How I finally solved the window seal peeling issue — steps that actually worked

I actually went the acrylic route last year for my De'Longhi Pinguino becasue that Velcro tape just turned into a sticky mess on my white UPVC frames. I ordered a 5mm clear sheet from a supplier called Cut My Plastic and it cost me about £25. I tried using a standard hole saw, but be careful because the plastic can crack if you go too fast. I found that running the drill in reverse for the first bit helps score the surface without shattering the whole sheet. For the seal, I used some 10mm closed-cell foam tape I found at B&Q. Instead of a friction fit, I used a few small turn-buttons screwed into the frame to hold the sheet in place. It’s been much better for keeping the humidity out during those 30C afternoons. My only issue is storing the giant piece of plastic in the garage during the winter, but it beats dealing with those leaking fabric bags every time there’s a light breeze.

Back in my day, we didn't bother with fancy acrylic. We'd just grab a scrap piece of 1/2 inch plywood and paint it white to match the window frame. It handles the sun way better than plastic, wich can warp if it's cheap stuff. If you're handy, you can even hinge it so you don't have to lug a giant sheet to the shed come October. Just make sure you're insulating that hose too. Doesn't matter how tight your seal is if that exhaust pipe is radiating heat back into the room like a space heater. I've been using an old reflective bubble-wrap sleeve for years. Makes a world of difference when it hits 30C.

I ditched the clear stuff entirely and went with a sheet of 25mm Celotex insulation board. It's a bit of an eyesore from the outside since it's foil-faced, but the difference in room temp was massive. Plastic lets the sun bake your room like a greenhouse, but the foam board acutally blocks the heat. I cut mine slightly oversized so it just friction-fits right into the window channel. For the hose, I didn't even bother with a hole saw; a sharp retractable knife zips trough it in seconds. When the sun hits it, the board stays cool to the touch while the rest of the window gets roasting.