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.
Buildings made of these insulated blocks are erected by using surface-bonding technology. This method involves stacking the blocks dry (Sparfil grinds its blocks to get a perfectly level surface) and then plastering on - or parging, to use the technical term - a quarter-inch layer of a cement-fiberglass mix that bonds the blocks together and makes them waterproof at the same time.
Conventional mortar bonding is avoided because the joints form a thermal bridge with the outside air.
The very first blocks to come out of the molds were good insulators, but the vibrations of conventional blockmaking machinery caused many of them to fall apart before they had time to set. Creating a mix that stood up to conventional manufacture, then, was the principal goal of the developmental program. Now that the goal has been achieved, the way is open to license Sparfil production far and wide.
Charles Hubbard, a Shelburne, Vt., architect, has been watching Sparfil progress over the years. He has used many other insulating blocks, the best of which he describes as ''R-12, but heavy and brutal to lay.''
Sparfil's product appealed to him from the start. And now that he is convinced of the quality, he plans to use the block in projects in which he is involved in Egypt, where ''keeping the heat out is as important as keeping it in over here.'' Mr. Hubbard describes the present block as ''an extraordinarily good product that could make as big an impact on the construction industry as the advent of drywall.''
Any manufacturer of quality concrete blocks will be able to turn out a good Sparfil product, in the Hubbard view. However, Sparfil's plan for the next year or so is to concentrate on construction in Ontario and Quebec. The company wants to establish a solid track record before spreading into other parts of Canada as well as the United States.
In many respects, that track record is already in place in the two Canadian provinces, where every conceivable type of building has gone up, ranging from banana-curing rooms and a wide range of homes, to commercial and industrial buildings, greenhouses, and a motel. All told, the buildings using Sparfil blocks now number in excess of 125.
One of the stumbling blocks to Sparfil construction is indecision as to who should erect the wall. Is it the mason, the plasterer, or maybe even the carpenter?
Apparently many masons instinctively reject the idea of laying the blocks dry. ''It's not natural,'' is a typical comment on the system. Carpenters would be equipped to lay the blocks, which in some respects behave like wood. They are half the weight of conventionl blocks and can be nailed and cut as readily as wood, given the right saw blade. But plasterers, who should always do the parging where a smooth professional finish is required, might just as easily lay the blocks in the first place.
Liz Bentley Fox, technical editor of Superinsulation Newsletter, published in Cambridge, Mass., has also been monitoring the Sparfil progress. Ms. Fox believes the block will be readily accepted in the Southwest and Florida, or wherever architectural styles include adobe, stone, or brick. But she sees the Northeast as conservative and reluctant to change the all-wood construction that has existed for centuries (though any veneer can be nailed to the Sparfil surface to change its appearance).
''I am constantly amazed,'' she says, ''that New Englanders who insist on the latest styles in autos, refrigerators, TVs, stereos, etc., still insist on housing styles that were around when the Union Jack was the flag of government here.''
For more information on the insulating blocks, write to: Sparfil International Inc., 5 Veronica Street, PO Box 235, Cobourg, Ontario, Canada K9A 4K5, or Hubbard Associates Inc., Irish Hill Road, Shelburne, Vt. 05482.