Dot and Dab or simply screw

[lsces]

I've been working on a project over the last year replacing a 20+ year old shed with something a little more substantial, but which is essentially just a summer house. It has a sauna and storage area one end and I went with an industrial style sip panel roof. What I am just trying to finish off is lining the main area which has two 8ft patio doors as one wall, and concrete block back wall. Which I've currently covered with 20mm polystyrene back plasterboard. Next step is securing it, but I've been getting conflicting advice ...
1/ Dot and dab - and add fixings for safety
2/ Butter the back so there are no gaps
3/ Just screw to wall since top will have coving, and bottom skirting.
3 is obviously the easy option, and just bash in fixings at 16" centres?
So does the adhesive add anything here? It's not like it's a living space and the only reason for the insulation is to keep the heat in a little over the winter - need the doors open at the moment to let the heat out :)

[Perry525]

From your description, it seems you have a single width block wall?
Two inches of polystyrene will help with the insulation, four inches will do a better job, you will loose that chilly feeling.
Using plasterboard adhesive will keep the boards in place, I prefer to cover the whole board with 6mm of adhesive (which makes them heavy but easier to position) the manufacturers recommend dot and dab. Try one and see how you get on. The plasterboard provides half hour fire resistance = are you likely to have anything in the room that will burn? Mechanical fixing will provide a heat bridge to channel your heat outside (not a good idea)

[chris_on_tour2002]

dob & dab would be my preferred choice. the polystyrene backed board will give plenty of thermal insulation given it's intended purpose, you'll lose a heck of a lot more heat through the patio doors, even if they are double glazed.