Straw Bale Construction
When six Franciscan Sisters in Hiawatha, Iowa, decided to build retreat cottages at their spirituality center, they chose to use straw bale construction.
Sister Nancy Hoffman and Sister Therese Pedretti helped plan the two houses, called hermitages, and wanted to do be innovative without disrupting nature. The Sisters believe in a strong connection between spirituality and ecology, and felt this building method meshed the two.
How it works
The cottages were constructed by stacking bales of tightly packed straw on top of each other to create walls, then stitching them together with nylon thread.
Steel rods were inserted in the bales to make the walls even stronger; the bales were then covered with chicken wire and stucco is applied to the surface. This sealed out moisture and prevents rotting.
Energy efficiency
According to the U.S. Department of Energy, straw is a form of cellulose that has reasonably good insulating properties; and because a bale can be up to two feet thick, a straw-bale wall has extremely high thermal resistance.
Another great feature of these houses is the heating system. Radiant floor heating was installed under the cement floor.
The houses also use solar energy to provide electricity. They even installed a special refrigerator that uses a fraction of the energy of a regular refrigerator.
Other benefits
The finished house is very quiet - the 18-inch walls block much of the outside sound. It's also a very healthy house, because of the natural exchange of air though the straw.
Costs
The final cost is impressive too - it's actually very inexpensive, with a price tag less than half of a similar traditionally-built home.
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