Not all ENERGY STAR choices are the same. Some are more energy efficient than others due to a number of factors, like how much heat they trap inside and how much heat from the sun they let pass through.
Picking the right ENERGY STAR window also depends on where you live. Each of these windows is certified for one or more climate zones in the ENERGY STAR rating system (Zone 1 is the warmest and Zone 3 is the coldest). Newfoundland and Labrador has two climate zones under this rating system and it’s important to know what model is certified for the zone you live in.