When we bought our current home, the windows were almost 30 years old. They were in terrible shape with gaps and sashes that wouldn't stay up. We shopped around and ended up buying Pella vinyl, double-hung replacement windows. My husband did the installation himself, which saved us a small fortune. They were actually really easy to install and fit snugly. We haven't had any issues with condensation or moisture. The windows have an energy efficient component to them called low E.They do not not conduct cold, so your home stays warmer in the winter and they do not conduct heat, so your home stays colder in the summer. The difference in our electric bill has been very noticeable and the difference in the fact that we no longer feel drafts is amazing. I also love the tilt in feature. This enables the windows, both top and bottom, to tilt in so you can clean inside and out. No more ladders! It's awesome! Pella windows also come with a limited lifetime warranty. This gives us great peace of mind. I highly recommend the Pella brand for replacement windows.