http://www.concreteconstruction.net/Images/Foam%20Domes_tcm45-340675.pdf
T he creators of a new energ y- s a ving building system are convinced that there is something new under the sun in dome constru ction. The new element is a method that Tecton Corporation of Boulder, Co l o rado has developed to build thin-shell domes for single-family h o m e s, ware h o u s e s, industri a l complexes and re c reational facilities. The buildings, once completed, look and perf o rm like other domes and utilize concrete as do many c o n ventionally built dome stru ct u re s. The difference lies in the way the domes are constru c t e d . Once the design of the building has been decided, a plastic balloon is shaped to the size of the exteri o r, then inflated to form an air stru ct u re. Op e rating from the concre t e base slab, pre p a red as any conve ntional concrete floor, a small cre w s p rays a layer of polyurethane foam onto the inside of the balloon. Steel re i n f o rcement (norm a l l y welded wire fabric) is then fastened to the polyurethane and shotcre t e is spra yed onto the re i n f o rc e d p o l y u rethane to the re q u i re d depth—usually about 2 1/2 inches. W h e re a complex and costly scaffolding system traditionally has had to be constructed before the conc rete shell could be cast, this system re q u i res only air pre s s u re for its supp o rt, and the balloons are re u s a b l e. Among the advantages of the system are energy and material effic i e n c y, long clear spans, dura b i l i t y and quick construction. Three basic laws of geometry and physics are u t i l i zed: (1) Volume to surface ratios: domes enclose the greatest volume of space for the least amount of surface area; (2) Ae rodynamics: domes have the most desirable aero d y n a m i c shape possible for any gro u n d s t ru c t u re; (3) Clear span: domes re q u i re the least amount of thickness to clear span a given distance. The following examples are used to illustra t e the relationship of the dome to these natural laws: • The dome typically uses 30 to 40 p e rcent less material than a conventional rectangular building of the same vo l u m e. • A dome can withstand 40 perc e n t m o re wind than a re c t a n g u l a r s t ru c t u re because of its aero d ynamic shape. • An example of favo rable span to thickness ratio is a dome in De l t a , Co l o rado (pictured) clear spanning 120 feet with concrete only 2.5 inches thick. Energy requirements of the structures En e rgy cost savings are not reflected in the initial cost of the d o m e. Howe ve r, as the cost of energy incre a s e s, the benefits become a p p a re n t . Po l y u rethane foam is an integra l p a rt of the dome, not just a blanket or filler. Urethane is a more effective insulator than glass fiber or expanded polystyre n e. The system uses app roximately 3 to 6 inches of p o l y u rethane on the outside of the c o n c rete shell. The design of the stru c t u res capit a l i zes on the thermal inertia or flywheel effect of concre t e. Like the Foam domes High performance environmental enclosures BY BRUCE M. WILKINSON Completed storage warehouse for Holly Sugar Corporation in Delta, Colorado. thick adobe homes of the So u t hwest, the dome gathers heat duri n g the day and slowly releases it duri n g the night. Co n ve r s e l y, the stru c t u re re q u i res little energy input and is able to deliver much the same savings in the use of fossil fuels as some solar heating systems, without the initial cost of installing such syst e m s. Heating and cooling costs are said to be up to 50 percent less than for a conventional stru c t u re. Due to the wide va riations in cons t ruction costs from one area to ano t h e r, the dollar savings over competing constru c t i o n methods—either for re c t a n g u l a r buildings or domes—are difficult to c a l c u l a t e. Dome prices thus far have ranged from $7.00 to $14.00 per s q u a re foot. Price va riation depends on size, location, owner re q u i rements and contract limits. As production increases and technology a d va n c e s, more cost adva n t a g e s could be re a l i ze d . Other advantages of the system The dome system boasts seve ra l i m p o rtant construction adva n t a g e s. Once the concrete slab is cast and the air stru c t u re erected, 70 to 90 p e rcent of the construction work can be conducted inside a cont rolled environment. Even where s u b ze ro tempera t u res are experienced, the tempera t u re inside the air stru c t u re can be controlled to p e rmit shotcreting. Ut i l i t y, electrical, mechanical and plumbing work can be