Insulating a shed.

dashcamdanny · 12-12-2018 12:08pm #1

Trying to insulate my 6x8 shed as cheap as possible.

Im trying to decide between 25mm kingspan which will cost about 150, and foil backed bubble wrap which will cost about 60.

Has anyone used either?

I have machine tools out there and are rusting due to condensation and damp. Plus its not very pleasant to be there at this time of year.

banie01 · 12-12-2018 12:11pm

A dehumidifier is more important than insulation at this stage.
Get the shed as dry as possible before you insulate.
Do you have any heating in there?
What is the shed construction?

dashcamdanny · 12-12-2018 12:19pm

banie01 wrote: »

A dehumidifier is more important than insulation at this stage.
Get the shed as dry as possible before you insulate.
Do you have any heating in there?
What is the shed construction?

Its only a timber shed. I keep a 35w heat tube for green houses running 24 hours as keep my timber stock I use fro projects from getting damp. The problem with condensation is when I go out to work in it. . I use a gas camping heater when in there.
COld steel on my machine tools gets wet as the temp rises. I really need to seal and vent it as well as insulate.

listermint · 12-12-2018 1:46pm

So wait....

Your drying timber stock in the shed... And you want to keep condensation at bay.

Take a step back for a second..

dashcamdanny · 12-12-2018 2:45pm

listermint wrote: »

So wait....

Your drying timber stock in the shed... And you want to keep condensation at bay.

Take a step back for a second..

No. Im not drying anything. I want to keep it dry. I buy expensive exotic seasoned woods for projects.

GreeBo · 12-12-2018 3:23pm

dashcamdanny wrote: »

Its only a timber shed. I keep a 35w heat tube for green houses running 24 hours as keep my timber stock I use fro projects from getting damp. The problem with condensation is when I go out to work in it. . I use a gas camping heater when in there.
COld steel on my machine tools gets wet as the temp rises. I really need to seal and vent it as well as insulate.

It sounds like venting is the biggest issue, if you are condensation problems.
Are you 100% sure the shed is weather tight or is there water getting in somewhere?

listermint · 12-12-2018 3:40pm

GreeBo wrote: »

It sounds like venting is the biggest issue, if you are condensation problems.
Are you 100% sure the shed is weather tight or is there water getting in somewhere?

Or the timber is fully seasoned.

dashcamdanny · 12-12-2018 6:17pm

Its a shiplap shed. There are holes everywhere. No water gets in.

Just wondering if any of ye have experience in insulating them.

GreeBo · 12-12-2018 6:24pm

dashcamdanny wrote: »

Its a shiplap shed. There are holes everywhere. No water gets in.

Just wondering if any of ye have experience in insulating them.

They are not really designed to be retro-insulated (or insulated at all really...)

Insulating it when there is already a moisture problem from an unknown source is going to make a smelly, gooey mess tbh.

You need to address where the moisture is coming from first.

If its a plain old shiplap then depending on how old and how well maintained, the timbers are probably soaked most of the time anyway. Just insulating behind this is going to cause mould.

Lumen · 12-12-2018 7:15pm

I don't agree with ventilating it. You're better off sealing it up and using a dehumidifier draining to a big tank or through the wall to outside.. There's no one living in it, so there shouldn't be a constant source of moisture.

Regarding heating, your 35W is going to do nothing. Even if the shed was air tight, conduction losses through the walls and roof are going to be more than that.

A dessicant dehumidifier will also heat the space.

I would re-think your budget. How much are your tools worth to you?

Lumen · 12-12-2018 7:18pm

Lateral thinking. Put the tools and timber in something like this.

http://www.carcovershop.co.uk/airchamber-protection.asp

my3cents · 13-12-2018 11:22am

The tools would benefit from a coating of wax https://www.axminster.co.uk/axminster-machine-wax-400g-101582

I'm insulating a shed atm. Its shiplap backed with Tuverk so I'm filliing between the uprights with glass fiber and then putting 6mm plywood over the lot. Roof needs some extra work and some additional timber before I can do the same.

The problem is the door its just full of gaps around the edges so I have a massive old thick curtain on the inside.

One shed already done this was an it works reasonable well.

Steve · 14-12-2018 12:46am

dashcamdanny wrote: »

The problem with condensation is when I go out to work in it. . I use a gas camping heater when in there.

