Age. We regularly replace skylights that have been on a roof for over 25 years. But we sometimes replace skylights that are less than 5 years old often because they were poorly installed. If age is the most common reason to replace skylights, incompetent installation would be number two. VELUX skylights rarely fail…and when they do it’s usually after a very long life.
Skylights fail in two ways…they deteriorate and begin to leak and/or they lose their thermal insulation and allow heat loss or heat gain. Just because your skylight isn’t leaking doesn’t mean it shouldn’t be replaced. Skylights made ten or fifteen years ago just didn’t have the technology to maintain their thermal insulation properties. Thermal gain/loss could cost as much as $200 per year per skylight in our climate.