Vic

Rusting is caused by condensation and condensation is caused by changes of temperature that cause the Dew Point to be crossed.

The trick is to keep the temperature above the dew point and slow down the rate of change of temperature.

My workshop is the same size as yours but, in my case, it is half of a double garage built in block and rendered under a tiled roof. I went to great lengths to insulate this – in the roof, in the walls, in a stud partition between the garage and workshop and under a false floor laid over the concrete base of the workshop area. All this slows the rate of temperature change. In the winter months ( November to April) I run a small, thermostatically controlled, oil filled radiator which maintains a low level heat. The cost of running this for the year is less than £30. When I work out there I have a convector heater to make things more comfortable.

I don't know if your tubular heater would be adequate ( I think 30W is a bit small to have much effect in the volume of your workshop) though the principle of supplying background heat is the same – but the vital thing is the insulation to slow the rate of temperature change.

Regards

Norman

Hi Vic

'The new workshop will be a timber cabin 5m x 3m, solid wood 44mm thick with an insulated floor and ceiling'.

Sounds like a solid workshop to me, I doubt if you'll need much background heating with that sort of insulation, My garage conversion, 6m x 3m, has two small 3 fin, thermostatically controlled oil fired rads as winter backup one at either end. I have to add that I've rarely had to have them on for more than an hour even at the coldest temp outside of -7*C as inside it's remained at approx + 5-6 *C so an hour on brings the temp up to a nice 16 -18*C.

Cheers

George.

Always try to maintain a "warm roof void" and by this i mean there can be no cross heat transfare from the outside of roof to inside as in winter this will cause condensation.The best form of roof insulation is the likes of kingspan tight up against the underside of the roofing boards to eliminate the inside heat contacting the outside heat and all condensation will be history.We always insulate on the outside and lay the Built up felt roof on top of that as then the underside of the roofing boards will always remain at room temperture even in minus degree temps..mininmun of 75mm insulation thickness for this to happen though.I have a 60 sq meter workshop at home with its own central heating (yea lucky me i hear you say LOL) and during the coldest winter days it never drops below 60 degree cent because i have 120mm kingspan on the roof. Hope this helps.

For some years I ran an 850 watt storage heater on Economy 7, backed up with a small dehumidifier. I had a thermostat controlling the power in and most of the time it used approximarely 30 kWh a week, rising to 42 kWh in really cold conditions.Internal temperature ran between 10 and 12 degrees centigrade. On the E7 tariff that cost between £1.65 and 1.97 a week.

It kept the rust at bay on my single garage size workshop which is an insulated block built structure inside a larger wooden shed, originally built as a chicken house in the 1940's

Recent changes to tariff pricings have made the advantage E7 once had much less competitive at some 50% increase in tariff rate and now with PV panels on the house roof capable of delivering 3KWh peak, I am seriously considering a 2kW convector heater to do the job instead. It warms the air and makes the occupant feel more comfortable, the modern units have built in thermostats and are very economical to run as a result. This coming winter will be the first time the new approach will be used.

I believe a big heating blast delivered in short intervals might be more effective than huddling over the storage heater as was the case previously. The PV input of course is the key in this instance and mopping up the 'free' energy in this way is much more attractive than paying the power company.. Hopefully, residual heat at the end of the day will still keep the shop above dew point during the night. I can measure and record that. I know all this reasonig falis dismally on dull days but the experiment will be revealing.

Regards

Brian

Edited By Brian Wood on 27/08/2014 18:59:20