Thinking about Heating and Cooling the Shop

[Paul McGaha]

My shop is my attached 2 car garage.

We have a heating and air conditioning company we like that we used a couple of years ago to replace our gas furnace and outdoor unit. I just called them and asked them to come out and look it over to see what the options and pricing are to heat and cool the shop.

It would be nice to be out there in the summer but fans only go so far. Here in Virginia we have a lot of 90+ temperature days in the summer.

The shop actually works a lot better with the door open and the assembly table moved outside but there are some things that could be done with the door closed.

We'll see.

PHM

[Don Bullock]

One of the woodworking magazines had an article showing how one of their writers built his own shop. As I recall he installed the type of HVAC that is used in motel rooms. Instead of installing it under a window he put it in a wall. It would be fairly easy to do and I'm sure would be less than a "central HVAC" system for the shop.

Whatever you do you want the shop HVAC system to be separate from your home system even though the shop is attached to the house. Adding the shop to the home's system would add a lot of particulates that would have to be filtered out and you wouldn't always want the shop heated or cooled when your system is running in the house.

[Paul McGaha]

Whatever we do it will be separate from the system that serves the rest of the house.

As we have gas to the house I would think a gas unit heater keeping the shop about 50 to 60 degrees would be great in the winter. As for the cooling I just dont know. Maybe some type of window unit or something similar, although at the moment we dont have any kind of window.

Probably a bit of a longshot in any case, Dont know that SWMBO is too much behind the idea. Dosent cost anything to find out what the options and pricing is though.

PHM

[David Kumm]

My shop is also in an attached garage, bigger than yours but concept is the same. I have a sealed burner direct vent gas furnace and a ductless split system A/C unit. Wisconsin has extremes, it may be that Virginia has mild enough winters that a heat pump type unit with a standby electic heater for the really cold days would work. Of course insulation is key. Dave

[Paul McGaha]

It could be that one of the mini ductless split system that Mitsubishi and others make might be a decent soloution.

Any of you guys have a system like this and is it working well for you?

Seems to be pretty affordable. Total installation costs looks to be about $2K. Unless I'm missing something.

PHM

[Matt Meiser]

The Modine Hot Dawg and similar unit heaters intended for residential garages are great. I have one in my shop and put one in my dad's garage. My thermostat has an extended lower range so I can set it for 42 and it doesn't cost us terribly much to keep my well-insulated shop above freezing all winter. When I want to work out there I kick it up to 62 unless I'm finishing, then I raise it up higher.

For cooling I did nothing and/or the window thing for several years. The window unit worked well enough but was a pain. Last fall we put a heat pump with natural gas aux heat in the house and moved the AC from the house to the shop with a blower unit which is a much nicer setup and I get to see out my window all summer.

[Jim O'Dell]

The hotel unit Don is refering to is a PTAC (packaged terminal ac). I framed in a hole in the wall for one of these when rehabbing my shop. A unit with 15k btu heat pump runs in the $725.00 range on line. Have to buy a sleeve for it to fit in, and the external grill of your choice on top of that, so probably in the 875 range. If you don't need the heat pump, the regular heat units are slightly lower in price. I'm not sure one of these will take care of my whole shop or not. If it was all one big room instead of 2, it probably would be fine. As it is, the mounting hole is in the smaller area that will mostly be assembly and finishing. Your situation may be different. Jim.

[David Nelson1]

My shop is also in an attached garage, bigger than yours but concept is the same. I have a sealed burner direct vent gas furnace and a ductless split system A/C unit. Wisconsin has extremes, it may be that Virginia has mild enough winters that a heat pump type unit with a standby electic heater for the really cold days would work. Of course insulation is key. Dave

1+ I have a 13000 BTU heat pump window unit by Emerson. It does a great job on A/C but the heat is a bit slow. Once warmed up it does a fair job of keeping it warm. Cost a few hundred bucks. With a sleeve no other mods needed except 220 single phase circuit.

[Larry Frank]

We put on an addition on the house and used a PTAC unit for heating and air conditioning a 12 x 24 room. It does a fine job for this room. I would also take a close look at the filters and cleaning the unit if used in a shop. It will pull a lot of dust and stuff in even if you have a good dust collection system.

