[Greenbuilding] Biochar as Annual Cycle Building Dehumidifier

[Koehn Chris]

We’ve recently completed a home using “chip and slip” walls: 12” deep Larsen trusses filled with wood chips coated in clay slip and manually compacted. The clay-straw / clay slip folk seem to be experimenting with variable ratios of clay vs. chips: I would quantify ours as “middling” - enough to bond the chips and a bit more. Not very scientific, sorry. Chip and slip was done last summer. Clay plasters are just about done being installed inside and out. Lots of mass, lots of clay.
My understanding of clay is that it’s quite hygroscopic, holding as much as 5X it’s own weight in water. So the walls take on moisture over our wet winters and release it during our dry summers. 
It’s early days, and the house is just now being occupied, but already the owners report comfortable indoor humidity (and temperature).
Since clay is readily available in most parts of North America, I’d consider it a better option than charred wood, based solely on it’s environmental impact.

Regards,

Chris Koehn
TimberGuides
Vancouver Island