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

 : ThermalBuck in Three Minutes

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

Product Sizes & Dimensions

ThermalBuck outperforms a traditional wood buck, and protects the integrity of your window installation. 

Testing & Technical

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

Thermal Bridge Coefficients

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

ThermalBuck solves the challenge of mounting windows with exterior insulation by extending the mounting point for windows, and creating a flush plane for cladding.
The Atlanta home of Building Performance Experts Grace and Corbett Lunsford, Home Performance You Tube channel.

7th generation Missouri homebuilder Rusty MacLachlan, J.R. MacLachlan Custom Homes & Remodeling 

Installing windows on a building with exterior insulation isn’t easy.

The window and the rigid foam or mineral wool need to line up on the same plane for good drainage, proper cladding attachment, and to prevent compression of the insulation. Rough openings have always been the weakest spot on any building for air and water infiltration, and “bumping” the window out only makes it more difficult to achieve a good air and water seal.

Traditionally a wood buck is built to extend the mounting point of the window to create a flush plane. But wood can rot, warp, and shrink over time. Wood is a poor insulator, allowing thermal bridging around each window and door. Not only does it reduce the energy efficiency of the building, it causes condensation to form, and potential damage from moisture – which can lead to extensive repairs.


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

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. 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. Dimensionally stable and strong, it will not warp, rot, or shrink, and helps to support the weight of the window. ThermalBuck outperforms a traditional wood buck, and protects the integrity of your window & door installation.

*We recommend ThermalBuck installation with tested & approved sealants  See our FAQ page under “Sealants” for more information 


Austin builder Matt Risinger features ThermalBuck on an episode or Risinger Goes Rogue

“Once you see it, you really understand the problem this solves for builders like me.”

 – Matt Risinger, Builder, Building Science Expert, Risinger & Co., Austin, TX

Introducing the ThermalTight™ System

ThermalTight makes it possible to manage water – air – vapor + thermal all in one panel, with one less trip around the building envelope. It combines two essential building envelope materials into one, easy-to-install panel: Neopor® GPS semi-vapor permeable rigid insulation by BASF, and a high-performance WRB laminated to the exterior of the panel, that acts as both a water and air barrier.

This is the future of the building envelope. 

Learn more at