When I was doing renovations for my parents, I focused on energy efficiency. The house is old, heating bills are like a mortgage. We decided to change the windows. We wanted Rehau, but it was important to find a normal installer, not a moonlighter. I found it through a forum https://elitokna.kiev.ua/ua/plastikovye-okna-rehau.html. The guys really work like human beings. They installed it carefully, removed the trash, everything according to technology. After a couple of weeks, the parents already noticed that the house was warmer, and the street was completely inaudible. It's been tested - it works.