Texas detached garage ceiling insulation

[merlin]

Okay, so I'm about finished drywalling the ceiling in my detached 2car garage.
It's in Houston, it's hot most of the year. Well, at least it's not cold very much.

I was going to put batts in the attic joists with paper backing. Yes, I know, I should have done this before drywalling, but..... A lot of info says that I need the poly, but I won't have a heater, only a window a/c. And I really don't want to take down the drywall to add the poly, either.

So, what I'm wondering is, will the faced batts be okay in this situation?

Thanks for the help,
Billy

 

[713Dakota]

Hey Merlin,

Yeah, yeah, first post... longtime lurker, chronic searcher. On to the question at hand...

I had this dilemma when I bought my house. I purchased a 1920's bungalow that had no insulation, and I mean none, anywhere, in Houston. I started fixing that right away. When researching my options, I was told by two different architects and a builder/friend that a vapor barrier in Houston is not as important as in a cold climate. I was kind of skeptical, but all three were pretty adamant. Besides, in your case, the facing on the batts is a vapor barrier.

I ended up doing diy'ing 14" of blown cellulose with no vapor barrier. You might look want to look into it. It's a little messy to install, but no itch, and the price can't be beat.

On another note; What part of town are you in? Judging by the "2 car detached garage" I'd guess you're at least outside the loop?

I'm in the Heights, stuck with a 10x20 three-walled dirt floor shed that masquerades as a garage. I've been plotting to tear it down and rebuild it since the first time I walked the property.

Mike

 

[ni[x]it]

No answer to your question, but I HIGHLY recommend you at least lay some radiant
barrier on the joists, over whatever insulation you determine is best.

 

[merlin]

Mike,

Thanks for that. The batt facing is a vapor barrier, but probably not a very good one, if laid in from the top side of the joists - no way to seal it up very good. I'm not really about having perfection, it's a garage, but just want to not cause problems down the road. Yes I've thought about the blow in, even dumping it in by hand and levelling it. On another site, they were adamant about having the poly up before sheetrock. I've rarely seen that in our area. We just don't heat that much of the year.

Good guess about location, Spring , I-45.

Thanks for taking the time to answer. You should start on yours, I've many years to get this far.

ni[x]it

Not sure I understand the radiant barrier on the joists. Wouldn't they be better under the rafters?

Billy

 

[CenTex52Chevy]

Merlin,

Long time lurker, first time poster.

Seems to be two schools of thought on installing radiant barriers. A search of the web will give you about 50-50 split on installing on the joist verse under the rafters. I'm going to go under the rafters. It will be a little harder but figure I don't have to worry about tearing it when I put anything on the joists.

 

[merlin]

CenTex,

You're right about that. That is what makes it harder to choose, when there's more than one way to about everything. I don't think I even need the radiant barrier, but who know, could add it some day.

You're up between Manor and Taylor? My grandma was from near Coupland a 100 years ago.

Thanks for the help.

Billy

 

[52RustRocket]

Yeah, under the rafters for a warm climate, and over the joist for a cold one. At least that's what I read while doing research on the foil. I'm about a third done with the radiant foil in my house attic.

 

[RacerX]

I just found this issue and I'm doing a similar project. I live in Houston, in the Heights, and I'm rebuilding my 2 car detached garage into a garage/auto shop with office / gameroom / storage over it. 713Dakota, we're neighbors! I also recently bought my son a 2000 Dakota that we put an engine in. Anyway, I'm framing the first story of the 30' x 30' garage now and preparing for the steel beam on Saturday to attach the joists to for the 2nd floor. downstairs is a 12' ceiling height for a lift. overall height is 29.5'. Insulation is in it's future also as all the outside walls are 2x6. I'm thinking of just using batts and then drywall.

 

[gbcamp72]

I'm just north of you in the woodlands neighbor, three car garage with one bay walled off as a woodshop. I have 4" fiberglass insluation in the walls and 6" in the ceiling. The ceiling still gets hot and the attic is defineitlly hot. If I did it over I would look into a radiant barrier so the ceiling under the insulation layer was cooler. I also insulated the one steel door and thta has been a big help as well. Your welcome to check it out if you would like.

 

[CenTex52Chevy]

Merlin,

I wasn't sold on the radiant barrier until the neighbor built their house. He put a radiant barrier in under the rafter and man did it make a difference. With temperatures topping 100 degrees for 40 plus days here it will probably be my next big project.

We are almost exactly half way between Manor and Taylor.

 

[kbs2244]

Rustbucket has the idea.
Everything is backwards in a hot area with air conditioning more inportant then heating.
Go with the local experts.

 

[merlin]

Centex, thanks for endorsement of radiant barrier. I was kind of skeptical of those - heard they can ruin the roof shingles, but then if you read enough, everything has a possible downside. I've got to quit reading.

Is this the kind you staple under the rafters? Any certain brand or place to get it? I'm interested in it for the house attic.

gbcamp, love to have a 3 car garage, but my neighborhood pretty much only has 2cars. But oh well, my hands are full just fixing this one up. Were pretty close to each other.

 

[anojones]

The vapor barrier thing can get confusing and I don't think there is a complete consensus on it. I'm in a different climate, hot and dry with cold winters- so have different heating and cooling needs-YMMV. However, the main reason for poly is to stop water vapor from leaving the heated side of the room and saturating the insulation and causing moisture problems (as the room heats, more water turns to vapor and migrates to the cooler side of the ceiling). It would seem in your situation you are mostly cooling and the AC would be removing moisture from the space and thus reducing vapor and thus decrease the need for poly between the sheetrock and the batts. I would think faced batts would be enough in your area, as your attic space is likely to be hotter than the garage space most of the year. If I remember correctly Houston is pretty humid, and in some very humid areas they either don't reccomend a vapor barrier or actually put it to the cold side (above the insulation) to prevent the humid air vapor from getting to the insulation and then to the sheetrock. A radiant barrier could work like that as well, but a well ventilated attic would probably be the best thing.

 

[merlin]

anojones, what you say makes sense and agrees with most of what I've found. I'm going with what you guys have generally agreed on. I'm probably making a bigger deal out of it than necessary for this climate. You're right, it is very humid, almost year round, with only 1 cold day. Okay, maybe a month or two.

Thanks,
Billy

 

[RacerX]

Merlin, I'm doing the same. Radiant barrier for the roof deck and side walls with felt then hardiplank walls. Insulation inside walls and ceiling (max depth. I have all 2x6 walls, even upstairs) and then they'll have sheetrock over that (after my air lines and wiring of course). My roof deck is 5/8" techshield and the walls are 7/16" for what it's worth.