I have stripped out the entire bathroom, a wall will get a small change so there will be space left behind it. In the future, we will install a heat recovery ventilator to get a better indoor climate, especially in the basement. I am thinking of installing either spiro or alu duct from the attic, through the bathroom wall down to the basement. Whether it will be some form of exhaust or intake air, it should not become cold, so condensation should not be a problem. I am thinking of installing a 125 mm alu duct, maybe add some extra insulation around it, and then plug both ends for now.
Am I thinking right or wrong, and is there a difference between using a hose or spiro for what I want to do?
Ventilation planning has not been done, but wherever the unit ends up, there must be a channel between the basement and the attic... And if this can be built into the wall, it's just nice.
