Milgard Ultra fiberglass only has single hung, no double hung; I went to their Simi Valley factory/showroom. Their Tuscany line has double hung. I was impressed with how easy it was to pull it in to clean the outside of window as compared to the Pella vinyl I tested at a Pella showroom. I was impressed with Pella’s wood with aluminum clad exterior but everything else, vinyl and fiberglass, looked very low end. The finish on the Pella fiberglass had a wrinkly texture that looked cheap. I am concerned with comments about the Milgard Ultra fiberglass finish peeling. Has anyone else experienced this? We are planning on replacing all the windows and frames on our stucco house in SoCal so I want to get this right. We have white trim inside and out so color not an issue.

I would think looking at the u-values of the frame styles does not suffice. One probably needs to take some sort of product of the u-value and the exposed area of the frame. Since aluminum frames are much thinner than other styles, there is less area to conduct and radiate heat compared to other styles. So I think looking at the whole window as a unit, the glass is much more significant than the frame. Especially here in the Bay Area - where outside temps rarely dip below freezing in the winter. Summer performance is much more important - especially on south and west facing walls. But again, with aluminum this is mostly a function of the glass - which is why I specified the SunCoatMAX glass. In retrospect I probably could have saved a few dollars, and gotten a little more ambient light, by not doing the SunCoatMAX glass on the north facing windows. When we were rebuilding our house, we rented a place that had vinyl window frames. Did not like the look, and did not like the way they worked. (Don't remember the manufacturer.) This post was edited by wws944 on Tue, Apr 15, 14 at 13:31

We redid our mid-century modern house last year. Our architect recommended "thin, black, aluminum" frames. Aluminum is great because it is so strong that the frames can be made very thin and sleek looking. Just what one wants for a modern design. We primarily looked at Milgard, Fleetwood, and Blomberg. (Blomberg is a small manufacturer in Sacramento which makes really nice aluminum products. No web site. But call them and they will send you a nice packet of info.) We ended up choosing Milgard and have no regrets. BTW, both Fleetwood and Blomberg make commercial level units. Milgard rates theirs for "light commercial". Energy efficiency wise, aluminum is normally not considered "great". And on my windows, if one touches the frame vs the glass area on a very hot/code day, there is a very noticeable difference in temperature. Mitigating this is that because aluminum frames can be thin, there is more glass area vs frame area compared to vinyl or wood. I should note that we opted our Milgards to the Solar Max glazing. If possible, and the cost difference is not too bad, consider the 'thermally broken' aluminum frames - such as what Fleetwood offers. Milgard offers thermally broken aluminum frames too - but when we bought ours it depended on which state you lived in. For some strange reason, they were not available in California! I gave the Milgard district sales rep a really hard time about this.

Updating this thread for others considering aluminum frames: We did install the Milgard aluminum windows. They are really neat looking! My one regret is that there are a few windows where the old had a fixed pane and a casement. I ordered double casements instead, and probably should have stayed with the original layout. This because the double casements have a lot more 'frame' showing than we originally had. A few other things: 1.) We had some problems making casements work in some bedroom locations - due to emergency egress requirements. Basically a Milgard casement must be 30" wide for egress. Narrower and it won't meet code - even though the hinges are on the jamb. Wider and it becomes too heavy to work right. So we had to use sliders instead. 2.) Energy-wise, Milgard offers 'thermally broken' aluminum frames, but, strangely, not in California. I did order our windows with Milgards "Suncoat Max" upgrade though. It is interesting to place ones hand on the frame and then place it on the glass. Big difference in temperature. However, combined with other things in the construction (e.g., IB Systems membrane roof, and Techshield radiant barrier decking), the house is staying suprisingly cool during the current heat wave. (Got up to 100° yesterday.) And the insulation and drywall have yet to be installed! So in our case the aluminum frames don't seem to be a big problem. But if one were to insist on thermally broken aluminum, then Fleetwood seems to be a better way to go. (FWIW, I gave the local Milgard area rep a hard time about not being able to order thermally broken in California. Seems silly that you can order them in other states, but not here.) 3.) Milgard delivery was *fast*. Like less than two weeks from order to delivery. 4.) A nit: Our frames are dark bronze color, almost black. For some reason the screws mounting the casement lock handles are bright colored. Yet other screws, such as the ones holding the screens, are black. I need to call Milgard to see if they can provide some black screws to make the bright ones 'disappear'. 5.) For the master bath, I ordered reeded obscure glass, on the thought that it kinda carried the theme of the reeded obscure glass in the sidelight of my front door. (Of course a workman accidently broke the original 1950s sidelight a couple weeks ago, so now I get to match the sidelight with the master bath instead...)