Skylights bring natural light but are prone to leaks and heat loss. Learn proper maintenance, flashing inspection, and when resealing is needed.
Flashing and Seal Inspection
The most critical part of skylight maintenance is the flashing—the metal pieces that seal the gap between the skylight and roof. At least twice a year (spring and fall), inspect the flashing from the roof or a ladder. Look for lifted edges, rust spots, separated seams, or gaps where the flashing meets the roof shingles. Check the rubber gasket or seal around the skylight frame—cracked or brittle rubber should be replaced. Inspect the skylight curb (the raised frame on the roof) for rot or deterioration if it is wood. Check the interior drywall around the skylight for water stains, bubbling paint, or soft spots. Early detection of flashing problems prevents interior water damage.
Glass and Dome Care
The skylight glazing material—glass or acrylic—needs regular cleaning to maintain light transmission and prevent damage. Clean the exterior at least once a year (spring is ideal) on an overcast day (cleaning in direct sun causes streaking). Use a soft cloth, mild soap, and water. For acrylic domes, use only water and a soft cloth—ammonia-based cleaners cause crazing (fine cracks) in acrylic. Inspect the glazing for cracks, chips, or yellowing. Yellowed acrylic reduces light and becomes brittle. Check the glazing gasket (the rubber seal between the glass and frame). A deteriorated gasket leaks air and water. Replace the gasket before the weather turns extreme.
Managing Condensation
Skylights are prone to condensation because warm, moist interior air contacts the cold glass surface. Excessive condensation indicates high indoor humidity. Solutions: run bathroom and kitchen exhaust fans; use a dehumidifier in humid seasons; ensure the skylight has a thermal break (insulated frame); install a condensation gutter (a small channel at the bottom of the skylight shaft that collects drips). For operable skylights, opening them briefly releases accumulated humidity. If condensation forms between double-pane glass, the seal has failed and the sealed unit must be replaced. Condensation inside the glass shortens skylight life and reduces energy efficiency.
Improving Skylight Energy Efficiency
Skylights can be a net energy benefit—passive solar heat in winter and natural light that reduces electric lighting. To maximize efficiency: install low-E coated glass that reflects infrared light while transmitting visible light. Use a skylight with at least double-pane insulated glass (U-factor under 0.50). Add cellular shades or blinds inside the skylight shaft—they reduce heat loss in winter by 40% and heat gain in summer. Exterior shades (on the roof) are even more effective but require professional installation. In hot climates, consider a solar-powered skylight with an integrated shade that opens and closes automatically based on temperature. Proper sealing around the skylight shaft prevents conditioned air from escaping.
When to Replace Your Skylight
Multiple factors signal that skylight replacement is more cost-effective than repair. A skylight over 20 years old with leaking issues likely needs replacement. Cracks in the glass or acrylic dome cannot be reliably sealed. Failed sealed units (condensation between panes) require full replacement. Deteriorated wood curbs that are soft or rotting require complete replacement. If flashing is rusted through in multiple areas, the flashing kit and skylight should both be replaced. Modern skylights offer improved technology: low-E coatings, impact-resistant glass, integrated blinds, and solar-powered operation. Replacement cost ($800–$2,000 installed) is comparable to the cumulative cost of repeated repairs.
Frequently Asked Questions
A quality skylight lasts 15–25 years. The glass or acrylic dome lasts longer than the flashing and seal, which typically need attention after 10–15 years. Cracks in the seal are the most common cause of skylight leaks.
A leak during heavy rain but not light rain suggests the water is overwhelming the flashing or the seal has minor gaps that only show under volume. Check the upper-side flashing and the skylight curb seal first.
Small leaks around the seal can be patched with polyurethane roof sealant. Loose flashing can be re-secured and sealed. If the leak is from a cracked dome or failed internal seal, the whole unit needs replacement—a professional job.
Clean the exterior with mild dish soap and water using a soft cloth or sponge—avoid ammonia or vinegar which can damage seals. Clean the interior glass with a microfiber cloth and glass cleaner. Use a telescoping pole with a soft brush for hard-to-reach skylights.
Older single-pane skylights lose significant heat. Modern double or triple-pane low-E skylights are as efficient as a standard window. Internal blinds or shades can further reduce heat gain and loss. In cold climates, an insulated skylight shaft improves efficiency.
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