Domes vs. Hurricanes
“When I originally wrote this segment for the web site in 2001, I had no idea how quickly the Dome of a Home would be put to the test. As we were building the dome, Tropical Storm Isadore came ashore and left a mess, but no damage. Then, in 2004, Hurricane Ivan slammed into Pensacola Beach wreaking enough havoc that it was called Ivan, The Terrible. Although many of my neighbors’ houses were piles of rubble or completely washed away, the dome suffered no structural damage. The Dome’s front staircase was designed to break away (which it did) to avoid damage to the actual structure. The 2005 hurricane season brought several storms to our shore: Tropical Storm Arlene in June; Hurricane Dennis in July; and Katrina in August. Hurricane Dennis was an extremely damaging storm to Pensacola Beach. Much to the community’s dismay, many of the repaired homes and buildings that made it through Ivan were decimated by Dennis. Again, the Dome of a Home suffered no structural damage. We had repairs to underground wells, exterior electrical and plumbing issues, etc. but no damage to the dome itself.” – Valerie Sigler
The air form concrete dome is a moving-water survivor. Not only does the dome’s round shape allow the water to flow around it, much as the ocean rushes around a light house, its weight, strength and durability allow it to stay in one piece during high winds and storm surge. The pilings are driven in a circle under the perimeter of the dome and connected with a circular concrete pile cap, which becomes the foundation ring beam. A circle of concrete is built attached to the top of each piling. The pilings then act as teeth in the ground and keep the building from sliding. The pile cap attaches the dome to the teeth, and then rebar is run into the floor. This prevents the moving water from lifting or moving the floor. The storm surge flows through the large openings in the lower section of the beachfront dome, leaving it undamaged. The beachfront dome is built with its main floor suspended from the dome, thereby eliminating posts that can be knocked out by storm surge from underneath the floor.
Hurricane Keith, a force 4 storm, raged for three days off the coast of Belize, causing no damage to the two concrete domes built there. The shape of the dome allows the wind to pass around the home, eliminating any serious pressure build up and easily withstanding 150 mph winds. A dome can withstand over 2300psf forces. (A 300mph tornado exerts 400psf.) Because the dome is not flat, the maximum air pressure against it could never be realized. The margin of safety is four times greater than on a flat wall.
Flying debris may harm the shutters, but will not harm the structure of the dome. Even if, on the rare occasion, a large object hit and punctured the dome, the damage would be very local and never cause serious structural damage to the home. There is a dome in Port Arthur, Texas that has survived three hurricanes with no damage. An interesting side note: During World War II, the Germans’ thin shell structures withstood Allied bombing. The bomb would either bounce off the structure or create a localized puncture that was easily and readily patched.
Another major advantage of the dome is that there are no shingles or roofing to be replaced during frequent tropical or winter storms. This is a monumental benefit for those of us with steeply pitched roofs that cannot hire a roofer, regardless on the amount of money offered. Steeply pitched roofs act much as a straight wall will in high winds and is adversely affected by the pressure exerted by the wind. Also, the new 5% deductible for our windstorm insurance determines that basically the homeowner will be providing the out of pocket money to replace the roof each and every time it is damaged. Also increasing the expenses is the continued rise in insurance premiums. The Siglers’ wind insurance premiums have more than doubled in the past year. Knowing ones roof is not going to blow off provides one with the assurance that the contents within will also be safe.
Mold and Mildew
Another advantage of the dome is the fact that there is no fiberglass insulation to become wet and essentially useless. Polyurethane foam is applied to the interior surface of the air form, eliminating the need for fiberglass insulation. The Georgia Pacific sheetrock products we used do not absorb moisture, thereby eliminating another source of the mold and mildew that can be even more devastating than the original storm damage. The mold and mildew takes an insidious toll on the livability of one’s home. I know several instances where the home made it structurally, but the mold and mildew growing on the wet insulation and sheetrock caused the owners to completely gut the structure.
