Questions on insulating attached garage walls & ceiling

[azone]

I'm in the process of remodeling my garage. I'm in the south bay los angeles beach areas so the temperature varies between 45 degree nights in winter and 90 degree days during summer.
I spend a lot of time in the garage so I want to insulate the walls and ceiling so that I can use a heater/ac.
The house was built in 1955 and garage was an addition that shares one wall with the house. All the walls are 2x4 (3.5") and the ceiling is 2x10's. There is nothing above the garage (actually the roof is used as a deck). The floor is epoxy coated with commercial product. The garage door is insulated.
The original owner did a really crappy job of drywalling the garage and also didn't appear to do anything to code so I decided to pull down all the 1/2" drywall & original stucco and take a look. This also gives me the opportunity place all the electrical, RG6 cable, CAT5 etc.. inside the walls.
as mentioned the common wall is stucco over 2x4 studs and the rest of the walls were 2x4 with 1/2" drywall. I'm going to drywall the whole thing with 5/8 type X. My questions are basically related to insulating.

1. Is R-13 in the walls and R-30 in ceilings the best I can do in this instance?
2. The walls are framed out and there's 2x4's across the top and bottom so they don't breath. I guess I don't have to worry about airflow or anything? I have a bunch of R-19 insulation left over from another job. Can I just use this in the walls?
3. I plan to use R-30 in the ceiling. Is there any reason to use any sort of barrier (poly) between the insulation and the drywall on the inside of the ceiling?
4. It's possible that me or future owner may build over the garage at some point. Is there anything I may want to keep in mind now that I'm doing this that would help in the event this happens? I'm assuming the roof would be ripped up anyways and I'd be staring at the 2x10's again so could do whatever needs to be done at that time.

any other words of wisdom are welcome.

 

[z28snksknr]

I'm by no means an expert, but my whole house has poor insulation and I'll pass on my learnings from dealing with it:

1- R-13 in the walls is fine. Most of the heat loss is through the ceiling / roof (heat rises). R-30 is probably overkill for your climate, in fact using the DOE's calculators (Here), I'm getting a recommendation for R-19 in the attic, R-13 in the walls. I would check the site out and put in your house's specifics since I assumed most inputs and used zip code of 90001 (LA). You may have different requirements if you are close to the ocean (?).

2 / 3- You'll get varying thoughts regarding vapor barriers on here, but I'm pretty sure it is a code requirement for new construction, and there is probably good reasons for that. There's a big push currently to install vapor barriers everywhere you can and to aim for "air tight" houses. That includes vapor barriers in all the walls and ceilings that are taped so as to be one continuous barrier. I'll tell you from being in a house that does not have it, I have drafts and air leaks EVERYWHERE and will be installing vapor barrier wherever I have access to the walls / ceilings as I re-hab rooms. It is AMAZING how much air can flow through walls. When I'm burning my fireplace, there is a gap between some paneling and the wall stud that's probably the width of a quarter. There is a full on breeze felt if you put your hand up to it. It is not an exterior wall and I suspect it is pulling air from the basement. Just giving you an example of how air "finds a way" . Don't assume because you have wood on top / bottom of a wal that it is "sealed". If wood framing was a good vapor barrier, they wouldn't require a seperate vapor barrier, right?

4 - Without knowing the specifics of what you have planned (or the next owner's plans), it's hard to say what you can do now to plan for the future. Can you give more specifics?

Hope that helps.