Ecovillage Design

Ecovillage at Ithaca - Straw Bale Timber Frame Houses

Straw bale building construction has become a popular way to build a low-cost ecologically sound structure. Like any technique or building process it pays to have a well-designed plan and experience on your side. Many straw bale building techniques fall into the Nebraska style of construction. While not necessarily the wrong way to build a straw bale house it is more susceptible to moisture infiltration and rot in moist climates prone to severe weather events. Nebraska style uses straw bales like legos to stack bales like blocks. Rebar is driven through the bales and secured into a foundation plate, ensuring bales do not shift. The roof is then set right on top of the straw bales. At this point concrete or an equivalent bonding agent can be applied as stucco to the walls. Unfortunately if the straw bales are not flawlessly sealed there can be moisture infiltration, then, your load bearing walls under stress from your roof are at risk of collapse.

However, emerging building practices take advantage of straw bale’s excellent insulating factor (R30 - the higher the value the less air infiltration) while minimizing the risk of structural failure due to moisture and pest infiltration. One such method is exemplified in the timber frame straw bale structures at the Ecovillage at Ithaca. The 800 straw bales used in the construction of two duplex homes at Ithaca in 2003 were from nearby Lodi NY and comprised of waste plant mater from wheat crop. The load bearing structures in these buildings were all harvested locally and milled from Aspen, locust, larch, and 19th century reclaimed maple barn beams. With a timber framed structure in place the straw bales are stacked end on end vertically between the frames. Once built up, the straw bales are sealed with a plaster mixture of lime, clay, straw, sand, and water. Moisture infiltration was greatly reduced on this project by constructing the straw bale timber frame building on a raised poured-slab concrete foundation (made from recycled wood scrap and cement).

Other environmental considerations include, salvaged sinks, kitchen stoves, hoods and backsplash tiles, a PV system, heat recovery devices on all hot water fixtures to limit the amount of water drawn from hot water heaters, and of course a 2500 Watt PV system. Here is a full list.These buildings illustrate how marriage of old world techniques and reuse principals like timber framing and salvaging indispensable goods can be incorporated with new heating, cooling and energy systems to produce a structure that actually takes waste products out of a landfills and growing fields.