Wisconsin 40x64 workshop needs HVAC suggestions

[DaveF.]

Hi guys, I'd love to hear your HVAC suggestions for the new workshop I'm building.

It's a 40x64 poleshed style construction with a 20x40 office space on the end away from the big garage door. Both areas have 11 foot ceilings.

The concrete floor has 1.5" of pink foam board insulation beneath it. The exterior walls have 1.5" of white beadboard (R6) plus 5.5" of fiberglass batts (R19). The interior wall will have the fiberglass batts (R19). The ceiling has about 16" of cellulose insulation blown in.

I'd like to keep the 20x40 space at about 68 degrees year-round. I'd like to keep the temp of the remaining 40x44 space above 50 degrees year-round.

Additional pics of the actual build in progress are available by following the link below in my signature area.

Suggestions???

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[jzglinicki]

Subscribed ... I'm in the midst of a similar project myself, only mine is just the 40x40 work area. I'm working my way through the existing threads but hoping to see some input for this one since your construction sounds very similar to what's planned for mine.

Joe

 

[DaveF.]

Subscribed ... I'm in the midst of a similar project myself, only mine is just the 40x40 work area. I'm working my way through the existing threads but hoping to see some input for this one since your construction sounds very similar to what's planned for mine.

Joe

Hey Joe, have you posted any pics of your build?

Dave

 

[theoldwizard1]

I'd like to keep the 20x40 space at about 68 degrees year-round.

So you definitely want it cooled in summer ! Perfect application for a mini-split heat pump.

I'd like to keep the temp of the remaining 40x44 space above 50 degrees year-round.

WOW ! That is going to be hard to do in summer !

It depends on if you want it cooled in summer AND if you have natural gas available. No cooling and natural gas available, any of a half dozen heaters.

If you want it cooled OR you do not have natural gas available, I would install a second, separate mini-split heat pump, probably with 2 air handlers.

 

[Ray916MN]

I'm curious about the recommendations for a mini-split. At 40x64 with an 11' ceiling the building volume is equivalent to 3500 sq. ft. with an 8' ceiling. Depending on where this is located in Wisconsin, the temperatures could be frigid enough to be a challenge to a heat pump.

At what building volume and outside to inside temperature gradient does it make more sense to use a conventional system as opposed to a mini-split heat pump?

 

[jzglinicki]

Don't yet have a build. Working on plans with a builder now for something to be put up in Spring. Have been getting a lot of great info from the board; so will be more than happy to share info from my own when the time comes.

 

[newbinga]

I just wanted to say great detail on the design, especially the dog in the office !!

Sent from my SPH-L720 using Tapatalk

 

[Dagny]

High eff. Gas furnace above door between rooms conventional split AC

 

[DaveF.]

So you definitely want it cooled in summer ! Perfect application for a mini-split heat pump.


WOW ! That is going to be hard to do in summer !

It depends on if you want it cooled in summer AND if you have natural gas available. No cooling and natural gas available, any of a half dozen heaters.

If you want it cooled OR you do not have natural gas available, I would install a second, separate mini-split heat pump, probably with 2 air handlers.

We live in a rural area of western Wisconsin about 30 minutes from the Twin Cities.

I don't have natural gas available, but I am planning to get LP (liquid propane). I believe most whatever runs on natural gas can be modified to run on LP.

I'm not planning to cool the large area. My assumption has been that it would be just too expensive.

 

[RedDirtRoad]

Dave,
I am a Mechanical contractor in the HVAC business.
I did a quick calc and come up with the following for your building.

Office:
20x40x11= 8800 cu ft.
8800cu ft x 6 air changes an hr = 52800cfh
52800 cfh/hr/60 = 880cfm
Your office needs 880CFM for cooling and
60,000 btu for heat @ 65 degree rise in temp.

Garage:
44x40x11= 19360 cu ft.
19360cu ft x 6 air changes an hr = 116160 cfh
116160 cfh/60 = 1936cfm
Garage needs 1936cfm for cooling
140,000 for heat @ a 65 degree rise in temp.

I am building the same size pole barn and I would reccomend using Reznor radiant tube heaters. If you place them over areas you will be working in most often then you could put them on seperate t-stats and operate them seperately as needed to keep your heating bill lower

As for the A/C a 2 ton unit and 5 ton unit would be needed for office and garage

These calcs are a quick way to get you close. I know others that use a different rule of thumb too. It also depends on insulation and how tight the building is too.
Good luck.

