So, I went and bought $400 or so worth of insulation, right? I carefully calculated the square footage of the walls and ceiling, and bought enough 16" R13 for all of it.
The problem is, I goofed. My ceiling is 24" OC. So I *could* just lay the bats across the rafters (as opposed to between them), but it kind of looks goofy that way, it's hard to keep them tight together, there's probably a code issue (not that it matters where I live, but still...) and somebody mentioned that I might want to go with something more than R13 in the ceiling.
The thing is, I don't know if you've priced insulation, but it's expensive as shit. So, I am going to go ahead and buy 24" wide bats for the ceiling, but am I really screwing myself by going with R13? The main part of the garage is used occasionally - perhaps 10 hours a week tops (including weekends). It's forced air, so it heats up in a hurry (or should - it's a 75,000 BTU LP furnace in an 832 sq ft garage). The office in the garage will be 10x12, and completely enclosed. It will be insulated extremely well, including the ceiling. It's small, so it's cheap. I also have the furnace setup to only heat the office, if I want (slow the fan waaaaay down, make sure there's an air return, etc).
But that leaves the rest of the garage. Assuming 10 hours a week, would you go higher than R13 on the ceiling? If it was living space and I was in there constantly I'd probably go nuts, but being that I only need it headed for a few hours here and there....what do you think?



 

I'm drunk right now but if I recall correctly, R-19 is called for in the ceiling. I am fairly familiar with IRC codes across the US. Some local codes mandate different from the national code. Check with your local code official. R-38 is called for if you are putting it against the roof decking, I think. Again I am drunk........

After you lay the insulation down over the truss bottom chord, cover it down to protect from windwashing with Tyvek.

Tyvek will protect the R- Value of your insulation.

IM me later for a sober explanation in detail.

Anyway, off to procure some pie!

WTF?

Dude, the minimum in California is R-19 for the attic and R-13 for walls.

Doesn't it, like, get cold in Ohio, dude? Like, white stuff on your lawn in Winter, bro?

I'm not zoned (no adopted code in my township) and there are no local code officials as a result. However, I do prefer to adhere to the national code, when it makes sense to.



If there's a really good reason why I should use R19 instead of R13 under the conditions/parameters I mentioned, then I might go for it.



I'm not sure what you mean about windwashing. It's in the ceiling, and the only way wind is getting  in there is through a ridge roll vent, and that ain't happening.





 

Probably pretty light since you're in OH. Have you looked into other types like cellulose or blown in fiberglass (perhaps buy bags of either and shovel it in yourself)? What about rigid foam under the trusses with fiberglass bats between them? Will there be drywall on the ceiling? If not, rigid foam in it's place would be nice, and add a few "Rs" to the rest of your insulation. If so, you'd only lose about an inch or two in height and still gain a little insulation.

No spray foam?

For a house you live in, sure. This gets heated for like 10 hours a week. There are 168 hours in a week. I'll be heating 10 of those hours.



Remember, this isn't living space. The furnace gets cranked up when I'm going to work on something for a bit.



 

Have you considered having some Cellulose insulation blown into your attic?  that might be the most effective and odds are not too much more than you may pay to cut and paste your roll your own...

Laying insulation on top of the beans means you can't use the attic for storage without crushing the insulation (which destroys the R-value of it!)

If you have trusses (vs. stick built with rafters) then you are way ahead to spray rather than trying to snake around the trusses to properly lay insulation batts.

Just my years of experience and .02 cents too!

BIGGER_HAMMER

I've thought about the blow-in route, but there are a couple of problems:



1. I will never store anything in the attic. Everything I need has a place in the garage, and the heirlooms are in the basement.

2. Since I will never store anything in the attic, I didn't bother buying drywall/OSB/whatever for the ceiling. If I blow insulation in, I'll need to buy some and hang it. Man, I reeeeeeeealy don't want to.




It seems to me (I could be wrong), that it would cost more when all was said and done to blow it in. I've got to get the shit, get the drywall (or OSB...either way), rent a machine to blow it (or pay somebody...even worse), etc. I could be wrong, though.

Sounds like I need to call Menards, and see how much R19 in a big roll costs. I have to assume it's cheaper than the 16" precut I used for the walls, per square foot. Then again, it'd be R19, not R13.



I just don't want to spend a fortune, if I don't have to. If this was going to be heated all the time, I'd go nuts with the insulation (I am for the office, since it will always be heated) because it wouldn't take long to recoup the initial investment. But it's heated infrequently, and the ROI might be a very long time.



I'll be returning a bunch of insulation, so that'll help. Hmmm.

IIRC Lowes will "loan" the blower machine at no extra charge if you buy so many bags of insulation. I have a similar situation but my ceiling is drywalled already with no insulation yet.

Windwashing - Fiberglass insulation works by trapping air. That gives it it's R-Value. If you have air moving on the fiberglass side(ie.. in the attic space) the insulation cant do it's job and may be reduced to R-6 or 7. To get the maximun effect and energy savings, cover  the exposed fiberglass side with Tyvek.

BTW, I scored some pie and I liked it!!

The blown cellulose is good stuff. It is usually wet when applied so make sure it has a chance to dry if you are going to drywall it.

Fiberglass will be easier and cheaper to install. Hell, you could use R-13 and see a gain if you protect the attic side of the insulation.

Don't return the R13.

Insulate between the rafters with R19 and lay the R13 on top (perpendicular to the R19)

if the house is attached to the garage protect your family and sheetrock the ceiling with 5/8 fireboard

It's detached. I started building it in August, and it's almost done!




 

This is the best idea.

R13 is very light.  I know that you don't heat it much, but it is still very light.

Hi Subnet,

I just bought from Home Depot 32'x 15" batts of R13, at $10 or so per roll on sale. Heating costs could skyrocket at any given time and letting your expensive heat escape is

They recommend that they are for basement use or interior wall use pretty much. For ceilings it is really too light, as heat rises and it will seek to escape that way, hence a higher R value.

Personally id drywall the ceiling just dont mud and tape it. Drywalling a ceiling with a lift isnt hard, imo and doesnt really cost that much to do.


Cheers

Dram

I'd go R-19 minimum on the ceiling.If you get snow or real cold,I'd go R-30.
Every dollar you spend on insulation is a long term savings on heating/cooling costs.
Pay now or pay later.
Licensed contractor,just so you don't think I'm talking out my ass.

You want r13 for 2x4 walls, r19 for 2x10 floors, and r30 2x for rafters or r38 for truss attics.

The majority of your heat loss will be the ceiling, as heat rises. The second worst area will be windows and the garage door.

I'm in MD, and i suspect your climate is similar to ours. Its flurrying here right now.

To me, there is nothing worse than an ice cold wrench and loosing half your knuckle when it slips.

There are usually manufacturer rebates, and sometimes tax credits you can claim when buying things like insulation. Look into it.

Also, garages are considered an area that is a fire hazard. People like to store lots of flammable chemicals in them. I would seriously consider hanging some fire rated sheetrock on the ceiling. Bare minimum, thick plastic as vapor barrier, otherwise your insulation wont really be doing you any good. With bright shop lights on the ceiling, the sheet rock would be a better idea.

As far as insulation being expensive, try looking for used stuff from demolition or construction companies.

As long as it is removed with a modicum of care it will be good to go.

Install the R-13 now if that is all you want to pay for, and throw some unfaced r-19 on top of it whenever you feel like spending the money.

And as far as codes go, there is no code for insulation in a Garage.  Only in living spaces. A Garage is not considered a habitable area.  Use whatever you'd like.