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High performance low cost buildings of straw
Agriculture, Ecosystems and Environment, 16 (1986) 281--284
281
Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
HIGH PERFORMANCE LOW COST BUILDINGS OF STRAW
DAVID A. BAINBRIDGE
Dry Lands Research Institute, University of California, Riverside, CA 92521 (U.S.A.) (Accepted for publication 24 March 1986)
ABSTRACT Bainbridge, D.A., 1986. High performance low cost buildings of straw. Agric. Ecosystems Environ., 16 : 281--284. Straw bale construction is ideal for highly energy efficient buildings. Techniques developed in mid-continental North America should be refined and tested throughout the world. Straw is a tremendous agricultural resource, not a waste to be burned in the fields or used as fuel.
INTRODUCTION
The last few years have seen a tremendous leap forward in building design. Homes are now regularly built in very cold climates that are livable throughout the winter using only body heat, internal gains (cookstove, etc.) and passive solar heating using south facing windows (Shurcliff, 1982). With very little energy for supplemental heat, typically 100--300 kwh, these homes are very comfortable indeed (Nisson and Dutt, 1985). Yet the cost of these homes, while comparable to conventional construction (Bainbridge, 1985) is still too expensive for most residents in the developed countries and far beyond the means of most people in the world. Many of these impoverished people live in homes that use traditional designs to maximize passive solar heating and cooling with appropriate window placement and use of thermal mass (Bainbridge, 1978), but the lack of insulation makes them barely tolerable to live in even with high consumption of costly and environmentally destructive fuels (straw, dung, etc.). DISCUSSION
A traditional building system once used in both America and Canada could resolve this problem and provide well insulated, inexpensive, and earthquake resistant homes for people around the world, and energy ef-
0167-8809/86/$03.50
© 1986 Elsevier Science Publishers B.V.
282
ficient farm buildings. Straw bales were once used in areas of the mid-continent of North America where w o o d was expensive and scarce (Welsch, 1973). The bales are used like large bricks. Stuccoed or plastered inside and out, these bale buildings have proven tough and efficient. One to three story buildings fifty years old are still in good condition and attest to the strength and durability of straw bale construction (Welsch, 1973; Argue, 1980). The insulation value of the straw bale will depend on a number o f factors including the density of the pack, moisture content (below 15% required) and t y p e o f fiber, yet is in the range of R S I - 0 . 0 1 - - 0 . 0 2 mm -1. This makes it easy to achieve high wall insulation values of RSI--5+ needed for superefficient buildings (Bainbridge, 1980). With proper window and building orientation and use of thermal mass (water, rock or earth) inside the building, very effective passive solar designs can be built very economically. Straw bales offer other advantages as well. They are easy to use (stack and pin), have very low loading so minimal footings are needed, and are strong enough to support the r o o f structure without additional beams or posts. Pinned together well with w o o d or steel pins they would also be stable and safe in earthquakes. Current practice (a few hay bale structures are still being built) is to plaster the bales inside and o u t over wire mesh (Argue, 1980; Strang, 1984), b u t fiber reinforced plaster or natural reinforcing materials such as a b a m b o o strip mesh might prove equally effective. Traditional designs often used wire mesh reinforcing, but some bale buildings were simply covered with sand/mud plaster without reinforcing (Welsch, 1973). The favored straw for bale building was rye straw, b u t almost anything that can be baled has been used, including Russian thistle, Salsola kali. Over-mature straw with little feeding value makes the best bales for construction. Some of the more promising straw crops include rye, wheat, wheatgrass, barley and millet (Table I). Roofing can be of any material, b u t would most logically be thatch, FABLE I Straw crops and their composition 1 Straw
Crude fiber
Crude protein
Digestible protein (horse)
38.5 36.9 36.6 38.0 37.4
3.6 3.8 7.7 3.6 3,8
-0.8 0.8 4.3 0.8 1.0
(%) Secale cereale Triticum aestivum Agropyron elongatum Hordeum vulgate Setaria italica
Rye Wheat Wheatgrass Barley Millet
' Ensminger and Olentine (1978).
(%)
(%)
283
another highly effective insulator. Thatch can be made rodent proof, will last 50--100 years (Staniforth, 1979; Evans and Green, 1983) and requires little wood. Where fire hazards are high or water collection is desirable, tile or metal roofs could be used with insulation on the ceiling (plastic bagged straw or glass fiber insulation) of RSI-7--10. CONCLUSION
Rather than burning millions of tons of straw every year as fuel to heat inefficient structures, or burning straw in the fields as waste, we should be using the straw to build efficient and comfortable buildings that need little or no supplemental heat. If only one-third of the annual world production of slender stemmed straw, estimated at 750 million tons (Owens, 1976), were to be used for building straw bale homes, 50--75 million efficient and comfortable houses and farm buildings could be completed every year. Developmental work is urgently needed on straw bale building using low cost materials for: plastering, foundations and construction of refined designs for hand or horse balers for areas too poor to afford the services of a motorized baler (a review of traditional baler designs (Smith,, 1948) would be a good starting point). A thorough performance test of passive solar straw bale houses in a variety of climates would also be of tremendous value. ACKNOWLEDGMENTS
With thanks to my wife for her support and encouragement.
