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PHIUS Verified Installation with Alpen

Alpen 925 Zenith Nail Fin Window + 2.5″ ThermalBuck

Energy efficient windows are an essential component of any high-performance building. But the installation was always a challenge for nail flange windows, which have to be mounted on the same plane as the exterior insulation.

ThermalBuck teamed up with North-American passive house window manufacturer Alpen High Performance Products to introduce their PHIUS Verified Window Installation Detail featuring the Alpen 925 Series Fiberglass window with 2.5″ ThermalBuck.

PHIUS Verified Window Installation Data:

Alpen 925 Zenith Nail Fin Window + 2.5″ ThermalBuck 

ThermalBuck effectively limits thermal bridging at the rough opening, provides a superior air & water barrier than a wood buck, and also a strong support for the weight of the window.

Passive house designers and builders now have the data they need to confidently include ThermalBuck into their specifications.


The Alpen HPP Zenith Series ZR-9/ 925 window features up to R-9.1 insulation, 99.5% UV protection, insulated frames, and Alpen Glass, Alpen’s renowned Suspended Film Technology. Every Alpen window has 9 key design features that make these highly engineered windows some of the best in the industry. Read more about the technology and craftsmanship of Alpen windows here.

Alpen High Performance Products is a national distributor for ThermalBuck. thinkalpen.com

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