AT THIS point it will probably do no good to tell you we have been foolish about the way we heat our houses, that if we were smart and able we would turn our homes to the sun, berm them up with dirt and pray the earth stays firmly on its present axis.

In lean times we make do with what we have.

It might be of some consolation, however, to know that engineers are more sober than the rest of us who take one look at the big picture and immediately fall into a panic. Looking through the telescope from the other end, they see problems of different dimensions altogether and set to work, gnawing almost impercetibly at the roots.

There are so many engineers that even though their tasks individually seem insignificant, their cummulative effect may become important after a time, even beneficial.

I cite the case of the oil-burning furnace, probably a great-source of aggravation to many home owners in the wake of the latest increases in fuel prices. Usually there is very little reason to look into an oil furnace unless something goes wrong. All the more reason to wonder at the immense attention some engineers have paid to them in recent years.

In fact, there was something to look at, something very wrong and correctable about oil burners.

Engineers have found, for instance, that most oil furnaces were installed without much concern for the space they were intended to heat. In most cases they are too big sometimes twice as big as the house needs.

This may seem a simple enough waste of a good oil furnace, but problems are seldom so simple.

When a furnace is too big for the house, it doesn't run as often. It starts and stops when it is needed and doesn't care that it may run only 30 percent of the time (even on the coldest winter days, reports the National Bureau of Standards) and the rest of the time just sits there.

The time the furnace is just sitting there engineers call "offtime." When the furnace is off, it busily sucks back air from the house it has already heated, air that cools off the heat exchanger and simply flies up the flue.

Engineers call this "inefficiency."

For nearly three years now, engineers at Brookhaven National Laboratory have been investigating "off-time" for the Department of Energy, looking for ways of making furnaces run more often (and consequently more efficiently) without turning people's houses into saunas.

They found that simply changing the size of the nozzle on the oil burner by about 25 percent, forcing the furnace to run more often but at a lower rate, can save 8 percent in fuel. Studies in New England have resulted in savings of 14 percent.

Sometimes to nozzle can be changed for one even smaller to save even more oil.

The process is known as "derating" and can be done by your oil service or heating contractor for less than $50 and should pay for intself within a year.

One of the problems with derating, authorities have found, is that it doesn't work for everybody because the measure of how oversized the furnace is depends on the number of people in the house and their heating habits. It can especially be a problem for people whose furnace heats the hot water as well as the house. If the furnace is "derated" and heats less (but more often) less hot water will be available.

In those cases, authorities suggest such things as improved shower heads that use less water but do a better job of spraying it. Some furnaces may be so oversized it is economical to derate them and install a separate hot water heater.

The serviceman who checks the efficiency of your furnace (by measuring the amount of carbon monoxide in the exhaust) should be able to tell you what your options are.

One of those options may be a new burner, one of the new and more efficient "flame retention" burners.

The head on these new burners, which costs $300-$400 installed, rotates the air and forces it into the combustion chamber at higher velocities than do previous models. The results is a better mix of oil and air so the furnace makes more efficient use of its fuel. And when the furnaces is off, the blower fan locks, preventing air from passing through the chamber, cooling the heat exchanger and escaping up the flue.

The National Bureau of Standards estimates that installing a more efficient burner can save up to 30 percent in fuel costs. Brookhaven Laboratory's initial tests have shown an average saving of about 16 percent. In the results of those tests for instance, it estimated one retention burner would use nearly 300 gallons less fuel than a conventional type burner.

At that rate, a "flame retention" burner can pay for itself within about four years.