perf o rmed during or after dome construction, with plumbing placed in the floor or interior walls rather than exterior walls. Since many companies count c o n s t ruction time as lost money, a key advantage of the new dome system is that a small crew of skilled w o rkers can work with unskilled local laborers to erect a typical comm e rcial sized dome in 30 to 45 days. Shell stru c t u res are much s t ronger than post-and-beam or s p a c e f rame stru c t u re s. A doubleshell stru c t u re built in 1957-59 in Pa ris clear spans 714 feet, with each c o n c rete shell only 2 3/8 to 4 3/4 inches thick. The pri m a ry reason for the strength of the shell is that the s t resses within it are mainly comp re s s i ve and concrete is much s t ronger in compression than in t e n s i o n . Nearly any floor plan can be accommodated with either a singledome design or a combination of d o m e s. Although the dome concept can be used for rectangular floor p l a n s, some dome efficiencies are lost. Openings of almost any shape can be designed into concrete shells either on top, between or aro u n d the bases of the domes. Ro u n d e d openings are most economical because their shape is compatible with the compound curved shell stre s s p a t t e rn s. Since the concrete shell separa t e s the foam insulation and other exterior materials from the interi o r s p a c e s, the dome carries a good fire rating. Many types of polyure t h a n e foam are available with a low flame s p read and the exterior of the dome can be coated with concrete or other materials for high fire or impact re s i s t a n c e. Structures in current use The Tecton Co r p o ra t i o n’s most i m p o rtant commercial ve n t u re to date has been the Holly Sugar project, a stru c t u re 120 feet in diameter and 44.5 feet in height with a surf a c e a rea of 11,310 square feet,( in De l t a , Co l o ra d o. With two access tunnels 28 feet long by 25 feet wide accounting for another 1400 square feet of usable space, the storage dome contains about 310,000 cubic feet. Other stru c t u res utilizing the concept include single and multifamily d we l l i n g s, an airplane hangar and c o m m e rcial offices. The application of the dome concept to va rious segments of the agri c u l t u ral industry is included in Te c t o n’s future plans. T h rough licensing arra n g e m e n t s and component supply, the ori g i n ators of the concept plan to make their technology available to a market seeking durable enclosures with unusual energy and material effic i e n c i e s. Plastic balloon is unflated to form an air structure. Polyurethane foam is sprayed onto inside of inflated balloon. HOW ENERGY-EFFICIENT ARE THE DOMES? Re p o rts from users of the Tecton system confirm the energy effect i veness of the dome stru c t u re s. Jonathan Zi m m e rman of Co m m u n ity Arc h i t e c t s, Bo u l d e r, Co l o ra d o, codevelopers of the system, has stated that the owner of a 3-story, 1770-square-foot dome house is e x t remely satisfied with the energy and cost savings the home prov i d e s. The house has been in operation through two winter heating seasons with only a small freestanding fireplace and the highest monthly electric bill for all heating and appliances has not exc e e d e d $23.00. The dome house was designed with an integral ve rtical wall solar heating system; the owner decided, howe ve r, that with a heating bill of approximately $10.00 per month, the completion of the act i ve solar collector system would not be necessary. Zi m m e rman went on to say that his firm has re c o n s i d e red the use of solar collectors for space heating in the dome stru c t u re s, as he feels that they are not needed. Solar collectors for producing hot water for domestic use are another matter, howe ve r, and are cost-effective for ye a r- round use. Another case invo l ves a dome in Co l o rado which houses a gymnasium for the Boy s’ Club of Bo u l d e r. Fred Zook, executive director of the c l u b, monitored the thermal perf o rmance of the stru c t u re during cold and warm we a t h e r. The inside ambient tempera t u re in the winter did not fluctuate by more than 3° Fa h renheit from 49 to 52° F despite succ e s s i ve days of 0-degree F weather and repeated opening and closing of entry doors. The only sources of heat in the building at the time we re electric lights and the warmth generated by the occupants. Du ring the summer months, the dome interior was said to be much cooler than an adjacent facility made of wood. PUBLICATION #C780405 Co py right © 1978, The Ab e rdeen Gro u p All rights re s e rve d