REFERENCES
Argue, R., 1980. The Well Tempered House. Renewable Energy in Canada, Toronto, Canacla, 218 pp. Bainbridge, D.A., 1978. The First Passive Solar Catalog. Passive Solar Institute,Bascom, Ohio, U.S.A., 72 pp. Bainbridge, D.A., 1980. The Second Passive Solar Catalog. Passive Solar Institute, Bascorn, Ohio, U.S.A., 115 pp. Bainbridge, D.A., 1985. Oregon Tests Superinsulation. Solar Age, Feb. 1985, p. 43. Ensminger, M.E. and Olentine, C.G., 1978. Feeds and Nutrition. Ensminger Publishing Company, Clovis, CA, U.S.A., 1417 pp. Evans, T. and Green, C.L., 1983. English Cottages. Viking Press, N e w York, pp. 29, 36 and 38. Nisson, J.D. and Dutt, G., 1985. The Superinsulated H o m e Book. John Wiley, N e w York, 316 pp. Owens, E., 1976. Farm Wastes. In: Food Production and Consumption. North Holland, Amsterdam, 541 pp. Sburcliff, W., 1982. Superinsulated Houses. Brickhouse, Andover, MA, U.S.A., 100 pp. Smith, H.P., 1948. Farm Machinery and Equipment. McGraw Hill,N e w York, 520 pp.
284 Staniforth, A.R., 1979. Industrial Use of Straw. In: Grossbard (Editor), Straw Decay and Its Effect on Disposal and Utilization. Wiley Interscience, New York, 337 pp. Strang, G., 1984. Straw Bale Studio. Fine Homebuilding, Dec. 1984--Jan. 1985, pp. 70--72. Welsch, R.L., 1973. Baled Hay. In: L. Kahn (Editor), Shelter. Shelter Publications, Bolinas, CA, U.S.A., 176 pp.
281
Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
HIGH PERFORMANCE LOW COST BUILDINGS OF STRAW
DAVID A. BAINBRIDGE
Dry Lands Research Institute, University of California, Riverside, CA 92521 (U.S.A.) (Accepted for publication 24 March 1986)
ABSTRACT Bainbridge, D.A., 1986. High performance low cost buildings of straw. Agric. Ecosystems Environ., 16 : 281--284. Straw bale construction is ideal for highly energy efficient buildings. Techniques developed in mid-continental North America should be refined and tested throughout the world. Straw is a tremendous agricultural resource, not a waste to be burned in the fields or used as fuel.
INTRODUCTION
The last few years have seen a tremendous leap forward in building design. Homes are now regularly built in very cold climates that are livable throughout the winter using only body heat, internal gains (cookstove, etc.) and passive solar heating using south facing windows (Shurcliff, 1982). With very little energy for supplemental heat, typically 100--300 kwh, these homes are very comfortable indeed (Nisson and Dutt, 1985). Yet the cost of these homes, while comparable to conventional construction (Bainbridge, 1985) is still too expensive for most residents in the developed countries and far beyond the means of most people in the world. Many of these impoverished people live in homes that use traditional designs to maximize passive solar heating and cooling with appropriate window placement and use of thermal mass (Bainbridge, 1978), but the lack of insulation makes them barely tolerable to live in even with high consumption of costly and environmentally destructive fuels (straw, dung, etc.). DISCUSSION
A traditional building system once used in both America and Canada could resolve this problem and provide well insulated, inexpensive, and earthquake resistant homes for people around the world, and energy ef-
0167-8809/86/$03.50
© 1986 Elsevier Science Publishers B.V.
