GREGORY LEHMAN:strawbale/cob duplex

Project overview

While taking a design class in college, it became a dream of mine to build a house entirely from raw materials after being introduced to A Pattern Language by Christopher Alexander. During my research over the next several years, I learned about ecological and traditional building. The space plan of the house is based on the traditional northern European “three-aisled hall house” with open central areas and small rooms, or niches, off to the sides.

I designed it as a duplex as I wanted to rent the lower level out to defray the cost of land and building. I rarely see duplexes in natural building literature, however this design decision was one of the best I’ve made. Two smaller separate dwelling spaces share a wall, driveway, and utility infrastructure, making a more efficient building

The house has a post and beam frame with locally found round logs as posts and rough sawn hardwood for beams. Cedar shakes cover the roof and local fieldstone is at the base of the walls.

One long side is cob while the other is straw bale. The north end is straw bale and the south end has many windows. I wanted to use both walling techniques to gain experience and placed the cob wall toward the western prevailing winds. I used lime-sand render for the exterior finish. As the site is wooded and well sheltered, the wall almost always stays dry despite being 10’ tall and not having a huge overhang. To avoid cutting large existing trees, the house was positioned with shorter end of the house facing south. I still did manage to have 2/3rd’s of the window area facing south.

The house’s tremendous thermal mass allows me on most winter evenings to start a fire at dinnertime, burn it hot, then shut it down at midnight. The house will coast until the next evening. There is a backup radiant heat system powered by an electric water heater. The rental unit is heated with baseboards, but is 60% below grade so has a low heating load.

The lighting is compact fluorescent; appliances are energy star where applicable.