Skylight Cleaning: What Homeowners Should Know
Updated: 5 hours ago
A skylight is the best window in the house on a bright day and the most neglected one the rest of the time. It points straight at the sky, so everything that falls lands on it, and it is usually out of reach from both sides.
Key points
Skylights get dirtier than vertical windows because debris settles on them and rain does not sheet off as cleanly.
The outside can usually be cleaned from the ground with a water-fed pole. Nobody needs to walk on your roof.
A yearly cleaning is a sensible minimum; under trees, twice a year.
Fog between the panes is a failed seal, not dirt, and cleaning will not remove it.
Why skylights get so dirty
A wall window sheds most of what hits it. A skylight catches it. Pollen, pine needles, leaves, bird droppings and tree sap all settle on the glass and stay until something removes them. Water pools briefly at the lower edge and dries there, which is why skylights so often have a dirty band along the bottom.
The U.S. Department of Energy notes in its daylighting guidance that skylights are one of the main ways to bring natural light into a home. A film of dirt works directly against that.
Why it is a poor do-it-yourself job
From outside, cleaning a skylight by hand means being on the roof. From inside, it means working overhead from a ladder, often above a stairwell or a bed. Neither is a good idea without training and equipment.
The numbers back that up. The CDC found that 43% of fatal falls in a ten-year period involved a ladder, and that work-related ladder falls alone sent an estimated 34,000 people to emergency departments in a single year. A clean skylight is not worth that.
How a professional cleans one
Outside: a water-fed pole reaches the skylight from the ground or from a safe standing position. A soft brush loosens the dirt and purified water rinses it away. Because the water has had its minerals removed, it dries without spots, which matters on glass you cannot easily wipe.
Inside: extension tools reach the glass from the floor where possible. Drop cloths protect what is underneath.
Around it: the frame and the visible flashing are rinsed, and anything that looks wrong is pointed out to you.
The window cleaning trade has its own safety guidance for this equipment. The International Window Cleaning Association publishes a water-fed pole safety module for its members.
How often should a skylight be cleaned?
Once a year is a reasonable minimum. If the skylight sits under trees, twice a year keeps sap and leaf stains from baking on. Many of our customers simply add skylights to their regular spring or fall visit.
Signs of a problem that cleaning will not fix
Fog or moisture between the panes. This means the seal of the insulated glass unit has failed. InterNACHI, the home inspectors' association, explains the cause in its article on condensation in double-paned windows.
Water stains on the ceiling or drywall around the opening.
Cracked or lifting flashing, or brittle seals.
These are jobs for a roofer or a glass company. A cleaning visit is a good moment to catch them early, and Andy will tell you if he sees any.
Common questions
Do you go on the roof?
In most cases there is no need. The pole does the work from the ground.
Can you clean plastic dome skylights?
Yes, gently. Acrylic scratches more easily than glass, so it gets a soft brush and plenty of water and nothing abrasive.
What does the manufacturer say?
Check the care instructions for your model. VELUX, the best-known brand, publishes tips for cleaning skylights inside and out.
Add it to your next visit
Skylights are part of our skylight, screen and mirror cleaning service, and the outside is cleaned using the pure water method. Request a free estimate and mention how many skylights you have.
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