Mick you will probably find that you need both, definitely insulate the roof, I would suggest using Celotex sheets, a minimum of 50mm thick but ideally 100 mm, brilliant insulation for workshops.If possible add insulation to the walls as well, the objective is to keep the temperature within the workshop as stable as possible, it is the temperature fluctuations which cause saturated air to deposit moisture as condensation on any cold surface when the air cools. In my workshop I have plenty of celotex insulation and during the colder months, October to March, I have a small oil filled radiator set on low running 24/7 which keeps the temp about 10 to 12 degrees. I also run a dehumidifier which comes on between midnight and 6.00 am, everyday and runs while the electric is on economy seven. The humidity reading in the workshop varies between 45 and 55 % relative humidity. Since I insulated and provided constant low background heat I have not had condensation and therefore no rust. I cant stress enough how effective insulation is in preventing condensation.

Dave

Insulate, insulate and insulate! Then maintain the temperature above dew point. Dehumidifiers help, but at zero Celsius, any water vapour in the air is likely to condense somewhere.

Compressor dehumidifiers don't work too well at low temperatures. The absorption type use more leccy, but that would help the temperature problem.

I'm just enclosing a lathe for the winter. It is in a sectional concrete panel garage with cement/fibre corrugated roofing sheets. It will have 100mm recticel behind, beside, in front and over on a concrete floor (may yet stand it on some insulation). I did get 5 sheets for about 50-60 quid, so looking for a bit more (rather than having a patchwork quilt at one end). Fingers crossed that there might be some at a sale on Saturday, but may need to think of visiting

the monthly sale at Kidderminster, unless I can find another similar auction site.

I bought two non-running meaco dehumidifiers via epay at about£40 quid apiece. Both repaired at zero cost (I was expecting to get one out of the two as worst scenario). One keeps my small insulated workshop (3.4×1.9×2m approx) warmish and dry, by running it an hour each night (uses 370W), so costs about 25p per week. The lathe enclosure may yet be connected to the workshop, so likely no, or little, extra running cost.

Three sheets of 100mm recticel travel easily on my saxo roof.

Hope that helps.

I have an up and over garage door which was just a skin of sheet steel to suck all heat out of the garage. I found that I could slide a 10mm sheet of celotax between the ribs and stays and so covered the whole door and tape the joints now the door can still be opened to let in the better half's car but the difference to heat is amazing. I also run a dehumidifier over night as it also gives off some heat as well as reducing the risk of rust.

David

Hi there, Mick,

NDIY, above, has said 'Compressor dehumidifiers don't work too well at low temperatures' – I'd put it stronger than that. Unless you can get the temperature up you won't get your money's worth from a dehumidifier.

You need to check that your space isn't too well ventilated or your dehumidifier will be trying to dehumidify the UK!!!

I've personally found that the Myford plastic cover has done a good job of keeping my ML7 rust-free – other folks have reported that they make things worse!?!?

If you're shopping for Kingspan or Cellotex, have a look at 'Seconds and Co Ltd.', they might be cheaper than your local Builders' Merchant despite their having to ship to your door. I bought 3½ sheets of 3" from them and was pleased with what I got.

Best regards,

Swarf, Mostly!

Edited By Swarf, Mostly! on 30/10/2017 17:20:24 (to correct thickness)

Edited By Swarf, Mostly! on 30/10/2017 17:21:31

It's your lucky day – St Albans MES website has an article on this.

A useful by product of the dehumidifier is 'distilled' water fro your boilers.

The absorption type dehumidifiers that give out heat may work better when cold but that makes them wasteful in summer, both days of it, so if you think the compressor type needs some heat it is better to add a separate heater.

+1 for Celotex insulation. I converted my single garage & fully lined the walls & roof with Celotex sheets, covered with 12mm OSB/plasterboard, works very nicely. For really cold days I have two small oil rads which after about an hr has the garage nicely up to approx 16* C… cozeeee; when I'm not in there the temp remains around 6-8 *C

​George.

I have a friend who has just solved the roof element of this problem. His workshop is in a detached single garage with a cenent/asbestos type of roof (as mentioned by HowardT). It dripped badly and the whole place was a rust-generating environment. He has just replaced the roof with a proprietary product consisting of panels which have a ribbed metal outer skin, a thick foam layer, then a ribbed metal inner panel. The roof is now leak-free and doesn't drip. Instead of insulating the walls, he runs a small tubular heater all the time. Seems to work. One benefit being that the workshop is never chillingly cold. The roof was replaced in a day or so, and the panels seem easy to work with. They look the same as the panels used on many newish industrial buildings. Not cheap, but good things seldom are.

If it was my workshop, I would insulate the walls. Speaking from experience of two previous detached workshops, insulating the walls and ceiling (or roof) makes a huge difference. I had a large garage-sized wooden workshop which was lined and insulated with Celotex. Then I had a small detached single-brick outbuilding which I strapped and lined, insulating with rock wool. I also installed a night storage heater in that one, and I could run down the garden and stand in my workshop at any time of the day or night, with the temperature at a constant 64 degrees. Not even a hint of rust. Joy.

Marcus

I bought a dehumidifier when I had an incoming main water supply leak in the house and a wall got damp. I ran it for months and was still taking three litres of water a day from it when the damp wall was no longer showing a reading on a damp meter. I think the above comment re dehumidifying the UK rings true. My workshop never suffers from any condensate or damp problems due I think to three things. The roof is full height of the house so a big area. Up and over doors are wooden. I run a fan through the colder months to keep the air moving around. My winter workshop heater is a diesel fuelled ex truck "Eberspacher" heater that uses its own fan to distribute the heat.

Fitting insulation should go hand in hand with fitting a vapour barrier.

Mike

We bought a Siemens iG500 heat pump clothes drier 3 years ago and it's been pretty darned good. It is clearly a lot more efficient than a standard, "throw it out the window" drier. We operate it indoors (without any ducting obviously) and the only byproduct is water that goes directly into the drain ia the drain hose. Efficient, as in there is little noticeable heat generated by it (it barely gets warm), nor are we piping massive volumes of saturated steam outside that we have generated at great cost. By condensing that vapour, the machine recovers most of the energy used to drive it out of the clothing.

It's also got a pretty effective humidistat that can tell how dry the clothes are and will terminate the cycle when the selected degree of dryness has been achieved.

It's easy to be cynical about energy ratings but that heat energy usage relates directly to energy bills.

Murray