T he creators of a new energ y- s a ving building system are convinced that there is something new under the sun in dome constru ction. The new element is a method that Tecton Corporation of Boulder, Co l o rado has developed to build thin-shell domes for single-family h o m e s, ware h o u s e s, industri a l complexes and re c reational facilities. The buildings, once completed, look and perf o rm like other domes and utilize concrete as do many c o n ventionally built dome stru ct u re s. The difference lies in the way the domes are constru c t e d . Once the design of the building has been decided, a plastic balloon is shaped to the size of the exteri o r, then inflated to form an air stru ct u re. Op e rating from the concre t e base slab, pre p a red as any conve ntional concrete floor, a small cre w s p rays a layer of polyurethane foam onto the inside of the balloon. Steel re i n f o rcement (norm a l l y welded wire fabric) is then fastened to the polyurethane and shotcre t e is spra yed onto the re i n f o rc e d p o l y u rethane to the re q u i re d depth—usually about 2 1/2 inches. W h e re a complex and costly scaffolding system traditionally has had to be constructed before the conc rete shell could be cast, this system re q u i res only air pre s s u re for its supp o rt, and the balloons are re u s a b l e. Among the advantages of the system are energy and material effic i e n c y, long clear spans, dura b i l i t y and quick construction. Three basic laws of geometry and physics are u t i l i zed: (1) Volume to surface ratios: domes enclose the greatest volume of space for the least amount of surface area; (2) Ae rodynamics: domes have the most desirable aero d y n a m i c shape possible for any gro u n d s t ru c t u re; (3) Clear span: domes re q u i re the least amount of thickness to clear span a given distance. The following examples are used to illustra t e the relationship of the dome to these natural laws: • The dome typically uses 30 to 40 p e rcent less material than a conventional rectangular building of the same vo l u m e. • A dome can withstand 40 perc e n t m o re wind than a re c t a n g u l a r s t ru c t u re because of its aero d ynamic shape. • An example of favo rable span to thickness ratio is a dome in De l t a , Co l o rado (pictured) clear spanning 120 feet with concrete only 2.5 inches thick. Energy requirements of the structures En e rgy cost savings are not reflected in the initial cost of the d o m e. Howe ve r, as the cost of energy incre a s e s, the benefits become a p p a re n t . Po l y u rethane foam is an integra l p a rt of the dome, not just a blanket or filler. Urethane is a more effective insulator than glass fiber or expanded polystyre n e. The system uses app roximately 3 to 6 inches of p o l y u rethane on the outside of the c o n c rete shell. The design of the stru c t u res capit a l i zes on the thermal inertia or flywheel effect of concre t e. Like the Foam domes High performance environmental enclosures BY BRUCE M. WILKINSON Completed storage warehouse for Holly Sugar Corporation in Delta, Colorado. thick adobe homes of the So u t hwest, the dome gathers heat duri n g the day and slowly releases it duri n g the night. Co n ve r s e l y, the stru c t u re re q u i res little energy input and is able to deliver much the same savings in the use of fossil fuels as some solar heating systems, without the initial cost of installing such syst e m s. Heating and cooling costs are said to be up to 50 percent less than for a conventional stru c t u re. Due to the wide va riations in cons t ruction costs from one area to ano t h e r, the dollar savings over competing constru c t i o n methods—either for re c t a n g u l a r buildings or domes—are difficult to c a l c u l a t e. Dome prices thus far have ranged from $7.00 to $14.00 per s q u a re foot. Price va riation depends on size, location, owner re q u i rements and contract limits. As production increases and technology a d va n c e s, more cost adva n t a g e s could be re a l i ze d . Other advantages of the system The dome system boasts seve ra l i m p o rtant construction adva n t a g e s. Once the concrete slab is cast and the air stru c t u re erected, 70 to 90 p e rcent of the construction work can be conducted inside a cont rolled environment. Even where s u b ze ro tempera t u res are experienced, the tempera t u re inside the air stru c t u re can be controlled to p e rmit shotcreting. Ut i l i t y, electrical, mechanical and plumbing work can be perf o rmed during or after dome construction, with plumbing