Ventilating a steel bike shed

[Adsibob]

I have an Asgard steel bike shed. It approximately 1.85m long, 95cm wide and 1.2m high, so just over 2 cubic metres in volume.  It consists of 4 steel sides (one of which is a door) and a flat roof, which I’ve covered in Seedum. It has ventilation holes at either end, but the holes on one ends have been obstructed by us building a low 80cm high wall in front of the shed.
 

The shed contents get mouldy as soon as the temperature drops to autumn/winter temps. There is still a 6cm gap between the shed and the wall, but I suppose it’s much more sheltered from the wind, such that the obstructed holes aren’t doing their job.

 

I’m hoping to fix this issue by drilling 1cm diameter holes into the shed, at a higher point on its walls, ie above where  the 80cm high wall reaches. 

 

Is this likely to fix the issue, and how many holes should I drill? The fewer the better, but I will space them out at regular intervals.

[SteamyTea]

How about a small fan, one from a PC maybe.

https://www.amazon.co.uk/Dealikee-Brushless-120mmx25mm-Computer-Radiators/dp/B0BXWB9T85

 

[gaz_moose]

id probably put some soffit vents in the top of opposing walls. get some with 1mm insect mesh already fitted or glue some on the back. 

[Marvin]

We have 2 sheds. 1 with a waterproofed concrete floor and no condensation problems (no rusty metal things) in 5 years, and one on a block paving floor with condensation problems (rusty metal items) every year. The floor might be the cause.....

 

Marvin

[SimonD]

I'm with @SteamyTea on this. Try to get a fan. I've got a secure metal garage I bought over 20 years ago to store motorbikes. Even with vent holes you get a lot of condensation internally simply as a consequence of the shed material and rapid temperature/humidity changes during the winter - sometimes I've gone into mine and thought the roof has been leaking only to see a lot of water droplets on the ceiling. There are a number of solar powered exhaust fans out there that you could use to help solve the problem, but it probably won't completely solve the issue of condensation on the metal.

[Adsibob]

Well I’ve ended up drilling about 70 holes into the thing, each hole has a diameter of 8mm so I’m hoping this will make somewhat of a difference. We are just storing bikes in there, no tools. Rust doesn’t really effect them as any bare metal is oiled. But mould did grow on some of the rubber bits. 
 

wish I’d known about the waterproofed floor, as we have laid a concrete floor, but there is no DPM. I guess I could paint a liquid DPM onto the floor, but probably won’t make a difference.

 

 If this doesn’t fix it, I will have to get a fan. There is actually some electrical lighting in the bike shed, so hopefully not too complex to run a feed off of that to power the fan, but I’m just a bit confused as to the practicality of such a solution. Would it need to be running 24hr a day or just come on a few times a day to clear the air?

[SteamyTea]

6 hours ago, Adsibob said:

Would it need to be running 24hr a day or just come on a few times a day to clear the air

24/7 as the fan I linked to was under 1 W.  So a couple of quid a year to run.

 

[Adsibob]

On 18/11/2023 at 21:39, SimonD said:

sometimes I've gone into mine and thought the roof has been leaking only to see a lot of water droplets on the ceiling.

So I experienced this today. Avidly searching options. There is an electrical supply to the shed, so it would be fairly easy to rig up a fan. Was there a reason you suggested solar?

[Adsibob]

I’ve found numerous fans that would work, including some very small ones. Do I need them to be IP68 rated? The easiest way to install a 60mm diameter fan for example would be to drill a 55mm diameter hole in the steel shed, probably at the top of one of its sides, and affix the fan from the inside against that hole. But when it’s raining and very windy, the fan would still get a bit of rain on it, even though it is installed on the inside of the shed. 
so should I be considering IP68 fans only? Or is there an easier choice?

[Adsibob]

Just thought I’d update this thread to tell everybody that I fitted a cheap manrose bathroom extractor with humidistat a couple of months ago and we cured the mould issue. The fan is on a lot, but not always. I am hoping that as it gets warmer it will be needed less, but at least bikes are now mould free, however wet they get when they are out.

 

 Prior to realising I needed a fan, I drilled some 50 - 60 holes into the sides of the shed (about two dozen holes on each side and 10 or so at the end). I now wonder if I should cover them up, to create a better barrier so that once the humidity level inside the shed drops, it takes longer to get humid again. Thoughts? I guess I could experiment with some masking tape, but would need to fit a v power meter to the fan circuit to get accurate results and can’t be bothered with that.

[joe90]

9 hours ago, Adsibob said:

I now wonder if I should cover them up,

Air movement is key and the fan is removing it but you need air going in to replace it. You say the mould problem is cured so I would leave it 🤷‍♂️

[Adsibob]

5 hours ago, joe90 said:

Air movement is key and the fan is removing it but you need air going in to replace it. You say the mould problem is cured so I would leave it 🤷‍♂️

Thanks @joe90. To be clear: I wasn’t planning on covering all the holes. Just the ones I added. The shed did come with lots of vents, but costly these weren’t enough.