Insulating a shed.

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listermint wrote: »

There is an obvious solution to this. Do all your work in the Kitchen.

If it wasn't for "her"

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Lumen wrote: »

Interesting. Maths time...

4.5sqm of 18mm OSB3 flooring with permeability of 0.38m3/m2/h at +50pa is going to let through 1.7m3 of air an hour containing 13g of water @ 100% RH @ 10C. So that's 320ml in 24 hours. But 50pa is only the test pressure, in reality it's going to be far less than that, and you only need to bring the humidity down enough to avoid condensation.

So I don't think dehumidifying an OSB3-lined shed is going to pose much of a challenge to a decent humidifier.

Losses from the door and walls are going to much higher.

Your OSB lining is acting like a harder wearing (and harder to install) breather membrane. It would be a good job though, combined with the dehumidifier.

hesker

Lumen wrote: »

Interesting. Maths time...

I have no real interest in this thread. Only picking up on the point re OSB.

Your maths is dependant on the permeability rating. Does OSB come with a certified permeability. Evidence on the web is that it is highly variable and some of that evidence comes from case studies here.

Lumen

hesker wrote: »

I have no real interest in this thread. Only picking up on the point re OSB.

Your maths is dependant on the permeability rating. Does OSB come with a certified permeability. Evidence on the web is that it is highly variable and some of that evidence comes from case studies here.

Some of it does, e.g. of this list of Smartply OSB3...

https://mdfosb.com/en/smartply/downloads

the only one I could find with air permeability numbers was the Propassiv product:

https://mdfosb.com/assets/uploads/downloads/SMARTPLY-PROPASSIV.pdf

...which isn't something I've come across in my local builders providers and appears to be about twice the price:

https://www.mcdonoghdirect.ie/smart-osb-plywood-c102x3405233

I was taking my OSB3 numbers from an empirical study here:

https://www.researchgate.net/publication/270287114_Air_permeation_rate_of_oriented_strand_boards_OSB3_and_OSB4

Note: the numbers in that study for ordinary OSB3 are MUCH higher than the ProPassiv, 0.38 vs <0.005.

hesker

Lumen wrote: »

Some of it does, e.g. of this list of Smartply OSB3...

https://mdfosb.com/en/smartply/downloads

the only one I could find with air permeability numbers was the Propassiv product:

https://mdfosb.com/assets/uploads/downloads/SMARTPLY-PROPASSIV.pdf

...which isn't something I've come across in my local builders providers and appears to be about twice the price:

https://www.mcdonoghdirect.ie/smart-osb-plywood-c102x3405233

I was taking my OSB3 numbers from an empirical study here:

https://www.researchgate.net/publication/270287114_Air_permeation_rate_of_oriented_strand_boards_OSB3_and_OSB4

Note: the numbers in that study for ordinary OSB3 are MUCH higher than the ProPassiv, 0.38 vs <0.005.

Yes the Propassiv stuff is certified but not easy to obtain. I could not get a local builders providers to stock some for me. I even tried to get the agent to leverage but no use. You’d need to be doing a whole house.

The regular OSB is variable from what I have read of studies done and OSB3 is more permeable than the others iirc.

dashcamdanny

https://www.youtube.com/watch?v=nMoeqeyjUis

Lumen

dashcamdanny wrote: »

https://www.youtube.com/watch?v=nMoeqeyjUis

I'd say almost all the gains from that foil covered bubble wrap are from air tightness rather than insulation. Reflective coatings are snake oil since radiation losses are negligible, and you need thickness for conductive insulation.

dashcamdanny

Lumen wrote: »

I'd say almost all the gains from that foil covered bubble wrap are from air tightness rather than insulation. Reflective coatings are snake oil since radiation losses are negligible, and you need thickness for conductive insulation.

Did you not hear.

He said its very special bubble wrap.

Lumen

dashcamdanny wrote: »

Did you not hear.

He said its very special bubble wrap.

It's argon-filled, right?

my3cents

Lumen wrote: »

It's argon-filled, right?

And still gas tight when you put a staple through the bubbles.

GreeBo

Draft tight, which is the issue in most cases anyway

dok_golf

Sorry to jump in on this thread, but, with a steel shed, do you need to put vapour barrier between the steel and the insulation?

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dok_golf wrote: »

Sorry to jump in on this thread, but, with a steel shed, do you need to put vapour barrier between the steel and the insulation?

If it was me, I'd prefer to be able to see the steel, and keep an eye on it.
But if you're going to insulate it, the general principle is to put a vapour barrier on the warm side of the insulation.

dok_golf

The shed is for drying furniture after spraying. The interior side of the insulation boards will have 1000-1200 gauge plastic on it anyway. When we built our timber frame house, we had to put vapour barrier across the studs ( after putting in the rockwool insulation ) so that it ran along the back of the plaster boards. Just wondering if the same theory would be appropriate here.

recedite

dok_golf wrote: »

The shed is for drying furniture after spraying. The interior side of the insulation boards will have 1000-1200 gauge plastic on it anyway. When we built our timber frame house, we had to put vapour barrier across the studs ( after putting in the rockwool insulation ) so that it ran along the back of the plaster boards. Just wondering if the same theory would be appropriate here.

Reason for your TF walls being like that is that if water vapour passed through the rockwool it would reach its "dew point" on the cold (exterior) side of the insulation, and collect there as condensation.
But TF walls also have a ventilated cavity between the timber stud wall and the outer leaf wall. Your steel shed would not have that. So if dampness got between the steel and the insulation somehow, how would it dry out? Would the steel be rusting away, on its interior surface, out of sight?
A shed is a shed, its not really designed to be insulated.


Because of your paint fumes, you probably need ventilation there, and not a dehumidifier. Maybe the best solution is a low wattage heat source combined with a throughput of air. So if the door is already a bit draughty, install a small vent at the far end.

Shed would not warm up because no insulation. However the small amount of heat would change the "relative humidity" of the air inside, ie the air would tend to dry out the contents of the shed more than unheated air. The heat would only need to be switched on in damp or humid weather.
In principle then, the small bit of heat is not to make the shed warm, it is to increase the water carrying capacity of the air inside the shed.

dashcamdanny

Massive difference. Got a little shop heater from screwfix and a 25m roll of foil bubble wrap for 50 euro.

Toasty.. And my equipment and materials are warm and dry.