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Mancave insulation

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Rob Wheatley11/06/2021 12:08:29
35 forum posts
12 photos

Hi all, finally getting around to insulating and boarding the Mancave over the next few weeks but have a question about the insulation.

The building is a 3m x 6m wooden "shed" 75x47mm frames with 20mm wooden cladding boards, I intend to put 9mm ply or osb on the inside for walls and want to put insulate the void, I did think about 50mm polystyrene or kingspan boards (very expensive) also rockwool but have found 25m x 1.2m silver "bubble" rolls for £75 each, 3 will do the whole thing.

Anyone used this sort of stuff and most importantly is it any good, blurb says it's equivalent to 65mm of rockwool which is about what i would get in the gaps but then have to think about damp and critters, the walls will be totally closed off but sure something will get in.

Thinking if the foil stuff works, damp is no problem then and if it is flat to the inside boards air can flow around the void to ventilate them.

Jeff Dayman11/06/2021 12:34:12
2178 forum posts
45 photos

Just a side note for whatever insulating material you use in the cave-

Check its' flammability rating if you plan to use soldering torches, welding equipment, or even angle grinders on ferrous materials in the shed. Best to have all fire-resistant materials if possible. I believe rock wool has low flammability. If the silver bubble rolls you mention are polyethylene film based, they may be quite flammable.

Speedy Builder511/06/2021 12:52:42
2416 forum posts
191 photos

Rob, I have used similar on my house here in France (-14 in winter +40in summer Deg C). Blurb says its as good as 200mm glass wool. Its NOT. Yes it gives a waterproof lining (Guaranteed for 20 yrs). I have since doubled up and put a second layer over the ceilings and marginally better. My workshop also has this space age multilayer stuff on top of 15mm boarding. It helps and doesn't take up much space, but there are better alternatives.


Douglas Johnston11/06/2021 13:18:56
760 forum posts
34 photos

I insulated a similar sized wooden shed about twenty years ago with the foil bubble wrap stuff and it does seem to work pretty well. One of the biggest benefits is keeping the inside temperature down in the summer. Before fitting the insulation the shed was unbearably hot in the summer but became much more pleasant after the insulation was fitted.


HOWARDT11/06/2021 13:32:05
780 forum posts
28 photos

I bought my shed new about 15 years ago, so good test of time. After putting it up I stapled polythene sheet to the inside, I think it was damp roof membrane sheet as it is thick and easy to use. Then I put mineral wool batts between the uprights, both walls and ceiling. Finally I boarded the inside with plasterboard, if I did it again I would use thin osb. Some board got wet when I had a roof leak and replaced the plaster board with 3mm packing ply, the sort of stuff used for making transport boxes, it’s probably the cheapest sheet material you can get. The only thing I haven’t done is the door, but if I spent more time in there I would make better fitting doors.

Journeyman11/06/2021 14:17:25
1035 forum posts
200 photos

I have 2" rockwool in the walls and 4" rockwool in the roof of my home built timber workshop. Works very well with the reclaimed double glazed windows. Cool in summer and only needs minimal heating in winter to maintain a workable and condensation free temperature.

If I were doing it again I would probably use Kingspan / Cellotex despite the price, seems to be the insulation of choice in most new build houses these days.


Samsaranda11/06/2021 15:51:48
1214 forum posts
5 photos

I used an aluminised plastic bubble foil to insulate one of my beehives last winter, I used one layer around the side walls, on the outside, when we had frosts it was covered in frost except for a large circle which coincided with where the bees were clustered inside, obviously radiated heat from the cluster which can be quite warm. Other beekeepers locally lost a few hives due to the winter weather but my bees survived well, so the bubble wrap type insulation’s are effective but of course you need to be wary of flammability. Dave W

jaCK Hobson11/06/2021 15:55:33
217 forum posts
76 photos

I'm guessing this is the sort of stuff:

That has a thermal resistance of 1.5 W/m3K

100mm of fibre glass is a bout 2.85

This 40mm stuff suggests 2.5 so a much better option for you.

Kingspan/Cellotex is better.

I decided to go Fiberglass - cost and easy (except I hate to handle the stuff)

jaCK Hobson11/06/2021 16:12:17
217 forum posts
76 photos

I'm adding a breathable membrane on the outside. Those ^^ figures for glass dissapointed me a bit so I might top it up with this for the membrane.

If that don't do it, then I need to make the walls thicker

Rod Renshaw11/06/2021 16:30:07
337 forum posts
2 photos

Despite the sales pitches, anything thin is likely to be a poor thermal insulator though it may make a good vapour barrier.

