Slapping a lid on winter

Arnie Fullerton envisions towns in the Canadian far north that will be almost subtropical in nature. They would sit on this nation's abundant tar sands, making extraction of the valuable energy much more pleasant than it currently is.

The British Columbia architect, working in collaboration with British, US, and German colleagues, has done a feasibility study - commissioned by the Canadian government -- on a typical mining community that might be expected to spring up on the 45 degree north latitude, where much of the Canada's mineral wealth lies buried.

At such latitudes the winters are harsh -- 60 degrees F. below zero is commonplace -- and long. Attracting workers to the area is difficult; keeping them there for more than a year or two is harder still, and the cost of constantly retraining so transient a work force, exorbitant. What the mining companies want, but are not getting, is a stable work force. They would like to attract whole families to the region rather than individuals. Establishing towns , such as Mr. Fullerton envisions, could do this.

Along with his international partners, Fullerton has planned a typical mining town whose core would be 36 acres under a translucent flexible bubble that would rise 200 feet at its highest point. At that height, an airsupported bubble such as this is would be invisible to the naked eye. But the familiar V pattern of Canada geese flying south for the winter would be clearly seen as would cloud formations and the stars at night.

Those living in this bubble of temperate comfort in an otherwise extreme climate, would experience warm, summerlike temperatures much as the region does now, but over an extended period (four to five months instead of the current three), and cool to chilly, fall-like winters far removed from anything now experienced that far north. Spring, too, would arrive much sooner. Late January should see the crocus pushing through and February would be tulip time.

Such a town would not be vastly more expensive to build than a conventional one, nor would it be energy intensive. It would, in fact, require no more energy to run than a conventional town at that latitude would use to keep its residents warm -- and confined -- indoors. Temperatures in such a town would range, according to the feasibility study, from lows where the mildest of hoarfrosts might threaten to around 90 degrees F. or 30 degrees C. In such a climate fresh vegetables could be grown year round and orange juice for breakfast would be picked fresh from the tree right outside the back door.

Does it sound as if the concept has come straight from the pages of a Buck Rogers comic strip? It has indeed. But, man's footsteps on the moon originated there, as well. ''We have the technology to build such a town right now,'' insists Fullerton. ''We don't merely have the technology,'' says David H. Geiger of Geiger Berger Structures Inc. in New York City, ''we have been proving it in practice for the past decade.''

David Geiger and Horst Berger were principally responsible for the world's first large (100,000 square feet) air-supported structure -- the US Pavilion at Expo 70 in Osaka, Japan.

Since then several dozen such structures have been erected around the world -- principally sports stadiums. ''We have come a long way from the (air supported) radar domes and warehouses of World War ll that began it all,'' says Mr. Geiger, ''but, as yet, the surface has been barely scratched.''

Air-supported roofs are made up of plastic films attached to a network of steel cables, which in turn are anchored to a concrete rim atop the perimeter walls. This flexible roof, in its inflated position rides on a bubble of air provided by fans, and often assisted by layers of rising warm air that stratify just beneath the dome. No interior support columns are needed.

These air-supported roofs came into being because they are most effective, readily erected, and vastly less expensive than conventional construction. Geiger enjoys making the comparison between the 50,000 seat Syracuse Stadium, with its air-supported roof, and the Montreal Olympic Stadium. In Syracuse, N.Y. , demolishing the old stadium, carting away the rubble, and erecting the new one cost $26 million; in Montreal, the crane rental alone equaled that figure.

The breakthrough came with the Expo 70 building. The elliptical design turned the roof into an airfoil, making the wind a friend rather than a foe. Exterior winds now hold up the roof, much as winds rushing over the wings of an airplane lift the plane. This made possible the construction of very much larger flexible-roof structures so that covering entire towns became feasible. In theory, the larger the structure the more fail-safe it becomes.

But such an expanse under one transparent roof seems to boggle the mind. It shouldn't, Fullerton insists, pointing to the renowned Crystal Palace. The all-glass structure, erected in 1850, covered 19 acres of London's Hyde Park. It was moved to a permanent site one year later where it stood until 1931 when it was destroyed by fire. Fullerton finds it ''humbling'' that engineers and architects, lacking the technology and the materials that we have today, could have built so vast a structure.

Astronomer Carl Sagan once described the planet Earth as a ''meadow in the sky.'' It is a green and hospitable ''meadow'' because it is surrounded by an atmosphere. Without this climate-modifying filter Earth would experience the extremes of the moon -- 120 degrees C. to -121 degrees C. from day to night.

