You may find cob cottages particularly cute, but taste isn’t reason enough to choose one natural building material over another. Like more manufactured products, different earth materials all have different uses: straw bale is a great insulator, cob is a nice thermal sink as well as one of the easiest materials to sculpt if you’re looking for lots of curves in your structure.
“There are a dozen ways you can build a wall using pretty much the same materials: clay soils, straw, sand, sticks”, explains natural building expert Michael G. Smith, “and each of those has its own particular sets of attributes as far as wall thickness, thermal properties, sculptural properties, speed, materials that they require, etcetera, etcetera so you might make different decisions based on your site, based on who you are, what you need as to which materials to use, but even within the same building different parts of the building need to do different tasks.”
So even in the same building, you might choose straw bale for one wall and cob for another.
In this video, Smith shows us some of the uses for straw bale, cob, slip straw, and clay wattle (a variation on wattle and daub) in the homes and buildings of Boonville, California’s Emerald Earth Sanctuary.