The fiberglass is better for energy performance, unless I'm missing something...

Lori is right -- the thermal/energy performance of fiberglass is better than aluminum. In addition, fiberglass is virtually unaffected by changes in temperature -- it doesn't expand or contract. Aluminum (and vinyl) will expand and contract, which can lead to failure in the seals over time.

Also, Integrity windows are almost maintenance free. They won't corrode or get dull like aluminum. I replaced a window in my house with Integrity earlier this year so I'm very familiar with the product. I still have some older aluminum windows in my house and I can't wait to replace them -- they are cold in the winter and the finish has gotten cloudy and pitted over time.

Does your architect have any financial incentive to get the Plygem windows?

P.S. I have a business relationship with Integrity, but I bought their product on my own dime (no discounts or special treatment). I can honestly say that it's a great product and my own experience with it as a homeowner has been excellent.

Thanks, Reinan - it is always good to hear from some-one who has used the product!!

The Integrity is definately what I would pick. Fiberglass is a better option then a wood clad aluminum window. The u values are not very good on the Plygem windows (barely hitting Energy Star). I didnt spend much time looking, but I could not find the other ratings easily, which typically means they are also nothing to brag about. I would question your architect as to the reasons he/she feels aluminum it better.
If I were buying a US window, I would pick the Integrity even if money was not a driving force.

Thanks Renovator8 - much appreciated!

Someone has now suggested we look at Inline fiberglass windows - any thoughts on how they compare with Integrity?

Inline is a Canadian company (if that matters to you) who uses a full heavy fiberglass frame that is insulated. (fiberglass inside and out). I believe they veneer the interior if you want a real wood look. Inline offers a much larger selection of glass packages if you are wanting to tune the windows for maximum energy efficiency. They have better u values and better infiltration numbers. All and all, they will be a more efficient window, but will most likely cost somewhere between the Marvin Premiums and Integrity, depending on your glass packages. They have triple pane options that only add around $50-90/ window.
Inline is one I would definately consider, as well as Fibertec (both Canadian). Thermotech is also great, but will be priced like the Marvins.

Inline is an all-fiberglass replacement window. It should not be compared with Marvin's Integrity fiberglass clad wood window.

It might be comparable to Marvin's Integrity all-ultrex window but I suspect it is more like the Marvin Infinity all-ultrex replacement window.

It might also be comparable to an Andersen all-composite (Fibrex) replacement window.

Inline would be comparable to Integrity from Marvin but with higher performance values in air and water infiltration and higher pricing. Inline windows are manufactured for new construction no, reason as far as I know they could not be used for replacement windows but they are not marketed as a replacement window.

Fibrex is not comparable as it is not fiberglass. IMO, fibrex is below any of the options on the table. I have messed with the windows in person and they definitely look like the cheap price you pay for them.

I have not been able to find an Inline window detail that shows a nailing flange and I have seen them advertized online as replacement windows.

Thanks, all. I'm also thinking about windows.

It looks like PlyGem has a much better warranty. Lifetime or, if the house is sold, 20 years for materials and 5 years for labor (it looks like Marvin's is just 10 years). To my inexperienced eyes, it looks like PlyGem has the best warranty I've seen. Would you trust it?

I wonder if it's Hyundai-type phenomenon, where a company uses a great warranty to try to compensate for a bad reputation. Hyundais are pretty reliable these days, but their quality rankings really improved _after_ they started the 100,000-mile warranty standard.

Even if PlyGem is fine, everything I've read says that fiberglass is best. Other things being equal, is there a reason to prefer aluminum?

Pretty much all the Inline I have been quoting recently have been commercial set in masonry so the quotes have had masonry strap anchors. I will have to look tomorrow and or ask my contact at the factory.

I just noticed that the lifetime warranty is only on PlyGem products from certain western plants, and does not appear to apply to Mira. Reading the Mira warranty, I'm much less impressed.

Here is a link that might be useful: Mira warranty

Reno- trust me, they can come with nailing flanges. They can come with a whole slew of other options including various depths of brick ledges with nailing flanges in them, some quite deep to give you "innie" windows if you prefer. A nice feature if you have thick walls, such as ICF or double stud.