[Charles Lent]

My 14 X 26 shop is heated and cooled with a 24,000 btu window style heat pump that I mounted high and through the North wall. It has done an excellent job for the 12 years that it's been in use, maintaining a temperature of 68 deg in the winter and 72 deg in the summer. It seems to be able to reach temperature within about an hour in the coldest winter day ( 10 deg) or the hottest summer day (98 deg) and the Virginia and North Carolina weather is very similar. Filtering the air has been my only problem, but I solved this by using pleated style paper air filters (the better ones) and changing or at least blowing them out frequently. The 12" X 20" X 1" filters will fit behind the front plastic grill if carefully positioned, but I was duct taping them on the outside before I found the right size that would fit inside. My shop has 3" fiberglass insulation in the walls and 6" in the ceiling and it's a stand alone building. I think your old house system will do fine in your shop if you mount the air intake grill high and use some good pleated filters in it. You may still need to use an air gun to blow out the evaporator coil every year or two, but otherwise it should be fine.

Charley

[Phil Maddox]

David - those units are not made to have a lot of "pick up", meaning they are made to set and forget. Turning the temp way up or down makes them run for a long time to catch up, in heating mode, this costs a lot of $$$.

If you can find a happy medium, leave it there you will probably save some money.

Good luck.

PM

[David Hostetler]

For starters, before you add any sort of heating or cooling system, you need to make sure you have plenty of insulation in your shop to make that heating and cooling effective. I am partially insulated, and even at that, my AC works its tail off to cool my 2 car garage shop. But then again, when I saw you posting about 90 + degree days my first thought was less than polite... A 90 degree day with humidity under 80% would be downright pleasant here! We have been hovering just above or below 100 with humidity in the 80 - 90% range... Needless to say, heating isn't my biggest concern.

So simply put, I heat with a 1500watt oil filled radiator, I cool with a 13.5K BTU portable unit air conditioner, my overhead air filter serves double duty to move the heated / cooled air around the shop and makes it comfortable.

[Michael Heffernan]

Paul,
My last shop, an attached 450 SF two car garage was heated with a Cozy Direct Vent Counterflow wall furnace with electronic ignition (DVCF403, 40k BTU). I installed a 7 day programmable wall thermostat. Set it to 50 degrees at night and at 65 degrees 30 minutes before I started work in the morning. My shop was well insulated with 1" rigid foam, studs, R-13 batt insulation, drywall on the walls, R-30 batt and drywall on the ceiling, insulated raised floor and rigid foam panels on the overhead garage door. This heater kept the shop toasty even on the coldest days here in Philadelphia. They are not the most efficient heaters out there, only about 75% efficiency. But they heat the space quickly (if well insulated) and are not too expensive to run, at least for me. I recommend the electronic ignition models as there is no standing pilot light to waste gas and relight. If you go with a gas heater for your shop and do a lot of finishing with combustible finishes, you definitely want a direct vent furnace. The fire chamber is sealed from the interior space; no chance of a fire starting. I purchased the unit from Grainger for about $1100, installed it in the wall, ran the 110v line for the blower motor and paid my HVAC guy $400 to run the gas line from my basement to the furnace, connect it and fire it up. Cozy and Empire are two of the manufacturers that make this type of direct vent furnaces. I did not install and A/C unit in this shop which I regretted. I should have put a 'through the wall' unit or a mini ductless spit system in.
Fast forward to my new shop. It's a stand alone 480 SF two car garage. No gas line to the space, but upgraded 100amp service in it. I went with a Fujitsu mini split heat pump system (15RLX, 15k BTU, 21 SEER, 93% efficiency). The shop has 1" rigid foam, studs, R-13 batt insulation, 1/2 plywood sheathing on the walls. The roof rafters have old insulation, about R-19, which I intend to rip out and apply spray foam insulation for better efficiency. Insulated raised floor, no insulation on the wood overhead doors, but weather sealed. I went with this Fujitsu model, because it has a wall mountable 7 day programmable thermostat option for about $120 extra. I can set the start time, and temp setback for the nights, so it is not running full tilt all the time. With the handheld remotes, as far as I was able to determine, you can only turn them on and off, or set a countdown of hours for it to run, and put it into economy mode. You have to remember to change it when you leave or it stays at the last setting indefinitely. I like the 'set it and forget' it with the wall mount programmable thermostat I have. With these types of units, you don't want to shut them completely down, as they are most efficient maintaining a temp, not bringing it up or down and extreme range of temps. For the winter, I set mine to 60 degrees at night (this is the minimum the thermostat will go) and up to 68 during work hours. As my shop is not as well insulated as it should be, the heat pump takes a while to bring up the temp on cold days, so I set it to come on about 90 minutes before I get there. It was comfortable, but on very cold days, with temps below 20 degrees, it never gets quite up to 68 until later in the day. With better insulation in the roof, overhead doors and single pane windows, I think it will work just fine.
Now that it's summer and we've been in the upper 80's and 90's with high humidity since early June, the A/C on the unit works like a charm. Set it to 72 degrees about an hour before work and raise it to 80 at night. The shop is cool and dry all day long. Doesn't have a problem keeping up even on the hottest days we've had so far.
With the new inverter technology in the new gen of heat pumps, they work quite well even in low temps. If you are consistently below 10 degrees F in the winter, it may not be the best solution. Anything above that with a well insulated space and these are probably the most economical systems to run.
I ran the 220v, 20 amp line to the units location and my HVAC guy installed the inside and outside units and wall thermostat, soup to nuts for $2700.
As others have said, with these unit's (or window or wall mounted A/Cs) be diligent about checking and cleaning the filters. Even the best dust collection system does not contain all the dust. I pull mine out weekly, gently blow them out and I'm good to go. Every once in a while I carefully blow air through the unit itself to clean off the cooling fins and the cover.
Keep us posted with whatever way you choose to go.


