HVAC for Retirement Shop Upgrade

[P51Mustang]

I have a thread started in the General Garage Discussion area (Retirement Shop Upgrade) on the details of the shop upgrade that I am planning. As I am new to Garage Journal, I am not sure what the guidelines are but I figured that it made sense to have the HVAC discussion on the shop in the HVAC area of the Forums. I would have no problem with combining the threads if that is the better way to do it.

OK, a quick summary on what I am looking at. I retired a few months ago and as a retirement gift, I am planning a major upgrade to my existing shop. My wife and I live on 6 acres in central Iowa, with corn fields on all four sides of us. The existing shop is in 40x60 machine shed. The machine shed is a very nice 2x6 wood framed building with a 12' ceiling height that dates back to about 1950 (the building runs north/south). The building has a white, metal roof and red , asphalt silding over 3/4" plywood. The north 20x40 section of the building has has been walled off, with a ceiling put in and a non-insulated concrete floor (this is where my existing shop is). The rest of the building (40x40) has a dirt floor with open framing right now. The existing shop area is heated and cooled but has poor insulation and is too small for my needs. The building has plenty of power as a service upgrade with all the wiring ran underground was done a few years ago. I also have an existing LP supply that the current shop heat runs on.

My plan is to use the dirt floored 40x40 south section for the new shop main area (no building foot print change will be made). A new, insulated concrete floor will be poured and the walls and ceiling will be finshed off in white metal (figure insulation of R19 in the walls and at least R40 in the ceiling). The existing 16' wide sliding door that is on the south end of the building will be closed off and a new, insulated overhead door (most likely 12x10 to 16x10) and a man door will be cut into the east wall of the building at the south end of the side wall. I am not 100% sure yet but most likely the shop will also have around a 10x20 kickout to one side that will be open to the main shop (this will be a grinding/welding/fab area). This gives me 1800 square feet to heat and cool.

The existing shop is heated with a large Modine hanging furnace (160,000 BTU) that I moved from another building on the place when we brought it years ago (an old hog buliding). This is a bit of overkill for the 800 square feet of the existing shop but the price was right. I have been cooling the shop with a 18,000 BTU window A/C unit that I cut a hole in the side wall for. On a above 90°, sunny summer day, the A/C will keep the temperture in the poorly insulated, drafty shop at around 80° or so (not great but better than outside).

I have been thinking about the best way to heat and cool the new shop space (cooling is as important to me as heat as I do not handle heat as well I use to and I plan to be in the shop a lot). Right now I am thinking about 3 different HVAC systems for the new space but I am very open to other ideas. Right now I only heat the existing shop when I am in it, so every morning it gets reheated from cold to 60/65° or so. I may think about keeping the new shop at a minimum temp of maybe 45 to 50 when I am not in it.

First, I can move the existing hanging furnace into the new shop. The price is right and I am sure that it is plenty big enough with a well insulated and tight space. One down side to this is it would be a bit hungry I am sure. It is also pretty old (at least 40 years). It works fine now but who knows for how long. With this option, I am guessing I would still go with window A/C units (most likely two I would guess).

The 2nd option I am thinking about would be to put in a correctly sized standard furnace with some duct work. This would give me the air handler to install an A-Frame for A/C into. More money up front but could be the best long term way to do it and help with the operating costs.

The last option I have been thinking about that has some good points, is to look at a mini-split system. My guess is I would need around 36,000 BTU for cooling with the upgraded insulation (would need to run some calcs). This would not be enough heat on the really cold days I would guess but it would save on operating costs on many days. I would move the existing hanging furnace over for backup heat when it got too cold for the heat pump to keep up. If/when the old furnace died, I would replace with another, smaller hanging furnace.

I have attached a shop plan and some photos that give a bit of the lay of the land. Any comments, questions and other ideas are very welcome.

Thanks,

Kim

 

[metlmunchr]

The last option I have been thinking about that has some good points, is to look at a mini-split system. My guess is I would need around 36,000 BTU for cooling with the upgraded insulation (would need to run some calcs). This would not be enough heat on the really cold days I would guess but it would save on operating costs on many days. I would move the existing hanging furnace over for backup heat when it got too cold for the heat pump to keep up. If/when the old furnace died, I would replace with another, smaller hanging furnace.

