A skylight is a glazed opening in a roof or sloped ceiling surface designed to admit daylight — and in operable models, ventilation — from above. Skylights can dramatically increase the light levels in rooms that lack adequate wall window area: hallways, bathrooms, stairwells, and rooms under a hip roof where wall window placement is limited. They also provide a connection to the sky that wall windows cannot replicate.
Fixed vs. Ventilating Skylights
- Fixed skylights — sealed units; admit light only; no opening function. Simpler, cheaper ($300–$700 installed), fewer leak points.
- Ventilating (operable) skylights — can be opened manually (pole or crank) or electrically (motor with rain sensor). Provide significant ventilation — a single 2×4 foot venting skylight can ventilate a 500 sq ft room. Cost $700–$2,500 installed depending on size and motorization.
- Tubular skylights (sun tunnels) — a small dome on the roof connected to a highly reflective tube that terminates in a diffuser on the ceiling. Minimal framing needed; works in small spaces; cannot ventilate; cost $500–$1,000 installed.
Skylight Glazing Requirements
Building codes require safety glazing for all skylights. The glass must be either tempered or laminated — never standard annealed glass, which would fall in large shards if broken. Most residential skylights use laminated glass because it stays in the frame even when cracked, preventing leaks until repair.
Common Skylight Problems
- Flashing leaks — the most common skylight problem; water infiltrates where the skylight frame meets the roof. Properly installed step flashing and a curb prevent this; failed flashing requires roofing repair.
- Condensation on interior surface — skylights have the lowest surface temperature of any glazing in the house (heated air rises and warms them, then cold night sky cools them rapidly). High-performance Low-E glazing and good ventilation minimize this.
- Cracked or yellowed acrylic dome — older skylights used plastic domes that craze and yellow with UV exposure; replacement with glass units is the long-term fix.
- Stale seal on operable unit — motorized skylights have a rubber perimeter seal that compresses with each operation; replace every 10–15 years.
