AROUND 6 o'clock one Friday afternoon, the power went off in a food-storage locker at a Peterborough, Ontario, cold-storage company. That locker was built of concrete blocks, and under normal circumstances spoilage would have been complete by the time the power outage was discovered on Monday morning. But after more than 60 hours without refrigeration, the temperature in the locker had risen a mere 5 degrees (from 38 to 43 degrees F.).
How did that happen? Concrete block, like brick and stone, is supposed to grab heat from one side and conduct it through to the other side only a little more slowly than if there were no wall at all.
The answer lies in the particular blocks used in the construction. They combine thermal mass with R-values ranging from 23 for a 10-inch block to 33 for a 12-inch block. This ability to store heat and then release it where it is not wanted at one-third the pace of normal masonry accounts for the thermal lag that saved the day for the food-storage company.
Polyurethane-filled cores and an aggregate that is 60 percent expanded polystyrene beads accounts for the insulating ability.
The insulating block is the product of a Canadian firm, Sparfil International of Cobourg, Ontario, which sought to combine the strength, durability, and fire resistance of conventional blocks with high R-values. It took $7 million in research and development and 10 years of effort, based on work begun initially by the West German chemical company BASF (developers of expanded polystyrene) before the goal was reached. That was in 1979, when the National Research Council of Canada tested the 10-inch block at R-10. Adding polyurethane to the cores raises the value to R-23.
Sparfil has done all this without sacrificing economy. The block itself is expensive. But as far away as Boston, walls can be built of the Canadian-made blocks at costs equal to or under those of conventional walls with the same insulating value. The ultimate aim is to have Sparfil blocks made in many separate locations so transportation costs can be minimized. Currently 500 miles is the maximum distance if the blocks are to remain competitive.