Hi there. We haven't completed the project yet, but I'm pretty sure my wife and I have decided on the window.
For our front (south facing under a front porch) picture window we are going to go with an Alpen 925 seires. Center of glass is u.08 (R-12.5) and whold unit is u.12 (R-8.3). We will be going with the high solar heat gain glass option.
While I am at it we decided we're going to replace the 2 large (also south facing with a proper overhang and mature decidious trees) horizontal sliders in my son's room. For those we're going to go with Alpen 725 series horizontal sliders. I would have prefered the 925 series for the performance upgrade but they only make sliders in 525 and 725. The center of glass on these are u.13 (R7.7) and whole unit is u.20 (R5). These will also be high solar heat gain glass.
The picture window is is ~21 sq. ft. and the price will be ~$1050. Each horizontal slider is ~20 sq. ft. and they are ~$1175 each. Plus shipping.
Obviously these are expensive windows, but I think it is worth it for the performance/comfort they will provide.
These really sound like impressive windows. Here is a link to their thermal performance specs:
http://www.alpenhpp.com/wp-content/u...nce_101313.pdf
I'll report back after we purchase/install them.
-Dave