If a window is not installed properly to the manufacturers specifications it does not matter if Bob Villa or Mr. Magoo installed it the manufacturer will not honor a warranty most every time.

The issue was more legal than improper installation. The windows were properly installed. Is there a requirement that an "authorized installer" sign off on completion of the install? Three years after the install something happens; the window maker is called and I invoke the contract. They cannot say "improper install" since I can show them the install is signed off by their "authorized installer" and thus I am protected.

Without having the facts of your case, I am trying to understand your question. I am a Marvin service person. As long as the windows are installed per the manufacturers specs then you have done your due diligence. The installation specs are based on AAMA specifications. In the case of Marvin, the only product that we require a certified installer on is a Lift and Slide unit. Again, if you have complied to these conditions, there should be no question as to your warranty being in place.

As long as you purchased these from a reputable company that is still in business you should be entitled to your claim, unless there is information you have not shared with us.

Sorry, this was a theoretical question. We have done no install yet. There are no claims. We are going to replace a number of windows using indeed a reputable company (that is not determined yet). We are attempting to match the window look we have now.

One company I talked to said that "they are more comfortable with their own installers to get the work done properly," and this raised the question. Further, again in searches I did in the window forum there were many cases of companies using "improper install" for all the problems including some bad engineering of their own windows.

The original poster said "if I have" - so I think this is just a matter of reading the warranty information before the purchase.

Marvin's online info' says:

Damage, defects, or problems resulting from causes outside Marvin's control are excluded from coverage under the Limited Warranty.

And then lists examples. Nothing there that says that you have to use a particular installer. But pretty clear that if they think the issue was caused by the installer (or the homeowner) that it isn't covered.

Sounds reasonable to me. But it sounded like the original poster is expecting the manufacturer to correct any problem whether they think it is their fault or not.

Richard - you posted while I was composing my previous post.

Was it Marvin or Andersen that said you should use their installers? What product(s) are you looking at?

Dennisgli: I am looking at Marvin or Andersen. It was a Marvin dealer that suggested using their own installers. However, when I was at Home Depot looking at Andersen, they were promoting their own installers bacause they would apply additional warranties through Home Depot and because "Home Depot will be here longer than Andersen Windows!" This leads to the obvious question that if in 20 years Andersen is gone, how will anyone at all have access to material to fix an Andersen window?

I am looking at Marvin, Marvin Integrity, and Andersen 400 windows. We need to replace casement windows, and we have to match the wood look inside the house with a colonial type grill. The whole window will be replaced. Currently we have custom made windows from 1994 that are failing, and the math shows it will be too expensive to repair and renovate the old windows. Actually if I were 25 years younger and had better DIY skills, I would try the repair myself. Many of the double pane lites are failing, and the experts tell me that 20 years is the lifetime and the failures will just increase.

Personally HD maybe around for a hundred years more than Andersen is around but that doesn't mean I would even entertain the idea of them or their contractors even picking up the cardboard boxes from the windows, let alone install the windows.

+1 to MWM's last comment.
On the install: factory "certifications" are typically not worth the paper that they are printed on. A poorly installed window can void the warranty whether it is certified or not, just like a properly installed window. Focus on finding a quality installer that you trust. The certifications are fine, but they are nothing more than window dressing in most cases.

I have known some people that should be considered certifiably crazy, but I am not sure that applies here.