I'm renting an appartment in a small appartment block, which got very hot last summer, and very moist in winter when hanging our laundry. The obvious solution would be to place a protable airco unit,but the problem is that we live near a very busy road, so opening a window even slightly makes conversation quite difficult.

However, there is an air vent, that is basically a hole with a vent cover through the 'inside' wall; when the vent is opened, there is a noticeable airflow of outside air entering the room, suggesting that there are also some holes in the 'outside' wall (visual inspection seems to confirm this, although it's difficult to see).

I was wondering if I could vent the airco in that hole, or whether venting in the wall cavity is a Bad Idea ©.

1 Answer 1


Moist warm air when it is exhausted behind enclosed walls (even slightly vented ones) have the potentially damaging effect of becoming condensate (water or moisture) if the temperature is cooler. Moisture is what mold spores need to thrive. Once they are established the colony can bloom and spread rampantly and unchecked out of sight. The health and safety hazards are well documented. A better solution for an exhaust for the portable air-conditioning unit to the outside is through the window. Open the window and measure the dimensions (L x W). Increase these numbers enough so that a piece of plywood overlaps and fills the edges of the window opening. Cut a hole enough so that the exhaust vent can go through.

  • I considered that, but the problem is that there's an additional glass pane on the inside for sound insulation, and that both the window and the glass pane open towards the inside, so the plywood construction would be quite complex.
    – Sanchises
    Oct 22, 2015 at 11:34
  • Than the only other option (if there are no other windows and doors) is to create an opening to the outside.
    – ojait
    Oct 22, 2015 at 15:01

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