The gas heater is likely the source of the moisture, try an electric fan heater instead.

As was said already, ventilation is your friend.

If you are going to insulate, pur a moisture proof membane on the warm side - in winter this will be the inside. Also allow somewhere for any moisture in the insulation to escape (i.e. ventilation).

Fully sealing the enclosed space will just cause more mold and rust.

Lumen · 14-12-2018 8:14am

Isn't it cheaper to dehumidify a sealed space than to heat a ventilated space?

M.T.D · 14-12-2018 12:02pm

If you use a gas heater in a cold room you will get condensation on any cold surface. It will show more on cold metal.
Dump the gas heater and get an electric one.

When I was using a shed as a work room and wanted it to be "cosier" I did a temporary (2+ years until I moved) insulation job.
I used 2 layers of packaging bubble wrap, big bubbles, not foil backed, came in a big roll from Viking. Just stapled to frames Then chipboard over that. The chipboard made the whole structure much more rigid.
I used bubble wrap and hardboard on the roof/ceiling.
For the door, original door with a layer of plastic and chipboard screwed inside.With some extra timber around the frame for doorstop and draft proofing. I Had a 2nd hand double glazed house window that I fitted for light and ventilation.

dashcamdanny · 15-12-2018 1:33pm

M.T.D wrote: »

If you use a gas heater in a cold room you will get condensation on any cold surface. It will show more on cold metal.
Dump the gas heater and get an electric one.

When I was using a shed as a work room and wanted it to be "cosier" I did a temporary (2+ years until I moved) insulation job.
I used 2 layers of packaging bubble wrap, big bubbles, not foil backed, came in a big roll from Viking. Just stapled to frames Then chipboard over that. The chipboard made the whole structure much more rigid.
I used bubble wrap and hardboard on the roof/ceiling.
For the door, original door with a layer of plastic and chipboard screwed inside.With some extra timber around the frame for doorstop and draft proofing. I Had a 2nd hand double glazed house window that I fitted for light and ventilation.

Thanks you everyone for the tips.

This is what im after.

Did you find much improvement in the comfort of the shed?

M.T.D · 15-12-2018 2:39pm

Made a huge difference.
Small blow heater used to warm the place quickly.
Moved my office in there one Christmas, to free up room in the house, and never moved it back.
Remember to insulate the floor.

Calahonda52 · 15-12-2018 2:47pm

As noted earlier, the sources of moisture in the air in the shed are
you
the gas heater: big source
some from the timer, maybe

depending on the value/portability of the tools: make an insulated box for them and keep it heated, maybe a devimat
unless the tools are kept at a higher temp than the dewpoint, then moisture will condense out.
http://www.dpcalc.org/

recedite · 18-12-2018 1:04pm

I reckon the moisture is coming from
1. gas heater
2. humid outside air blowing through the gaps
3. human lungs/breath while working in the shed.

I'd suggest lining the shed with a breather membrane instead of insulating it.
Don't add ventilation, but do install a dehumidifier draining through a hole to the outside (will require an electricity supply, but you have that already for the 35W heater) Net result should be a lower ESB bill.

Also, orienting the window towards the south will help (picks up solar gain)
if the shed is empty it is quite easy to shift or rotate it small distances using a long lever or crow bar. That might also require shifting the blocks around under it.

GreeBo · 18-12-2018 1:58pm

recedite wrote: »

I'd suggest lining the shed with a breather membrane instead of insulating it.
Don't add ventilation, but do install a dehumidifier draining through a hole to the outside (will require an electricity supply, but you have that already for the 35W heater) Net result should be a lower ESB bill.

What will a breathable membrane do to help condensation in this scenario? (without insulation)

my3cents · 18-12-2018 2:09pm

GreeBo wrote: »

What will a breathable membrane do to help condensation in this scenario? (without insulation)

The membrane stops drafts any half decent shed will have one in place on the frame under the timber cladding. If there is one already a second one will create an air gap which should help keep the shed warmer. If there is no membrane under the cladding then putting one on the inside will just cut out the drafts.

Its breathable so your shed doesn't rot from the inside out. Any non breathable membrane will stop and collect moisture that can rot the timber.

GreeBo · 18-12-2018 2:16pm

my3cents wrote: »

The membrane stops drafts any half decent shed will have one in place on the frame under the timber cladding. If there is one already a second one will create an air gap which should help keep the shed warmer. If there is no membrane under the cladding then putting one on the inside will just cut out the drafts.

