Shop temperature control

[RJSakowski]

Wintertime heating consists of replacing heat lost to the environment. Heat loss is proportional to the difference in temperature so from an efficiency standpoint, lowering the temperature when you are absent will mean less makeup heat needed to replace that lost. I did this on my home in the 70's as we were gone working for 10 hours during the day and asleep for 7 hours at night. I lowered the temperature during that time to 45º, turning it up to 65º when we were there. I had installed a programmable thermostat so the heat would come on a half an hour before we got up in the morning and before we returned home in the evening. I recorded the furnace run time during on/off times and even including an hour for bringing the house up to temperature as part of the off time, I had a 50% savings in fuel.

However, in the shop, there is another reason for maintaining as constant a temperature as possible. If the room is cooled down during times when you're absent, the machines will come to at or near that lower temperature. When you raise the temperature, any moisture in the air can condense on the cold machines, potentially causing a rusting situation. This is less of a problem in winter because the relative humidity is lower then but it is something to be concerned about.

I try to keep the relative humidity in the house and shop at or below 50%. In winter, this isn't an issue since typical Wisconsin winters tend to be below freezing for highs. In the summer though, I run a dehumidifier from mid May until mid September.

 

[WisJim]

I'm in western Wisconsin, an hour east of Minneapolis/St.Paul, Minn. When we moved to town a couple of years ago, I built a new garage and shop building, 24 by 40 feet with a 12 by 40 upstairs. It has spray foam insulation (3" in walls, 4+" roof), plus 2" foam board under the floor and around the perimeter. The single car garage area is also insulated from the shop areas with a 2x4 wall with fiberglass batt insulation. I run a dehumidifier year around in the metal shop area. The warmest it has gotten this summer, even after more than a week over 90F outside, is 76F in the shop area and 85F in the garage. Garage is warmer due to opening and closing the overhead door and bringing in the hot car. In the winter the garage gets down to freezing but seldom below 30F and the shop areas haven't gotten below the mid 30s. I can warm up my shop spaces (two 12x24 wood and metal shop areas) with a 1500 portable electric heater, I'm contemplating a minisplit heat pump after good experience with them in our old former farmhouse home.
Insulation makes a LOT of difference.

 

[Batmanacw]

I'm in western Wisconsin, an hour east of Minneapolis/St.Paul, Minn. When we moved to town a couple of years ago, I built a new garage and shop building, 24 by 40 feet with a 12 by 40 upstairs. It has spray foam insulation (3" in walls, 4+" roof), plus 2" foam board under the floor and around the perimeter. The single car garage area is also insulated from the shop areas with a 2x4 wall with fiberglass batt insulation. I run a dehumidifier year around in the metal shop area. The warmest it has gotten this summer, even after more than a week over 90F outside, is 76F in the shop area and 85F in the garage. Garage is warmer due to opening and closing the overhead door and bringing in the hot car. In the winter the garage gets down to freezing but seldom below 30F and the shop areas haven't gotten below the mid 30s. I can warm up my shop spaces (two 12x24 wood and metal shop areas) with a 1500 portable electric heater, I'm contemplating a minisplit heat pump after good experience with them in our old former farmhouse home.
Insulation makes a LOT of difference.

It was 90⁰ yesterday and my shop got up to 75⁰ because I had the machine shop open to the fabrication shop. It dropped down to 70⁰ over night with no input from me. It's been near 70⁰ all summer with me running the ac while I'm in there just to lower humidity.

My shop is really easy to keep cool.

I'm just deciding the best solution for keeping it warm "enough". If it cost $40 a month to maintain 50⁰ I think I'd be pretty happy with that. In the grand scheme of things that isn't a lot of money for grabbing warm handles and warm micrometers.

 

[RJSakowski]

Heat pumps don't fare well in Wisconsin winters. They are at their lowest efficiency when you need them the most. Their efficiency is only slightly above that of resistance heating and their throughput is drastically reduced. I have a mini split which I use mainly for cooling in summer. I generally turn the unit off from late fall until mid May. I am heating/cooling a well insulated attic space and generally get enough heat from the house below to keep the room at 60º. If I need a quick warmup, I have 4 KW worth of baseboard resistance heat which will usually warm the room in sbout 20 minutes.

Using a heat pump with a geothermal heat source is a different matter. They can be very efficient in Wisconsin where ground temperatures are around 50º -54º . Unfortunately, the upfront cost can be prohibitive for a modest need. I would expect a very long ROI.

 

[Batmanacw]

Heat pumps don't fare well in Wisconsin winters. They are at their lowest efficiency when you need them the most. Their efficiency is only slightly above that of resistance heating and their throughput is drastically reduced. I have a mini split which I use mainly for cooling in summer. I generally turn the unit off from late fall until mid May. I am heating/cooling a well insulated attic space and generally get enough heat from the house below to keep the room at 60º. If I need a quick warmup, I have 4 KW worth of baseboard resistance heat which will usually warm the room in sbout 20 minutes.

Using a heat pump with a geothermal heat source is a different matter. They can be very efficient in Wisconsin where ground temperatures are around 50º -54º . Unfortunately, the upfront cost can be prohibitive for a modest need. I would expect a very long ROI.

1500 watts will heat my shop to very reasonable temperatures in 30 minutes or less starting from 40⁰ ish. That cost about $0.07 with a $40 heater.

Of course there are more efficient options that cost thousands. That's what seems to be lost in the discussion.

I'm deciding between maintaining 40⁰ and warming things up or maintaining a higher theoretical temperature by running my heater at 600 watts non stop. Probably the difference between $20 and $60 a month at the absolute maximum.

 

[RJSakowski]

If you aren't concerned about thermal expansion or condensation issues, a programmable control to turn the resistance heater on 30 minutes before your intended occupation would work. The newer ones can be controlled via your smart phone from anywhere with cell reception or a Wifi hotspot.

 

[woodchucker]

any chance you can replace your window air conditioner with a window heat pump (if they have them)?

 

[Batmanacw]

any chance you can replace your window air conditioner with a window heat pump (if they have them)?

My window unit cools my shop for $5 to $10 a month. I really don't need to improve on that part. Heat pumps don't do well when I need the heat the most.

I'm not buying expensive equipment for a tint shop. I'm just deciding between maintaining heat or dropping it down and heating up.

 

[Batmanacw]

If you aren't concerned about thermal expansion or condensation issues, a programmable control to turn the resistance heater on 30 minutes before your intended occupation would work. The newer ones can be controlled via your smart phone from anywhere with cell reception or a Wifi hotspot.

Unfortunately no wifi in the garage. I'd set up a second heater to start an hour before I come out.

 

[Shotgun]

Go to SanTan Solar and order 3 or 4 of their cheapest panels so that you get around 120V running them in series. You can get 250W panels for less than $50. Build you an awning/car cover/??? out of them, then run them through a baseboard heater place low near your machines.

Less than $500, and you've got that "base" heating for free thereafter. I've got about five tons of cast iron in my shop to absorb and re-emit the thermal energy.