Finally, a solution that doesn't break the bank and allows you to keep your existing windows. We bought ours primarily for additional soundproofing as our builder used dual-pane glass. It makes a measurable difference - 20 dB. The bonus is the insulation value. It's been a mild spring and our main bedroom at the front of the house facing the morning sun is much cooler. I suspect it will be warmer in winter as well. If you follow the self-measure and installation instructions to the letter, they go in easily. We have floor-to-ceiling windows, so we had massive inserts, but it was still manageable for two people.