height, with 2x4 walls. I have insulated the walls with R-13 and drywalled, but I can't drywall the ceiling as it stands. The plans were spec'd as unfinished, so the 2x10 joists are 32" OC as collar ties. Strapping is not an option because 2x10's over a 24' span are only rated to hold the weight of drywall when installed 16" OC, so if I strap the ceiling as it is, it will sag from the weight.

Here is an early pic:

The soffits are vented and there is a ridge vent running the length of the garage. My original plan was to use metal panels on top of the joists, but I would rather leave the joists open for storage. The 2 5K watt electric heaters do a good job of keeping the place warm, although I know I am losing a ton of heat out of the ridge vent

What I am thinking of doing is stapling Reflectix (not Prodex, did some reading on that stuff LOL) on the roof rafters. This would create an airspace so that air flowing from the soffit to the ridge can't mix with inside air. I know the foil has a very low R value on it's own, the R value will be created by the air layer in the rafter bay.

Thoughts and comments appreciated.

 

[Empty Pockets]

Might help. Any insulation is better than none, but I wouldn't expect a lot of insulting from that arrangement

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[7th Kahuna]

Had you considered foil faced rigid foam insulation panels attached to the ceiling for the time being? They don't weigh much and come in a variety of thicknesses. If you don't like the foil look, there are non foiled options as well. You could even give them a coat of paint. The downside is they are (or at least were) flammable. I remember my dad using them on a project when I was a kid. I lay on top of one and remember it getting warm pretty quick. They do work. The seams could be taped with aluminum tape.

My dad and I are working on a new shop right now. We've gone the rounds with the city. The space will be heated and air conditioned, the walls and ceilings insulated, but all the city sees is a garage and insists on all the typical open vents around the floor and peak. Fortunately the plans didn't call for a ridge vent. The inspector went back to check.

 

[buddyboy]

run 2x10's between your collar ties, then you'll be 16" centers, block it, run electric for lights, insulate and drywall

 

[buddyboy]

2x10's at that length don't really allow for storage anyway

 

[braidmeister]

The double bubble foil is good, but kind of a pain in the **** to install on the ceiling. It is referred to as a radiant barrier - not insulation, so R values don't apply. It just radiates heat to the side it comes from.

Rigid foam, as mentioned, is probably the best for insulation and ease of installation. Obviously you'd run them 90deg to the joists.

 

[Burbman]

Was thinking that also, rigid foam on the rafters, it would be up high enough to be away from sparks and heat and the foil coating would help.

Right now I have very light storage over the collar ties, empty plastic bins, coolers, and the like. Easy access with a step ladder.

 

[moneypit_k5]

If you are worried drywall will sag the joists, how on earth do you plan to use the area for storage?

I do think your idea of using some kin of vapor barrier to create an air space is a good one. IMo, whether its reflectix or just plastic sheeting, it will accomplish the same thing. reflectix is like snake oil of old.

 

[moneypit_k5]

ya' know, another option might be to find some other type of wall covering. sound board from home depot is super light, and would screw to your joists, might have to washer up the screw.

 

[chaosracing]

Why not just use white metal panels for the ceiling, then blow in insulation? The metal might cost a little more, but you also do not have to finish the metal or paint it like drywall. Plus it will span the 32" no problem. You just have to add blocking where ever you plan on having electrical boxes at.

 

[rburke65]

Have to figure out the weight you can apply to your ceiling....the weight of the insulation, ceiling itself, etc.