Potential Issue with Condensation

[Mark-UK]

Hi all,

I’m really hoping someone can help me prevent potential condensation problems. Here are the details:


I have a single skin breeze block shed for woodworking (so plenty of tools that might rust).

Shed measures 6m x 5m.

The walls outside are rendered.

The roof is flat, made of fibreglass, sitting on top of OSB, on top of timber joists.

The joists measure 170mm deep

I’m placing 100mm thick Kingspan (TR26) insulation boards between the joists.

I only have one entry point, a standard sized door. There are no windows though I plan to put one in later on.

The walls of the shed are bare breezeblock with no insulation as of yet.

As far as I can tell, when the door is shut, there is no airflow inside the shed.

I’ve uploaded a drawing detailing how I will be doing the insulation. The Kingspan senior tech told me there needs to be at least a 50mm gap around the insulation board.

With the above set up, what is the best procedure to take to prevent condensation and moisture build up? If my tools start to rust, I'll cry.

In case it is important, the shed floor is concrete and has a Damp Proof Membrane to prevent rising damp.

My only idea is to cut rectangular holes in the fascia(?) and place vents over the holes. These holes would be at the exact same level as the space between the joints. Apart from the vents, I have no idea how to proceed.

I should add I'm very inexperienced in building/construction work.

Thanks all.

 

[John D v2.0]

I would say without a bit of heat or a dehumidifier you'll struggle to improve things, insulation on its own can't make a room drier. Even houses without heat can get condensation.

 

[^woody^]

See this and other threads for the roof www.diynot.com/diy/threads/hybrid-flat-roof-design-in-dormer-window.522774/ the insulation rep is not fully correct.

As for general condensation, a cold shed will always experience condensation to varying degrees. Ventilation can help, but it's not the panacea.

 

[phatboy]

Oil your tools - cheapest way!!

 

[Mark-UK]

See this and other threads for the roof www.diynot.com/diy/threads/hybrid-flat-roof-design-in-dormer-window.522774/ the insulation rep is not fully correct.

As for general condensation, a cold shed will always experience condensation to varying degrees. Ventilation can help, but it's not the panacea.

Thanks for the link, I'll check it out.

 

[Mark-UK]

Oil your tools - cheapest way!!

That's a good idea. I have to be careful though because I'll be using planes, saws, chisels, etc.

Any particular brand of oil I should use?

 

[phatboy]

That's a good idea. I have to be careful though because I'll be using planes, saws, chisels, etc.

Any particular brand of oil I should use?

I just use standard 3-in-1 stuff, and an old rag

 

[Mark-UK]

I just use standard 3-in-1 stuff, and an old rag

Brilliant.

THank you

 

[Mark-UK]

I'm also going to buy a good dehumidifier (the desiccant type).

www.meaco.com/dehumidifier/home-dehumidifiers/meaco-dd8l-junior-dehumidifier-multi-award-winning

Been told that will solve a lot of the issues with condensation.

 

[^woody^]

That's a good idea. I have to be careful though because I'll be using planes, saws, chisels, etc.

Any particular brand of oil I should use?

Have a look at the "rag in a can" idea. Paul Sellers on Youtube demonstrates it well.

 

[Mark-UK]

Have a look at the "rag in a can" idea. Paul Sellers on Youtube demonstrates it well.

Yes, I've watched that and it's a great idea. I'd totally forgotten about it to be honest.

 

[Mark-UK]

So, with the possibility that the Kingspan insulation technician I spoke to is wrong about leaving a gap around the insulation boards, which configuration below would you say is best for reducing moisture/condensations?

 

[geraldthehamster]

The air gap should be on the cold side of the insulation, but only makes sense if the gap is ventilated. Otherwise put the insulation hard up against the roof. But this is all to do with preventing condensation in the roof straucture, rather than the shed. Personally I think you're unlikely to have a problem. Condensation in buildings usually occurs when warm air hits something cold. There won't be a source of heat in your shed.

 

[Mark-UK]

Hi Gerald,

So with the cold side of the shed, would config. (C) be the best one to go for?

I would be heating it during the cold winter months so perhaps I need to take that into account. I am buying a dehumidifier as well.

 

[geraldthehamster]

So with the cold side of the shed, would config. (C) be the best one to go for?

That would be correct assuming the void is ventilated. I still think this is overkill for a shed. You may be heating it, but unless you're living in it where will the moisture come from? Condensation is caused by moisture held in warm air condensing out when the air is cooled, as cold air can hold less moisture. Why are you heating it? Will you be working in it?