We live in an 1890s Victorian house with the original double hung windows. We love the character of the windows, but did not love our energy bills in peak seasons. Another concern we had is that because of the double hung construction there are small gaps where the windows overlap that are impossible to seal unless you compromise the functionality. Because we have these gaps, during the winter months we were having issues with tons of lady bugs coming inside to hibernate. We are very happy with our Indow inserts! I was a little worried about the self measure process, but Indow has a great system to check for errors. We ordered two rooms (7 windows total), and had no issues with any of the inserts fitting. I love that you can’t even tell they are there. While we never really opened the double hung windows, I do like that we were able to keep this original construction to the home while increasing performance. We are planning to order the rest of the upstairs rooms because we love them so much!