It seems that the most vulnerable part of a house's exterior is one of the most neglected parts as well. I've come across quite a few window sills and casements that have deteriorated to a hopeless point and it would end up costing a ton of money to fix the problem correctly. What usually ends up happening is that the builders depended on the paint to shed water off the sill and keep it from soaking into the wood. But we all know that paint is very temporary outside; it can also be deceptive. We might think that the surface is sealed but a small crack can let water in slowly and then the rotting begins. Wrapping windows with aluminum protects them from water and sun. They can also be painted if a new color is preferred in the future.