The Sustainable Design Center

Bio-regionally Appropriate Architecture Collaboration and Planning for a Cleaner, Healthier Planet

Southwest Austin Straw Bale

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Home in the Oaks, Austin, TX. Architect for a 1964 s.f 2 story straw bale home with a hybrid framing system. The design takes advantage of the site’s many mature oak trees and natural rock outcroppings (showcasing the 24″ heritage oak at the southwest corner of the home) while orientating the buildings to take advantage of passive solar heating cooling and natural ventilation concepts. The result is a home with a long axis within 15 degrees of a true east-west orientation, with a garage on the southwest side. This takes advantage of prevailing wind patterns (predominate breezes are from the southeast) by using the garage as a wind break to funnel breezes to the home and deck. The deck is shaded by the oaks and has a roofed area for inclement weather.

The 2 story great room was one of the owners original design goals and the central factor in the building layout. The large open space is accentuated by the exposed heavy timber frame which-when combined with the straw bale walls-gives a timeless old world feel and provides natural light while protecting the space from the harsh summer suns of Central Texas. All bedrooms have flow through ventilation, ceiling fans, views of the trees and a timber framed vaulted ceiling. The master bath has high ceilings, natural light, a clawfoot tub and stone walk in shower.

The homes energy efficiency starts with the passive solar orientation and appropriately sized roof overhangs. The straw walls provide an R value of approximately R 30. The roof is insulated with 9-1/2″ of spray foam insulation (R=3.6 per inch). All of the doors and windows have a U value of less than or equal to .32 and the roof overhangs provide shade from the Texas sun. The metal roof reflects heat, provides a long lasting durable surface and is a necessary component in the owners plans for a future rain water collection system. This home which was completed in November 2013 is in the process of being rated and should achieve a 5 star rating from the City of Austin Green Building Rating Program.