Anyone insulate and HVAC their attached garage?

[Slappy]

I'll insulate my 2 car garage add some heat , I might replace the cement floor as a neighbor's tree has made the floor heave right down the middle (roots) the tree is now gone & I plan on a full shop in there , so if replace the slab ,I'll go with a  liquid radiant slab for heat . as far as cooling the house doesn't have A/C & the wife would Kill Me  [scared]  if I added A/C to Garage  L O L    [embarassed]  

 

[RKA]

Howard, I don't know the size of your ceilings, but for an insulated garage, that sounds way too big.  With 600sf, I would go with an 18000 BTU inverter minisplit.  That should leave you ample overhead.  I installed a 24000 BTU minisplit in a similar sized space with 11ft ceilings.  I oversized specifically for the heat side which loses efficiency and output at sub 20F temps.  The compressor will run flat out For about 10 mins to cool a hot garage then scales back using only 1/3 or less of its peak electrical draw to maintain temps.  Were it not for the heating, I would have gone with the 18 (even if I lived in TX).

I'm not sure why they are recommending a conventional split system (and one that oversized).  One thing with the conventional units, they wont scale back compressor speed as needed.  they just run flat out until you hit the set temp.  On an oversized unit that wont be long enough to get the humidity out of the air.  You really need to size them right.  You have more latitude for over sizing with inverter minisplits.  The minisplits are very efficient, quiet workhorses.  No regrets here, I'd do it again in a heartbeat!

 

[PaulMarcel]

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.  But it's okay, how hot can it get in Arizona?

I had a 30k BTU Fujitsu mini-split A/C-only installed (I do not need any heating, thanks).  As the others said, what's excellent about the inverter design is that it works constantly, but scales itself back.  My garage shop (a 3-car garage with 8' ceilings) can go from 94º to 80º in about an hour with it if the sun is down; takes 90 minutes or so during daylight (this is due to the sunlight on the garage door).  It is easily tolerable in there after maybe 15 minutes since the air handler blows straight down where I spend 70% of my time.  After it has the shop at 78º, it greatly scales back the air handler.  Even full-on, it isn't very noisy; once it scales back, I can record video with the microphone in the air stream and it really doesn't pick up much (granted, it has a wind sock).

The air handling is so good at mixing that during the day when I'm in there, it will feel cooler and more comfortable than the house.  The house is set to 74º while the garage is set to 78º.

I agree with the others about the conventional recommendation... it's too large; significantly oversizing a conventional A/C unit makes it cycle too much and kills it.  When someone recommended a conventional unit to me, I talked to a GC I play hockey with and an energy efficiency expert I know; neither had anything to gain by selling me the wrong stuff.  Both independently said the conventional A/C recommendation is because they know how to do that but not the mini-split.  Get someone who does them regularly.

For me, the 30k BTU Fujitsu had only a $200 premium over a 28k BTU.  Unlike conventional units, you can oversize an inverter system as it just means it will backoff that much quicker; everything is variable speed in those systems.

 

[SittingElf]

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. 

Paul,

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 had a 30k BTU Fujitsu mini-split A/C-only installed (I do not need any heating, thanks).  As the others said, what's excellent about the inverter design is that it works constantly, but scales itself back.  My garage shop (a 3-car garage with 8' ceilings) can go from 94º to 80º in about an hour with it if the sun is down; takes 90 minutes or so during daylight (this is due to the sunlight on the garage door).  It is easily tolerable in there after maybe 15 minutes since the air handler blows straight down where I spend 70% of my time.  After it has the shop at 78º, it greatly scales back the air handler.  Even full-on, it isn't very noisy; once it scales back, I can record video with the microphone in the air stream and it really doesn't pick up much (granted, it has a wind sock).

The air handling is so good at mixing that during the day when I'm in there, it will feel cooler and more comfortable than the house.  The house is set to 74º while the garage is set to 78º.

I agree with the others about the conventional recommendation... it's too large; significantly oversizing a conventional A/C unit makes it cycle too much and kills it.  When someone recommended a conventional unit to me, I talked to a GC I play hockey with and an energy efficiency expert I know; neither had anything to gain by selling me the wrong stuff.  Both independently said the conventional A/C recommendation is because they know how to do that but not the mini-split.  Get someone who does them regularly.

For me, the 30k BTU Fujitsu had only a $200 premium over a 28k BTU.  Unlike conventional units, you can oversize an inverter system as it just means it will backoff that much quicker; everything is variable speed in those systems.

