Never heard of that here either. Can't say with certainty that it isn't true, however they definitely need to provide some additional grounds for denying that claim IMO.

HomeSealed - here's the full text of their "additional grounds" - does it influence your opinion one way or the other?

"We have determined it is not a warranty due to the following; your inner dome had a thick, greasy residue on them, this is only on the inner dome, not the outer layers. Enclosed is a sample from your skylight. You can feel the grease on the skylight compared to the side of the skylight that did not have access into your home. Occasionally, when there is not enough ventilation in a home, products like hairsprays, cleaners, oils and fragrances can attach to the acrylic when a home is not ventilated adequately.

"If the acrylic was defective, all layers would be cracking/crazing. In this case it has been determined that there is some type of internal environmental contributing factors. We have made this determination due to the fact that only the inner layer of the skylight is beginning to have some cracking/crazing issues.

"In summary, your domes will crack again and it will not be a warranty replacement."

There is a residue on the skylight, although I think they're overstating their case by causing it a "thick, greasy residue". I suspect it's from the fireplace located in the same room as the skylights. It's a modern fireplace insert with glass doors, but there often is a little smoke in the room when we're first starting the fire.

Here's one photo of the window "beginning to have some cracking/crazing issues".

Acrylics do not like a lot of common items found in the bathroom and products used in the bathroom. And something definitley made this Acrylic brittle. (Search acrylic chemical resistance). That said, I find it hard to be believe that the amount of solvents or alcohols presented to the skylight would result in this kind of failure (chemical resistance testing using involves complete immersion in the chemical being tested). I'd ask them for an analysis of the residue, ie how can they make that determination without knowing what the reissue is (would require outside testing of the residue). Is there any disclaimer in their warranty about exposure to things in the bathroom?

the last part in lkbum's post is key IMO. At this point, it really depends on how the warranty of the product is written, and if there are exclusions that this would fall into. The more vague and general the terms, the more I'd expect them to need to prove a correlation between that residue and the cause of the damage.... All that said, if they continue to balk, you may need to weigh the cost and effort of pursuing this to the point of litigation vs the cost of simply paying for the new unit.

Thanks all for being a sounding board. I will admit my gut response to the letter is that it sounds like a load of crap, but I also recognize that this is an area in which I have limited knowledge or experience, so I am doing my best to gather information in a (relatively) unbiased fashion.

Chemicals: I did look up "acrylic chemical resistance" but can't get very far, not knowing what the residue is. The windows did, however, start to crack within about 5 or 6 months of installation, so any exposure was minimal.

- The skylights are not in a bathroom (they're in our living room).

-We don't use a lot of cleaning products, and no air fresheners or diffusers or anything like that.

-Our fireplace is used 2 to 5 evenings (fire burning for a max of about 6 hours) a week during the winter. As I said before, it's a modern fireplace insert with glass doors.

-I did have a new floor with glued application installed as part of the remodel. I think the new floor was in place well before the skylights were installed, but I'll try to check that.

Heat: We do have skylight shades (I'm sure they trap heat) but the timing isn't right. They were installed early this summer, well after the inner domes had already started dropping broken pieces onto the screens.

I'd like to think that with such a spectacular failure in such a short length of time, the company would want to make it right, whether or not the warranty allows them to slip out of it, but maybe that's just me being naive.

If the problem was a "buildup ... you should see the same thing happening again.

I can think of several things:

1 - skylights were improperly stored and contaminated before they were installed with something that weakened the dome

2 - Skylights were improperly installed not square and the stress on the domes started them cracking (no greasy stuff needed)

My money is on Door # 2 ... not square and they gave under the stress.

That said, I find it hard to be believe that the amount of solvents or
alcohols presented to the skylight would result in this kind of failure

For that to happen, you would kill everyone in the house with the fumes.