The wood fiber insulating panel, manufactured in a dry process, with its innovative, asymmetrical bulk density profile, combines the highest ecological standards with reliable building science to create cold climate cavity roof and walls that promote drying to the exterior. Agepan THD is made of woodfibre, wax and polyurethane adhesive. The combination of materials creates a board that will act as a high perm layer for the exterior of a thick roof or wall framing cavity (2x8 or more). When placed as exterior sheathing, the R5 board will break the thermal bridge of framing and needs no additional membrane placed over it due to the wax content applied at the fibre level in the manufacturing process.

Agepan THD is not a structural board and will not pickup shear loads. THD is at the heart of the "reversed wall" where the shear panel (Ply/OSB) is moved to the inside to act as  the shear, air barrier,  vapor retarder layer  while the THD is placed at the exterior and regulates cavity moisture by venting water vapor into the ventilated rain-screen gap. In this assembly type,  it's common to place furring strips over the now interior shear layer to create a service cavity. The board size is not the standard 4'x8' material and never joins on framing. The oversized tongue and groove of an Agepan THD board creates a joint that can be walked on at 24" centers and placed between framing - and never over framing. The board size is roughly 24" x 89" and 14.5 ft2 per panel. Please call us for more installation information.


This board is always in stock in our Tumwater, WA facility and is available for shipment by motor-freight anywhere in the USA. Please advise us of intent to use on large projects eight weeks in advance to help us manage our inventory and ensure availability.


  • Exterior insulation ideal for breaking the thermal bridge on walls & roof in wood framed buildings
  • Large tongue & groove joints mean the panels "float over framing" and join anywhere. No need to layout and join panels at framing
  • High permeability (20 US Perms) promotes "drying to the exterior" for cold climate walls when used in a vented rainscreen applications (3/4" gap required)
  • Integrated WRB: wax impregnation deflects bulk water and allows additional WRB membranes to be left off
  • Very good summer heat protection due to high heat storage capacity
  • Windproof and water-repellent
  • Special tongue and groove joint stops the weather and "windwashing"
  • Easy assembly thanks to chambered tongue and groove profile

Notes: Minimum 3/4” battened & vented rain screen gap required. Exterior wall sheathing does not require additional WRB. Apply with box nails for initial set then follow with screw from exterior batten face into framing with minimum 1 -1/2” penetration into framing. Can NOT be used for shear and lateral loads. We advise consulting your project engineer to ensure all loads are properly accounted for. 

To price a large or small project just give us a call or email: (360) 866-8779 -or-

Small Planet Supply no longer stocks the 5/8" thick DWD series board due to import and logistics restrictions.

The Agepan THD N + F is an in dry-process wood fiber insulating board) with surrounding tongue and groove profile, the requirements of EN 13171 and the DIBt approval Z-23.15-1508 (part of the approval for the thermal insulation system Knauf WF THD N + F meets with the approval number Z-33.47-673). The digested wood fibers are sprayed with formaldehyde-free PUR binder and pressed into a single-layer plate having an asymmetric density profile. This achieves the pommel WF THD + N F exceptional properties in use in a thermal insulation system.

Agepan Videos

Innovative Woodframe Construction

Hammer & Hand 

Agepan DWD and THD - What's the difference?

The DWD and THD series are made of the same 3 ingredients: Woodfibre, wax, and PUR adhesive, retain the same high perm ratings of 18-20 US perms, and both need no additional WRB. Where they differ is in density.

Our original DWD was a high density board (565kg/m3) that promoted drying to the exterior but did not break thermal bridging due to the thermal conductivity of it's higher density. The new THD board carries the same properties as the original DWD but adds the low conductivity of a low density board (230kg/m3). 

Small Planet Supply no longer stocks the 5/8" thick DWD series board due to import and logistics restrictions