New Construction- 24x46 Attached 1100 Sqft- HVAC

[purduecrew]

Hello All,

I know there are many threads on here about similar cases but I do want to ask specific questions about my setup.

Construction this summer, 4 car open style garage. Will have 4- 8x10 doors. 1100 sqft. I'm finding online calculators saying I need 125K BTU heat for cold months ( not that bad in Nashville). That seems excessive to me but I don't know for sure.

For AC in the summer( seemingly more critical in this climate, its calling for about 33K BTU. I have no idea if this is right or not.

I have looked at the mini splits everyone discusses but don't like the idea of it taking forever to heat up. I will probably try to keep the garage around 40 in the winter but will want to ramp it up fast on weekends to do projects. Am I wrong on that? I figured either way I would need a modine in the corner and a mini split or could I find a good forced air setup used? Thoughts?

 

[outdoorspace]

What kind of insulation? My 24x40x16 is post frame with R19 walls, R25 roof, R19 OH doors, and good air sealing. It's near Charlotte with a 24k mini split heat pump. It takes about 3 hours to go from 40 to 65. In the summer it has no problem at all. It also has a "dry" mode to keep my tools from rusting.

 

[purduecrew]

What kind of insulation? My 24x40x16 is post frame with R19 walls, R25 roof, R19 OH doors, and good air sealing. It's near Charlotte with a 24k mini split heat pump. It takes about 3 hours to go from 40 to 65. In the summer it has no problem at all. It also has a "dry" mode to keep my tools from rusting.

I can tell you!

So if I don't upgrade, it will be:

Stick built
R13 walls
R38 ceiling
R10 Insulated overhead doors

I would only have 9 foot ceiling too, compared to your 16, or do you have a loft?

Which unit did you purchase? Do you have the issue others talk about with not being able to keep it on a low setting?

 

[spudley]

Off topic but you will regret 8' wide doors (unless you strictly work on motorcycles).
Plenty of combinations of wider doors that will look good at 46' wide.

 

[outdoorspace]

I can tell you!

So if I don't upgrade, it will be:

Stick built
R13 walls
R38 ceiling
R10 Insulated overhead doors

I would only have 9 foot ceiling too, compared to your 16, or do you have a loft?

Which unit did you purchase? Do you have the issue others talk about with not being able to keep it on a low setting?

I do have a mezzanine but it's all open to the same space.

I got the ECOX 19 seer unit and wifi module for $1200 shipped. It's really made by Midea, like a lot of other mini splits. Yes the lowest setting it will do is 63. I just leave it off when I'm not in there, it hasn't frozen inside. I'm working on getting it tied into the home automation, with that I can turn it on at whatever temperature.

The garage attached to our house is R13 walls, and it's fine without any additional heat. So you should be fine as I think your climate is not much worse than ours.

I think my diligence in air sealing helps keep the heat in. It's also not much warmer in the mezzanine which means there isn't much stack effect.

 

[purduecrew]

Off topic but you will regret 8' wide doors (unless you strictly work on motorcycles).
Plenty of combinations of wider doors that will look good at 46' wide.

They are 8 tall, 10 wide.


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[purduecrew]

I do have a mezzanine but it's all open to the same space.



I got the ECOX 19 seer unit and wifi module for $1200 shipped. It's really made by Midea, like a lot of other mini splits. Yes the lowest setting it will do is 63. I just leave it off when I'm not in there, it hasn't frozen inside. I'm working on getting it tied into the home automation, with that I can turn it on at whatever temperature.



The garage attached to our house is R13 walls, and it's fine without any additional heat. So you should be fine as I think your climate is not much worse than ours.



I think my diligence in air sealing helps keep the heat in. It's also not much warmer in the mezzanine which means there isn't much stack effect.

Thank you for all the information! Would a forced air furnace be a better idea? Im sure they arent near as cheap.


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[ripperd]

With your climate I would look heavily into a mini split or two. Your heating needs are modest, cooling is probably a bigger deal if you want it cool in the summer. And mini splits will do both, pretty efficiently.

114kbtu is waaay high for that. 45kbtu would heat that just fine.

We have an attached 950sqft insulated garage and it is -3 F out right now and a 45kbtu only cycles every half hour or hour for a couple mins to keep it at 50 degrees.

 

[purduecrew]

With your climate I would look heavily into a mini split or two. Your heating needs are modest, cooling is probably a bigger deal if you want it cool in the summer. And mini splits will do both, pretty efficiently.

114kbtu is waaay high for that. 45kbtu would heat that just fine.

We have an attached 950sqft insulated garage and it is -3 F out right now and a 45kbtu only cycles every half hour or hour for a couple mins to keep it at 50 degrees.

Thats more like what I was thinking. Need more help on the cooling side. It would just be nice to buffer the garage at 45-50 all winter. May I ask are you in HVAC?


What system are you running to keep it at 50 degrees?




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[ripperd]

Thats more like what I was thinking. Need more help on the cooling side. It would just be nice to buffer the garage at 45-50 all winter. May I ask are you in HVAC?


What system are you running to keep it at 50 degrees?




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I do not know a lot about HVAC, and do not cool our garage at all. It is also too cold here in MN to really use a mini-split for heating, unfortunately.

I have a beacon morris 45kbtu unit heater, using separated combustion.

 

[dcg9381]

Mini-splits are heat pumps, typically without electrical "emergency" heat. They decrease in effectiveness (just like all heat pumps) as you approach and go below zero.

If that we my garage and climate and my main concern was "fast heat" - I'd have two separate systems. I'd do a 36k mini split for cooling and "moderate heating" and I'd have a different solution for electrical assist heat.

 

[UpstateNY]

Upstate NY, cold winters, well-insulated 1200 sq ft, heat with radiant with 50k water heater and have no problems doing so.

 

[Showkey]

Agree with others on the heat side 1000 sqft in a much colder climate is heated with 45-50k BTU.