IMO, this is your best option for economical operation. If you look at the max capacities of a single 36K unit vs two 18K units, you'll find that the pair of 18K units will have a max capacity in both heating and cooling that's greater than the single 36K. The SEER rating is also higher on the smaller units, and the cost of two 18Ks is the same or less than the 36K.

If your use of the shop is heavily into woodworking then mini splits might not be the best solution. They're really designed for living space use and the included filters are matched to that use. You can't add additional filtration without significantly affecting fan performance and unit efficiency. Regular filter maintenance helps, but the finest dust will still pass thru and deposit on the cooling coil where it is a major pain to clean.

 

[P51Mustang]

Thanks for your comments.

At least right now, no major plans for woodworking. I do have some woodworking equipment but I do not use it that much.

The main shop is for car work. I have several cars/truck waiting their turn to get restored as well as a 65 Mustang road racing car that I need to finish the build on and to keep running.

 

[dshop]

you might look seriously at a heat pump, with a building that size...it's what I did 15 years ago here in Raleigh and it works just fine.
spend your money on insulation. I had the building spray foamed all the way up the sides and across the roof.
heat pump will handle it with proper insulation. mine is 40x60 also. stick built.

 

[P51Mustang]

dshop,

Thanks for the input. These are the type comments that I am looking for!

I have thought about a heat pump and it is very much one of my options. It does get pretty cold here in the middle of Iowa (it was -13°F air temp Thursday night and just before Christmas we had very high winds with a wind chill of -40°F) and I am pretty sure that I will need backup heat with a heat pump and/or mini splits. As I already have a hanging propane furnace that I can move from the old shop, my gut feel is that using mini-splits with the existing furnace may be the lowest cost way heat/cool the new shop but I have not ruled out any option yet. So far my propane costs have been fairly good (the shop tank was just filled for $1.94 a gal) but who knows long term. I am guessing that my power costs are around middle of the road right now but again who knows in the future. The new shop space will be well insulated with R19 in the walls and at least R40 in the ceiling.

 

[Yankeefarmer]

I installed a Mr cool universal in my 1200 sq ft shop. It easily heated up my shop at -8 this weekend. No aux strips installed. Since it’s my shop, not our house, I felt that the worse that would happen on the coldest days is the shop might be a little cooler than I wanted. Now I can’t see that happening.

Here’s a report from a YouTuber who installed one in his house:

 

[P51Mustang]

Thanks, that is great info. The more that I am looking at it, a heat pump of some kind may well be the best way to go. Since I have my existing propane furnace to use as a back up and to heat up the space quickly when needed, mini splits of some kind may make the most sense.

 

[Yankeefarmer]

I avoided minisplits because of their low tolerance for dust, ineffectiveness at uniformly distributing the conditioned air, and feeling that, with needing multiple heads for 48’ long dimension of my building, I’d need to have at least two control units. The conventional air handler with ductwork allows me to draw cold air at floor level, then discharge the hot air downward from the ceiling. I have 15 foot ceilings, no perceptible temperature differences as I walk around, a single point of control, and easily changed conventional filters.

Edited to add: all for under $5K with self-install.

 

[P51Mustang]

Your bring up many good points that I will have to think about. Thanks!

 

[Black Oak]

I'd seriously consider Radiant Floor heat in the new floor . There is no comparison to forced air . Mini splits are great for AC , but will struggle in the coldest months . Do some research on radiant heat .

 

[P51Mustang]

I will, thanks!

 

[Yankeefarmer]

I'd seriously consider Radiant Floor heat in the new floor . There is no comparison to forced air . Mini splits are great for AC , but will struggle in the coldest months . Do some research on radiant heat .

