Dome on the range: oblate ellipses efficient

Buildings in the round can deliver lower operating costs and reduce risk to perils from weather and fire

Domes are all backward. The insulation is on the outside, the concrete is inside. The forms stay in place forever. Dome buildings are an example where form is functional.

“The look of the dome is different. But so are the benefits,” said Andrew Trapp of Canadian Dome Industries in Saskatoon.

Virtually fire and weather proof, concrete dome buildings are more efficient that their stick, stone or steel counterparts due to their structure.

“You can heat (a storage) building with a few lightbulbs,” he said.

A welded vinyl bubble is attached to ring of concrete, varying in height depending on the design and intended use. It is inflated, coated and insulation is applied to it, creating a condensation-free outer hull for the structure. Concrete is then spray-applied to a rebar skeleton on the inside of the insulation. Interior coverings, walls or paint are then constructed.

Door and window frames are formed in advance of the initial skin’s development.

“The buildings have any number of window and door options. You can get pretty creative because the insides of the structures are fully open, no posts anywhere,” said Trapp.

“Fires like we had last year can be hard to resist with conventional buildings. But domes are incredibly safe that way. The (skin) might scorch, but that is about it,” he said.

“Wind, tree-falls, nothing is getting in.”

Because of the compressive state the dome remains in, radiating all of the load to the outside of the dome, ultimately to the ground through its foundation, the amount of concrete needed to build is lower than might be imagined. At the base of the walls for a 2,500 sq. foot building it is about five inches thick, four at the top.

“The price of construction is about the same as any other building, on a per square-foot basis. The big savings are with the exterior finishes and maintenance. And of course the heating and cooling,” he said.

Priced at about $90 per foot for the building’s exterior, the structures compare favourably to other insulated systems. As these get larger the cost of construction per square-foot falls.

The ultraviolet-light-protected fabric skin has a 25- to 30- year life, after which stucco could be applied as a permanent finish.

“Some people use them for homes. Others for farm shops or storage buildings. Originally, they were developed as potato buildings. They wouldn’t condense (moisture) on the insides, letting farmers store (and condition) potatoes. But they are used for a lot more things today,” he said.

“As heated farm shops they are pretty hard to beat for efficiency … and as a farm asset, they are going to last forever on the Prairies,” said Trapp.

“We can form them as (ovals) and in other shapes. The only limits are the walls at the edges, and you can extend those (vertically) with concrete walls,” he said.

“If you need volumetric storage, they can’t be beat. You can fill them completely with dry products or liquids,” he said.

The nature of the oblate ellipse building allows for walls or lifts to be attached to the roof and carry nearly any practical load. And that design also creates a lower ceiling with straighter walls at the footing. A 25-foot ceiling height comes with a 55-foot diameter building, but structures up to 300 feet wide are possible.

“There is also very little construction waste with domes, making them an even more sustainable choice. Because all of the materials are engineered you can put the leftovers from construction in a big pick-up (truck),” he said.

In Western Canada, as well as farm buildings and homes, churches have also been built using the system.

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