Shed venting

[Gragson]

I've got a fairly new 8 x 10 shed, apex roof, barn white painted inside, rubber floor down over wood floor, 4 glass windows that don't open and double doors. Timber panels were outside for a bit and did get rained on fairly often. Base is fairly well raised on slabs. With all that described. it feels colder and damper inside shed than outside, put a remote weather sensor in there and it tracks around 20% higher relative humidity inside than outside when the doors have been shut for a while.

Not going down the insulating root as this shed will be used to work in hot or cold

What I'm looking for advice on is louvre vent placings for better air flow to help bring the dampness/humidity down.
I've read that on e.g. greenhouses you want them bottom and top to let airflow in lower and warmer air out at the top. But thats for growing plants..

Any advice on where I should place louvre vents on a shed that will be closed up at night to bring down the RH?

 

[Danez]

I've got a fairly new 8 x 10 shed, apex roof, barn white painted inside, rubber floor down over wood floor, 4 glass windows that don't open and double doors. Timber panels were outside for a bit and did get rained on fairly often. Base is fairly well raised on slabs. With all that described. it feels colder and damper inside shed than outside, put a remote weather sensor in there and it tracks around 20% higher relative humidity inside than outside when the doors have been shut for a while.

Not going down the insulating root as this shed will be used to work in hot or cold

What I'm looking for advice on is louvre vent placings for better air flow to help bring the dampness/humidity down.
I've read that on e.g. greenhouses you want them bottom and top to let airflow in lower and warmer air out at the top. But thats for growing plants..

Any advice on where I should place louvre vents on a shed that will be closed up at night to bring down the RH?

On my shed I've got a vent louvre above the door and another one at the back, same position/height.

One thing i need to do though as in heavy rain a bit of water can get in so I've been considering getting some sort of mesh to go behind it?

 

[tigdlo]

As you need air flow then opposite corners one low and one high, the further apart the better. Venting will help it dry out but preventing ingress of moisture would be better.

 

[Melvyn Best]

I had condensation problems when my shed was first built, it is insulated, the walls and ceiling lined with 12mm ply. It had a vent at the top of the double glazed window . In the end I put a vent in the bottom of the door so air circulates , since then I have had no problems

Must type faster

 

[addjunkie]

Computer type fan inside running all the time to move the air too.

 

[gaz1]

As you need air flow then opposite corners one low and one high, the further apart the better. Venting will help it dry out but preventing ingress of moisture would be better.

is the shed barn infilled on the walls ?

note putting vents in will make it red hot in summer as well if its hot outside

 

[Alan Reynolds]

Oddly i had an opposite problem. My new 18x8 pent roof shed had the front and back roof edges with open areas and the shed was damp and cold. In fact because the wind flowed in the front and out the rear, my bald head got frozen. I sealed the open areas with tight fitting ply and it’s now completely dry and you can feel it’s noticeably warmer than outside.there is no insulation but a 2k fan heater warms it up quickly and has to be turned down to 1k in a very short time. The cladding is 20mm thick though.

 

[Blobber]

Pesonally I would insulated, will keep the cold out in winter and the heat out in summer

 

[Gragson]

On my shed I've got a vent louvre above the door and another one at the back, same position/height.

One thing i need to do though as in heavy rain a bit of water can get in so I've been considering getting some sort of mesh to go behind it?

The ones I'm spying are mesh integral behind, on the rare occasion I might get horizonal blown in rain through the vents I'm not sure I can do anything about it other slow down airflow with more mesh behind. Rare tho.

As you need air flow then opposite corners one low and one high, the further apart the better. Venting will help it dry out but preventing ingress of moisture would be better.

Noted, thanks, will look at that vent spacing, moisture ingress does not appear to be the issue, if anything its too moisture/air flow proof internally.

@Melvyn Best I hear you, cheers

Oddly i had an opposite problem. My new 18x8 pent roof shed had the front and back roof edges with open areas and the shed was damp and cold. In fact because the wind flowed in the front and out the rear, my bald head got frozen. I sealed the open areas with tight fitting ply and it’s now completely dry and you can feel it’s noticeably warmer than outside. there is no insulation but a 2k fan heater warms it up quickly and has to be turned down to 1k in a very short time. The cladding is 20mm thick though.

This is a 20mm clad shed allegedly/mostly but nowhere near the size of yours.

Pesonally I would insulated, will keep the cold out in winter and the heat out in summer

Ya big poof - but I might well do come autumn, its for dirty work mostly grinding wheeling etc so see how it goes through summer to get the RH down.

Vents ordered anyway and will be sited given advice - thanks a lot gents

 

[gaz1]

This is a 20mm clad shed allegedly/mostly but nowhere near the size of yours.

but mines the same as yours and i have a flat roof on mine

its also solid red brick walls

loverly and cool in summer as ive retreated there sometimes on a red hot day

nice and warm if i put the rocket stove on, infact way too hot in there in no time i find

is it better insulated oh yes and i have a solid steel door on it and because i have a wall gap between 2 walls it does allow some air to escape up between them at the door

bottom of the door its got a gap on it as well

 

[minimutly]

A lot depends on where you live. We live facing the westerly winds off the Irish Sea - it’s wet a lot, even when it isn’t raining. So I decide when to ventilate, and when to run my dehumidifier.

 

[Ross365]

I installed louvre vents in my (very old) 10x8 last autumn to try keep humidity down after I found things were tending to rust too much. I put them as high as I could near the apex at the the end walls, one above the door, one on the far end. I don't have any measurements, but I do feel that they have worked and I'm glad I did it.

 

[Aerohead]

Same as Ross365 for my metal shed, plus full DPM under the patio slabs on sand floor and never had any metal shed moisture.

Screening on the vents cuts way down on bug visitors.

 

[Gragson]

Went with the above advice and placed 2 screened type at either ends (inside an out, so 8 total) way up directly opposite.
The RH is now tracking 15 - 20 % lower on wet days which is a big difference as was tracking around 10% over compared to outside.

 

[MattF]

A good through flow is helping then?

 

[Ross365]

It may be more a case of warmer air (carrying water vapour) convects up and out rather than through flow. Those RH measurements really do show how effective the vents are, irrespective of quite what the mechanism is!

 

[Gragson]

It may be more a case of warmer air (carrying water vapour) convects up and out rather than through flow. Those RH measurements really do show how effective the vents are, irrespective of quite what the mechanism is!

Yes I think it is exactly this, when I used to have the doors closed it would creep up and by morning the RH would be well above outside. It was just too air tight after I had filled gaps in the eves.

A good through flow is helping then?

Definitely the mrs is now asking for the same in her shed pad thing - but priorities and all that...

 

[MattF]

It may be more a case of warmer air (carrying water vapour) convects up and out rather than through flow. Those RH measurements really do show how effective the vents are, irrespective of quite what the mechanism is!

It does seem a confusing affair, airflow, relative humidity etc. At least to me. You'd think that when it's pulling in air, it would be the same as outside, yet the values can differ. I'll never understand this malarkey.

 

[Gragson]

Admit I am only going by these remote weather sensors (which i have an unhealthy obsession with - 7 dotted around and all I need to do is look out the f*ing window!)

But as well as the numbers there is a notable difference in the feel when opened up and no dew on the inside windows.

Wanting to keep tools and gear n there and RH is a big no no for that

 

[eLuSiVeMiTe]

A good through flow is helping then?

I didn't have quite enough ply left over when I made my door so I left a 2" gap at the top.
Done a good job of venting and 5 years later still dry as a bone inside