.The best insulator is air but it needs to be trapped in something porous or fibrous to stop convection currents taking the heat away. And there needs to be a reasonably thick layer of it, 2-4 inches perhaps, more is better. Loft insulation material is likely to be the most cost effective easily available insulation.

Conventional wisdom suggests:

If your shed is timber framed, then vapour barrier ( suggest thick, 5000 gauge, polythene but other products are available) fixed to the inside of the frame, and then covered with ply etc to screw shelves to.

And loft insulation wedged in the spaces within the framework,

Then builders' (breathable) paper ( which is waterproof but not water vapour proof), fastened to the outside of the frame.

And then the outer cladding.

Then if any water does get into the insulation, it can dry out through the builders' paper and the cladding.


Pete Rimmer11/06/2021 16:44:21
1075 forum posts
69 photos

Where in Kent are you Rob?

Howard Lewis11/06/2021 18:04:54
5348 forum posts
13 photos

My shop is 6'9" x 10'9" external, with 19 mm cladding on 50 mm frames with 12 mm lining, on three walls The door end,carrying a fire door is 100 mm thick. 8' high at the front, 7'6" at the rear.

No windows, for security, and would be covered by the shelves, anyway!

The firedoor has a 6 lever lock, and hinge bolts.

The roof is 12 mm ply on both faces of the 50 mm frames. All the voids are filled with glass fibre

Originally, the roof was felted, but is now covered with a rubber sheet.

The floor is 18 mm ply on 8 x 2 frames.

being in temperate climate, a 2 Kw fan heater soon makes it cosy, and the thermostat shuts it down in less than 15 minutes. After that it runs for short periods.

The small walking area of the floor is covered with raised plastic mats. (Good insulation and for storing swarf ready for twice yearly cleansing! )



Nigel McBurney 111/06/2021 18:58:49
926 forum posts
3 photos

We have a proffesionally built timber stable block,weatherboard externally, over breathable membrane,one unit is only covered internally up to 4 ft high with plywood ,the remainder is not covered and the membrane is exposed,this membrane has fell apart and reallyuntidy, Our bungalow roof was old style felt and batten under the tiles,severe storm damage involved the whole roof covering and battens being replaced the new covering is black permeable membrane which is supposed to repel water, which it did not and the loft is noticeably colder. My workshop is 120 year old second hand timber tongue and groove externally over a layer of building quality polythene,the 2inch cavity is filled with fibre glass loft insulation.inside is a further layer of tongue and groove. Now every building guide states that membranes must be permeable,well on my workshop the pothene works well (14 ft sq) is warm ,dry,no rot or fungus on the timber,been there for 35 years and and still in good condition

Rob Wheatley11/06/2021 19:54:41
35 forum posts
12 photos

Thanks for the answers guys, so thinking 50mm rockwool with a vapour barrier would be the safest bet then, 60m² is about £200 plus the barrier, 3 rolls of the bubble would be £225.

Did put a breathable barrier behind a lot of the cladding but one side does get a bit damp if it rains very hard, typical it's the side I cannot get to, think its where the rain comes off the roof and hits the fence rails next to the wall bouncing into the side.

Will staple the barrier in first then the insulation.

I'm in the medway towns Pete, are you in Kent too then?

Pete Rimmer11/06/2021 21:14:34
1075 forum posts
69 photos

I'm in Gravesend. I might be able to sort you out with some insulation but I won't know until next week. They have (or at least had) some on site this week that was getting chopped up and thrown away.

Rob Wheatley11/06/2021 22:49:17
35 forum posts
12 photos

Oh cool, I won't be starting it until probably Thursday, if I can get the ply delivered, insulation was going to be from wickes or B&Q.

Any idea of what thickness it was?

How much do you want for it?

Pete Rimmer12/06/2021 06:23:55
1075 forum posts
69 photos

Thickness was probably 30 or 40mm but don't let that put you off my own workshop uses the same type of insulation and I get no condensation at all, plus it;s very cool in summer.

This stuff is being used as transport protection boards for some very expensive insulated wall panels. They make a big pile of them then cut them all up and skip them. If there's any left I'll try to get you some. If I can it won't cost me anything so I'll charge you the same.

Terry B13/06/2021 08:59:46
14 forum posts
5 photos

In February I lined the underside of my garage/workshop asbestos roof with "Recticel Instafit Insulation Board" from B&Q.

Before I fitted it In previous summer it used to get too hot to work in there and in winter frost on the underside of the asbestos roof.

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