282
ficient farm buildings. Straw bales were once used in areas of the mid-continent of North America where w o o d was expensive and scarce (Welsch, 1973). The bales are used like large bricks. Stuccoed or plastered inside and out, these bale buildings have proven tough and efficient. One to three story buildings fifty years old are still in good condition and attest to the strength and durability of straw bale construction (Welsch, 1973; Argue, 1980). The insulation value of the straw bale will depend on a number o f factors including the density of the pack, moisture content (below 15% required) and t y p e o f fiber, yet is in the range of R S I - 0 . 0 1 - - 0 . 0 2 mm -1. This makes it easy to achieve high wall insulation values of RSI--5+ needed for superefficient buildings (Bainbridge, 1980). With proper window and building orientation and use of thermal mass (water, rock or earth) inside the building, very effective passive solar designs can be built very economically. Straw bales offer other advantages as well. They are easy to use (stack and pin), have very low loading so minimal footings are needed, and are strong enough to support the r o o f structure without additional beams or posts. Pinned together well with w o o d or steel pins they would also be stable and safe in earthquakes. Current practice (a few hay bale structures are still being built) is to plaster the bales inside and o u t over wire mesh (Argue, 1980; Strang, 1984), b u t fiber reinforced plaster or natural reinforcing materials such as a b a m b o o strip mesh might prove equally effective. Traditional designs often used wire mesh reinforcing, but some bale buildings were simply covered with sand/mud plaster without reinforcing (Welsch, 1973). The favored straw for bale building was rye straw, b u t almost anything that can be baled has been used, including Russian thistle, Salsola kali. Over-mature straw with little feeding value makes the best bales for construction. Some of the more promising straw crops include rye, wheat, wheatgrass, barley and millet (Table I). Roofing can be of any material, b u t would most logically be thatch, FABLE I Straw crops and their composition 1 Straw
Crude fiber
Crude protein
Digestible protein (horse)
38.5 36.9 36.6 38.0 37.4
3.6 3.8 7.7 3.6 3,8
-0.8 0.8 4.3 0.8 1.0
(%) Secale cereale Triticum aestivum Agropyron elongatum Hordeum vulgate Setaria italica
Rye Wheat Wheatgrass Barley Millet
' Ensminger and Olentine (1978).
(%)
(%)
283
another highly effective insulator. Thatch can be made rodent proof, will last 50--100 years (Staniforth, 1979; Evans and Green, 1983) and requires little wood. Where fire hazards are high or water collection is desirable, tile or metal roofs could be used with insulation on the ceiling (plastic bagged straw or glass fiber insulation) of RSI-7--10. CONCLUSION
Rather than burning millions of tons of straw every year as fuel to heat inefficient structures, or burning straw in the fields as waste, we should be using the straw to build efficient and comfortable buildings that need little or no supplemental heat. If only one-third of the annual world production of slender stemmed straw, estimated at 750 million tons (Owens, 1976), were to be used for building straw bale homes, 50--75 million efficient and comfortable houses and farm buildings could be completed every year. Developmental work is urgently needed on straw bale building using low cost materials for: plastering, foundations and construction of refined designs for hand or horse balers for areas too poor to afford the services of a motorized baler (a review of traditional baler designs (Smith,, 1948) would be a good starting point). A thorough performance test of passive solar straw bale houses in a variety of climates would also be of tremendous value. ACKNOWLEDGMENTS
With thanks to my wife for her support and encouragement.
REFERENCES
Argue, R., 1980. The Well Tempered House. Renewable Energy in Canada, Toronto, Canacla, 218 pp. Bainbridge, D.A., 1978. The First Passive Solar Catalog. Passive Solar Institute,Bascom, Ohio, U.S.A., 72 pp. Bainbridge, D.A., 1980. The Second Passive Solar Catalog. Passive Solar Institute, Bascorn, Ohio, U.S.A., 115 pp. Bainbridge, D.A., 1985. Oregon Tests Superinsulation. Solar Age, Feb. 1985, p. 43. Ensminger, M.E. and Olentine, C.G., 1978. Feeds and Nutrition. Ensminger Publishing Company, Clovis, CA, U.S.A., 1417 pp. Evans, T. and Green, C.L., 1983. English Cottages. Viking Press, N e w York, pp. 29, 36 and 38. Nisson, J.D. and Dutt, G., 1985. The Superinsulated H o m e Book. John Wiley, N e w York, 316 pp. Owens, E., 1976. Farm Wastes. In: Food Production and Consumption. North Holland, Amsterdam, 541 pp. Sburcliff, W., 1982. Superinsulated Houses. Brickhouse, Andover, MA, U.S.A., 100 pp. Smith, H.P., 1948. Farm Machinery and Equipment. McGraw Hill,N e w York, 520 pp.
284 Staniforth, A.R., 1979. Industrial Use of Straw. In: Grossbard (Editor), Straw Decay and Its Effect on Disposal and Utilization. Wiley Interscience, New York, 337 pp. Strang, G., 1984. Straw Bale Studio. Fine Homebuilding, Dec. 1984--Jan. 1985, pp. 70--72. Welsch, R.L., 1973. Baled Hay. In: L. Kahn (Editor), Shelter. Shelter Publications, Bolinas, CA, U.S.A., 176 pp.