unit and it drops the temp of my bedroom (4M x 4M) by about 10 degrees. I agree about the vent pipe - you can either use the foam rubber sheet they supply you with but with hinged windows (as against sliding windows) you still end up with huge gaps to let in the hot air and as you the alterntive is a 4" hold through the wall........BUT in a true diy fashion i built myself a window wedge from scrap wood that fits in the opening of the window when its about 1/3 open with a hole for the vent pipe and sealed round the edges with pipe insulation. So not i just need to open the window to it fullest extend, then shut it on the wedge and insert the vent pipe - it makes a good seal all round including top and bottom.......it works great....only problem is it is a bit on the large size but still it works
gin