Another "What is the best HVAC system for me?" thread.

[Dave88LX]

Location: Baltimore, MD (just south of)
Size: 48' x 28' x 8'
Average Daily Temps:
http://www.weather.com/weather/wxclimatology/monthly/graph/21122?from=36hr_bottomnav_undeclared

Nov - 36
Dec - 29
Jan - 24
Feb - 25
Mar - 33

May - 75
Jun - 83
Jul - 88
Aug - 85
Sep - 78

There are two overhead garage doors, I want to say they measure ~9 x 7, they look like "standard" sized doors to me.

There are two small windows (~24" x 36"), and a regular door (~30" wide).

Built on 2x4 construction, so I will have R13 or R15 in the walls, depending on what's recommended. I have a "pointed" style roof. Ceiling and walls will both be drywalled. Unsure if I will use loose-fill insulation or R-30/R-38 in the ceiling. Unsure of draft/leakage.

I want to say that a good average working temp would be to warm it up to ~60*, and cool it down to ~68-70*? Let me know...I can work in a bit of chill during the winter. I would say I have "average" sensitivity to heat, and don't mind chilly. I'd like to **** the humidity out of the air during the summer of course.

With those numbers, I would need to increase the temp by ~40* during the winter. Using this calc: http://www.heatershop.com/btu_calculator.htm , I need 102,400 BTU / 30,000 watts at "avg insulation/leak".

I was thinking that a wood stove would be more economical in that I can pretty much find enough wood around here to last me for quite a while, for free, versus paying electric or oil heating costs. I checked with my insurance company, and a wood stove is covered.

But, that would leave me with needing a cooling solution.

Thoughts, or any direction you want to point me in? More questions?

Thanks!
- Dave

 

[cw_racefan]

Dave -

Same area as you, and I went with a 2-ton mini-split for my 32x36. I don't heat/cool 24/7, only when I'm in there. This past winter was my first with the heat pump in there (obviously a mild winter for us), and the garage never got below 40 or so with no heat on. I'm insulated the same as you're planning. I've never tried the heat pump below 30 or so (it has no backup heat), but when I have used it, it heats up or cools down the garage pretty quickly. I just have a torpedo heater if it's too cold for the heat pump to function.

Craig

 

[Dave88LX]

Is this a "heat pump" type system like I would have in my house? Heat pump inside, A/C thing outside?

 

[cw_racefan]

Sort of. It's a ductless mini-split heat pump. They're pretty popular in Europe and the Caribbean. You have a small outside unit, and then an all in one unit inside (blower, etc) that hangs on the wall. Only requires a 3-4" penetration for refrig. lines/drain/etc. Do a google search and you'll find tons of them. Mine's a relatively inexpensive no-name off of Ebay, but so far so good. The guy that evacuated the lines and checked the charge for me said it looked pretty decent quality wise from what he could see.

You can see the inside unit in the attached pic.

[/IMG]

 

[Dave88LX]

Oh wow, that "little thing" heats up and cools the whole thing? Do you have cool/hot areas in the winter/summer where it can't reach very well?

 

[cw_racefan]

Down near the floor stays cool in the winter, once the slab cools off, but nothing too terrible. It's probably not the most even heat/cooling, but for my use it has worked out great. It does have moving vanes to help distribute the conditioned air. It's not as small as it looks either, it's about 4 feet long. Again, I haven't been out there when it's been below 20-25, so YMMV.

The main reason I went that route was I have no access to gas, so would have had to install a propane tank, etc for heat.

 

[canmorechef]

Hi Dave
Not sure if you use natural gas in your area but if you can take a look at the Hot Dawg Heaters for garages. Here in this part of Canada it can get down to -22F in the winter and after seeing how warm my nieghbors garage was this winter I decide to get one put in mine. It is smaller than yours only 24x2x8 . The whole thing with a 55 ft gas line unground to my garge is $1900 can. or $1880 US.
Talking with the installer he said they are the easiest to install and the systems never breaks down. It can be vented out the side wall so thier is no need to go through the roof wich is a hassle if your garage is finished inside, not sure if this is a valid option but I put a link to the manufacturere below.
http://www3.modine.com/v2portal/pag.../building_HVAC/market_level_3_content_013.htm

 

[gesoffen]

There's a big consideration:
Do you plan on maintaining your temps at your desired levels or will it be more "on demand" with a lower constant set point?

If you plan a set it and forget it mentality, you're likely better off with a heat pump/ac system that has an emergency heat function. The mini-split that cw showed us above is a great option and they do make them with a resistance heater for emergency heat. Seeing as how you already want an AC system, the heat pump part of it is very minimal additional cost.

If you plan a lower set back and crank it up to working temps on demand then I'd say you're better off with a fossil fuel heater with plenty of excess capacity to take the chill off. Your best bet here is probably a radiant style heater. For cooling loads, you'll still need a mini-split or similar ac unit and you can use the heat pump side of it to maintain you low set temp. Just size the ac system up a bit more than usual to cover the "on demand" load.

IN general, I'd recommend against a wood stove. They won't do anything to maintain any heat in the garage when you aren't there so you're asking a wood stove to take the chill of the air as well as warm up the entire contents of the garage (cold cars and concrete floors have a LOT of thermal inertia). It would take quite a bit of time to warm up the space/contents from a near freeze. Also, you'll need to tend to the fire throughout your work time as well as keep an eye on it after you're done. Also, if you work with any kind on solvents or other flammable chemicals, you have to be very careful about vapor combustion. Of course, you have to worry about this too with your fossil fuel heater but at least you can turn that off pretty readily.

 

[sam 8]

Dave,

Planning to add on and create a total of about 1300 sq. ft. of shop.
I am at about 2000 ft. elevation in the Sierras, our temps are not much different than yours. We heat the house with wood, and a couple of small space heaters.
What is a deal breaker for me and wood heat in the shop is heat-up time. Due to a large chunk(s) of metal in me, being cold in the shop is not going to happen. Going out and building a fire then waiting an hour or so for the place to heat up won't work for me, time is too precious out there.
I am going with a propane fired Reznor shop heater, 125,000 BTU. Street price on these are around 1k,. I am actually bringing propane in to the house just for this purpose, we've been all-electric for almost 30 years.
I'll keep the thermostat at 60 in the winter, and crank it up when I walk in. 20-30 min later it'll be around 70.
I'd look at other options besides wood, there must be some.