Author Topic: Anyone insulate and HVAC their attached garage?  (Read 25331 times)

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Offline Tom Bellemare

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Re: Anyone insulate and HVAC their attached garage?
« Reply #30 on: September 16, 2013, 11:06 AM »
I lived in Houston close to 30 years and for those 30 years, there were about 4 months of the year when A/C was almost required. There were about 6-8 months when the weather was almost perfect. For about 3 of those 4 months, it was not uncommon for it to be 95 degrees and 99% humidity.

I have a friend in Spring Branch (Houston neighborhood) that added on an office space to the back of his house about 12 years ago. It was about 25' x 25' with a vaulted, timber frame ceiling that went up about 15' in the center with almost no insulation. It had about 5' tall windows on 3 sides. He added a split unit to it and could take that room down to meat locker sort of comfort in July.

I would go with what Matt Risinger suggested any day. As Tom pointed out, check and change the filter often!


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Offline RKA

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Re: Anyone insulate and HVAC their attached garage?
« Reply #31 on: September 16, 2013, 11:35 AM »
If I were the cynical type, maybe because a 3.5 ton unit is also about $3500 so maybe that was part of the recommendation.  I have 10' ceilings in the garage so it's a lot of volume to cool.  I already had 220 run to the spot where the split unit is going to mount on the wall so that would save me some install cost.  Paul, I like your idea of getting an oversized unit.  I didn't know the rules for conventional A/C (don't get too big of a unit for the space) didn't apply with the split type.  I'm just sick of sweating through 100 deg evenings trying to get something done in the shop and then going back into the house because of it. 

FYI...for either the conventional split or the mini split you'll need that 220 run terminated at a disconnect box near where you plan to install the condensor unit.  Generally the mini-splits accept at 220 to the condensor, then another 16-18 ga. run is made between the condensor and indoor unit for power and control. 

Offline HowardH

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Re: Anyone insulate and HVAC their attached garage?
« Reply #32 on: September 16, 2013, 11:47 AM »
Fortunately, the main panel is on the garage wall about 5-10' away from where the compressor will be placed.  Should be a pretty easy install. 
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Offline PaulMarcel

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Re: Anyone insulate and HVAC their attached garage?
« Reply #33 on: September 16, 2013, 01:29 PM »
I have an attached garage that is partially insulated; the steel garage doors are still a significant source of heat even with the foam insulation I stuffed into the cavities. Add to that my two outside walls are drywalled (so closed cavities) but with no insulation. 


What did you use for insulating the garage doors?  I've seen a post is some forum elsewhere about some kind of pink stuff from HD?  I have vertical lift doors I want to insulate against the morning sun hitting them, and holding heat in winter (Florida).

I just bought sheets of 1.5" thick rigid foam insulation. There are "garage insulation" kits that are basically that sheet pre-cut for a profitable convenience.  Push it into the recesses of the door.  When I first did that, I thought it would help a little.  The next day I went into the garage and thought  it mustn't be as hot out as usual and only later realized it was because the foam was helping that much.  I have 'windows' along the top segment of the garage door. On the side I don't use, I put white posterboard in the window then put the foam (otherwise it would have all the brand labels showing outside...)  On the side I'm in, I still have the windows uncovered and I know it is a significant source of heat, but I want to see out and not be completely in a cave!

Get an infrared thermometer.  You can get cheap ones at Harbor Freight that read things accurately for me. Point around your garage and see where the hotspots are. I could do more work to make the garage door better.

Oh also note that at least for my installation, it would be pretty easy for me to take the unit with me when I move. They'll come to bottle the refrigerant then remove the refrigerant lines.
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Offline Steve Rowe

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Re: Anyone insulate and HVAC their attached garage?
« Reply #34 on: September 16, 2013, 03:17 PM »
We are moving into another house in 3 weeks and it has a 3 car garage which is 600 sq ft.  I originally thought about putting in a split system but two different HVAC companies have told me it would better to install a 3.5 ton conventional A/C system.  It would put out a lot more air and be more efficient.  I will be insulating the main doors and the attic space.  Two of the three walls are shared with the house so I should be good there and I believe the outside wall also has insulation.   I'm not doing a furnace, just the air handler.  We are close enough to Fall to wait until Spring to do it.  No sense spending the money to have it sit for 6 months.  Are the just trying to sell me a more expensive system or will the split system not be robust enough to handle the Texas heat and cool a 600 sq ft. space?

I have a 3 car detached garage (936 sq. ft.) with 10 foot ceilings that I put a conventional 2 ton heat pump in nearly 3 years ago.  Walls are 4" with fiberglass insulation, ceiling has 12" of blown in cellulose and, I insulated the metal garage doors with 1" styrofoam insulation with the metal reflective mylar.  Temperature in my area is about 3-5 degrees F cooler than than the Dallas area and the humidity runs about the same.  I talked to 3 HVAC contractors about my choices and these included a mini-split, a 16 SEER conventional heat pump, and a standard 13 SEER conventional heat pump.  Without fail, all of them recommended the standard 13 SEER unit and this was based on me not leaving the temperature setting constant (i.e. - when I wasn't in the shop, I intended to increase the thermostat setting to 83F in the summer and lower it to 58F in the winter).  They only recommended the high efficiency units if I intended leaving the thermostat alone.  If I were to treat the shop as 'living space' and maintain a constant temperature, I would have chosen one of the high efficiency alternatives.

These are my observations thus far;
1) The A/C cycles normally during the summer and usually maintains a comfortable 78F.  My garage doors face west and get a good 4-5 hours of direct sun in the afternoon.  On the hottest of days (100F+) the A/C will run continuously during the late afternoon period and temperature will creep upward but maintain 79F.  The exposed metal on the inside of the garage doors is hot to the touch when this happens.
2) I cannot say what it costs me to operate since I put in more energy efficient windows in the house at the same time I installed A/C in the shop.  Even with a rate increase, I have noticed no appreciable change in my electric bill from what it was before.
3) Even with the absolutely miserable summer last year with way too many 100F+ degree days, I was able to use the shop and stay comfortable.
4) The shop humidity is much lower and I have yet to see any rust develop on any of my machines during this period.  It has been over a year since I have waxed any tables.
5) I need to improve the air tightness of the shop around the garage doors. 
6) Next time I paint the exterior, I intend on using a metal reflective paint as a primer on the outside of the garage doors followed with an overcoat of insulating paint.  I will most likely use Hy-Tech paint for this application. 

Hope this helps.