Alpen HPP makes “cadillac” windows in my opinion. The specifications are far beyond Milgard as I’ve pointed out, and they have a lot of information available about their windows on their website that shows the quest for very high energy efficiency in their products. There are many recommendations for the windows on green building forums and sites. Some prefer the uPVC technology from Canada or Europe for a bit higher ratings at less cost, but uPVC is a cheaper product overall than fiberglass so I’m not impressed by the differences.
As mentioned before Alpen uses a “Mirror Film” technology that is manufactured in Chicago by Southwall and unlike other window companies has had success with its use. This film creates a third or forth pane within the window to capture heat and lower the u-values. They pair this technology with a super insulated fiberglass frame that holds its shape and spacers that maintain a good seal within the window. They offer a limited life time warranty to the original owner/purchaser of the windows, excluding color fade, screens, and labor. Still a very good warranty in the industry.
Originally I had Mark send a quote for Series 725 which was the Alpen mid range window. Since then Alpen has released an upgrade version of their 525 series using a new spacer that improves the performance.
Energy Star uses the test data from the National Fenestration Rating Council to determine efficiency. The data used are U factor, the measure of heat transfer through the window, Solar Heat Gain Coefficient, the measure of solar energy transfer (low ratings block heat from the sun), Visual Transmittance, the light that gets through the window–higher values equal more light, air infiltration, the measure of air leakage through the closed window and Condensation Resistance, the amount of condensation that builds on the window surface.
Generally the more expensive the window, given similar construction materials, the better the NFRC figures, at least that is what I have found in shopping. I wanted to find the best figures for the money. That is an arguable measure. My daughter’s new windows and doors are Energy Star. They have the minimum ratings to make that designation and perform well for her normally built stick house. The cost was typical builder supply cost and that is about an order of magnitude lower. So $300 retail for a door vs. close to $3000 for a special order high performance door. Custom special order doors are also that expensive though so compared to Pella or Anderson or even the more energy efficient Milgard, the price difference is much less. We are trying to produce the most energy efficient, highest LEED rating, closest to Net Zero home that we can afford and that makes sense for the final value of our property.
Even within the Alpen window lines, the 725 was mid-range with great performance, but the 925 is their highest rated window–and has Passive House approval. But they are even more expensive. We would have gone with 725 but Mark’s advice is that the 525-S is a better “deal”. Great performance for less cost.
The 525-S series has better air infiltration figures than the 725. The seal must make the difference as the numbers typically are .05 for the 725 and .02 for the 525-S. Otherwise the 725 have lower U factors. A fixed glass low profile higher solar factor window is .16 while the same 525-S fixed glass window is .17. So with that difference we have switched to the 525-S series for the more affordable performance.