Am I doing right when I plan to build an outer wall?

[lasseboy]

I am building an insulated porch. I plan to build the exterior walls like this:
from the inside: interior drywall, 195x45 stud, 19 cm insulation, asfaboard, 2 cm battens, then vertical siding.
Is this crazy or does this work?

 

[mångstekta]

sounds good... just remember the plastic, between plasterboard-insulation...

 

[ByggaNytt]

There are many ways and it depends a bit on how the rest of the house looks.... Another suggestion below that insulates a little better:
Gypsum
Plyfa/OSB if you want to hang heavy things, like coat racks, etc.
45*45 lying down, here you also run all electricity, etc.
45 insulation
Plastic
45*145 standing
145 insulation
etc.

http://www.familjenlindstrom.se/images/byggahus/teknik/el_installationer/el_kok.jpg

 

[lasseboy]

The rest of the house is:
On the plastered surface, it has been bricked up with white mexi bricks. and asking someone to build the porch will probably be expensive.
Regarding the plastic, do I need plastic on the outside too?
Bought 195x45 yesterday, for the bottom and top parts in the frame construction so maybe one should change to 45x45 horizontally then 145x45 vertically.

 

[ByggaNytt]

No, no plastic on the outside - you can't have double vapor barriers. The plastic should only be on the warm side of the wall. Inside the panel, there is usually a wind barrier or exterior gypsum.

For the timber, you can:
* Split it yourself
* Complement with a 45*45 if the total wall thickness allows it
* Replace
* Leave it as is, the savings with a crossed frame structure on just a porch won't be gigantic...

 

[Mikael_L]

Inside the panel, there is usually a wind barrier or exterior gypsum.

Or the asfaboard that TS mentions in the first post ... That works too.
The wind barrier/asfaboard/exterior gypsum/weather barrier should be installed to be ... exactly, airtight. No gaps where the wind can blow in.

Regarding plastic, install plastic if you have it in the existing walls. Be as meticulous as possible in connecting it to the existing plastic and be careful to make the plastic film as airtight as possible otherwise. The rule of thumb is that you should be able to blow air into the house so there is an overpressure, and it should leak as little as possible through the plastic layer. (Of course, you shouldn't have overpressure in the house, but as a principle...)

If there is no plastic in the existing walls, I would skip it on the extension as well.