 

[theoldwizard1]

I'm curious about the recommendations for a mini-split. At 40x64 with an 11' ceiling the building volume is equivalent to 3500 sq. ft. with an 8' ceiling. Depending on where this is located in Wisconsin, the temperatures could be frigid enough to be a challenge to a heat pump.

At what building volume and outside to inside temperature gradient does it make more sense to use a conventional system as opposed to a mini-split heat pump?

We live in a rural area of western Wisconsin about 30 minutes from the Twin Cities.

I don't have natural gas available, but I am planning to get LP (liquid propane). I believe most whatever runs on natural gas can be modified to run on LP.

Total building volume does not have a lot to do in the decision to use a mini-split heat pump. The number of rooms (conditioned spaces) is actually more important (from a cost standpoint) as each room will (typically) need it own air handler (possibly 2).

While most heat pump have a significant drop off in their efficiency below freezing, there are some that remain 100% efficient down to near 0F. Carefully shopping is required.

I can guarantee you that you will save money using a heat pump over propane, especially in the man-cave area !

In the garage area, a heat-pump will also save money, but the question is how many years it will take to pay back. Radiant tube heaters or a ceiling hung furnace are cheap to install. You will likely need more than 1 if you want the temperature to be uniform. Same is true with a mini-split; 2 air handlers for the garage.


The biggest down side with a heat pump is power outages, especially if you live in an area where extended (> 12 hours) outages are somewhat common during the winter. While a furnace can run on a small generator, a heat pump requires a LARGE generator or something like a propane fireplace as a backup.

 

[DaveF.]

So the mini-splits or heat pumps run solely on electricity? No propane?

 

[pseudorealityx]

So the mini-splits or heat pumps run solely on electricity? No propane?

Correct. Think of a heat pump as an air conditioner running backwards. It cools the outside and the waste heat is pumped into your space.

 

[pseudorealityx]

My recommendation would be a mini split for the office, and an LP garage heater hung from the ceiling. Maybe radiant if you use the doors a lot in the big space.

 

[pseudorealityx]

Dave,
I am a Mechanical contractor in the HVAC business.
I did a quick calc and come up with the following for your building.

Office:
20x40x11= 8800 cu ft.
8800cu ft x 6 air changes an hr = 52800cfh
52800 cfh/hr/60 = 880cfm
Your office needs 880CFM for cooling and
60,000 btu for heat @ 65 degree rise in temp.

Garage:
44x40x11= 19360 cu ft.
19360cu ft x 6 air changes an hr = 116160 cfh
116160 cfh/60 = 1936cfm
Garage needs 1936cfm for cooling
140,000 for heat @ a 65 degree rise in temp.

I am building the same size pole barn and I would reccomend using Reznor radiant tube heaters. If you place them over areas you will be working in most often then you could put them on seperate t-stats and operate them seperately as needed to keep your heating bill lower

As for the A/C a 2 ton unit and 5 ton unit would be needed for office and garage

These calcs are a quick way to get you close. I know others that use a different rule of thumb too. It also depends on insulation and how tight the building is too.
Good luck.

This might work, but it's certainly not the way I would do it.

65 degree temp rise?

 

[DaveF.]

My recommendation would be a mini split for the office, and an LP garage heater hung from the ceiling. Maybe radiant if you use the doors a lot in the big space.

That is the way I've been leaning. I do not plan to use the large door much in the winter.

Do you have brand and model number suggestions?

Location suggestions?

 

[DaveF.]

While most heat pump have a significant drop off in their efficiency below freezing, there are some that remain 100% efficient down to near 0F. Carefully shopping is required.

We are currently experiencing low temps of -10 to -24 degrees. That's not counting windchill.

Will this eliminates mini-splits as an option?

I do have very good insulation, and when it is that cold outside I'm ok if the inside doesn't go up as high as normal, as long as I can keep it in the 50s. We don't get too many of those very cold days.

 

[theoldwizard1]

We are currently experiencing low temps of -10 to -24 degrees. That's not counting windchill.

Will this eliminates mini-splits as an option?

I am NOT an expert. I am repeating specs from sales brochures. Mitsubishi is the one brand that brags about low temperature performance.

View media item 43975
Find a local installer and talk to them.

The cost saving of a heat pump over a propane furnace, especially in the man cave area, could be quite large, even if you add a propane fireplace or electric baseboard heat as a back up for those super cold nights !

If you were not planning on A/C in the garage area, a heat pump probably not a good fit there.