Domes vs. Tornadoes
“During Hurricane Ivan, Mark stayed in the home with the MSNBC news crew. Throughout the storm, the increase in pressure and noise convinced them that tornadoes whirled around them on several occasions. The tornadic offspring of Hurricane Erin in 1995 drove lumber through the roof of conventional home. But, the Dome suffered no damage from the tornadoes spawned by Ivan, the Terrible.” – Valerie Sigler
As the Siglers know personally, hurricanes can spawn tornadoes. The stress created by a 300 mph tornadic winds would increase the compressive pressure in the concrete shell to 1098 psi.
Domes can easily withstand 2394 psi using design strengths of 4000 psi, easily giving it a margin of safety that is nearly 1 ½ times its minimum design strength, although the margin of safety is probably more like three or four. Tornadoes separate a house from its roof when the wind exerts pressure and lifts the roof off. Since there is no roof to lift off and no straight walls for the tornado to build pressure against, domes are virtually tornado proof.
Domes vs. Fire, Termites, Rotting, and Corrosion
Because a dome is constructed with concrete, there is no wood to burn. Obviously, this reduces the risk of fire. Even a dome with multiple flooring can remain fire resistant by using aluminum studs. Once again, because of the does concrete structure placed on concrete pilings, there is no threat from termites because the wood they thrive on does not exist in the concrete home. The dome also eliminates the risk of other insects and creatures living in your wall space, as there are no spaces in your walls to infest. Concrete does not decay and rot as a wood structure does.
There is virtually nothing to corrode or rot on the concrete dome home. The procedure uses Air form and urethane foam that is immune to corrosion. The rebar is placed so that it is protected by concrete, reducing corrosion.
Domes vs. Earthquakes
Earthquake forces do not even approach the design strength the air form concrete dome is built to withstand. It would take an external force many times as large as the earthquake to approach the design strength of the concrete itself.
Domes vs. Rising Energy Costs
“The Dome of a Home is 1500 square feet larger than our previous conventional home located on Pensacola Beach. Yet, my electric bill is consistently less than my previous electric bill. With rising costs of power such a concern, I consider the dome’s energy efficiency more important than ever.” – Valerie Sigler
Because free air circulation eliminates hot or cold corners and dead air pockets, dome structures can easily reduce heating and cooling costs by 75%. The externally insulated concrete shell exploits the concept of thermal inertias, radiating warmth to the interior spaces, while moderating room air temperatures. There is none of the heat loss found with wood studs. The virtually airtight outer skin makes infiltration a controllable component of cool air or heat loss. In Alaska, the 8000 square foot Trinity Christian Center has an average heating bill of $72. With the rising energy costs, the monolithic home can offer the owner reduced expenses.
The use of polyurethane, which is a plastic, enhances the home by giving it an even temperature. This foam has the highest insulation value of any building insulation. Since the insulation is bonded to the outside of the concrete, it reduces the amount of heat being transferred into or lost from the concrete to outside conditions. The fact there are no joints or seams, therefore, no leaks, gives the dome an R-value in excess of 60.
Domes Building Costs
“Having the Dome of a Home survive over 5 tropical events in three years makes it the best money we have ever spent in construction. With all of the recent hurricanes, building supplies are becoming increasingly expensive. Building a structure that takes into consideration the hazards of its environment is the only option that makes sense.” – Valerie Sigler
When building a non-coastal dome, prices are comparable to conventional housing. But great savings can be realized when building a dome on the beach. Building a dome on the beach makes economical sense in several areas. Significant savings can be made on the piling package alone. Conventional structures require pilings to be placed every ten feet underneath the home, resulting in a nightmare of poles. The monolithic structure requires that pilings be placed only around the perimeter. As a result, a completely open area can be created under the home to park several cars, entertain, or become outdoor living space. Obviously, with pilings on the perimeter only, there are far fewer pilings to purchase. The savings on the piling package for a 3000 square foot home can be $40,000 or more. Because there is no roof, several thousand dollars can also be saved on the hurricane-strapping package that secures the roof to the structure. This money can be spent on finer amenities. Everyone would prefer to spend money on creature comforts, rather than pilings that support a conventional home.