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.
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
Improving the energy-efficiency of new and existing construction has long been a focus of the building industry. When it comes to insulation, exterior is the choice of many architects and builders, because it eliminates the thermal bridging through the studs.
However, continuous insulation presents its own unique challenges with installing windows and flashing the rough openings. The mounting point is no longer flush with the sheathing, it must be extended out to meet the exterior insulation depth. Rough openings are always a weak spot for potential water infiltration – and extending the mounting point for windows compounds the problem.
Until ThermalBuck hit the market, there really wasn’t a good way to insulate and create a thermal break around the mounting points of windows & doors. The traditional method to bump out windows was to build a wood window buck. Wood does extend the mounting point, but it doesn’t hold up well to moisture, and it has a low insulating value. With an r-value range of 4.4 per inch, ThermalBuck is a better insulator than wood. But how much? We performed some third-party testing to find out.
Thermal Transfer Performance: ThermalBuck vs. Wood Buck
Using thermal imaging, we recorded the performance of ThermalBuck against a traditional wood buck in a controlled environment. In the two mock-ups below, three temperature sensors were placed on both the ThermalBuck installation (l) and the wood buck installation (r). The temperature condition on the exterior of the structure was -6.67 ºF, and the indoor of the structure 72.76 ºF.
These photos show two window installations side by side. (l) ThermalBuck (r) traditional wood buck.
54% More Heat Transfer with Wood vs. ThermalBuck
On the exterior of the structure (point A) the wood buck looses 7.88 ºF, or 14.55 ºF total degrees from the outside temperature. ThermalBuck only loses .11 ºF , or 6.78 total degrees from the outside temperature. The wood window buck allows twice as much energy to escape, while the window installation with ThermalBuck is effectively limiting thermal bridging.
ThermalBuck High-Performance window buck creates a significant thermal break at the mounting points of windows & doors. Using ThermalBuck as part of your continuous insulation solution is an effective way to limit the amount of thermal bridging that occurs through your building envelope.
To learn more about thermal bridging, see what the experts have to say at greenbuildingadvisor.com
Editor’s Note: This article was updated in July 2018. The testing results and thermal images were not changed.