I agree- radiant floor is the most comfortable heat you can provide, if you plan to heat to a constant temp 24/7. With current energy costs, I‘m not willing to do that for 6 hours/day, 5 days a week I’m typically out there. My heat pump handles the setbacks just like a furnace would. But the shops of the guys I know with radiant floor heat are incredibly comfortable. One has natural gas, the other a large outdoor wood burning furnace that he maintains 24/7.

 

[P51Mustang]

That is one worry that I have with radiant floor heat also. I most likely will not heat the shop all the time and as it does get cold here. I could still put the existing propane furnace in to get it up to temp quickly but I still have to do something for A/C and the up front costs could still get very high.

I am still in the planning stages so nothing is off the table and getting all of these inputs from everyone is great!!!! Keep them coming.

 

[Black Oak]

The initial heating of the slab is the most costly , maintaining that level is less costly .It's t he on / off , up / down that kills you . True of both radiant and mini splits .

 

[428PI]

Mini splits are great for AC , but will struggle in the coldest months

For a retirement shop plenty good. I heat my downstairs of my house (1300 sq ft) with 27k worth of minisplit kept the hallway (where there isn't a wall unit) above 60 degrees in the coldest of days here (Kansas and it was below zero that night). Just oversize unit perhaps 25 percent from what they say for cold. BTW: My furnace in my central heat is 115k. I do turn it on and throw some wood in it when I want it warmer in the hallway, kitchen and tv room.

 

[P51Mustang]

Thanks for all the comments. You guys have given me a lot of ideas to look into. Keep them coming. They are all great. Having my existing hanging propane furnace that I can move into the new shop should help with some of the options.

 

[WisJim]

I would seriously consider mini splits based on my experience with them over the past 7 years or so. Get one that is rated for low temperature--my Fujitsu units work well down to 15 below and then start losing efficiency. We had a self-installed solar electric system too, so I figured the heat and cooling from the mini splits was much less than any other source except the wood heat from our own trees.

 

[P51Mustang]

From what I have been hearing and my research, mini-splits are at the top of my list right now. I am guessing that I would most likely move my existing furnace over to the new shop area also to cover me if needed on really cold days and to help with a quick warm up when the shop has been setting cold or when the overhead door has been open on a cold day. If I only had to fill the LP tank once a year (or less) that is OK (the furnace and the tank were paid for a long time ago).

I should look into adding some solar electric also. I have a horse pasture next to the shop building that has a nice view to the south that would work well for ground mounted panels (no horse any more and no plans for another).

 

[My Old Tools]

I avoided minisplits because of their low tolerance for dust, ineffectiveness at uniformly distributing the conditioned air, and feeling that, with needing multiple heads for 48’ long dimension of my building, I’d need to have at least two control units. The conventional air handler with ductwork allows me to draw cold air at floor level, then discharge the hot air downward from the ceiling. I have 15 foot ceilings, no perceptible temperature differences as I walk around, a single point of control, and easily changed conventional filters.

Edited to add: all for under $5K with self-install.

My shop is 40' long. Mounted at the mid point, it cools it all just fine. I didn't need or want to cool above 9' off the floor. Mine is a 36k MrCool in a 30x40x12 with 22 feet to the peak. For heat it does ok. When we had -8 for 5 days it kept the shop about 50. I run a simple box fan in the winter to push the warm air down.

 

[Yankeefarmer]

My shop is 40' long. Mounted at the mid point, it cools it all just fine. I didn't need or want to cool above 9' off the floor. Mine is a 36k MrCool in a 30x40x12 with 22 feet to the peak. For heat it does ok. When we had -8 for 5 days it kept the shop about 50. I run a simple box fan in the winter to push the warm air down.

I’m glad it’s working well for you.

Here in New England, heating demand far outweighs cooling. I have nothing against mini-splits. I have two mini split systems. The first one is an 18k in my old 28x28 shop, which I installed for cooling. It does that very well. It also heats adequately down to about 35 deg outside temp, but doesn’t move enough air to provide good warmth at the far wall which has OH doors. That‘s ok, because that shop has a propane furnace for heat. We also have a Fujitsu Halcyon multi-split in our house that has a 24k head in our 24x36 great room. You can feel it throw the conditioned air about 30 ft and, since it’s a well insulated, heavily windowed room, works well. We don’t use it for heating except in spring and fall, when demand is light, because we heat with wood through the coldest months.

