Skylight gone cloudy or yellow
A skylight that has slowly yellowed or gone milky is an acrylic dome that has spent decades in the sun. The plastic has broken down and no cleaning will bring the clarity back. The same aging makes it brittle, so a dome that looks tired is also one that can crack in the next hailstorm or under a fallen branch. Replacement is the answer, and it is a chance to fit glass.
The symptom
What you are seeing
- The room under the skylight is dimmer than it used to be and the light has a warm, slightly dirty cast. From outside the dome looks frosted or amber, and cleaning it makes no difference because the haze is inside the plastic rather than on it. On the room side there may be fine cracks in the surface, a chalky feel or a corner where a piece has already flaked away.
- Have a look at the whole unit, not just the dome. Old acrylic skylights sit on a wooden curb with a metal frame, and the seals between the dome and the frame dry out at the same rate as the dome itself. If there is a second dome inside the first, check whether the gap between them has gone cloudy with condensation, which means the seal has failed. Note the size and shape of the opening; that decides what can replace it.
Most likely first
Likely causes
Sunlight breaking down the acrylic
Ultraviolet light slowly changes the plastic, turning it yellow and then opaque. Domes fitted decades ago were rarely coated against it, and after a few decades of California sun they have simply worn out.
Heat cycling
The dome heats and expands every afternoon and shrinks every night. Over thousands of cycles the plastic crazes, and the network of tiny cracks scatters light, which reads as fog.
A failed seal between two domes
Double domes trap air between two layers. When the seal at the rim gives way, moist air gets in and condenses, and the skylight fogs from the inside in a way that changes with the weather.
Grit and cleaning damage
Acrylic scratches easily. Years of wind-blown grit, and the occasional scrub with the wrong cloth, roughen the surface and add to the haze that the aging has started.
The honest rule
Repair or replace
There is no repair for a dome that has aged through; it is replaced. The choice is what to replace it with. A new acrylic dome is the quick like-for-like option and it will do the same thing in another twenty years. A glass skylight in a frame made for the opening does not yellow, insulates better and can be had with a coating that cuts the afternoon heat, and it is what we usually suggest if the curb and the roof around it are sound.
The rest of the assembly decides how big the job is. If the wooden curb is soft or too low for the new unit, it is rebuilt while the roof is open. If the flashing was improvised or has been caulked repeatedly, it is replaced with a kit made for the new skylight rather than reused. Where the covering around it is close to needing replacement, the skylight is better done with the roof, so the flashing is laid into new covering once rather than disturbed twice. We will tell you which of those apply after looking at the curb, because the dome alone never tells the story.
What fixes it
The service for this, and where to read more
Service
Skylight installation
A new or replacement VELUX skylight, with the surrounding roof work and agreed interior finish included.
Service
Skylight replacement and repair
We inspect the skylight and nearby roofing to find the source of moisture before recommending a repair.
Related problem
Skylight dripping or fogging up
Moisture at a skylight has three different sources and they need three different fixes.
Related problem
Ceiling stain that appears after rain
A stain that darkens or spreads after rain means water is getting through the roof and reaching the drywall.
Questions
Asked about this problem
Can a yellowed dome be polished or restored?
Not once the color is in the plastic. Polishing removes surface scratches, which helps a little on a young dome, but the yellowing and the crazing run through the material and the polishing takes off what little protective surface is left. Restoration products buy months, not years.
Can the new skylight be glass instead of plastic?
Usually, yes. A glass unit needs a frame and a curb that suit it, and the opening may need adjusting to a standard size, but most old dome openings can take a modern glass skylight. Glass stays clear, insulates better and stands up to hail and branches that would crack an aged dome.
Is a cloudy skylight urgent?
Not on its own. It is a sign of age rather than a leak. What makes it worth planning is that the same aging has made the dome brittle, so the first heavy hail or a branch can crack it and turn a scheduled replacement into an unscheduled one in the rain.
Free estimate
Find out what it costs
Tell us what's happening at your property, one step at a time. We'll review your request during business hours and arrange a free inspection.
What happens after you send it
- We call during business hours to set a time.
- A free visit. We measure on site and nothing is signed at the door.
- The proposed work and the price, in writing.
- (925) 555-0100Phone
- Mon–Fri 7:00 AM – 5:00 PMHours
Sat by appointment · Sun closed
100 Example Road, Brentwood, CA 94513 · office@example-roofing.demo
Your property answers are saved in this browser as you go. About saved answers.
Having trouble? Use the short form
Thanks. We will call during business hours to set up the inspection.
That did not send. Call (925) 555-0100 instead and we will take the details over the phone.