What's up with the skylights?

[Michael Thomas]

I've not before seen anything quite like the condition of are thermal glazing at this skylight (actually, two skylights in the same roof in similar condition), and I'm wondering if I'm seeing some process other than normal blown seals...

[Markus Keller]

I would say blown seals. However, I can't remember the last time or ever that I saw blown seals on a Velux or Anderson skylight. I'm thinking the original install may have something to do with it.
Head flashing looks odd, side flashings aren't attached, bottom flashing very rusty, rust at screws. Wondering if screws penetrated seals during install or if the frame was torqued to cause seal failure; i.e. uneven, unflat frame to roof install thereby torqued the glass unit when closed.
Not like it matters much ... replace.
Maybe send the pics to Velux, they might be interested. Not from a warranty standpoint but in general.

[C.Johnson]

IMO it seal failed a long long long time ago......and was just never repaired, any chance you can find out from previous owner when they first seen it? I bet years ago

[Michael Thomas]

... Wondering if screws penetrated seals during install or if the frame was torqued to cause seal failure; i.e. uneven, unflat frame to roof install thereby torqued the glass unit when closed.
Not like it matters much ... replace.

A closer look at what's happening at the bottom of the skylight:

[Dom D'Agostino]

See it all too often in Florida.

[H.G. Watson, Sr.]

Sure I can think of another possiblity creating similar "appearance"

Chemical attack, surface pitting, etching, and hard-to-clean deposits.

Causes: overspray, blowing, runoff of chemicals from sealing/cleaning of concrete, masonry, roofing, etc. Other environmental factors/atmospheric pollutants that vary from place to place - dripping deicing solutions from aircraft (near airport?), factory discharges, acid rain, etc.


Ex. NaOH (Sodium Hydroxide, aka lye, caustic soda, sodium hydrate) + "glass" don't "mix"! Lye residue from use of common household laundry bleach solutions, not neutralized and/or sufficiently flushed.

Ex. HF (Hydroflouric Acid).

Fumes or direct application of oven cleaners, drain cleaners, etc.

Use of common "ice melt" solutions above dealing with ice dams for example.

Not cleaning windows regularly and when doing so, not cleaning properly, spraying on certain solutions directly, and esp. in hot sun; i/s or o/s, use of improper solutions to do so, abrasive actions, etc.

Fantastic, or original forumula 409, brutal on glass.

Of course if acrylic not glass...Add sun exposure to the list.

Slope looks very shallow. Surface shingles look newer than skylights - perhaps re-shingling project compromised skylight installation.

[Dom D'Agostino]

Chemical attack, surface pitting, etching, and hard-to-clean deposits.

Other environmental factors/atmospheric pollutants that vary from place to place - dripping deicing solutions from aircraft (near airport?), factory discharges, acid rain, etc.

Ex. NaOH (Sodium Hydroxide, aka lye, caustic soda, sodium hydrate) + "glass" don't "mix"! Lye residue from use of common household laundry bleach solutions, not neutralized and/or sufficiently flushed.

Ex. HF (Hydroflouric Acid).

Fumes or direct application of oven cleaners, drain cleaners, etc.

Use of common "ice melt" solutions above dealing with ice dams for example.

Not cleaning windows regularly and when doing so, not cleaning properly, spraying on certain solutions directly, and esp. in hot sun; i/s or o/s, use of improper solutions to do so, abrasive actions, etc.

Fantastic, or original forumula 409, brutal on glass.

Of course if acrylic not glass...Add sun exposure to the list.

Slope looks very shallow. Surface shingles look newer than skylights - perhaps re-shingling project compromised skylight installation.



Of course you just have to laugh at some of the nonsense posted here by certain posters.
Watch out for the "chemical attack". ;)

[Mark Logan]

I have seen this quite often here in New England. Usually when replacing the glass on these I have found that there is a large area of the seal that has failed causing large amounts of condensation. I have actually seen the glass broken from the water build up freezing in the winter.

[Alton Darty]

Of course you just have to laugh at some of the nonsense posted here by certain posters.
Watch out for the "chemical attack". ;)

Can't speak for the poster but I don't think that he was referring to a intentional & malicious release of a chemical by an individual or group. Instead he may have meant the chemicals contained in the atmosphere compromising the integrity of the unit. "Acid rain" comes to mind.