propane heaters

Propane would make it worse as it produces water vapour

I sometimes use a calor heater in my workshop but have a window open to keep the moisture down

I would put up a false ceiling of insulated material as it would be the cold roof causing the water vapour to condense and provide a bit of ventilation let the damp air out

then maybe some heating like an electric tube heater

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember bob saying something like:

About a litre of water per kg burned, iirc. Iow, a lot, so ventilation is a good idea, which kind of defeats the purpose.

Propane is C5H12 so the equation for its burning is

C5H12 + 8O2 = 6H2O + 5CO2

Since the atomic weights are near enough C = 12, H = 1 and O = 16, 72 g of propane (5x12+12) gives 6 x18 = 108 g of water.

So 1kg of propane will make (1000/72)*108 = 1.5kg of water.

Yes considerably worse. It might actually rain inside, these things produce so much water vapour.

Immensely worse, yes.

Yes. without a flue, gas heating is almost a waste of time to control condensation.

Much depends on if the heater has a flue or not. Without it, it will make matters worse, with one, better.

(vapour barrier + insulation on the ceiling would work better)

No, that's pentane. Propane is C3H8.

In the right ballpark, but it's actually a little worse.

C3H3 + 5O2 -> 3CO2 + 4H2O

So 1kg propane gives 2kg of water.

the metal roof needs insulating somehow. Is it corrugated metal? - obviously fibreglass is the cheapest option, but you'd have to find a way of getting it to stay up there - if there's internal rafters, you can cut the fibre to fit inbetween these, then staple garden netting over the timbers to prevent it falling back down. Doesn't look fantastic but does the job

Are these comments about gas heaters generally or only in the OP's uninsulated workshop? I ask because I see B&Q stocked full of butane heaters each winter. Why would anyone buy them if they are that bad? Are they better inside an insulated house?

When our CH broke in the winter, I used fan heaters. I suppose fan heaters can start fires but thought they were safer than these butane heaters since there seems to be a story most years about someone being poisoned by them.

Unflued, like the portable gas fire type, produce around a litre of water for every kg of gas burnt.

Which is fine if you still have power... There were several stories last winter that a failure in the gas supply and the giving out of fan heaters to those affected soon lead to the failure of the local electricity supply as well.

We have a portable butane heater for when the power goes. Just looked at it's rating plate 4.2kW (knocks the spots of a fan heater...) and burns 301g/hr flat out, so thats a mug full of water per hour. We don't need to use it flat out, it normally runs on one or two (from three) radiants. How much moisture does a human put out per hour?

At a guess, cost. I have no idea how actual running costs stack up against electricity. This is left as an exercise for the student.

Chris

Maybe another factor. How much does 15kg Butane cylinder cost on the return empty, take away full basis?

Well as long as B&Q et al don't advertise the drawbacks, then students, pensioners and those on a tight budget will be tempted. After all, it's a gas heater i'nt it? and much cheaper than those in the gas showrooms.