Shed roof insulation

JohnBoy

Hi,

Slightly out of the ordinary question for the insulation experts.

I'm building a steel shed at the moment. for use as a garage/workshop.

I'm considering throwing some wool into the walls and roof and I'm wondering if anyone has an opinion on whats being suggested to me.

from the bottom up
chipboard/ply/osb
4 inches of wool in a 4 inch cavity
slaters felt
steel cladding.

I'm not looking for any sort of super performance, to be honest I'm more interested in keeping it cool in the summer time than keeping it super warm in winter, just maybe not brass monkeys cold.

I'm gonna be lining the interior with the ply anyway so I'm figuring why not stick some wool in there while I'm at it.

my main concern is condensation on the cold steel roof.

I know that kingspan et al do lovely composite insulated panels. these also have lovely prices though.

RKQ

It really depends on what you will use it for.
It might be easier to install 8 x 4 sheets of aeroboard to the walls, 100mm thick.

Condensation can be a big problem, which is solves by composite panels.
It is possible to install wool. Have a look at manufacturers web pages for details /specifications etc.

Most people install plastic sheeting below the cladding, with an air gap, which seems to solve the condensation problem.

(Opening the structure daily, allowing the wind in will keep it dry) Avoid using chipboard as it soaks up moisture, swells and degrades.

sydthebeat

In order to keep it cool in the summer you will need to incorporate a heavier insulation than EPS or PU / PIR. I think the 4" of rockwool is a good idea in this instance. The rockwool would actually absorb more heat than lighter insulations, plus the stud structure can be used as a service cavity as well.
Make sure the felt is breathable.
Make sure the OSB is breathable. Some manufacturers use glues that are non breathable. If unsure use chipboard.
I will assume the stell cladding is profiled thus there will be a certain amount of ventilation around the structure. This is also necessary.

JohnBoy

one man says to use chipboard, one doesnt.....

hmmm

rkq if you're suggesting what I think you are and to use aeroboard and not finish it (maybe you're not) then no way hosea. there'll be an occasional spot of welding going on, exposed aeroboard would be verrrrrrrrrrrrrry dodgy.

plus wool is ten times handier to cut and fit than aeroboard. less messy too.

yeah the steel is regular box profile so it should ventilate nicely above the felt.

sydthebeat

The reason i said chipboard is that, as RKQ correctly states, it absorbs moisture. However, with his construction the moisture can go nowhere, thus would decay. My construction would allow this moisture pass all the way to the steel cladding and be ventilated off. Both constructions are acceptable..... either allow for breathing or dont.

I would still prefer rockwool due to the heavier insulative property.

RKQ

No way hosea. I'd never suggest leaving Aeroboard exposed! Kids in there for one hour and you'd have Santa's Grotto! Shelves wouldn't stay up either.

Wool is easier to install, certainly in roof.
But it can slip down in walls, leaving gaps at top.
Aeroboard is cut with a saw or melted with large battery and thick wire.

Its a shed so air tightness shouldn't be an issue.:D

Just to be clear, I'd finish walls internally with ply or osb ( never chipboard )

JohnBoy

ah, ok, i was wondering alright.

Chipboard would be my preference to be honest.

it's cheap, available in 8x2 t&g and has a reasonable finish.

ply is more expensive but has a nice finish, but I dont think it's available t&g

osb is in between, available in t&g 8x2 but has a nasty finish. (although i think t&g osb is pricey)

RKQ

Would chipboard on the ceiling be cheaper than another metal skin?

I would ply walls where shelves were going and chipboard rest of wall.

I seen a trendy shop completely lined with varnished osb, looked quite well to be honest. Osb is very strong but you still get a better fixing in ply IMO.

Good luck and keep us updated with you decision and the final result.:)

JohnBoy

chipboard would be cheaper than plain galvanised sheet, so I'd imagine it'll be cheaper than a dedicated ceiling cladding.

This is what i'm building, as of last night