I originally had planned to install a 43,000BTU LG cassette split in the ceiling of my three-car, 960SF garage, but the dimensions of the cassette wouldn't fit in between the joists without very expensive mods.  My electrician suggested a Mitsubishi split system (34,000BTU) using TWO smaller cassettes in the garage that would fit and allow for more even distribution. I will probably go with that system, though significantly more expensive. I would greatly prefer the ceiling mounted cassettes over the wall-mounted mini-splits. Better distribution both my contractor and I think.

In our area, (Space Coast in Florida), we have both extreme heat in the summer, and occasional freezes in the winter. Additionally, humidity is a serious problem in the late spring, all summer, and early fall. As a result, I need a system that has both AC and heat, PLUS an absolute necessity for a dedicated dehumidifier within the system I install that can run without the AC or Heat when I'm not working.  I want to match the humidity level in the workshop with what is normal inside my house. That should greatly limit wood movement when producing projects that end up inside the house, once the moisture level of the wood is stable prior to making whatever...

I also have an attic above the garage, and while it's used for storage and an access for various utilities and electrical systems, it needs more insulation....or a powered exhaust fan. Haven't really decided how to manage that yet.

Cheers,

Frank

 

[HowardH]

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. 

 

[amt]

I regularly see 100F temps outside, so I decided to install a AC unit a few weeks ago.  I can go from 100 to 70 within about an hour.  I did oversize the AC unit at 18,000 BTU (for a 500 sqft space).  I looked in to mini-splits, but the cost was coming to $2500 or more.  I simply bought a window unit for $500 and installed myself.  It's not the prettiest thing, but it saved me $2000. Wouldn't you rather have $2000 more to spend on tools?

If I were in the shop 8 hours a day, I would have gone with a much more efficient unit (like a mini split).  However, for my use (at most couple hours a day), the up front cost of the higher efficiency units would not pay off soon enough.

One of the biggest improvements I made to resist the heat was getting a well insulated garage door.  I have something like R12 in the door itself, and all of the panels seal to each other with a rubber seal.  The second most important improvement for keeping cool was the metal roof.

 

[SittingElf]

I regularly see 100F temps outside, so I decided to install a AC unit a few weeks ago.  I can go from 100 to 70 within about an hour.  I did oversize the AC unit at 18,000 BTU (for a 500 sqft space).  I looked in to mini-splits, but the cost was coming to $2500 or more.  I simply bought a window unit for $500 and installed myself.  It's not the prettiest thing, but it saved me $2000. Wouldn't you rather have $2000 more to spend on tools?

If I were in the shop 8 hours a day, I would have gone with a much more efficient unit (like a mini split).  However, for my use (at most couple hours a day), the up front cost of the higher efficiency units would not pay off soon enough.

One of the biggest improvements I made to resist the heat was getting a well insulated garage door.  I have something like R12 in the door itself, and all of the panels seal to each other with a rubber seal.  The second most important improvement for keeping cool was the metal roof.

There are a lot of us who would also simply use a good window unit.  Unfortunately, I as well as others, live in fascist controlled HOA's. (Home Owners Associations).  Window units are strictly prohibited in our gated community.  It becomes a federal case just to get "permission" to paint the trim on your house...even the same color! Grrrr! [mad]

 

[HowardH]

My HOA is spelled S P O U S E.  : :  Would never go for the window unit plus I would have to cut a major hole in the brick. 

 

[deepcreek]

I was going to suggest an Amana PTAC unit as a better option than a window AC but it requires a thru-wall installation.

Otherwise, your best bet for that small of space is a mini-split.  The minimum tonnage of a conventional unit is still way too much to operate properly.

You AC guy is probably not familiar with mini-splits and they may not sell them at his supplier.  Most AC contractors are "brand loyal" to wherever they have an account.

I would choose the mini-split brand you want and then find out where they are sold to contractors.  Then go to that distributor and ask for a recommendation for a good residential installer who can buy the unit and put it in for you.

 

[tbellemare]

Hi Frank,

It just so happens there is an article in a recent Fine Homebuilding that deals specifically with air conditioning a garage, how to do it the right way and that is basically what Eric suggested; a ductless minisplit.

Here's a link to give you an idea from a fellow Texan about the way he does it

Good luck too, we lived in Houston for 2 years and there are only about 2 months of weather that are proper for humans to be outside or in an garage without A/C

http://www.finehomebuilding.com/item/31322/garage-ac-wrong-way-right-way

Glen

Matt Risinger, the guy in the video referenced above, is also a Festool user...

Tom

 

[tbellemare]

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!

Tom

 

[RKA]

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. 

 

[HowardH]

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. 

 

[PaulMarcel]

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. 

Paul,

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.

 

[stvrowe]

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.
Steve