As soon as I put the Indows in our two kitchen windows, I could feel the draft stop. It was summer, so I was a bit concerned that the kitchen would become very hot. But no--even though there's only one outlet from the central air conditioning in that room, and of course a kitchen has lots of heat sources. Having the Indows in let the air conditioning function to cool off the kitchen, which it never had done before. A week after the Indows arrived, we had a new kitchen entrance door installed by Pella. That added to what Indow had already accomplished, of course. But even by themselves, the Indows made a huge difference. Can't wait to see how much warmer it will be in winter, which is why we got the Indows. We chose not to get Pella windows because we like the originals and no replacement will be like them. The Indow is truly not noticeable unless you are actually looking at the outer frame, instead of through the window at what is outside. And Indow is about half the cost of a Pella window--and that's including the extra shipping charge for the 3 x 6 windows we installed.