I have an Elementhus from 1989 where we need to move some windows. When I started tearing into the exterior walls, I found that there is no real air gap behind the exterior cladding. The construction looks like this (from the inside out):
* 9mm board
* plastic foil
* 170mm stud with 170mm insulation
* 12mm "porous board" (no idea what it is, not asfa, much more porous)
* 45mm stud with 45mm insulation
* wind barrier
* 22mm+22mm cladding
That is, the only ventilation comes from every other cladding board, which creates a 22mm air gap. The facade currently shows no signs of moisture problems.
I haven't seen this construction solution before, was it common in the past?
Now that we are moving windows, the simplest option is to continue with the same solution, and I will use asfa-board in the middle. Is that okay, or will there be problems with moisture since the cladding is not fully ventilated?
* 9mm board
* plastic foil
* 170mm stud with 170mm insulation
* 12mm "porous board" (no idea what it is, not asfa, much more porous)
* 45mm stud with 45mm insulation
* wind barrier
* 22mm+22mm cladding
That is, the only ventilation comes from every other cladding board, which creates a 22mm air gap. The facade currently shows no signs of moisture problems.
I haven't seen this construction solution before, was it common in the past?
Now that we are moving windows, the simplest option is to continue with the same solution, and I will use asfa-board in the middle. Is that okay, or will there be problems with moisture since the cladding is not fully ventilated?
An air gap is a modern invention to keep the panel dry if painted with disgusting plastic paint.........As long as the panel can breathe outward, there is really no need for an air gap behind the panel. It's just that everyone builds that way nowadays because you "should"..........
Modern and modern. Everything is relative, but it's not that new. 
An externally ventilated air gap is a common and well-proven solution, but a wall can be built in many different ways. There are more examples of walls without an air gap - sandwich walls made of concrete and cellplast for example.
An externally ventilated air gap is a common and well-proven solution, but a wall can be built in many different ways. There are more examples of walls without an air gap - sandwich walls made of concrete and cellplast for example.