Matrix IMA: The Neglected Hazards of Snow and Cold

In my mountain house, (Figure 11), preheated fresh air is injected whenever the fan circulates the air, but in many buildings constructed recently, the inside air in the winter is 10 to 30 times more polluted than Los Angeles on a smoggy day. Unvented kerosene heaters can be deadly in tightly sealed dwellings. Any burning appliance, such as a stove or fireplace, must have a fresh air source near the combustion and a flue to the outside.

Architects already are concerned over outgassing of formaldehyde from particleboard, plywood, and some foamed insulation. Now we realize that the emission of radon, a product of radium decay, from the stone masonry and concrete may constitute a deadly threat. This is a factor to consider when designing passively heated buildings in the cold country. Building codes must be revised to require sufficient interior air changes, proper venting, and to curtail interior use of toxic materials.

Air-to-air heat exchangers are a promising way to avoid indoor air pollution. They extract heat from air being vented from the building and use it to warm the fresh air being brought in. They are well adapted to places where large volumes of air are needed, such as heated parking garages, or places where makeup air is required, such as in large office buildings where the interior is warmed by the lighting and the office workers themselves. Smaller exchangers can be used domestically. In the cold country, where air is very dry, health problems can arise from the injection of too much untempered outside air. If the interior relative humidity falls below 50 percent, throat and eye irritation occur. To correct this, humidifiers should be added to makeup air in cold climates.

Foundation design depends upon the freeze/thaw cycle. Where there is no underlying permafrost, the architect must insulate all around the building to keep the ground underneath from freezing. When the ground outside the foundations freezes, the entrapped moisture expands, forcing the surface upward. This is particularly true with fine particle soil that contains a great deal of moisture. When the ground thaws, it sinks back. If the ground freezes in the fall and stays frozen until spring, the forces on the foundation are not as great as they are when there is frequent freeze-thaw. One solution is to sink the foundation far enough into stable material that can withstand the freeze-thaw forces. Another is to coat the foundations with a slippery material so that the frozen earth cannot adhere to the building and the ground can rise and fall around it without damage. Where there is no underlying permafrost, foundation insulation should be carried below the active freeze/thaw layer so that heat from the building affects the surrounding ground as little as possible.

Where the surface ground is permanently frozen during winter months and the buildings are constructed on underlying permafrost, it is critical to keep the interior building heat from melting the underlying layer. If the permafrost melts, portions of the building will sink into the mud. In downtown Dawson, a Canadian Yukon town that underwent rapid development during the Klondike gold rush at the turn of the century, one can see what can happen when these principles are ignored (Figure 12). The foundation posts of the hospital must be cut off about every second year to keep the building reasonably level.

The 10-inch-diameter posts that supported a part of the original territorial commissioner's residence (now housing for elderly people) move up and down five inches a year. Settlements of as much as three feet have occurred along the walls of the public school.

In permafrost country, foundation movement can be avoided by elevating the building on stilts driven through the active layer with their bases permanently anchored into the permafrost. Cold air must be permitted free circulation below the structure. If the building is too large for stilts, it can be set on a thick pad of well drained crushed rock through which cold air circulates in large pipes. The pad does not trap water and is not active. It isolates the building from the underlying permafrost.

In Barrow, Alaska, an inflatable dome to be used as a garage was erected without a floor; the permafrost was expected to support the weight of the vehicles. Instead, the heat of the building melted the permafrost and the vehicles sank into the mud. Such air supported structures work better for temporary than for permanent use in the far north.