Ask yourself this question. There are 8,760 hours in a year. How many of them is the outside temperature below 0F ?

Another bonus is you don't need a "furnace room" or duct work !

 

[DaveF.]

I am NOT an expert. I am repeating specs from sales brochures. Mitsubishi is the one brand that brags about low temperature performance.

View media item 43975
Find a local installer and talk to them.

The cost saving of a heat pump over a propane furnace, especially in the man cave area, could be quite large, even if you add a propane fireplace or electric baseboard heat as a back up for those super cold nights !

If you were not planning on A/C in the garage area, a heat pump probably not a good fit there.

Ask yourself this question. There are 8,760 hours in a year. How many of them is the outside temperature below 0F ?

Another bonus is you don't need a "furnace room" or duct work !

Great info, Old Wizard! Thanks for posting

 

[fastjohnny]

I can assure you the Hyper Heat unit from Mitsubishi is what it's cracked up to be, I've got a 12kbtu unit in a 24 x 26 area above my garage, producing not just warm but HOT heat in single digits. My back up should temps fall below the curve of heat production is electric radiant as needed (ie Eden Pure heater which heated the place prior to installing this)

 

[pseudorealityx]

We are currently experiencing low temps of -10 to -24 degrees. That's not counting windchill.

Will this eliminates mini-splits as an option?

I do have very good insulation, and when it is that cold outside I'm ok if the inside doesn't go up as high as normal, as long as I can keep it in the 50s. We don't get too many of those very cold days.

For sure, you'll need some other source of heat for those extremes. I'm not familiar enough with designing for your climate, but I think I might 'eat' the cost of straight up electric heat during those times rather than doing a LP furnace.

As mentioned, a furnace would also need ductwork, a space to put it in, venting to the exterior, etc. But that's something you need to look at for yourself.

Maybe you could just move to a warmer climate?

 

[CNGsaves]

If you go propane, don't skimp on the tank as fellow GJer had very large shop and needed 1,000 gal propane tank (after first trying 500 gal tank) !! You want LPG tank big enough that you can purchase at discount during summer months, but will be enough fuel to get you through the winter.

Other decision is whether you want Separated Combustion (ie separate flue for combustion air & separate flue for exhaust). Those heaters will have S in the model numbers.
EXAMPLE . . . Reznor UDAS125 would be separate combustion 125K Btu
http://datasheets.globalspec.com/ds/305/Reznor/C7F145E9-A6B1-496F-8C93-7C07150BAA10

A normal Reznor would have UDAP model number.

If you plan on doing lots of dusty work, or woodworking, painting, etc with fumes then you'd want the separated combustion.

 

[Ray916MN]

...

Ask yourself this question. There are 8,760 hours in a year. How many of them is the outside temperature below 0F ?

Shouldn't the real question be how many hours of the yearly hours of projected use (not total hours in a year) will the outside temperatures be below 0F. The upfront costs of a heat pump, combined with the potential need and associated costs for augmentation are offset by the efficiency of these units particularly when both heat and AC are desired. The payoff comes sooner when the units are used over more hours in a year at temperatures where they are most efficient.

 

[JimL]

Put the outdoor unit for the mini split in the shop area. Just need an exhaust fan for use in the summer, but it would be working in a 50 degree environment all winter.

 

[pseudorealityx]

Put the outdoor unit for the mini split in the shop area. Just need an exhaust fan for use in the summer, but it would be working in a 50 degree environment all winter.

Keep in mind that in the winter, it will pull heat out of the garage pretty quickly. If we use the 2 ton size, that's an extra ~24,000 BTU loss in addition to the skin loads.

 

[xtahoex]

Also love the dog!

 

[theoldwizard1]

I can assure you the Hyper Heat unit from Mitsubishi is what it's cracked up to be, I've got a 12kbtu unit in a 24 x 26 area above my garage, producing not just warm but HOT heat in single digits.

Always nice to hear "real world" confirmation of a product !

My back up should temps fall below the curve of heat production is electric radiant as needed (ie Eden Pure heater which heated the place prior to installing this)

Having a "backup" is a good idea !

 

[meathooker]

We are currently experiencing low temps of -10 to -24 degrees. That's not counting windchill.

Will this eliminates mini-splits as an option?

I do have very good insulation, and when it is that cold outside I'm ok if the inside doesn't go up as high as normal, as long as I can keep it in the 50s. We don't get too many of those very cold days.

In my experience yes, it will eliminate them as an option. Also heat pumps are very slow to recover which is key (imo) in a garage.