Which material should NOT be used in building a skylight?

Using annealed glass in building a skylight is not recommended due to its lower strength and safety characteristics compared to other materials like tempered glass, polycarbonate, or acrylic. Annealed glass is produced by slowly cooling the glass to relieve internal stresses, making it more likely to break under impact or thermal stress. In a skylight application, where the glass is exposed to various weather conditions and often comes into contact with significant thermal expansion or contraction, the risk of breakage increases. On the other hand, tempered glass is created through a heat treatment process that increases its strength and makes it much safer because, when broken, it shatters into small, blunt pieces rather than sharp shards. Polycarbonate and acrylic are both durable and lightweight alternatives known for their impact resistance as well, making them more suitable for skylights.