Heating a Workshop

[Hilel Salomon]

Hi folks,
I have a 20 by 40 workshop here in the VA mountains and it gets downright cold. I have a wood stove by most of the heat flies up to the top. Thought about a modine hot dawg, but I would first like to try to keep the wood stove heat. My roof is metal over the felt and I never insulated between the tress joists. My thinking is that the water would ruin the insulation and lead to wood rot, but there must be a way to handle this. Any and all recommendations would be very welcome.
Regards, Hilel.

[George Morris]

I use a hot dog propane heater in my small 24x13 shop in upstate PA It works great. I did insulate walls and ceiling if you don't insulate all the heat is wasted. Just my thought! George

[Myk Rian]

If you want to keep the wood heat, put a 2ft box fan, or even a ceiling fan near the peak, run it on slow speed, and direct the heat back down.
Propane and other types of open-flame heaters introduce humidity into the air. Something that iron-topped tools don't like.

[David Christopher]

Propane and other types of open-flame heaters introduce humidity into the air.


how does it do that.... wheredoes the water come from ?

[David G Baker]

I have the Modine Hot Dawg, it is a 75K natural gas fired unit. The only thing I don't like about it is the unit uses shop air for its air supply. I wish I had a unit that used outside air instead.
You need to find a way to vent your attic space, soffit vents and roof vents so moisture that migrates from the heated space has a way to escape. Then you need to insulate the heck out of the area above your ceiling after you put one up.
If you don't insulate or put a ceiling in, you can probably get some help with a ceiling fan or something similar as has already been posted.

[Chuck Saunders]

Propane and other types of open-flame heaters introduce humidity into the air.


how does it do that.... wheredoes the water come from ?

product of combustion hydrocarbon + oxygen

2H5C5 +15O2 = 10CO2 + 10H2O

[David Christopher]

its amazing, I heated my shop for 2 years with a propane heater and now a NG heater. never ever had rust, moisture. even use laquer for finishing with no moisture

[Joe Chritz]

The ventless heaters introduce a lot of moisture into the air. The vented units like the HotDawg (which I have) don't intro nearly as much since most of the combustion is vented outside. There is still an open flame so some must get inside but with a vented unit the amount would be so small as to be a non issue.

Insulation is likely the major problem in the OP's post. My shop is roughly the same size with 10 foot ceilings and I use the above mentioned HotDawg 45K unit to keep it at 49 when I am not out there. A very small (Boxwood) wood burner is used when I am. It gets hot enough I have to really damper the stove down.

Two other easy helpers. A cheapy fan, I have a 20 year old oscillating fan that runs non stop 24/7/365 and ceiling fans, which I find I don't have yet. An air cleaner unit would do similar, just something to keep the air moving down and around.

Joe

[Jason Beam]

its amazing, I heated my shop for 2 years with a propane heater and now a NG heater. never ever had rust, moisture. even use laquer for finishing with no moisture

Being in Florida, maybe your air was already saturated! :eek::cool::D:D:D

In many areas, it's desert-dry in the winter and that propane or kerosene really wets things - it may also be worsened by rapid heating which causes condensation of all that fresh new water vapor the burning process put out.

[lou sansone]

my Connecticut shop uses a 80kbtu oil fired furnace - about 1300 sq feet .. seems to do fine

lou

[Frank Hagan]

its amazing, I heated my shop for 2 years with a propane heater and now a NG heater. never ever had rust, moisture. even use laquer for finishing with no moisture

The water vapor is in the flue gas, so if your heaters are vented you won't see an increase in humidity. The vent-less heaters add all the products of combustion back into the room, including the water vapor and carbon monoxide that usually goes up the vent in a vented heater. How some states still allow the ventless heaters is beyond me.

Anyway, I think the OPs original request was for info about insulation too:



My roof is metal over the felt and I never insulated between the tress joists. My thinking is that the water would ruin the insulation and lead to wood rot, but there must be a way to handle this.


I have never dealt with a metal roof, so I don't know how you would insulate between the trusses on one. My suspicion is that you would just use standard kraft-faced fiberglass insulation without a vapor barrier. I'm thinking the insulation would keep the metal roof from forming condensate because it is, well, insulated from the warmer shop space and basically the same temp as the outside. But I know there are people here who know more about it.

[Jeff Nicol]

Hilel, Is it just open to the roof? Is there wood decking down first then the steel put on top? If you have not enclosed the ceiling and can still get to the deck between the trusses you should be able to insulate it. The best way would be to hire some one to spray the expanding urethane foam inbetween the trusses, this does two things. It seals the inside from the outside and keeps moisture from getting to the metal roof. You could also use rigid foam board and tape all the joints and get about the same thing. It is a lot of work but the added heat in the shop will be worth it! Also the buliding should have a ridge vent on it to let air convect from the eaves where a perforated soffit or fascia vents are installed. This will let any moisture that gets into the unheated space between the deck/felt/insulation have a place to rise up and exit the building. Venting is very important. You also could put plastic sheet to cover the whole ceiling and then put in the fiberglass insulation or insulation first then plastic. Heat loss is caused by air movement and if the whole thing is sealed and taped any moisture in the shop can not get to the metal.

