A/C for Garage Shop in Texas

[Edward Bartimmo]

I am in Houston, Texas. I am combating high heat coupled with high humidity. My shop is a 2-car garage. Above the garage is an enclosed attic area. I have replaced the garage door with an insulated door. This alone cooled the garage by at least 5 degrees compared to outside.

I know there have been a number of posts on this topic. I have read quite a few and still haven't come up with a answer. These are the specific challenges that I am facing:

(1) Garage door must stay
(2) Side walls are brick with hardy plank attic above garage
(3) HOA will have fit if whatever I do can be seen from street
(4) Do I need to put vapor seal / thermoseal around garage door???
(5) How to cool garage at reasonable cost???


Open for suggestions...

Thanks,
Edward

[David Hostetler]

What subdivision are you in? Various HOA's have different rules. And you can do different things to conceal things.

In my situation, the best option I came up with is....

#1. Fully insulate doors.
#2. Add garage door seals. (Attaches to trim, basically a rubber gasket that goes around the door opening and seals against the door.)
#3. Insulate the attic above the garage.

These steps alone keep my shop down to the low 80s while it is in the upper 90s here in the bay area.

The next step I did was to add a dual hose 13.5K BTU portable A/C unit, and duct it through the post between the garage doors. I used 5" louvered vents that are painted the same color as the siding. This stays, when not in use, hidden behind a large flower pot so the HOA can't see it.

I can make my shop downright cold when it is in the upper 90s outside, but it takes a while to get it there, and I have to have a box fan moving air around to do it...

I could use to insulate the side walls, and that is on the to do list, along with a sub panel and added power.

As far as energy usage goes, insulate insulate insulate. Oh yeah, I am also adding radiant barrier foil from Attic Foil up in Dallas...

[Richard Link]

Edward,

I too am a Houstonian and had a similar problem. This is a 2 car garage with no windows that is attached to the house. Uninsulated walls, uninsulated doors. Somewhere in the spectrum between a greenhouse and an oven during the summer months.

I solved it with three steps:

1. Replace the old garage doors with insulated doors.
2. Had the walls retrofitted with blown in cellulose insulation
3. Installed a mini-split AC unit

Current setup keeps things very comfortable at all times of the year. Still not quite as dry as the interior of the house (seal around the garage doors isn't so great) but it is worlds better than before.

Richard

[Edward Bartimmo]

Unfortunately, I did not have the foresight to have had the walls insulated before they were sheetrocked. Subsequently, I paneled all the walls with 3/4" Plywood on top of the sheet rock, which allows me to afix anything anywhere without worrying about finding studs. This shortsightedness also extended to not insulating between the sheetrocked ceiling and the 3/4" paneled floor of the attic. In both cases it is to late to go back and retrofit (cost, space, and time prohibitive).

I need to get the vapor barrier for around the garage door. Has anyone tried to put a window unit through the attic and extend some ductwork into the garage?

[Mike Hicks]

Edward, that's an easy fix with the wall insulation. Big box stores rent the machines and sell you the insulation. Cut a strip at the top of your 3/4 and pull it off all the way around the room. Use a hole saw the diameter of the nozzle on the insulation blower hose and cut a hole in each cavity between the studs. Fill the cavity and replace the strip of 3/4 at the top and the hole is covered. Insulated walls.

[Edward Bartimmo]

Mike,

Thanks for the tip on retrofitting the insulation. This may be an item to wait until it cools off in a few months. This will require me to unhang and move a lot of things to even gain access to the wall behind the boards. There is a lot of equipment, tools and wood hanging in walls.

I broke down and bought a portable AC unit (12,000 BTU) from HomeDepot. I did a little jimmy rigging just to see how it would handle cooling off the garage. Yes, jimmy riggin involves venting it into the attic above the garage for a 2 hour test run. Not as impressed as I hoped.

Gable fan going into the attic over garage this coming weekend.

[Vic Barton]

I live down I45 right on the Coast. The only thing I would add is you might want to also get a Dehumidifier. I run one when the AC is not on.

[David Hostetler]

Well think about what that portable unit has to work with. Fighting LOTS of heat gain due to no insulation, then picking up the air for its heat exchange from the attic... IF you can manage to get it to give you more than 10 degree drop, you are doing quite well...

In order for this to work, you have GOT to get that space insulated, and reasonably sealed up.

Venting through the attic isn't exactly a great idea as you are exchanging hot moist air with even hotter moister air... It might work, but you are venting VERY hot and VERY wet air into your attic. Get it out of there as FAST as you can... Do you have attic fans? If not, you really need them. All that extra heat can end up impacting the rest of the house...

[Stew Hagerty]

Mike,

Thanks for the tip on retrofitting the insulation. This may be an item to wait until it cools off in a few months.
__________________________

I broke down and bought a portable AC unit (12,000 BTU) from HomeDepot. I did a little jimmy rigging just to see how it would handle cooling off the garage. Yes, jimmy riggin involves venting it into the attic above the garage for a 2 hour test run. Not as impressed as I hoped.