It was my experience with the 18k unit that settled me on the ducted system for my new shop, and I couldn’t be happier with it. Although the ceiling in more than 50% of the shop is 15 feet high, the ducts are at about 11’ high, the height of the ceiling in the machine shop area which has a loft above. Thus, I’m not intentionally heating or cooling above that 11‘ level, especially since all my return air is collected at floor level. I find that my mini splits have to be set above desired heating temperature or below desired cooling temperature due to them sensing air temp at their inlet. With my ducted system I use a conventional programmable thermostat.

 

[Mr onetwo]

Radiant tubing in the floor with a Viessmann boiler all day, every day.This is a retirement shop....your old bones will love the warm floor...trust me.If you have a long wall oriented to solar south I would seriously consider a passive solar collector on that side.Also, spend all your money on insulation(spray foam) and minimize the size of the overhead doors.Worst mistake I made on my shop was having a single 16x8 door.

 

[P51Mustang]

Thanks for the radiant floor heat comments! I have thought about radiant heat a little bit and have not ruled it out completely. There is some radiant heat used around here but not much (houses or shops). I am not 100% sure why not much is used but it may have to do with the cost of basically having to buy two sets of HVAC equipment as with 90° plus (even pushing 100° once in a while) days in the summer, air conditioning is very common in this area. My current shop has air conditioning and it will be a must in the new space (a few years ago I came down with heat exhaustion after several days of road racing strapped into a Mustang with a 115° heat index, since then I do not handle heat as well as I used to). I will get some radiant cost estimates so I know what the overall cost is. The new shop area will be well insulation.

I agree on the overhead door size. I am hoping to get away with a 12x10. I do need the 10' high to be able to clear some of the stuff that will be in the shop at times.

 

[Mr onetwo]

Keep in mind you don't have to use a boiler per se. You can feed the floor with a propane hot water heater and the correct pump...simple and not expensive.Just get a heat pump for mild weather heat and a/c as necessary.The correct tubing is dirt cheap and you will have foam under the slab anyway.

 

[P51Mustang]

Thanks

 

[Mr onetwo]

Going back to your plan...I would not wall things off.The space will not be huge when you get it filled up...keep it as open as possible.Makes it easier to change things around.Another good thing about radiant floor heat is that you are not blowing dust around...things stay much cleaner.

 

[P51Mustang]

Not walling off old part of the shop in the long run is an interesting idea and something to think about. I am OK with the cold storage area being open to the rest of the shop. I do think that I would want the office area to be walled off so I can heat and cool it 100% of the time as I may not want to heat and cool the shop all of the time. I was looking at doing the shop the way that my layout shows was to save some money on the amount of new floor I would have to pour (only a 40x40 slab in place of 40x60) and to keep the current shop fully functional until the new space was ready. I could still do this as a Phase 1/Phase 2 project. The big question would be if the old floor in the existing shop would be OK to keep in place if I opened up the whole 40x60 space or if I would have to redo the 20x40 floor. This would be mostly be a budget and time question I guess. I was figuring that using a 10x20 section of the old floor for the welding/fab area would not be a problem but I wonder how having 1/3 of the space with the old non-insulated floor would work out with any kind of heat (I am guessing that this could be a major issue with radiant floor).

Again, something to think about.

Thanks.

 

[Mr onetwo]

In my opinion, as long as the building envelope is tight with good insulation levels it will not be a problem.You may have to run the floor 5 to 10 degrees warmer than normal.Over the years I have changed my preferences as far as control and temps go.I don't use outdoor reset or set back tstats and I run the floor warm.In testing the difference in fuel usage is insignificant and the system response is so much nicer at slightly elevated floor temps.

 

[Mr onetwo]

You could use a small radiant propane like this could be utilized in the welding(existing) area for spot heating...not expensive. This is a good one https://www.reverberray.com/products/commercial-industrial/high-intensity-luminous/dr-series/