Shop heating question

How about this:

I'm planning on using the larger version in my shop. A key feature is that it's a proper vented furnace, so unlike the ventless ones, it's not dumping moisture and combustion gasses into the space. Another option would be an RV furnace, pretty similar and you might be able to get a used one from a wrecked RV cheap.

With full R-14 and relatively small external sides, you might be able to get by with electric heat. Operating cost is higher but materials are much cheaper.

Other than that, get a gas fired unit, 45k btu should be plenty, make sure it is the VENTED type. Hang> As some of you might remember i'm making a shop out of a 20 foot

Whatever you use must be direct vented or your stuff will rust. Mr Heater or a HotDawg are likely candidates. Do the research to figure out how much your NG, Propane, or electric cost is per BTU and make your decision.

Wes

How about radiant floor heat? takes care of the cold floor, does not take up much floor space, no venting, no introduced moisture, no duct work.

Don't even think about it until you've got the insulation in place. Use a de-humidifier to try to keep the humidity under control until you can add the insulation. At the moment, any heat you can introduce is going to go straight through the walls of the container without stopping. After you've got it insulated, you'll be looking at maybe 2000btu/hr or 700W for a comfortable temperature. At that point, you can consider using the de-humidifier as a significant part of the heat input.

In the meantime, if you want to work in there, get a 1 kW quartz patio heater. It'll make you feel warm without trying to heat all of Canada :-)

Mark Rand (brought my well insulated workshop up to shirt sleeve temperature today by running the 1.4 kW surface grinder for 5 hours :-)

Mark, seriously? only 700 odd watts? and yes although cooling was not discussed i was thinking towards a small high efficiency window air conditioner for my dehumidifying input. I'd love to find the HVAC heating and cooling calculations since i know the volume and insulation factors and how many btu an hour i need

Gas infrared tube heater. It will heat you, the floor, the tools, and the walls, which will eventually heat the air. In my opinion, the ONLY way to go in a structure like that.

Many floor mounted units can be hung or wall mounted as well.

FWIW:

I design for -20 F in Vermont - I'd think you might want no less in ON.

Making a pair of optomistic assumptions - R14 all around (no lossy doors, etc) and no ventilation (which is a terrible idea when the place is occupied, fine when it's not) I come out closer to 1400 watts. -20F outside, 68F inside, 88F delta.

700 watts would be fine under those assumptions at about 24F, or lower if you let the shop temp run lower - ie, if you run the shop at (or down to) 50F, you're good to 6F.

You should assume that reality will be somewhat worse, due to doors, intentional or non-intentional ventilation (intentional is a very good idea), and imperfections in the insulation, depending on what your insulating method is.

Running the numbers on the degree day data can give you an idea of how fast (or slowly) additional insulation will pay off at current fuel prices, etc. At some point, if you ventilate, an air-air heat exchanger makes a much bigger difference than more insulation on the building.

Try a few high-wattage floodlamps.

I did a quick check on your numbers, came out with about the same as yours at 1368 watts for -20F. The assumptions are VERY optimistic but the container is designed to be very air tight.

Thanks

Insight like this in essentially the same climate as me (A few more hills your way, otherwise we even get the same snowstorms) Is priceless.

Your figures are showing me i need to insulate the floor as well and that just having a windbreak under the shop wont be enough.

Only one other question is the figure of 5-10 air changes an hour in the right ballpark when welding? I've seen a few guides most say 8 the one that was Tig specific said 5-10 I'm guessing might be high when i only weld intermittently and that for obvious reasons these guides are erring on the side of safety.

but if i have to do that many air changes then it makes perfect sense that the heat recovery vent is worth its weight in gold. even if i do

3 air changes that leaves the air in there for only 20 minutes to heat the shop.

Thanks for the insight

Brent Ottawa Canada

Wow..almost as much as cable tv.

So does anyone here watch cable 24/7?

Gunner

Sorry, I was elsewhere..

Looks like Lawrence has expanded on my rough calculation somewhat. I will admit that I'd omitted the area of the ends of the container and had assumed ambient at 0C. But it was a first stab at the problem.

I think that doing a payback calculation on the insulation and heating is probably well worth while if you want to work in comfort during the winter :-)

Mark Rand RTFM

well i was figuring at least twice that from heating alone and had always figure the waste heat of my tools wouldn't hurt but would be insignificant overall. Now i see the waste heat of my tools can ALMOST heat the whole shop depending on which are in use and that a significant portion of my summer cooling will be flushing tool heat.

it appears however that i NEED to insulate the floor as well to make those calculations work and that will involve some interesting logisitics... or perhaps spray insulation

I also think i found a salamander heater i can borrow for the early phases of construction so i might make a lot more progress than i expected to a lot earlier than i expected to.

I wish i had asked these questions sooner

Brent Ottawa Canada

I've got to imagine having a comfortable shop to work in is a lot more productive than having cable TV.

For insulating the floor, the most practical would be spray foam to fill the bays underneath between the steel channel joists. If you can tip the container on it's side one of the spray foam companies could probably do it pretty cheap. Fiberglass batts stuffed into those cavities would insulate, at least for a few minutes before 90,000 field mice moved in.

That's "biofuel powered radiant floor heaters", thank you very much. ;-) The hantavirus exhaust is kind of annoying, though.

Spray foam is probably the ticket. Either that or shopping for a refrigerated container which is presumably pre-insulated (though I don't know to what level), but as I recall this one is already bought and parked. Other option would be to lay rigid foam inside the floor, and deck over that, losing a few inches of headroom. Not sure how well that would work with machinery on top if the floor deck isn't a concrete slab (a mode I'm familiar with in non-portable shop construction - the slab spreads the load so that most normal machinery is not a problem).

Sit the whole thing on 4"-6" of EPS foam? It'll take the pressure without significant settlement and rodents shouldn't be a problem if the external lining of the walls is taken below soil level.

Mark Rand RTFM