Insulate Insulate Insulate. It's the number one thing you can do to reduce the interior temp. Rather than put it off, I would move it to the head of the list.
A/C units work by removing heat from the inside and dumping it outside. The hotter it is outside the less efficient they are. By dumping it into your attic (which was no doubt hotter than outside) you dramatically reduced the effectivness of the unit. Plus the added heat pumped to the attic will spill back down into the lower level. I would say it was not a valid test. Instead try closing your garage door down on top of it then blocking up the rest of the opening. It will be as though you put it through a wall.

[Bret Johnson]

Edward,

I too have a situation similar to you. I started by insulating the attic with R-19 batts as they were on sale at Lowes for $20 off the original price. I also put the reflectix wrap on the garage door and I am able to keep the garage at about 85-88 degrees when it is 95 and above outside. One of my side walls is not insulated and the other is only have insulated with an office on the adjacent side. With fans on it is tolerable. Next year I want to install an a/c I am going to buy an 8,000 btu unit mount it near the ceiling and vent the exhaust into the attic and through a duct to exit out a soffit vent.

Bret

[Tom Jones III]

I'm in Houston and I've had pretty good success with minimal effort. I've got a 3 car detached garage. I insulated the attic with the heaviest stuff that Home Depot sells around here and I installed a powered roof fan. This made a huge difference. Next I installed a window AC unit by cutting a hole in the wall. Finally, I insulated the west facing wall. This also has a significant improvement. Eventually I will insulate the rest of the walls and do something about the garage doors.

I couple of you mentioned that you installed insulated garage doors, where did you get yours? Does this do anything to seal the gaps between the door and wall or does it just insulate the door itself?

[Richard Link]

Edward, that's an easy fix with the wall insulation. Big box stores rent the machines and sell you the insulation. Cut a strip at the top of your 3/4 and pull it off all the way around the room. Use a hole saw the diameter of the nozzle on the insulation blower hose and cut a hole in each cavity between the studs. Fill the cavity and replace the strip of 3/4 at the top and the hole is covered. Insulated walls.

Not to dissuade you from Mike's excellent advice, but....

When I was planning the insulation of our garage, I considered going the route above - renting a machine, cutting holes in the drywall, blowing it in myself, etc. Sounds easy to do and no big deal. The internet is full of rosy sounding explanations of how easy and fast it is.

Do NOT underestimate the work and pain involved in that process (not to mention the potential lung damage). I ultimately chickened out and hired someone to do the job. Two experienced guys worked almost two full days in the most miserable conditions you can imagine blowing in the cellulose. A million holes to cut in the garage walls, then patch, paint, etc. Debris everywhere. An incredible mess not to mention that it just isn't something you can do by yourself since you need someone to run the machine while you blow, etc. Seriously, I felt bad for those guys and the cost was really very minimal to have someone else do it. I mean very minimal. No way it would be worth it to do it yourself.

Bottom line: I'll usually try to do almost anything myself to save some $ but do yourself a favor and hire someone to do that job....

Richard

[Stew Hagerty]

I couple of you mentioned that you installed insulated garage doors, where did you get yours? Does this do anything to seal the gaps between the door and wall or does it just insulate the door itself?

I put on Clopay Insulated Doors when I built my home. I live in NE Indiana so my reason for insulating was to both keep it cooler in the summer and warmer in the winter. I used what are referred to in the industry as "sandwich doors". They are 2" thick have a steel skin on both the inside and outside surfaces with polyurethane foam sandwiched in between, resulting in an R Value of 17.2

http://www.clopaydoor.com/Home.aspx

[Will Rowland]

I couple of you mentioned that you installed insulated garage doors, where did you get yours? Does this do anything to seal the gaps between the door and wall or does it just insulate the door itself?

I had my insulated garage door installed by Hollywood Door on Antoine. Very pleased with their service, and price, and I shopped it pretty hard.

Around the edges of the door frame they installed a flexible plastic strip that seals against the door as it closes. Works great.

FWIW, I currently have a 12000 BTU portable unit in my 26 x 24 x 10 detached garage in Houston. At present the walls and ceiling are not insulated, though I do have radiant barrier roof decking, the insulated garage door, and low E-366 windows. I can only get the garage down to 85 F in the late afternoon with the unit running on "Max Cool". However, the humidity is significantly lower inside, which helps. I do leave the unit running in "dehumidfy" mode during the week, but on Friday night set it to Max Cool and leave the unit in that mode all weekend.

The eventual plan for my shop is a 24k BTU mini-split heat pump, and full insulation, but I've been trying to first get a lot of hours working in the shop in order to confirm positions of outlets, machinery, computer etc before finishing the wiring and closing up the walls.

[Edward Bartimmo]

Gable Fan going in attic directly over garage. Curious to see how much this effects temperature in the garage. Also, installing the weather strip along garage door.

Agreed that insulating the walls would be significant. All walls are sheetrocked and then paneled in 3/4" plywood. From a convenience and cost standpoint affixing/sandwiching a styrofoam insulation panel between the sheetrock and plywood would be a dream come true.

Is there a big difference in performance between foam insulation panel and spray in insulation into the walls???