monolithic vs. fiberglass

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monolithic vs. fiberglass

Postby brent » Fri Sep 05, 2003 9:32 am

I saw a post on the board referring to the domedr.com website where fiberglass domes are being sold. While these domes are not as versatile in design as the monolithic dome, I am more interested in structural longevity and ease of maintenance. These are the first qualities that attracted me to the monolithic dome along with energy economy. The fiberglass dome is touted to have an R-40 equivalent and I think that while the monolithic dome is likely more insulated, the fact that the fiberglass dome is cheaper and more easily constructed makes up for some insulation inadequacy. I'm interested if there are more structural and or maintenance considerations that go into choosing between a monolithic or fiberglass dome. :?

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Postby Anonymous » Fri Sep 05, 2003 10:08 am

Wow indeed.

I just saw this on that site:


2 Story Domes
2900 Sq. ft. $69600, Big Momma


I've also been looking at Timberline Geodesic Homes ( http://www.domehome.com ), but more because of their outside appearance than anything. My hubby is more use to the traditional looking homes and these are as close as I've seen from domes listed on the net. The only thing I don't like about Timberline's side is that they don't list any prices.

So far I'm leaning towards Monolithic, and I'm getting the hubby to sway that way too.
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Postby brent » Fri Sep 05, 2003 10:43 am

I could hardly believe the price difference. I'm concerned however, about long term cost difference. The insulation doesn't seem as good as the monolithics so, energy cost will be higher.

I feel your pain. I have spent two years so far trying to sway the wife to dome living. I looked first at the wooden domes including Timberline, Natural Spaces and Econodome. The natural spaces seem to have the most experience but I was turned from wooden domes by an Uncle who has recently been involved in rebuilding several domes in East Texas. He said that the expansion of wood timbers is highly variable even from piece to piece of the same lot. The result is much "heave and ho" in the structure. The domes then tend to pull themselves apart. The long term maintenance is thus rather high. These domes require structural repair within 20-30 years or about the same frequency as a conventional home.

I have found two sites, http://www.domedr.com and http://www.domesintl.com/homes/index.shtml. I think they are same product. Let me know if you find any other websites.

Thanks,
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Postby Arnold » Fri Sep 05, 2003 10:59 am

Fire is the other big problem with fiberglass. Your insurance cost will be much like standard house.
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Hybrid Fiberglass / Monolithic

Postby Kevin » Fri Sep 05, 2003 3:27 pm

The nice thing about the fiberglass dones (from what I can tell) is that they have a very durable maintenance free exterior. The Monolithic seems superior in every other way.

How about using the fiberglass form in place of the airform -- then spraying polyurethane and shooting concrete as normal?

This would result in a hybrid structure with longevity both outside and inside. No need for coatings, but you'd have the structural integrity and thermal flywheel....
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Postby jtownse2 » Fri Sep 05, 2003 5:48 pm

A very expensive outer coating I would say.
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Postby brent » Sat Sep 06, 2003 9:24 am

Yeah, that certainly is the most expensive outer coating I can imagine (bar gold). I don't mean to insight a war of monolithic vs. fiberglass here. I think this is something worth discussing.
The fire hazard is lower than it is for a conventional home. The fiberglass is not batting and therefore not saturated with air to serve as oxidant. Also, the fiberglass is only a thin layer beneath which is polyurethane. To put this in perspective, growing up in Texas, tornadoes are a real concern. I have survived two near misses (i.e. tornado passing within 1/4 mile) but I have never been in a house that caught on fire. There can be no argument that if a fire occurred that the monolithic would have greater survivability than a fiberglass. As far as fire insurance goes, premiums are based on home replacement. In other words on the cost of the home. For a 2900 sq. ft. home that cost $232,000 (monolithic- $80/sq. ft) the insurance will be comparable to the same home that cost only $150,800 (fiberglass- $52/sq. ft).
What I would be most interested in is water and tornado resistance. I have read of past problems with the monolithic dome where the polyurethane became saturated with condensed water vapors associated with the vapor drive created by the hot exterior surface. The vinyl covering while thick is not impenetrable and small puncture marks require repair. Also, concrete is porous and allows water vapor to penetrate. Finally, sealing the base of any dome to the foundation is a vital step. Because of porosity, the monolithic dome can develop seepage problems. On the other hand, fiberglass is not porous and so should suffer less problems associated with both vapor drive and seepage. The manufacturer of the fiberglass dome boasts an 8000 psi puncture resistance. This equates to more than three times the force delivered by a 15 lb 2 X 4 travelling at 100 mph (the Texas Tech tests for tornado survivability). The question then becomes can a tornado lift the lightweight fiberglass shell, even though anchored to the foundation. I know the answer to this one when it comes to the monolithic.

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Postby Minnesota » Sat Sep 06, 2003 8:55 pm

I agree vapor drive could be a problem but I have a feeling that it is relatively rare. I also will not argue about concrete being somewhat porous but think a concrete coating on the outside of a dome would stop vapordrive because the concrete will absorb radiant heat and keep the airform underneath of it cool. One feature to keep in mind about a monolithic dome is it's sheer mass. This aids in strength, weight, and increases it's ability to act as a thermal flywheel.
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Fiberglass vs Monolithic

Postby DBS » Sat Sep 06, 2003 9:33 pm

I am delighted you will look at both for your new home. But you should be aware there have been several fiberglass home companies go into and out of business while we have been developing the Monolithic Dome. I have truly wondered why.

Consider that fiberglass is not permanant. Look at the "permanant" fiberglass boats. Over time they develop hull problems. The sun is brutal. Second look at the price. All housing took a ten percent increase last year. and some the year before. So compare apples to apples. We are finding it take about $40 to $45 per square foot to finish the inside of the dome. That leave $7 to $12 per sf for the fiberglass shell in the cited example. Don't kid yourself. Low ball prices are only available in manufactured houses.

If you want the best of all worlds put the "chainshell" on the Monolithic Dome. I can absolutely tell you that such a Monolithic Dome will be around two to ten times as long as the fiberglass or the wood dome. And never will the energy efficiency be duplicated unless they are lined with the thermal mass of the Monolithic -- nor will the have the disaster resistance.

The fiberglass does have a possible place in the short term housing market. Such as vacation cabins. work camps. ets.
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Postby jtownse2 » Sat Sep 06, 2003 9:42 pm

I will agree with you, that fiberglass is some pretty tough stuff. Having worked around forty yrs.with it in and out of the aerospce industry. It would be a lot cheaper to make a small repair on a dome on a rare instance with a different coating than to have the coating fiberglass. But if you feel more secure with a fiberglass coating, go for it.
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Postby brent » Mon Sep 08, 2003 3:40 pm

Thanks DBR. Those are some useful numbers. I suspicioned that the $52/ sq. ft. was a bit low. At $69,600 for a 2900 sq. ft. home the price is $24/sq, ft. Add in the $50/sq. ft. finishing cost (I want a nice interior) and we get $76/ sq. ft. Hardly any difference from the $80-90/ sq. ft. given at the online evaluator (@$40,000 total cost difference).
As far as repair, I had forgotten the number of times I repaired an old bicycle tire with a vinyl repair kit. That does seem a bit simpler than fiberglass and epoxy patching that would be required for a fiberglass shell.

Why do the fiberglass companies have such a short lifespan? May I offer that it is at least in part because they don't have a discussion board.

Thanks,
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