Yet, except for some tropical regions, additional man-made climate modifiers -- even the tiniest igloo is a climate modifier -- are necessary here on earth for man to live and work in comfort. A transparent bubble over a town provides a second filter that would produce a ''green meadow in an otherwise hostile winter environment,'' to quote Fullerton. Such a bubble-protected town would be simply an enlarged version of the present passive solar house.

The clear membrane covering would:

* Shield the town from wind, eliminating the biting wind-chill factor in winter. In summer it would reduce dust and exclude the flies and mosquitoes that frequently discourage people from settling here.

* Trap some of the warmth from the winter sun and slow down the loss of heat generated within the town. In effect, the heat that escaped through your window panes would stay around long enough to keep your lawn green and your children playing happily in the sandbox even in January. Prototypical studies suggest that the energy used in such a bubbletop town would be no more and possibly less than in a conventional town.

In summer, a partial reflection of the sun's rays off the membrane would cut down on unwanted heat buildup.

* Reduce building costs. Architecture would be simple and more easily erected. Structures would need little weatherproofing in the absence of rain, snow, and particularly the freeze-thaw cycle; heating systems would not be so elaborate; site services (water, etc.) would not have to be buried yards deep to escape the frost. Materials would last longer and maintenance would be low.

* Make possible year-round gardening, including small-scale food production in a normally food-expensive region of the continent. Roofs, with little or no water to shed, would be flat enough to accommodate private gardens.

With temperatures held slightly above freezing even in midwinter, a wide range of plants could be grown, including citrus.

''Once we discovered a viable (transparent, durable, and fireproof) skin material many of the psychological problems envisioned for such a town disappeared,'' says Fullerton. The flexible roofs of current stadiums let in the daylight but are not transparent so that there is an indoor feeling to the area, light and airy as it might be. ''We think it is important to reproduce the outdoors (though climatically improved) as closely as possible,'' Fullerton says. Hence the need for a transparent skin. In this respect, it is interesting to note that while bees will not happily work in a glass-enclosed greenhouse, they will do so without any reservation in one enclosed in clear plastic.

The mezzom environment, as Fullerton terms so large an enclosed area as the one he envisions, can in no way be described as ''indoors.'' Rather it is a piece of the outdoors held in one place to create a microclimate.

Critics have suggested that such towns would provide ''dull, one-season living.'' Not so, say the planners. There are indeed marked seasonal changes where temperatures range from the hot and humid 80s in summer to winter lows where a mild frost might threaten.

In addition, Miami-type temperatures are contained only within a relatively small area. Mines and factories would be outside the comfort of the living zone (you couldn't have chimneys belching smoke in an enclosed space). Many of the residents would have to work outside and recreational activities such as cross-country skiing would take place outside the confines of the town. ''There would be many opportunities to leave the town,'' Fullerton points out, ''but always there would be the welcome embrace of a mild climate to return to.''

Obviously there would be no pollution-producing machinery tolerated in such a town. Cars would be parked around the perimeter and such transportation as existed within the enclosed area would be electrically powered as would lawnmowers, unless one preferred a push mower. Air exchange between the town and outdoors would take place regularly (as it does now in a home) so that burning the breakfast toast (or any small, smoke-producing fire) would not cause insurmountable problems.

In the far north of Canada snowfalls tend to be light. And the snow itself is dry and fluffy so that it would quickly blow off the roof. On the other hand, even an occasional heavy fall would melt because of the high temperatures just beneath the transparent skin.

The larger these air-supported structures, the more fail-safe they become because of air stratification. Hot air rises to exert a pressure beneath the roof, helping support the roof. In winter, the temperature differential between the warm air just beneath the dome and the intensely cold air outside would magnify this support so that in many instances there would be no need of mechanically produced interior air pressure at all. With such a large volume of air trapped beneath the bubble, deflation would take between 20 and 25 hours to complete even if an entire roof panel (1,000 square feet) were somehow to be ripped away. This is more than enough time to repair the roof. Even with no repair , the roof would eventually hang in its pre-inflated position well above the highest building in town.

Shortly after it was completed an exceptionally heavy fall of wet snow (12 inches) caused the roof of the Hubert H. Humphrey Metrodome in Minneapolis to deflate. As the stadium was still incomplete at the time, the heating system that would normally have melted away the snow was inoperative and the fan system lacked the additional boosting power (called for in the design) to support the additional 12 pounds per square inch pressure placed on the roof by the snow.

As a result, the roof partially deflated until suddenly shifting snow ripped a hole in one of the panels, at which stage total loss of pressure caused the roof to fully deflate. In this position it hung, as it had for three months during construction, 70 feet above the field and 20 feet above the highest bleacher seat. A new panel was installed and the roof reinflated four days later.

''Even when everything went wrong,'' said designer David Geiger at the celebrations to mark the reinflation, ''the roof proved itself in its fail-safe mode.'