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Undesirable moistness


FridgeFreezer

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I have a very lovely steel-framed shed in which the 109 and all my tools and junk valuable treasures are stored. Due to the way it was built on a pre-existing concrete slab, the cladding does not hang down over the outside of the slab but sits on it. I have run a bead of concrete approx 2" high all round the inside to keep surface water out, which mostly works barring the odd bit of seepage :ph34r:

However, there is still the inevitable condensation and moist air, and it's noticable that a few bits and bobs are getting surface rust on them, especially at the end furthest from the door.

So - without costing a fortune in electric/gas/diesel/wood, setting the shed on fire or melting my credit card, does anyone have any tricks, tips, etc. on how to keep the place a bit dryer and better ventilated?

Suggestions / ideas so far have been to add an air vent at the affected end of the shed to help airflow (entirely sensible) and perhaps use a small solar panel & PC cooling fan (both of which I have kicking around) to move air around a bit.

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An air vent at the top of the shed where the condenstation is worst, and one at the opposite end but lower to the ground should help with air flow. That and insulate it with old carpet, etc, glued to the inside of the shed should do the trick.

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Regarding insulation, if you've room in the roof of your shed house, there are schemes running for £3/roll of rockwool insulation. I know it's a pretty bold step in terms of fitting it all, and you might not have room, but at £3/roll it's worth thinking about?

Obviously, it's only for your house, but there might be some left over for your shed.

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Dehumidifier, dehumidifier, dehumidifier.

You only need one, but fit, forget, and get on with the enjoyable aspects of your life.

I suggest reading this thread, http://www.canalworld.net/forums/index.php?showtopic=34649&pid=616596&st=0entry616596

Note the recommendations about dehumidifiers that don't need the cooling cycle to operate, and will therefore operate below freezing, of which this is an example http://www.meaco.com/proddetail.asp?prod=DD122FW

Being a Land Rover owner you may want a larger version, but I'd have thought something "Perfect for flats and smaller houses" would be OK in the more open area of your workshop.

My only other suggestion is that you make a shelf and put it as high as possible on a wall, situated side on to the wall so that airflow is unimpeded. Warmer air carries more moisture, and air is always warmer near the ceiling.

HTH

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Fridge, as I have a similar workshop, you want to have a look to make sure you've not got leaks coming through the fasteners that secure the roof pannels to the beams that run horrizontally along the roof. I had this and water would then run along theses beams to a joint (the beams overlap on mine) where the water would drip over the car, bench etc. I found drilling through the horrizontal beams as they go over the main frame so that the water runs onto the frame and down to the edges of the workshop. I also invested in a load of shelving recently to keep things off the ground as you'll always have to put up with a certain amount of moisture as they're not that well sealed.

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Cheers guys,

The roof panels are already felt-coated on the underside to prevent drips/condensation, there is the odd bit of seepage around the perimeter which leaves a bit of damp on the floor but it's noticably the corner furthest from the door and hence with least airflow.

I intend to panel most of the shed with hardboard/chipboard just to provide a bit of insulation in future.

Meantime I think I'll try rigging up a low power fan to circulate air a bit in the moist corner as a first pass at the problem. A small wall-wart PSU and a PC cooling fan or two will draw naff all power (<1W).

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I've seen a steel shed with the same problem - and a good solution!

Solar was the answer - in two parts.

First, paint the outside of the roof matt black and cover with rigid plastic sheet, providing insulation on the outside. Even in the winter, the black roof gets hot enough to warm the inside significantly.

The second part is a photovoltaic panel to run a circulating fan.

In the summer, he slid shiny Aluminium sheets between the roof and the plastic cover to reflect the light and the photovoltaic to power an extractor.

This chap didn't have mains in the shed - so a dehumidifier was not an option. This solution is much more environmentally friendly though.

The trouble with insulation alone is that the tools inside are still cold enough that water will condense directly out of moist air. So you need either heating or dehumidification.

Si

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This is going to sound a little odd, but here goes anyway.

Get yourself a hessian sack full of rice from your local asian supermarket. The rice will absorb moisture from the air and ease the condensation problem.

Probably wont cure the problem completely, but as Mr Tesco says, every little helps. Cheaper than a dehumidifier too.

Oh, and probably best not to have the rice with your sweet and sour either.

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Rockwool and a dehumidifier such as this one will do the trick. You can pick up a proper dehumidifier (not the in-house kind but an industrial type used for drying out houses after a flood) fairly cheap second hand.

Yeah, for what it's worth I tried several of the "domestic" dehumidifiers and none of them lasted more than a couple of years. I've had 2 of the EBAC ones (CD35) going 24-7 now for 6 years with nary a bother.

Jeff.

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Regarding roof insulation like Rockwool, I agree it is effective. But Rockwool is horrible to handle. If I had to choose between rolling naked in Fibreglass or Rockwool it would be Fibreglass any day, but fortunately I dont't. Anyway, if you want to insulate your roof say, please remember if it's doing its work, somewhere in the middle of the insulation the dewpoint might be reached , and you may therefore get condensation inside the insulation. I thnk you are supposed to allow air to circulate between the roof inner surface and the top of the insulation, or cover it with a vapour barrier, or maybe use one of the other materials like Kingspan, otherwise you can get sogginess build up on the top of the insulation. Nigel

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from building regs, if you are planning on converting a loft in to a useable room, then you need to leave 50mm between insulation and the felt as this will allow the moisture laden air to head up to the ridge and out through a ridge vent. This will mean, hopefully, that the dewpoint will be on the roof and will not cause your insulation to get soggy and breakdown.

Chris

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Thanks John.

The shed I saw looked like a greenhouse / potting shed from outside with a 'glass' roof and was surprisingly warm even with snow on the ground outside! It was a good job as he had no other sources of heat in there.

Si

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