¯     Earth-Sheltered Design

      Earth-sheltered design uses the earth as a major part of a building's thermal control system.  This “tempering” by the earth is accomplished in three ways.  In a direct system, a large part of the building’s exterior is in contact with the earth, and conduction through the walls, floor, and other building elements regulates the inside temperature.  With an indirect system, the building’s interior is conditioned by air brought in through the earth through systems like earth-tubes.  Lastly, an isolated system uses earth temperatures to increase the efficiency of a geothermal heat pump by moderating temperatures at the condensing coil.

 

¯ Hybrid Structures

      Hybrid buildings are an outgrowth of idea-sharing within the natural building community.  Several building techniques can be combined for increased building efficiency or for artistic effect.  An example is combining a thermal-mass technique, such as cob or adobe on the south side of a house, with an insulating-type system, such as straw bales or straw-clay on the north, east and west sides, thus taking advantage of the best qualities of each system. 

 

¯ Solar Energy

      Solar design refers to the use of the sun's energy for the heating and cooling of indoor spaces.  In this approach, all or part of the building takes advantage of energy characteristics in air and materials, created by exposure to the sun.  Passive solar means situating and shading a dwelling properly in order to take full advantage of the natural movement and orientation of the sun during daily and seasonal heating and cooling cycles.  See more discussion of passive solar heating.

     A building using a large thermal mass (such as that built with adobe) absorbs energy from the sun (solar gain) and radiates the energy throughout the home.  This flow of free heat is regulated by vents that control the air circulation, allowing the occupants to achieve the right ambient temperature in any given area of the house.  Simply by orienting a building to use passive solar gain, a homeowner can save 10–20 percent of heating energy.  A whole-system design can save more than 75 percent of heating energy with integrated solar gain, thermal storage, and well-insulated shell components.

     Proper orientation of the home to take advantage of the sun's seasonal position can result in a pleasant space washed in natural light, and a warmer space in the winter while avoiding too much sun and heat in the summer.

 

¯ Straw Bale Construction

     First used by the pioneers to build homes in the Plains, straw bales are relatively inexpensive to buy and build with.  Straw bale construction uses baled straw from annually renewable crops of wheat, oats, barley, rye, rice and others to create walls then covered by stucco.  The thick walls offer superior insulation, averaging R-48 for an 18" wall.  With a natural plaster of mud, lime-sand, or cement, straw bale walls "breathe," and together with the sound-absorbing qualities, provide a quiet, healthful interior environment. Straw bales can also be combined easily with other natural building systems.

       Straw bales are used most commonly as infill in a post-and-beam structure, where the framing structure supports the weight of the roof.  Bales are secured to a foundation with pins or strapping.  They are laid in a running bond and pinned together using rebar or wood stakes.  The roof is then attached to a top plate. 

 

¯  Straw-Clay (Leichtlehm)

     Leichtlehm is a German technique in which loose straw is coated with a clay slip and tamped into forms as an infill for timber-frame structures.  Occasional horizontal members spanning between the exterior frame are placed in order to "lock in" the straw-clay mass.  The frame is usually fully visible on the interior of the building to take advantage of the beauty of the timber-frame joinery.

     Once each layer is complete, the form is moved up and the next layer is tamped until the wall is complete.  The walls are allowed to dry thoroughly, and then are coated with a mud or lime plaster.  Highly accurate buildings are possible with the timber frame and straw-clay technique, allowing a "natural" structure that can look similar to conventional housing.

 

¯  Timber Framing

     Timber frame homes are beautiful, strong, open and light, energy-efficient, and versatile.  The oldest method of building wooden structures, timber framing uses exposed timber-frames surrounded by materials such as straw-clay or straw bales to take advantage of the beauty and structure of wood while eliminating its unnecessary use.  A crane lifts the huge timbers and swings them into place, and the builder taps the hand-cut mortise and tenon joints together with a mallet and pounds in the wooden pegs that are the only nails.  When the timbers have all been fitted into place, the frame looks and acts like the skeleton of the house, defining its outline while holding all the structural weight.

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