Hi All I want to replace the existing trickle vents on my upvc windows as they are the world's biggest and most unsightly things i've ever seen. I'm unsure how to measure for them though, do i just measure the hole in the frame and get a pair (inner and outer) to fit the hole or is there some mystical formulae? thanks I've attached picture of the existing vent so you can marvel at it's awfulness
I am guessing you just need to measure the hole in the window frame and get vents that cover that. Also measure distance between screw holes in case you can get matching distance. Some of the more experienced guys on windows on here will no doubt be of more help