Lots of info but it takes time or money to do it right!

Good luck,

Jeff

[Joe Chritz]

Just to add since I forgot the insulation part.

I am with Jeff on this. If you are getting condensation on the roof then it is likely not vented well enough. You should be able to insulate between the ceiling trusses and vent the attic well and be fine.

The spray urethane foam is the greatest stuff for insulation you will find. Once it is sealed up nice you won't believe how comfy it will be. It is about 0 or -1 right now and I just started a fire in my little stove. It will be up 20 degree in my 24x30 in about 30 minutes tops. That is with 1 - 1 1/2 inches of urethane foam on the walls and a bunch of cellulose loose fill in the attic.

Joe

[Hilel Salomon]

Thank you all for your generous advice. Part of the problem is due to the builders. They put up the shop while I was down in SC and my kids were living here. I had made furniture but knew less than nothing about outdoor construction, and when I came up, the structure was up and the roof was on. I found out that the studs were put up in a drunken crazy way. No two distances between them are the same, and the variance is between 13 and 26 inches!!!! I fired them on the spot and got someone to help me put up the siding. When I realized how much buckling was going on, I put up firewalls and that took 10 hour days for more than a weekend. Each firewall had to be measured and cut individually. Anyway, I couldn't insulate it with any standard insulation and used sheets and put fiberboard over that. I wanted to get working in my shop in a hurry. The rafters (I guess trusses) are at least, standardized and are 24 inches apart on center. I was told that I needed to leave at least 2 inches of space on the trusses and insulate only about 3-4 inches.
As you all can see, I still don't know much about construction. I do enjoy working in the shop and in the summer, two very large window airconditioning units and power side vents in the loft keep me quite comfortable. I could spend the winter down in SC, where my shop is heated nicely, but I need to take care of my grandchildren a lot and I love the mountains during the winter.
For anyone living near here, I would welcome you to visit. I feel that woodworkers are a special and exceptionally nice group of people.
Thanks again, Hilel.

[Frank Hagan]

When you look up, do you see the trusses and the underside of the metal roof?

[Dick Sylvan]

its amazing, I heated my shop for 2 years with a propane heater and now a NG heater. never ever had rust, moisture. even use laquer for finishing with no moisture

I live in Houston and we almost always have some level of humidity as I am sure you do, as well. So, the marginal amount of humidity from the heater is probably not noticeable. I heat my shop on our occasional cold days with a window unit a/c- heater unit. Works great for , at least, outside temps in the 30's. Hasn't yet been colder than that, so don't know how it would do at lower temps.

[Brent Leonard]

Didn't read all posts so someone may have stated this.....

If you allow your shop to get cold, (i.e., over night) then heat it up with a vent free propane heater,

two things happen,

the propane burning will put additional moisture into the air, even in humid environments. then you have the problem of warm air around COLD cast iron or metal.
all that equals a perfect environment for moisture to collect on your metal surfaces.

Kinda like pulling an ice cold can of soda or beer out of the fridge in the heat of summer. The moisture collects on the cold surface due to the dew point or saturation point.

It's not just your TS top or jointer beds, think about the inside of your motors too! Go with a VENTED propane (if you go propane or Nat Gas) and don't allow the shop temps to get real cold then a quick heat up.

just my opinion.

[Jack Kenney]

product of combustion hydrocarbon + oxygen

2H5C5 +15O2 = 10CO2 + 10H2O

Try:
4(H5C5) + 25(O2) = 20(CO2) + 10(H2O)
and you get 20 Hydrogen, 20 Carbon and 50 Oxygen atoms on both sides of the equation and it balances. Then your chemistry teacher won't make you do your homework over.

Sorry, I couldn't resist.

Jack

[David Christopher]

I guess the reason that I have no problems is my shop NEVER gets under 70 degrees ( I HATE COLD )

[Dave Lessley]

I put in two 5K Dayton electric heaters in opposite corners of my 24x30 shop with independent thermostats. I have R19 in the walls and R30 in the ceiling. Living in SW Washington we have moderate temps most of the time. We had a short bout of cold weather for us any way (mid 20's) and had no problem keeping it warm. In fact I found I needed to turn it down a little to about 64 degrees for a comfortable short sleeve working temp.

I have a couple of 220 hour meters I want to hook up to find out how much they are running.... once I find them.

[Chuck Saunders]

Try:
4(H5C5) + 25(O2) = 20(CO2) + 10(H2O)
and you get 20 Hydrogen, 20 Carbon and 50 Oxygen atoms on both sides of the equation and it balances. Then your chemistry teacher won't make you do your homework over.

Sorry, I couldn't resist.

Jack

My face is completely red! I can't even come up with a good High School level defense. Thanks for catching that Jack.
Chuck

I will write redox equations 50 times for penance

[Wyatt Holm]

A magic heat blower system attached to your chimney works wonders. When you first build a fire you notice most of the heat going up the chimney. The magic heat captures some of that heat and broadcasts it through the room.