Insulating storage room in shed

Wavehopper

Hi all, I'm looking for a bit of advice on how best to insulate an unused stable I have inside my shed.
2 x external walls and 2 x internal walls are 6" block on edge and external and internal walls are plastered
Stable is 15ft x 10ft and 8ft high (stable itself isn't roofed separately - it is open right to apex of the shed)
I want to use this for storage for things I want to move out of the house that I don't want getting damp and tools that are starting to rust in the shed

Here is what I was thinking:

Floor:
1200guage dpc
4" x 2" frame (studs at 600mm centres)
100mm PIR insulation in-between frame
18mm OSB board screwed to frame

Walls:
3" x 2" battens with dpc glued to wall side of batten - battens at 600mm centres
100mm PIR insulation (screwed to battens just to hold in place until OSB board fitted)
11mm OSB board screwed through insulation into 4" x 2"
(Would I be better fixing a 4" x 3" timber stud to the battens and insulating in-between the studs and then OSB board screwed into the stud?)

Roof:
One wall is 8ft high, other 3 walls are higher as part of main shed
But I can run joists from the 8ft wall to a purlin on one external wall (span is 10ft)
6" x 2" purlin on top of 8ft internal wall
6" x 2" joists (10ft long) over to external wall (there is already a purlin at right height)
100mm PIR insulation between joists at 400mm centres
11mm OSB board on bottom of joists
18mm OSB board on top of joists (for additional storage on top)

Would an air-tightness membrane taped the whole way around the room after insulation is fitted before OSB board is fitted be complete over-kill or not make any difference to how warm the storage room would stay?
If it would make a difference, I'd take the cost and effort of doing it - I just don't know if it's worth it.

Any advice on above would be appreciated.
Thanks.

MicktheMan

What is your heat source?

Wavehopper

Hi MicktheMan,
I was thinking of a Dimplex Quantum RF Storage heater, likely 700W which is rated for up to 14sqm. I might even get away with 500W with the level of insulation and the size of the storage room and the fact that this isn't a living space.

Wavehopper

I was looking into how best to insulate this storage room some more and here is what I'm now thinking:

Floor:
1200guage dpc
100mm PIR insulation (taped at seams and edges with wall insulation)
18mm t&g OSB board as floating floor

Walls:
3" x 2" battens with dpc glued to wall side of batten - battens at 600mm centres
100mm PIR insulation (screwed to battens just to hold in place until OSB board fitted)
11mm OSB board screwed through insulation into 4" x 2"

Roof:
6" x 2" joists (10ft long) over to external wall
100mm PIR insulation fixed under joists (taped at seams and edges with wall insulation)
I'm not going to sheet under this, just leaving insulation sheets as the ceiling
18mm OSB board on top of joists (for additional storage on top)

Wavehopper

Do I need to consider any ventilation in this room with insulation and heater?
If I do, any advice on how best to that?
Could I put 4" pipe and vent on one of the internal walls into other part of shed which is already well ventilated and not as cold as vent out to external wall?

blackbox

Even sub-zero temperatures won't cause damage to your tools etc.

You need to concentrate your efforts on keeping them dry, not warm.

Wavehopper

Thanks blackbox
Should I consider a small dehumidifier in the insulated storage room rather than a heater then so?
e.g. something like this that has option of a drainage hose that I can plumb to outside trap. This has auto switch off depending on humidity so it shouldn't be costly to run

Meaco DD8L Dehumidifier | Buy in Ireland

monseiur

Re. floor - before you proceed double check if the DPM/visqueen should be under or over the insulation. In flat roofs for example it has to be on the warm side of the insulation - I have a feeling that is also the case in your situation so have a chat with an expert first.

Yellow_Fern

You want to create a space that can stick to 50% relative humity and and above 10c.

Calahonda52

Damage to the tools is caused as follows.

Tools get to say 5 degrees and then there is a sudden blast of warm moist air introduced, moisture in the air condenses on the cold tools as they don't heat up in time.

Fingerprints on metal surfaces are also attractive so a quick rub down with WD 40 helps here

So keeping the RH down is key, if u have it too low you may warp the timbers so the 50/10 guidance above by YF is a good compromise.

The dehumidifier, some of which heat as well, idea points to open shelves and maybe even a small circulation fan to avoid stagnant moist air hiding in closed presses

Lumen

Have you priced this up yet?

If you just need to keep a few tools in a humidity controlled environment, a car bubble would do it.

Wavehopper

Thanks for replies and suggestions on this. Yes Lumen, I priced this up at around €1500 and have some of the materials got already. Good suggestion re bubble but I think I'll go ahead with the storage room as planned. I want to put shelving in and store some larger items like spare furniture so the room would be more robust and it's a storage room that I'd have for the long term.