What you choose to use for your walls, whether you are trying to maximize insulation or thermal mass, will have a dramatic effect on the performance of your home. Not only does each material have a unique look and feel, it’s performance varies widely and it’s important that we choose the right material for the right situation.
Besides straw bale, the following is an overview of some of the natural building techniques employed by Dirt Craft, including their suitability for various projects.
Light straw-clay makes use of fibre, typically straw, though wood shavings have been used in part or entirely as a replacement for straw, and clay slip to create a wall that is both massive (lots of thermal mass) and insulating. Just enough clay slip is used to coat the straw, holding it together in a powerful matrix. The walls make use of forms and the clay slip coated fibre is pressed into the wall cavity created by the form work. The walls, once dried, are covered in earth plaster. And unlike cob, which is has curves and irregularities (part of the appeal if you ask me), the form work used with light-clay creates straight walls, with all the right angles you’d find in a more conventional home.
Building with light-clay is significantly faster than cob but tends to use significantly more wood, particularly 2 by 4’s (i.e. dimensional lumber), which a person could entirely avoid in a cob structure. The benefit of light-clay, though, is that it is both insulating (approximately R-1.6 per inch) and massive; the walls are dense and usually a foot thick. So like cob, light-clay is a great material for passive solar design and with a heat source like a rocket mass heater or masonry heater, it could be adapted to work in a wider range of climates than cob.
Cob is earthen masonry made from clay, sand and straw. Its thick walls (often a foot or more) are free formed from the ground up. It is one of the easiest, most elegant and least expensive building techniques available, though it is labour-intensive. Cob has incredible thermal mass making it ideal for passive solar design and its versatility is unmatched by any other material. Cob walls, once erected, are covered in earth plaster.
Cob is not big on insulation, so its use as a primary building material is limited to warmer climates, though cob homes are becoming increasingly popular in British Columbia, including on Vancouver Island, the Gulf Islands and parts of the interior. Cob may also be integrated into parts a home in less temperate climates, such as on southern exposures and for interior walls.
Cob is also an amazingly adaptable material and can be used for many things. Typically, we use cob to build the ever popular wood fired oven, as well as rocket mass heaters, benches and garden walls, and even for making sculptures.
How We Can Help:
Please visit our Building Services – How We Can Help page for information on how we can help with your project. For hands-on learning, check out our Upcoming Workshops where you’ll learn the skills you need to complete your own project.
Have a look at our consulting services if you require more specific information for your ideas or project.