ThermalBuck extends the mounting point for windows & doors, and insulates the rough opening to limit thermal bridging. 

How it works

Window installation with exterior insulation is a challenge. Solve the problem with ThermalBuck.

Installation Steps

ThermalBuck outperforms a traditional wood buck, and saves time on your window installation. 

ThermalBuck vs. wood

PHIUS Verified Psi-Install Data:
Alpen 925 Zenith Nail Fin Installation
with ThermalBuck.

Thermal Bridge Coefficients

News & Events

It’s time for JLC LIVE – Get Your Free Pass! February 28, 2018

ThermalBuck is headed to JLC Live 2018 on March 23rd & 24th at the Rhode Island Convention Center, in downtown Providence. And we’d like you to be there. JLC Live New England is widely known as the best hands-on construction show in the business. Focused on live product demonstrations and popular… Read more

ThermalBuck to Exhibit at Better Buildings by Design January 18, 2018

When we think of leaders in energy-efficiency and sustainability, we think of Vermont. It’s no surprise Vermont ranks among the top 5 states in the nation for the advancement and support of energy efficiency, and has long maintained a pioneering role among the states in this arena. The American Council for… Read more

If a window isn’t installed properly, it won’t matter how energy efficient it is.


High performance wall assemblies are becoming more common as builders work to make homes more energy-efficient, and meet energy code requirements. But builders know attaching windows with rigid foam or mineral wool isn’t easy. Traditionally a wood buck is built to extend the mounting point, but wood can rot, warp, and shrink over time. It’s not easy to flash wood bucks, and be confident that you’ve got a good air & water seal to prevent moisture intrusion. Wood also has a low insulating value, and allows thermal bridging around the rough openings, reducing the impact of the exterior insulation.  


ThermalBuck solves the challenge of installing nail flange windows & doors with exterior insulation by extending the mounting point to create a flush plane for cladding – but it also insulates the rough opening, limiting thermal bridging around windows & doors. Coated with a waterproof resin and secured to the rough opening with an air & water barrier sealant* and nails, it’s simple to install and easier to flash than a wood buck. ThermalBuck saves both time and money when installing nail flange windows with continuous insulation – with more performance. 


The continuous insulation solution for the high-performance building envelope.

*We recommend ThermalBuck installation with DAP Dynaflex 800 Modified Polymer Sealant or Dow Corning 758 Silicone Sealant 

Alpen Certified Installer attaching window into ThermalBuck


Simplify Window Installation

ThermalBuck solves multiple problems when using exterior insulation and/or rainscreens. It extends the mounting point of windows & doors to create a flush plane for cladding attachment. In addition, it allows for structural attachment to prevent the compression of insulation and preserve a tight wall assembly. 

Consult the window manufacturers’ recommendations, then add an additional 1/2″ on all 4 sides to accommodate ThermalBuck.  (see installation for example)

Side by side rough openings with ThermalBuck window buck installed shot from interior


Improve Performance and Efficiency

ThermalBuck simply does more than a wood window buck. It insulates the mounting points of windows & doors, and simplifies flashing. Dimensionally stable and strong, it helps to maintain the integrity of the window installation. ThermalBuck is part of a continuous insulation solution, and an essential part of the efficient building envelope. 

R-values range from 4.4 to 17.6. View the results of our thermal testing and see how ThermalBuck outperforms wood 2:1.  

Build Green and Live Green

Using ThermalBuck to improve your window installation means you’ll use fewer natural resources to heat and cool your home year-round. Not only will that save you money, it’s better for the environment too.  

ThermalBuck reduces thermal bridging and prevents moisture from accumulating, which improves your indoor air quality – and that benefits your family’s health.