Workshop Insulation

[Martin Prior]

Jamie, you have your priorities right.

Fresh from treatment, tanalised timber has a huge water content. We normally air-dry it for at least a month before use in warm weather and much longer at this time of year. Wood doesn't respond well to attempts to dry it rapidly.

Going back to my earlier comments about dehumidifiers: Our garages and workshops are all timber sectional buildings built either by ourselves, or my predecessor in the business, dating back a far as 1973. The buildings are still in good condition. Cars, tools, machinery and materials are kept in them and I've stored bare steel for years with no corrosion issues. I've never used a dehumidifier, or a heater other than during working hours in cold weather.

I have, however, sometimes had calls from customers who have had problems with damp. Maintaining good air circulation around the outside of the building is essential and if the building doesn't have a roof overhang at the sides, gutters are highly advisable.

Dehumidifiers have often been present and my problem with them is that as they dry the air inside the building, they also dry the timber cladding from the inside. Wood is not a particularly stable material; it behaves like a sponge and if one side of a board is dry and the other side damp, water will simply be drawn from the wet side to the dry side. You'll never win. I've seen buildings with permanently sodden, rotting boards that miraculously dry out within a few weeks once the dehumidifier is switched off. The timber will find its own balance.

[Bruce Nicholls]

Martin I have to bow to your expertise when it comes to sheds. I guess that our boat with 2.5 metres below the water and a wet bilge is a different beast to a shed. I would certainly have take your experience into account when we do come ashore and build the inevitable shed.

[Charles Levien]

An interesting thread— one small contribution which might be worth considering is the use of foil backed insulation. 
Our home is substantially insulated with foil backed polystyrene— it works well but it does interfere with mobile phone signals. We’ve got round this by using our hub.
Of course, the shed is a great place to escape unwanted calls —————

Charles

[Jamie]

My own preference is 50mm fibreglass insulation, with a 9/10mm ply lining - neither very expensive in the great scheme of things.

Martin,

Do you use any sort of membrane between the wall and the insulation?

Thank you.

Jamie.

[Martin Prior]

Bruce, I suspect that the conditions on the boat are quite different. At 2.5m depth there's considerable pressure pushing water though permanently immersed boards.

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Jamie - On our own buildings, no. If customers specify it, then we use a breather membrane such as Tyvek - the texture is a bit like J-cloth.

[Jamie]

Jamie - On our own buildings, no. If customers specify it, then we use a breather membrane such as Tyvek - the texture is a bit like J-cloth.

Thank you, Martin.

[Chris KC]

I spent a bit of time and effort a year or two back putting kingspan (or something similar) between the rafters of my detached brick and breeze block garage (a small double) in the hope of making it habitable in the winter. I'm afraid it didn't make a jot of difference, and without some sort of space heater, for which I don't have space, the only way to keep semi-warm is to run a small oil-filled heater which I pretty much stand on top of. Not really workable. I thought about installing a 'ceiling'. but I store a lot of stuff in the roof void and it isn't quite big enough to make a loft out of.

With this in mind I turned my attention to my small lean-to shed, which was essentially a wobbly pile of concrete blocks. The wall was taken down and rebuilt with a single skin of reclaimed brick. The space is adequate for odd jobs such as a gearbox strip-down and rebuild, and warms up nicely with an old Aladdin stove. The roof however is corrugated PVC sheet and the warm, moist air - even without the heater - condenses on it in cold weather giving rise to a modest indoor rain storm. The space is copiously ventilated. I suppose the answer is an insulated roof, so that the interior surface is not so cold? I have a small wooden double-glazed conservatory close by and it is dry as a bone, but the roof is twin-skinned: Corotherm perhaps. I like the PVC roof as it is transparent and lets in bags of natural light, but any ideas on how to stop the indoor rain would be welcome.

[Howard Wright]

Hi Chris

An Alladin stove will kick out a huge amount of moisture!!

When I first re-roofed my shed in the last house I used galv sheeting and blocked up the ends with eaves fillers.  It rained inside constantly in the winter.  Removing the eaves fillers helped a lot.

I don’t think you can stop condensation in a transparent roof without some form of double skin.  I have used polycarbonate on conservatory roofs in the past with very little condensation.  Several web based sellers also offer roof kits but they can be a little pricey.

Cheers

Howard

[Bruce Nicholls]

Chris, Just an idea. The best natural insulator is air. Putting a second clear skin with an air gap to create a dead air space but let the light through may do the job. Back on our boat I did this to the windows in our deck-house using a heat shrink film, bought cheaply off ebay, stuck with double sided tape to the inner window surrounds to give an approx 2 inch air gap. Condensation which we had in buckets before ceased and the heat input fell and comfort level rose to an amazing degree. Also easy to remove and replace as required seasonally. You would of course need to seal the edges of the existing roof but expanding foam would make an easy job of this.

[Chris KC]

Thank you both.

Howard yes point taken about the Aladdin, I plan to use it though at least until I have used up my stock of paraffin!
For now the only realistic alternative is an electric heater but that poses challenges of its own.

Bruce yes I like your thinking. The roof needs replacing anyway, I've given up for this year though as I need a warm, dry spell to do it. I considered corotherm but it is quite a bit more costly, and due to the layout of the roof it needs to be effectively 'disposable' as it obstructs access to things which need to be got at now and then. So I think I will replace with a better PVC roof but yes, a second skin however humble looks like it might provide a remedy.