Methods and Materials
There are over a dozen natural building methods in practice today and the nuances of designing and building with natural walls is substantially shaped by region and climate. Where other settings contend with earthquakes, fire or flooding; in the Northeast we must adapt to a harsh and wet climate. GreenSpace Collaborative has, over time, developed robust and economical wall, roof, plaster and foundation details that stand up to persistently wet and cold conditions. This has been an important part of our contribution to the field of natural building in our area.
Natural, renewable materials in an energy-efficient envelope
Suitable building materials are all around us in the natural world, yet we overlook their ability to provide lasting and appealing structures without relying on engineered materials to encapsulate or support them. Timber, plants, earth and stone in minimally processed forms provide a versatile, inexpensive and renewable building palette for foundations, floors, walls and roofs. Although commonly used throughout history and over much of the world today, these proven methods and materials have been replaced by less sustainable but fashionable alternatives. GreenSpace Collaborative relies on ingenuity, persistence and shared experience to rediscover or reinvent ways to build with nature’s renewable resources.
Straw Bale Walls
Most of our homes feature highly insulating straw bale walls with a continuous skin of natural plaster, inside and out. These straw and plaster walls are beautiful, rugged, thermally efficient and environmentally beneficial. Distinctive wall contours are the aesthetic hallmark of a straw bale home. Walls are 18 to 24 inches thick, which renders a feeling of solidity and permanence exceeding conventional construction. As a result, straw bale buildings provide exceptionally quiet and peaceful interiors. Given their high R-value, these walls have a natural ability to insulate against heat loss which significantly reduces heating and cooling costs. With low-tech labor requirements, straw bale construction is fast and substantially reduces the amount of wood used in production. Our practice slows the consumption of lumber and makes wise use of straw, which has been considered unwanted agricultural waste in many regions.
Straw Light Clay Walls
Straw light clay walls are comprised of loose straw coated with a clay slip, which serves as a binder. This material is then compacted into a form and allowed to dry. Depending on the season and the climate (variables are wind and humidity), a 12”-thick wall may take a month to several months to become fully dry. These walls provide reasonably good insulation and also act as a thermal storage medium.
Woodchip and Clay Slip Walls
A recent innovation in modern German clay-building techniques is the use of wood chips bound with clay. This material acts as an insulation infill for exterior and interior walls. Wood chip light clay is comparable to straw light clay in construction method and physical characteristics although the production and manufacturing process is much easier. It has a shorter setting, tamping, and drying time. Woodchip and clay slip walls are generally more efficient and less labor-intensive than straw light clay although does not likely provide quite as high an insulation value as other natural wall options.
Earthen and Lime Plasters
The most striking aspect of a natural home is its solid-feeling wall structure with Natural Plasters on both the interior and exterior wall surfaces. The hallmarks of natural homes, especially straw-bale homes, are the result of natural plasters: depth of color, wall durability, visual texture, and a singular beauty. Interior finish plasters offer a rich palette of options for adding depth, color, and beauty; examples are clay plasters with a casein wash or a lime plaster with a lime wash. Exterior plasters do best with a durable and breathable lime plaster finished with a lime wash. GreenSpace Collaborative can help guide clients in selecting an appropriate choice and make the best recommendations based on a list of priorities such as durability, beauty, climate, and embodied energy.