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Was at UL when the Xanadu projects were being constructed. There are fire retardants that can be used with polyurethane to reduce the flame spread & penetration (at least enough to get a UL listing),...however, as with most dome homes, ventilation is the main factor to consider in a climate such as Puna.
The last Xanadu (in Kissamee, FL) was demolished, in large part to the amount of mold & mildew that developed when it was no longer cared for as a tourist spot...
The big thing with all of these dome structures is the ventilation in the dome...unless the ventilation is well engineered, water vapor will develope into a huge problem...
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Designed by someone that has worked with domes is key
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I was once considering trying to make a living space out of a steel arch structure. I saw utube videos of people doing just that. They sprayed foam on the inside of the steel arch. I started searching about the use and hazard of such foam. Apparently there are a fair number of large steel arch storage structures in the midwest used for storing large quantities of potatos, insulated with spray foam on the inside. Generally speaking not much bad has happened, but in one instance, when welding was being done, a fire started. While you can hold a chunk of foam in a flame and the foam won't continue to burn when withdrawn, that's just a small piece. Apparently it is a whole different story when the foam is on the inside of the structure. In this case the foam started to burn, slowly, a couple of times in the immediate vicinity of the welding and it was easily extinguished. This perhaps led to a certain degree of complacency on the part of those involved. The last time the fire got away from them. This was a large open agricultural structure without, as far as I know, any individual rooms. All that was necessary was for people to look up, see the fire, and run, which they did. The last ones almost didn't make it because the fire spread so fast. The fire was inside a tube of insulation (the interior of the insulated steel arch) and there was no where for the heat to go. Huge difference between that ans a small exposed chunk of insulation. Whodathunkit but the difference in flame spread was incredible. Reminds me of when a decade or two ago I helped set off the fireworks from Flat Island in Kailua Bay. As part of the pre-event orientation the professionals showed us volunteers how much difference it made to have the craft paper covering on the green gunpowder-impregnated wick material. They rolled out 10 feet and removed the craft paper from the first foot. They lit the bare end. It took something like 30 seconds for the bare section to burn one foot. The remaining 9 feet that had the covering burned in something like 1/4 of a second.
So, I am not sure how safe exposed foam on the interior of a dome would be.
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Yep, The fire issues are real. What I don't know is whether any progress has been made over the years on developing fire resistant polyurethane foam.
Assume the best and ask questions.
Punaweb moderator
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A few years back, I thought about a wood dome for Hawaii. Over many decades, I'd looked at most of the different systems and was not impressed until I saw this system:
www.econodome.com
The owner has built and refined his system over about 4 decades. Started out in CA and moved to IL. From earthquake country to tornado alley. He had some nexus with HI and knew some of the quirky things like stamped drawings by a HI architect and hi-bore requirement. He even showed my a drawing on a catchment system that seemed to be functional. A lot of the objections that I have had about wood domes he had addressed.
If I was to build a wood dome in HI or anywhere else, I would do one of his. I think he is sort of the 'Rob' of the wood dome world  . A nice guy who isn't pushy about what he sells/builds. I did glance at their home page and see that their orders are backed up 3 months.
He does sell a manual with a full set of plans for about $50. I bought it and it was well worth it to see the level of detail he had thought his system out through. A FWIW, his wood joinery is quite tight and shows in the pictures.
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Domes are a challenge for water catchment and windows that you can leave open but not let the rain in.
Jerry
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quote:
Originally posted by kalakoa
A geodesic dome beats any other construction for structural integrity and price/square-foot.
When it comes to "making it watertight", all other construction methods beat a geodesic dome.
making it with long-lasting materials, sufficient air flow, sufficient light, minimal radiant heat, and water tight sounds like a nightmare with all those nooks and crannies exposed to the intense sun and rain. With my background in rot repair, I love buildings with simple roof geometry and large overhangs, here in Hawaii.
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You can avoid all of the problems with a geodesic dome by makiing a true shell out of ferrocement. Look at this image http://pacificgunite.com/ferrocement.htm This dome is water tight. It has a vent at the top to allow the hot air to escape. The little "eyebrows" over each arch are gutters that direct rain water to collector pipes embeded in the concrete columns. There is a 3' overhang around the perimeter that could easilly be larger. The roof doesn't leak and will last for more than a lifetime. When my engineer visited the job he told the owner that he would be coming over to her dome if there were ever a hurricane warning.
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If I wanted a dome I'd have Peter built it. No question.
Assume the best and ask questions.
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This below was a polyurethane dome fire. I was working in the industry at the time for the then president of our national trade organization. I spent a week up there researching the cause. As has been said here the foam is an insulator and keeps all of the heat in which caused the foam to release a gas, like any plastic will, that flashed a fire really quickly over the surface. Interior foam is not allowed to be exposed but must be covered by 1/2" of gypsum plaster or equal. So concrete does that and sometimes the foam is used as a form to spray the concrete on to.
Jan. 17, 1996 3:53 PM ET
MAUNA KEA, HAWAII MAUNA KEA, Hawaii (AP) _ A fire apparently started by a cutting torch killed three construction workers building a huge, $400 million telescope atop Hawaii's highest mountain. Twenty-three others were injured.
The blaze broke out Tuesday in the Subaru Telescope Project, also known as the Japan National Large Telescope, on 13,796-foot Mauna Kea.
The three construction workers were trapped in the upper level of the observatory's dome. They succumbed to toxic fumes generated by burning insulation, said Hawaii County Assistant Fire Chief Garfield Arakaki.
Construction began in 1992 on the telescope, billed as the largest and most expensive single-mirror telescope in the world. The 315-inch telescope was to be completed in March, with installation of a 26-foot mirror in 1997.
The extent of the damage to the observatory and its effect on the timetable for completion were not immediately known.
A workman with a cutting torch was modifying an elevator on or near a 40-foot-high observation platform when dripping liquefied metal ignited insulation, said Donald Hall, head of the University of Hawaii Institute for Astronomy, which oversees activity at the summit.
Two workmen with fire extinguishers were unable to control the rapidly spreading fire, he said.
Killed were Marvin Arruda, 52,; Warren Kaleo, 36; and Ricky Del Rosario, 38. Three others were in fair condition with smoke inhalation Wednesday. The rest of those injured were treated at a hospital and released.
A county helicopter fighting a brush fire nearby rescued a worker stranded on top of the dome. The worker was not hurt.
The observatory was considered Japan`s first major science facility built outside the country. Twelve other observatories are atop the mountain.
Jay
Jay
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