Heating A Wooden Shed

[Enrie Membership]

I've just had a 6' x 6' shed erected in the garden to house a few stationary engines which I want to keep above freezing in the winter. I do have an electrical supply nearby. What are folks thoughts on the most efficient form of heating that will keep the shed just above freezing point?.

Electrical Tubular heater 5' 200w (has the advantage of having a frostat onboard)

Old fashioned paraffin heater (I would have to light it if the temperature was liable to drop below freezing)

Any thoughts, comments or suggestions welcome

[Martin Brown]

Insulate the walls as best you can with polystyrene sheet. Try and avoid drafts.

That or a modest fan heater on its frost stat setting.

Absolutely not unless you want everything to rust to blazes from the resulting humidity. And if anything goes wrong get covered in soot - very bad for greenhouse plants. Also you need ventilation as well to sustain the flame.

Electric heating on a thermostat. You might want to monitor the dew point rather than

[damduck-egg]

Do mean you one of those standalone heaters or a fixed one with a flue?

Paraffin will produce water vapour , almost equivalent to the amount of Paraffin used. Not ideal in the proximity of things that can rust like old engines. A heater with a flue will help but some heat will go up it as well so the electric may well be cheaper to run.

G H

[The Other Mike]

If it is not in total shade during the day then a solar air heater and some decent insulation in the structure like PIR foam (Kingsapn/Celotex etc)

[Tim Watts]

Dessicant based dehumidifier - mine can run at 300W or 600W and it's a double win - bit of warmth and the air is dried out.

If you have a fairly airtight shed it seems to work very well. My shed has 50mm celotex on the floor and about 60% of the walls (rest and roof is a later tuit) and 600W can bring the temperature up a good 10-15 degrees - but it doesn't need to run that hard to keep the humidity below about 40-45%.

[Tim Watts]

I wouldn't - modern fan heaters can be a horrid fire risk - bit of fluff builds up inside the front grille and you get a red-hot spot (I've seen it).

If you just want a pure heater, oil filled radiator is the safest bet, or a dehumidifer.

[Tim Watts]

+1 to the celotex - reduces vapour transmission and gives a way/reason to seal up the draughts with foam too :)

[Peter Parry]

Dehumidifier suitable for low temperatures. Dries and heats air.

[Jeff Layman]

Absolute nonsense. I've been using fan heaters in greenhouses for over

20 years. All sorts of crud on the elements - spiders' webs, dust, small dead leaves, other plant-based material, etc, and I've never seen or smelt evidence of burning. After about eight years, I did have one element go o/c, though, and I've had a thermostat fail with crud on the contact points. And I only use the absolutely cheapest 1 - 2kW fan heaters.

Anyway, if someone was really concerned about fire, they could always use a ceramic-element fan heater.

[Brian Gaff]

Yes, also insulate the floor and roof as a lot of the heat in my old now defunct shed was lost through those means. I am going to try to make something similar this year, but it looks like I'll have to get somebody in, but the costs seem to go a bit mad if you want anything other than a boring old shed these days. Brian

[tabbypurr]

all electric heaters are 100% efficient. Radiators are the lowest fire risk, low loading tubular heaters next. Bowl heaters the greatest.

NT

[Tim Watts]

No it's not - and your experience is probably based on your heaters being 20 years old.

I was running fan heaters in the early parts of my bungalow renovation (10 years ago) and I bought "decent" ones. Except they were plastic. I caught one with a red hot spot on the element and right in front of that, the plastic grill was melting.

The others started doing that and I had to take them to bits to clean the fluff out.

Mordern fan heaters IME are unsafe by design.

I've been using fan heaters in greenhouses for over

Or an oil filled rad like I suggested - probably the safest of all electric heaters.

[Tim Watts]

Because my shed is felted, I can't do the roof yet (or the wood will get trapped between 2 impermeable layers).

I'm planning to strip the felt, celotex the top, batten a ventilation space in, ply and finish with something nicer - some plastic tiles or shingles.

The ply will let me extend the roof a foot all round to give water shedding away from the wall too.

[Huge]

I completely concur. Awful things.

[Martin Brown]

Mine have always been fine in the greenhouse too.

The other option are the rod type oil filled heaters. The main advantage of a fan heater in a modest sized space is that it stirs the air around so you don't get cold spots where condensation can occur.

[Andrew Gabriel]

Seen enough of those at Repair Cafes that I would never leave one running unattended.

Number 1 failure mode is the dessicant disk jams so it's no longer rotating, and the heater then heats one spot continuously, and it burns it.

Also seen one where the mica element supports in the fan heater part had fallen to pieces and the element wire coils had dropped out in clump against the dessicant disk, burning it.

[Andrew]

My Ebac homedry has a circuit board with a 555 timer.

Once per hour it operates a solenoid valve in the gas stream reversing the flow of warm refridgerant through the cooling coils, so the ice crackles, melts and falls off. It does this for about 3 mins and then reverts to normal operation.

QED, should work at very low temperatures.

I bought it 2nd hand in 1988, it's been around the world, to the pacific for 2 years, and back. Still going strong.

You can buy special heating cable that is mains rated.

[Tim Watts]

Thanks for that - I was a bit cautious about the heater in them as I know it runs hot.

I rigged my shed unit so it's only allowed to run when someone is home and "awake" (controlled through ZWave) (at home + awake is a notional thing based on based times of day mostly)

How flammable is the desiccant disc, do you reckon?

Oh well - oil filled rad or intrinsically safe heater bar for the OP then, unless he can run his at safe times.

[Tim Watts]

I wonder if anyone still makes a unit like that?

I'd prefer the safety of a refrigerant unit (based on what Andrew said earlier) but the purpose is to keep a shed dry so it will get cold.

[Andrew Gabriel]

I've no idea. It looks like a cardboard honeycomb, but I think it must be more fire resistant than cardboard, although it did char.

The shed I did for someone uses an old oil filled radiator. It's rated 1kW, but mostly it runs with a half-wave rectifying diode to halve the power output.