2050 Sustainable Materials Series: Cordwood

• Embodied Energy:

Cordwood buildings typically have significantly lower embodied energy than other construction solutions, provided the wood used is local, or better yet, sourced on-site. When considering the fact that the wood needed for these walls requires very little engineering work prior to installation, there is minimal waste or energy consumed processing it.

However, the inherent energy contained in the wood through the sourcing process (cutting the trees, logs etc), combined with any distance that the wood must travel to the site, can impact its embodied carbon drastically.

• Operational Energy Efficiency

The thermal performance of cordwood walls can achieve excellent performance, depending on the thickness of the walls and the type of insulation being used. The thickness of cordwood walls can be adjusted for specific climates relatively easily.

However, the wood often shrinks within the mortar, creating cracks that can significantly reduce the R-value (or thermal performance) of the wall. Therefore, repairs to seal cracks must be made to retain the targeted insulating factor.

• Longevity:

Even though the longevity of cordwood buildings could be a matter of dispute, it can be retained if appropriate measures are in place. Proponents say most wood shrinkage and rot can be avoided by carefully choosing well-seasoned wood and creating overhangs to protect the walls. Detractors claim that even with these considerations, the wood in the walls often rots, shrinks, and can be severely damaged by insects. However, the risk of rot or insect damage can be avoided by ensuring the following:

• Use dried, debarked softwood logs such as cedar
• Use as slow slow-setting mortar mix as possible
• Keep the logs from touching within the walls by creating wide mortar joints

Both sides agree that some shrinkage of your cordwood walls will occur, so it is important to know how to address these problems as they appear.

• Cost:

Typically, there is significantly less upfront out-of-pocket cost associated with cordwood construction in comparison to a standard concrete / stick frame house of similar size.

The simplicity associated with the construction method means that in many cases, labour is carried out primarily by the owner, meaning that it does not require highly skilled or trained builders to execute its construction.

• Ground conditions:

Construction plans for proposed cordwood construction buildings are subject to the building inspector’s approval. Prior to construction, soil conditions on the site must be assessed and approved to support heavy cordwood masonry walls.

This is not typically an issue, but a consideration that must be made before designing or procuring any of the materials.

Panchami Pandharikar, Environmental Designer