Trying to keep the heat out

[TWX]

Hey everyone,

Here in the Phoenix area I have a cinderblock-constructed flat-foam-roof workshop with interior dimensions roughly 24'x38' by 9' high. The two insulated garage doors are on the 38' segment and are roughly 16'x7' and 10'x7', facing South. The 2"x12" ceiling joists are exposed and there's only insulation in a small part of the roof where the previous owner had started before giving up. The garage has a heatpump without auxiliary heat. It's capable of keeping the garage down to about 80' if I run it constantly. Subsequent to moving in I've added some Dow extruded polystyrene 1.5" thick insulation to the West wall. This insulation on the West wall is currently fully exposed, installed with glue made for foam insulation. It's in a part of the garage where a car that isn't being worked on is parked, so there's no real threat of fire near the insulation.

The material itself was on the wall with a couple of nails at the top at the old house in the old garage, just barely hanging there. I took it down when we moved. The problem is, on the South wall in the new garage, there's about 2' above each garage door and a couple feet between the doors and between one door and the wall that are just painted cinder block. This year we've had record numbers of days in excess of 110°F, and we had a $475 power bill last month, so I'm trying to reduce the cost to keep the workshop cooled to 85°-90°F as much as possible. I've already installed those PVC garage door weatherstripping boards around the outside frames to seal the gaps between the garage doors and door frames, but I'm thinking I need something for the cinderblock walls on the South, and possibly East sides.

I can't find the same insulation that I had previously bought. When I bought it originally it came in 2'x8' sheets, and it came from Home Depot. They appear to no longer sell it, nor does Lowes.

Given that I probably can't get the same thing as I had, any suggestions as to what I should get? To insulate the area around the garage doors I'll need three 4x8 sheets- one for the tops above the doors, and one more to use to fill in the other gaps. Since there are 2x6 boards flat against the wall for the garage doors to bolt to I figure that using no thicker than 1.5" thick is the best choice. Would it be better to get aluminum coated? I used extruded back then because it seemed better than expanded. Is there something better yet out now?

Lastly, the area over where the car is parked is not sheetrocked because there's not much risk of fire. Further over is where I plan to actually work, and while I don't know how to weld yet, eventually I might want to learn. Is any bare insulation safe enough to install bare without a sheetrock or other layer over it?

Thanks,

 

[Warrenator]

I've looked into the foam board insulation too, the various manufacturers say all sorts of things about a "fire rating" and say it is "Flame retardant," but don't actually show any data at all about how long and at what temp does it ignite, and most importantly, no building code I have seen allows exposed foam insulation in an area that has to be fire protected.

You could do a real non flammable insulation like rock wool or fiberglass, but it needs to be held in place by something, or will just get dusty and horrible.

In my garage I'm doing sheetrock, with fiberglass insulation on top. A lot of guys on this board have bare plywood walls, or foam insulation, and say it is "no problem," but I figure why not just do it up to code and fireproof. Sheetrock and glass wool insulation is actually pretty cheap.

 

[TWX]

On the 38' dimension, 30' of the floor is level with the driveway, and 8' on the east end (so 8'x24') is raised about four inches. This raised area is where the workbenches and most of the stationary tools, compressor, the shelving units that are bolted to the wall, and the plumbing for the bathroom (not currently built, just a utility sink) are located. There's also a whole lot of electrical stuff on the wall, much of it unused as the previous owner had been using a three-phase converter for his mill, and the converter and mill left, but most of the wiring was left behind in 3/4" thin-wall metal conduit. The east end does get some sun through the morning, but the house blocks part of the wall until the late morning hours, and it's not as hot in the morning anyway. The 8' section of wall on the south side is where the sink is located, so unfortunately it'll be a PITA to insulate that section. That might wait for when I actually install the bathroom in earnest, as I'll have to remove everything currently there anyway.

The north wall has shelving and storage against it, and will likely remain that way for some time. That wall gets up to somewhere toward ambient outdoor air temperature, but doesn't see any real direct sunlight. It'll probably be last to be insulated, if ever, due to the difficulty in moving everything.

The raised area would be the highest priority to sheetrock over, as that's where I'd imagine I'd be closer to a wall and have to deal with risking exposed insulation. The car stall near that area is also a good candidate for sheetrock. The sections further west are probably lowest priority, as they're more for parking than for work.

It's only money, right? *smirk*

I guess tomorrow I'll go by Lowes and Home Depot and compare what I see, and if I like something I'll get three 4x8 panels of it to at least get the area above and next to the garage doors.

 

[72Anthony]

You should research radiant barriers for the roof and walls...very effective in high temperature areas such as AZ & TX. There are various products available for retrofit (some more effective than others). They also require an air gap to work ( the air gap can be the room itself, in the case of applying a radiant barrier to the inside of a garage door), so you need to make sure the product type fits with your particular conditions.

 

[TWX]

Well, I just picked up three 4'x8'x1.5" panels at Home Depot that have a foil lining on both sides. They're rated for R9.4, made by "RMax", called "Thermasheath". They were kind of pricey at $26/each, but once I factored two more tubes of the appropriate glue (bringing me to 3 and a half now) and a new utility knife to cut the stuff it made more sense to spend the extra $20 for the better ones over the R6-rated expanded stuff.

It looks like Home Depot has now started partnering more heavily with Owens Corning, which explains why they stopped selling the Dow product. Thing is, the Owens Corning product line doesn't include anything over 1" thick, and the Thermasheath at 1" has a higher rating than the pink stuff, for not a lot different in price. So, they dropped the product that really worked well, as 1.5" thick is the same thickness as a 2x board if those are already against the wall, and is also closer to if one had existing framing against a block wall that used 2x2 or 2x3 boards.

Plus, I really didn't want to have pink walls in my workshop. They'd clash with the blue '73 Charger and the light blue '78 Cordoba... *grin*

 

[upstater]

FWIW... I installed a small solar fan in the ridge cap recently of a 24x28 2 story garage I built. It really helped to evacuate the stagnant air up there and helped cool the upstairs. They aren't much money and are essentially free to operate.

http://www.sunrisesolar.net/

 

[djjsr]

What color is your roof? I have a flat roof on my shop that was black. I coated it with a white sealer and it made a HUGE difference.