Sealing windows for air conditioning

[Ceto]

I now have a portable air conditioner in my office, hooray. Only it has to vent through the window; it came with a spiffy fitting to put under a sliding window, but our windows are the sort that open outwards from the top. So at the moment I'm using it with one window open, which isn't ideal. I've been trying to think of ways to seal the openings around the window, but the best I can come up with is maybe a total bodge up using polythene - and I'm not even sure how I could stick that on given that I can't put sellotape on the paintwork.

Any ideas?

Buy some 2 inch thick sheets of foam which you can cut into the right shape to fit the window openings and put a hole in for the hot air outlet. Then wedge in place.

This is what my neighbours suggested when they got sick of the sight of spare underwear being used to plug the gaps in my window.

you can also use hardboard or some other rigid material.

You just want to board-up the window opening with something that you can cut a round hole in.

if this is your own house and you want to do a proper job, you could core-drill a hole in the wall like you would for an extractor fan, cooker hood or vented drier.

I stuffed an old cushion in the gap. Does the trick nicely.