We've had built a stud wall using 3x2 inside a long external, solid wall in order to provide insulation. The stud is insulated with 75mm PIR and there is approx 2" air gap between the stud and the external wall.
This is in a single-storey, wooden construction building with open roof, no ceiling. We have to allow for movement in the external walls which means we cannot bridge the two walls with anything rigid. So the stud stops about 2" below the eaves - this is also required as the building could shrink and needs breathing room so it cannot 'fall' on the stud wall.
As it is now, you can get your hand in the void behind the stud wall, the top is totally open all the way along. I know normally these days such walls are sealed to prevent warm air condensing inside the cavity but we cannot do this.
An obvious solution is to pack the gap at the top with mineral wool but I am wondering since it is not sealed, if we should actually prefer air movement in the void like in old houses where trying to prevent draughts can cause problems.
Another option is we could cap the top of the stud with a sort of fascia, which has just a tiny gap to the external wall like 1mm.
My fear was with the open pitched roof, we might get hot air in the top of the roof flowing down the roof as it cools slightly, and 'falling' into the void where it immediately cools a lot and gets condensation.
So - stuff the top with insulation, cap it, leave it open, or something else?
This is in a single-storey, wooden construction building with open roof, no ceiling. We have to allow for movement in the external walls which means we cannot bridge the two walls with anything rigid. So the stud stops about 2" below the eaves - this is also required as the building could shrink and needs breathing room so it cannot 'fall' on the stud wall.
As it is now, you can get your hand in the void behind the stud wall, the top is totally open all the way along. I know normally these days such walls are sealed to prevent warm air condensing inside the cavity but we cannot do this.
An obvious solution is to pack the gap at the top with mineral wool but I am wondering since it is not sealed, if we should actually prefer air movement in the void like in old houses where trying to prevent draughts can cause problems.
Another option is we could cap the top of the stud with a sort of fascia, which has just a tiny gap to the external wall like 1mm.
My fear was with the open pitched roof, we might get hot air in the top of the roof flowing down the roof as it cools slightly, and 'falling' into the void where it immediately cools a lot and gets condensation.
So - stuff the top with insulation, cap it, leave it open, or something else?
