Simple, economical exterior wall construction.

[Novisfixaren]

A 40 sqm bedroom will be added to an existing building. (a summer cottage but will be used in winter)

To match the adjacent building, 145mm lock board should be used.

The wall will be built on a concrete slab.

But what is the simplest way to construct the wall? The adjacent walls have asfaboard, but I’m considering windproofing fabric?

There will be minimal electrical work, which can be done from the ceiling.

From outside to inside:
Cladding board/nailing battens/windproofing fabric/195mm studs + insulation/vapor barrier/drywall

Is it unwise to not have battens or OSB behind the drywall?

 

[useless]

Yes, it's stupid not to have anything behind the drywall. The cheap version is probably double drywall, but I prefer something you can screw into with normal tools.

 

[Novisfixaren]

Leaning towards this: Cladding board/nailing batten/breathable membrane/195mm stud + insulation/vapor barrier/OSB/drywall

Then I'll run the electricity in the stud frame outside the vapor barrier "is this dumb?"

 

[useless]

That's how it has been done for many years, so it probably works well. Nowadays, one usually installs the vapor barrier and then adds an additional 45mm of framing to create a service cavity inside and avoid puncturing the vapor barrier. If desired, the space can be insulated before nailing it closed.

 

[Novisfixaren]

Okay but since there is very little electrical wiring to be done, I think it feels unnecessary with extra 45x45 studs...

 

[useless]

Yes, it is mostly if you have to meet the density requirements for new constructions.

 

[Rabbithole]

Yes, then it somewhat breaks the thermal bridge. So one alternative would be:
Klädselbräda/nailing battens/wind barrier/145 standing stud + insulation/plastic/45 lying stud + insulation +electrics/OSB/gypsum