Stopping air movement/drafts when you have a condensation problem is probably not wise...

Also the air gap between two breathable membranes isnt going to add any meaningful insulating benefit.

Its breathable so your shed doesn't rot from the inside out. Any non breathable membrane will stop and collect moisture that can rot the timber.

The shed will rot if you condensation on the inside and a barrier stopping air movement.

You need to remove the cause of the excess moisture.

recedite · 18-12-2018 11:13pm

As well as stopping the humid outdoor air blowing through, if used in conjunction with a dehumidifier a breather membrane can help retain the dehumidified air inside the shed.

There's not much point trying to heat a shed 24/7 when what you really want is a dry shed. For the short time you are in there, just heat it with a plug-in electric heater from power city. It will heat up very quickly.

If the shed is not heated 24/7 then the insulation is a waste of money and effort.

Lumen · 19-12-2018 9:22am

I don't understand the logic of combining a dehumidifier with a vapour permeable membrane.

recedite · 19-12-2018 10:27am

Lumen wrote: »

I don't understand the logic of combining a dehumidifier with a vapour permeable membrane.

Purely in theoretical terms, you have a point.
I'm thinking more in practical terms, for a shed. There is going to be more vapour coming in from gaps in the floor and the door than through the membrane. The dehumidifier can deal with that.

If you line the shed with plastic, there is going to be condensation and water droplets on that plastic somewhere, collecting and soaking into the adjacent timber. And that's where the rot will begin. There is always some small tear, or overlap, or nail hole.

Droplets just will not accumulate on a breather membrane, but it still keeps out most of the (humid) draughts and contains the dehumidified air inside the shed.

Lumen · 19-12-2018 11:26am

Yeah, it just seems that the only way you're going to prevent dew inside an unheated shed is by having it sufficiently air tight and vapour impermeable so that the atmosphere inside is dry enough to avoid the day/night dew cycle. You're aiming for consistently lower absolute humidity than outside.

Air tight floor is easy, glued T&G OSB will do that. The door is a bit harder.

my3cents · 19-12-2018 11:30am

Lumen wrote: »

Yeah, it just seems that the only way you're going to prevent dew inside an unheated shed is by having it sufficiently air tight and vapour impermeable so that the atmosphere inside is dry enough to avoid the day/night dew cycle. You're aiming for consistently lower absolute humidity than outside.

Air tight floor is easy, glued T&G OSB will do that. The door is a bit harder.

The starting point here is a shed that is just cladding on a framework. Anything non permeable up against the wood is going to cause rot.

hesker · 19-12-2018 12:12pm

Lumen wrote: »

Air tight floor is easy, glued T&G OSB will do that.

I think there is plenty of evidence against this. Depends on the origin and thickness of the OSB

listermint · 19-12-2018 12:17pm

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

hesker · 19-12-2018 12:19pm

Lumen wrote: »

Air tight floor is easy, glued T&G OSB will do that.

I think there is plenty of evidence against this. Depends on the origin and thickness of the OSB

Lumen · 19-12-2018 1:13pm

hesker wrote: »

I think there is plenty of evidence against this. Depends on the origin and thickness of the OSB

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.

recedite · 19-12-2018 1:55pm

listermint wrote: »

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

If it wasn't for "her"

recedite · 19-12-2018 1:58pm

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 · 19-12-2018 2:57pm

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 · 19-12-2018 4:08pm

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 · 19-12-2018 5:01pm

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 · 20-12-2018 1:31am

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

Lumen · 20-12-2018 7:43am

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 · 20-12-2018 3:11pm

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 · 20-12-2018 3:55pm

dashcamdanny wrote: »

Did you not hear.

He said its very special bubble wrap.

It's argon-filled, right?

my3cents · 20-12-2018 3:58pm

Lumen wrote: »

It's argon-filled, right?

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

GreeBo · 20-12-2018 4:28pm

Draft tight, which is the issue in most cases anyway

dok_golf · 20-12-2018 11:57pm

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?

recedite · 21-12-2018 3:28pm

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 · 22-12-2018 12:15am

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 · 22-12-2018 11:14am

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 · 03-01-2019 12:44pm

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.

Insulating a shed.

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