I am not a fan of the Pella Impervia product and certainly not in comparison to the Marvin Infinity.

A full frame replacement is not a necessity and will not yield you much more glass or a more proper installation if the insert installation is done properly.

We have Marvin Infinity fiberglass in our garage. We did full frame replacements (casements). We installed 4 sets of double casements and they are lovely and easy to clean (prior windows were wood painted interior and aluminum coated exterior). They are lovely.

just had one elevation of home installed with marvin infnity fiberglass inserts.Purchased the argon 272 as opposed to the 366 glazing.Clincher was the product with installation and service are provided by same vendor.did not want to break up purchase at one source, installed by another source, etc. I am told these are good windows, have yet to stain and topcoat and finish trimming and caulking,on the interior. Rear of home gets more weather fluctuations..so, researching a clad product or seeking info as year 2013 will bring higher standards for energy star rating including triple glazing.Windows are complex.Will say these sliders are easy to operate and look good. Also got some casements;not sure they are better than other brands.Exterior looks far better than other"replacement windows" that you see thrown up all over the place from TV vendors [many of those are vinyl, I realize.]

No one would ever deny that the Infinity is not a pretty window.