It could be that one of the mini ductless split system that Mitsubishi and others make might be a decent soloution.

Any of you guys have a system like this and is it working well for you?

Seems to be pretty affordable. Total installation costs looks to be about $2K. Unless I'm missing something.

PHM

[Paul McGaha]

Hi David,

I spent the first 30 years of my life in Louisiana so I'm all checked out on hot and humid weather.

You're right it's not as hot and humid here in Virginia as it is in Texas and Louisiana. The hot season isnt anywhere near as long here in Virginia as compared to Louisiana and Texas also. Still, It does get pretty hot here for 2 to 3 months of the year. Hot enough to make me want to air condition the shop or not go into it to much for a couple months of the year.

PHM




For starters, before you add any sort of heating or cooling system, you need to make sure you have plenty of insulation in your shop to make that heating and cooling effective. I am partially insulated, and even at that, my AC works its tail off to cool my 2 car garage shop. But then again, when I saw you posting about 90 + degree days my first thought was less than polite... A 90 degree day with humidity under 80% would be downright pleasant here! We have been hovering just above or below 100 with humidity in the 80 - 90% range... Needless to say, heating isn't my biggest concern.

So simply put, I heat with a 1500watt oil filled radiator, I cool with a 13.5K BTU portable unit air conditioner, my overhead air filter serves double duty to move the heated / cooled air around the shop and makes it comfortable.

[Scott T Smith]

Paul, I have done something similar to what you're exploring in my previous two shops (2.5 - 3 car garage shops). For heat, the best solution that I had was a recycled high efficiency gas furnace unit that came out of an apartment (water damage to the bottom of the unit - was only 2 years old when I got it). My HVAC guy did the removal, and gave the unit to me for free. A simple sheet metal box on top of it with a vent, and a makeshift filter in the bottom and I was set. The nice thing about this is that I could leave it on 40 degrees or so in the winter, so that the paints and finishing material did not freeze, but when I wanted to come in and work it would heat up the entire space in only a few minutes.

I've used the electric radiators as well, but the gas unit was more cost effective.

For cooling, I've gone with window units (mounted through the wall) as well as the Mitsubishi mini-split system (which I installed myself). The mini-split was great because it was quiet and very energy efficient. The downside was that it would not cool the space down very quickly; I pretty much had to leave it running all of the time. Window AC units are nice mainly because they are inexpensive; the mini-split cost me around 1,700 back in '08 (and the are more expensive today), versus a few hundred for window units. Mini-splits are more energy efficient though.

If you're working on a budget, I would spend the $ first in insulation. My current 5300 sq ft shop is cooled by a 2.5 ton AC, mainly because my walls are R50 and my ceilings are R80 equivalent (heating is radiant in the slab). Second, if bucks are tight see if you can pick up a used gas furnace and a new window unit. Don't be afraid to cut a hole through the wall and frame up an opening for the window unit, instead of sacrificing a window. You might want to even install two on opposite sides of the shop for faster recovery time when you have been working in the summer with the doors open.

If bucks aren't so tight, then a mini-split would be my next option, with the understanding that I would be leaving it on most of the time. The drawback is that if you have the doors open for an extended amount of time, the mini-split will take a while to recover the room.

A third option is to add a window unit through the wall is the mini-split does not recover fast enough for you.

[Paul McGaha]

Thank you all for your thoughts and taking the time to post them.

I think I'm leaning towards a mini split system or adding a window and a window unit.

Probably have to wait for next years shop budget as this years is too far gone.

PHM