placed in the floor or interior walls rather than exterior walls. Since many companies count c o n s t ruction time as lost money, a key advantage of the new dome system is that a small crew of skilled w o rkers can work with unskilled local laborers to erect a typical comm e rcial sized dome in 30 to 45 days. Shell stru c t u res are much s t ronger than post-and-beam or s p a c e f rame stru c t u re s. A doubleshell stru c t u re built in 1957-59 in Pa ris clear spans 714 feet, with each c o n c rete shell only 2 3/8 to 4 3/4 inches thick. The pri m a ry reason for the strength of the shell is that the s t resses within it are mainly comp re s s i ve and concrete is much s t ronger in compression than in t e n s i o n . Nearly any floor plan can be accommodated with either a singledome design or a combination of d o m e s. Although the dome concept can be used for rectangular floor p l a n s, some dome efficiencies are lost. Openings of almost any shape can be designed into concrete shells either on top, between or aro u n d the bases of the domes. Ro u n d e d openings are most economical because their shape is compatible with the compound curved shell stre s s p a t t e rn s. Since the concrete shell separa t e s the foam insulation and other exterior materials from the interi o r s p a c e s, the dome carries a good fire rating. Many types of polyure t h a n e foam are available with a low flame s p read and the exterior of the dome can be coated with concrete or other materials for high fire or impact re s i s t a n c e. Structures in current use The Tecton Co r p o ra t i o n’s most i m p o rtant commercial ve n t u re to date has been the Holly Sugar project, a stru c t u re 120 feet in diameter and 44.5 feet in height with a surf a c e a rea of 11,310 square feet,( in De l t a , Co l o ra d o. With two access tunnels 28 feet long by 25 feet wide accounting for another 1400 square feet of usable space, the storage dome contains about 310,000 cubic feet. Other stru c t u res utilizing the concept include single and multifamily d we l l i n g s, an airplane hangar and c o m m e rcial offices. The application of the dome concept to va rious segments of the agri c u l t u ral industry is included in Te c t o n’s future plans. T h rough licensing arra n g e m e n t s and component supply, the ori g i n ators of the concept plan to make their technology available to a market seeking durable enclosures with unusual energy and material effic i e n c i e s. Plastic balloon is unflated to form an air structure. Polyurethane foam is sprayed onto inside of inflated balloon. HOW ENERGY-EFFICIENT ARE THE DOMES? Re p o rts from users of the Tecton system confirm the energy effect i veness of the dome stru c t u re s. Jonathan Zi m m e rman of Co m m u n ity Arc h i t e c t s, Bo u l d e r, Co l o ra d o, codevelopers of the system, has stated that the owner of a 3-story, 1770-square-foot dome house is e x t remely satisfied with the energy and cost savings the home prov i d e s. The house has been in operation through two winter heating seasons with only a small freestanding fireplace and the highest monthly electric bill for all heating and appliances has not exc e e d e d $23.00. The dome house was designed with an integral ve rtical wall solar heating system; the owner decided, howe ve r, that with a heating bill of approximately $10.00 per month, the completion of the act i ve solar collector system would not be necessary. Zi m m e rman went on to say that his firm has re c o n s i d e red the use of solar collectors for space heating in the dome stru c t u re s, as he feels that they are not needed. Solar collectors for producing hot water for domestic use are another matter, howe ve r, and are cost-effective for ye a r- round use. Another case invo l ves a dome in Co l o rado which houses a gymnasium for the Boy s’ Club of Bo u l d e r. Fred Zook, executive director of the c l u b, monitored the thermal perf o rmance of the stru c t u re during cold and warm we a t h e r. The inside ambient tempera t u re in the winter did not fluctuate by more than 3° Fa h renheit from 49 to 52° F despite succ e s s i ve days of 0-degree F weather and repeated opening and closing of entry doors. The only sources of heat in the building at the time we re electric lights and the warmth generated by the occupants. Du ring the summer months, the dome interior was said to be much cooler than an adjacent facility made of wood. PUBLICATION #C780405 Co py right © 1978, The Ab e rdeen Gro u p All rights re s e rve d
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