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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

ALPEN High-Performance 725 series fiberglass window installation with ThermalBuck™

ALPEN Window Installation at NAPHC2016 to Feature ThermalBuck

Alpen High-Performance Products will feature a window installation with ThermalBuck at the 11th Annual North American Passive House Conference Sept 21-25th in Philadelphia, PA.

Known for manufacturing super-insulating, thermally efficient residential and commercial fiberglass windows & doors (as well as architectural glass), this Colorado-based window manufacturer has over 30 years of experience in glazing technology, and an excellent reputation for craftsmanship and performance.

In 2013, Alpen HPP was the very first manufacturer to receive certification under the Passive House Institute -US (PHIUS) Certified Product Performance Data Program.  This certification uniformly and independently verifies product performance for use in the passive building industry.

Alpen HPP has since been joined by 10 other major window manufacturers in receiving this certification, including Intus, Marvin, and Zola.

Continuous insulation throughout the building envelope without any thermal bridging is one of the key building-science principles of a passive building.  Testing an installation of their 725 Series window with ThermalBuck, is just one of the ways Alpen is committed to finding the best ways to solve their customer’s challenges, and continually provide exceptional service.


The PHIUS is a non-profit organization committed to making high-performance passive building the mainstream market standard. It’s membership-based branch, the Passive House Alliance US (PHAUS) was formed in 2010, and now supports over 800 members across the US.  For more information on the key building-science principles of a passive building, please visit phius.org.  

ALPEN HPP