Peak Building Products out of Watertown, MN is now offering Optiwin windows from Germany. Thermally broken frames and heavy duty construction put them up there with the best windows in the world. Their products are Passive House certified by the Passive House Institute but their unmatched R-values of 10 and better make them a great choice for any type of construction in climate zones with above average heating or cooling loads. Optiwin also offers glazing options that allow for passive solar heat gains, which are desirable in heating climates such as Minnesota. Find out more at, or at
Before I forget, Optiwin also makes a stunning entrance door called the “Frostkorken Door”. Again, the R-value performance is incredible. In recent calculations I found that the entrance door to an average size residence alone can have significant impact on the heat loss.

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