This article was originally published in the March/April 1993 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.



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Home Energy Magazine Online March/April 1993




From the Southwest, Unconventional Insulations

The sunny Southwest is home to some new and offbeat ideas about building insulation. Plastered straw bales, first used as a building material by settlers in the Sandhills of Nebraska in the 1890s, are now reemerging as an energy-efficient and frugal insulation material. Matts Myhrman of the straw bale consulting firm Out On Bale of Tucson, Ariz., builds with straw and teaches others how to do the same. The standard bale, 20 in. wide, works just fine, he says. Bale walls, without any frame and with a post-and-beam configuration, support a conventional roof. Plaster inside and stucco outside weatherize the walls and give them a recognizable appearance. Leroy A. Sayre, chief building official of Pima County, Ariz., says of the straw bale construction, We don't know what the structural aspects are yet. They have concerned us the most. Nevertheless, based on diminished planetary resources, he issued Myhrman an experimental straw bale building permit.

In the fall of 1992 Myhrman delivered a straw bale seminar in the Sacramento Valley town of Carmichael, Calif. In that agricultural region, rice straw, usually burned after the harvest, would suit straw bale construction and could help to reduce the air pollution which blankets the valley at that time of year.

The Arizona Department of Commerce is promoting Energy Art to give that state's construction industry a boost and to increase the energy efficiency of energy-hogging concrete block homes. The department is creating a fake Southwest adobe with the use of sprayed urethane foam, but this technique will probably leave homeowners wondering if the use of this low-mass product is the way to create thermal mass for the passive solar home? In the application process, blocksulation, made of polystyrene, jackets the block walls. Then wire, lath, and stucco precede sprayed, textured urethane which is then sprayed with a sealant for an artistic facelift. The urethane wall is not flammable, though it will melt and emit toxic gasses if exposed to flames, according to Mark Anderson of Santa Rosa, Calif., who specializes in urethane construction. Commerce Department Spokesman Kirk Rossi does not foresee that the energy-saving aspects of Energy Art will interest homeowners. His analysis shows a ten-year payback. He expects it instead to be popular because it will increase the home's resale value.

P.I.S.E. (for Pneumatically Installed Stabilized Earth) is the name chosen by builder David Easton of Napa, Calif. for the rammed earth process he is developing. Pise de terre is the French name for this centuries-old architectural technique. Easton stabilizes normally highly conductive earthen aggregate with portland cement (his concession to wary customers more than an essential ingredient) and pours it into monolithic wall forms where it is compressed with a pneumatic tamper. The process does not call for further insulation.

John F. Long Homes, the biggest residential builder in Phoenix until the economic downturn, has taken steps to reduce the heat loss from rammed earth walls in the company's Solar One Development. The earthen walls in the 24 homes at Solar One are surrounded by 2 in. foil-faced rigid isocyanurate, 1 in. polystyrene, and stucco.

Finally, a printer in New Mexico, Eric Patterson, and a professor in Minnesota, Stanley Shetka, are each independently making high-grade, lightweight, cork-like building blocks out of recycled paper. Shetka and Patterson each have recently applied for a patent. Tests of the paper adobe process are currently under way by state and federal laboratories. Patterson expects the tests to show the conductivity of his blocks to be higher than cellulose.

-- Garry Tanner

Garry Tanner is a demand-side energy specialist who recently completed the Energy Management and Design Program at Sonoma State University in Rohnert Park, Calif.


Alternative Insulations--How Good Are They? Insulation values and densities for new and offbeat materials from the Southeast are not known, but the closest things to them are given. Conductivity R-Value per inch Density New material Known material1 (Btu-in./hr-ft2-deg.F) (hr-ft2-deg.F/Btu-in.) (lb/ft3) _______________________________________________________________________________________________ Plastered straw bales Straw (est.) 0.4-0.5 2-2.5 -- Sprayed urethane foam Urethane 0.2 5 1.5 Pneumatically installed stabilized earth Dry Sand 2.3 .4 95 Dry Clay 3.5-4.0 .2-.3 63 Healy Clay 5.5 .2 90 Paper adobe Paper 0.9 1.1 58 Cellulose 1.7 .6 94 _______________________________________________________________________________________________ 1. From 1967 Fundamentals Volume of the ASHRAE Handbook.

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