Glass Vs Acrylic, What Exactly Is the Difference?
- Cost
- Velux fixed skylight models are cheaper than acrylic. Custom glass skylights cost more than custom acrylic skylights.
The View- Glass skylights have a near perfect transparency rating. Acrylic by it’s nature, can add a wavy distortion to the view and are usually tinted bronze.
- Durability
- Glass has factory seals that are warranted for twenty years by the manufacturers.
- Acrylic needs to expand and contract from thermal expansion and this wears out the gaskets that hold the acrylic dome in its frame. And acrylic will yellow and get brittle over time.
Survivability- Tempered glass tends to survive punishment better than acrylic. Glass has to have its edges protected inside a sturdy frame and can survive most hailstorms.
- Acrylic will not hold the same weight as glass can—think snow load.
- Design
- Acrylic skylights use 1980’s design technology. The better ones will have thermal break (which separates the interior and exterior thermally) aluminum frames, however glass has much better thermal insulation standard in every skylight.
Condensation- Manufacturers of acrylic aluminum-framed skylights drill holes in their condensation gutters to allow the water to weep out. However this lets cold air and causes condensation. Velux skylights are 21st century technology so you don’t have to worry about heat & cold transfers or condensation.
- Appearance
- Glass is flat low to the roof, giving a streamlined look, while domed acrylic skylights stand out and look out-dated.
Noise- Glass is much better insulated, and reduce unwanted outside noise by up to 50% less than a acrylic skylight.
- Maintenance
- Velux skylights come with Neat® glass coating to keep your skylight cleaner longer, leaving the surface virtually spotless. Acrylic requires regular cleaning and care to ensure long term usability.
In our opinion from thirty-five years of experience, glass skylights are better, and what we always recommend.
My roof does not have much slant. I have an acrylic dome that is now failing (7 years). Roofer recommends a flat glass style. Since it is flat, when it snows won’t the snow just lay there and block the light? Or does it melt quickly?
Phyllis, The reason the roofer recommends the flat glass is because it is a better quality skylight (probably a Velux brand) than an acrylic dome. However, what we do is put an adapter on the curb to give it more of a pitch or angle. This way water runs off and takes the dirt with it, which is our biggest concern. Snow will sit on it and eventually melt, but that is okay. You get diffused light right through the snow. Also, if this is a Velux skylight I would make sure they are using the laminated glass, which is the best at blocking summer heat and damaging sun rays.