How much ventilation do I need (mould again)

[formula400]

Right, went in the shed today, some very small fine mould in forming on the roof.

I’ve not finished putting up all the insulation boards (it’s a slow process due to time )

Basically how much ventilation do I need/should I have.
The shed is 5 meter long and 2 meters wide.

I’ve attached a picture of the vents over the door and at the rear. Other than those 2 there is nothing.

One suggestion I’ve had is turn 1 or 2 of the sealed windows into something that can open and close.

[formula400]

Front

[Count Steer]

The vents will only do so much. You probably have static air where the mould is. I'd be tempted to get a greenhouse heater (fan heater basically but I assume a bit more robust that the cheapie indoors things - I got a couple, one to keep the condensation at bay in the conservatory and one for my cabin). Just stick it on slow blow and don't worry about using the heat (or set it to come on at 7° - which is what the heaters are set at in the cabin and conservatory. There's a panel heater on thermostat in the cabin, the blower is really only to move the air around or a quick burst of heat if I just pop in for a short visit).

[formula400]

Something like this?

https://www.greenhousepeople.co.uk/prod ... nthracite/

[Count Steer]

Something like this?

https://www.greenhousepeople.co.uk/prod ... nthracite/

Looks a bit deluxe compared with mine.

In some greenhouses they suspend the fan/heater from the eaves but I guess they do a fair bit of air circulation in summer too.

[Mussels]

Years ago I had a 3x4m plastic shed and condensation was a nightmare. I fitted a 5" PC fan attached to a solar panel to draw air out and it sorted the problem straight away.

[Skub]

Something like this?

https://www.greenhousepeople.co.uk/prod ... nthracite/

That'll fatten up your leccy bill if you leave it on permanently.

[Count Steer]

Something like this?

https://www.greenhousepeople.co.uk/prod ... nthracite/

That'll fatten up your leccy bill if you leave it on permanently.

Only needs the fan to move the air around. Can put it on a timer so it does an hour or two a couple of times a day. Then crank up the therms if working in there.

[ZRX61]

Ya don't need much, a small desk top type fan will move enough air.

[formula400]

So move air no heat ???

Does the fan need to rotate or be fixed?

[ZRX61]

So move air no heat ???

Does the fan need to rotate or be fixed?

One that rotates 90deg stuck in corner ... maybe attached to the rafters/roof & angled down a bit. Leave it for a month & assess change in mould.

[Count Steer]

So move air no heat ???

Does the fan need to rotate or be fixed?

Yup, just push the air around. (Heating/cooling air is one of the reasons for condensation 'cos warm air holds more moisture than cold...which is why you get condensation on windows). If the fan is a reasonable size it shouldn't need to rotate. (I find the rotate mechanisms are, generally, a bit frail anyway but, if you have a desk fan, give it a go. The good thing is that the mechanism is mechanical so if it jams it doesn't really matter).

Mussels idea of forced ventilation is the ideal so a Ventaxia or bathroom extract fan would draw air in through the vents as it pushes it out. You can still have dead air spaces though. In a smallish shed it should be pretty easy to stop that problem.

[formula400]

Cool, thanks guys, I’ll get a small fan and timer plug and go from there.

How long do you think I should have it on for???

1 hour morning and 1 hours evening?

[Count Steer]

Cool, thanks guys, I’ll get a small fan and timer plug and go from there.

How long do you think I should have it on for???

1 hour morning and 1 hours evening?

Tricky one. In an ideal world it would either be constant or triggered by the Relative Humidity in the problem area. However, I'd aim the timer at the periods when things are cooling ie afternoon/evening depending on where we are with winter.

[formula400]

How about 2 of these

[Count Steer]

How about 2 of these

No pic but if it's an HG 150mm kitchen/garage extract it should work a treat and run happily for extended periods. I'd think one would do - you'll need a louvre on the outside I guess. @Mussels is probably the best source of info on this as he's done something similar.

Edit...just realised the shed is 5m long. I'd still start with one extract if the mould is around one end only.

[Mussels]

For my 12 sq m shed I used a 5" fan and it worked a treat, solar powered so it was only on when the sun shone. The shed was plastic and had no damp proofing so wasn't off to a good start, it did have holes everywhere so plenty of ventilation.
I'm taking a different approach with my new garden office as I'm sealing it up pretty well and it has me in it often, that's getting a small dehumidifier I just bought and moisture barriers all round.

[MrLongbeard]

No pic

Amazon links don't always play nicely on here, search for B087M4RQH3

[Count Steer]

No pic

Amazon links don't always play nicely on here, search for B087M4RQH3

Yup. That's the 150mm one I found by peering into the link.

I'm a bit surprised the mould has appeared so quickly. Having just had my cabin exterior painted - which involved removing the trim around one of the windows because it wasn't in great shape being on the face most exposed to the sun and the rain and finding some damp in the frame - I'd be giving the exterior a hard stare to check if there's any possible water ingress too.

[formula400]

So I did some investigation today, and I’ve found these water drops on the top of the shed (please excuse the fact there are gaps) they seem to run along the Center beam or what ever it’s called.

So the sheds pretty warm, all the wood inside and along that part feels warm and dry, it’s been hammering it down the last few days as well and I am sure water is Not getting through the roof.

So my guess it’s condensation
And the fan should eliminate that right ?

Going to order something tonight (anyone have a good suggestion on what to order, or just go with my link above)