Insulating a garden workroom
A workroom that is used in winter needs insulation, and insulation changes the way the wall handles moisture. A cold uninsulated shed is wet and dries out; an insulated one has a warm side and a cold side, and water vapour from the warm side will condense when it reaches a surface cold enough. The build-up has to account for that or it will quietly rot.
Working from the outside in, the order is cladding, a ventilated batten cavity, a breather membrane, the insulated stud zone, a vapour control layer, and then the internal lining. The breather membrane keeps liquid water out while letting vapour escape outwards. The vapour control layer on the warm side limits how much vapour gets into the construction in the first place.
The vapour layer only works if it is reasonably continuous, so it is lapped at joints and dressed carefully around openings. Every service run punched through it is a hole, which is why it is easier to plan sockets and switch positions before the lining goes on than to cut them in afterwards.
The floor and roof deserve the same attention as the walls. Insulation between the joists with the cold air still moving beneath the floor, and insulation between the rafters with a ventilation gap left above it under the deck, keep both surfaces from becoming the cold spot where all the moisture in the room decides to collect.
100 mm insulated stud depth
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