The main con of vinyl replacement windows is that they can be less energy efficient than wood or metal frames. Vinyl frames are not as good at insulating against the elements, so you may not be able to reduce your energy costs as much as with other materials. Furthermore, vinyl windows can become discolored or warped over time due to changes in temperature and humidity, so you may need to replace them sooner than expected. Additionally, vinyl window frames can’t be painted or stained.