Since 1972 a group at Princeton University have been studying energy use in houses, using 31 town houses with identical floor plans in Twin Rivers, N.J.

The group has been measuring and modifying the energy used for air conditioning and water heating, especially energy used for space heating.

Among the goals was to determine what should be done in a house to reduce energy use. They found that standard insulating and weatherstripping (retrofitting) for the "textbook house" should be supplemented by retrofitting houses in ways which must be determined individually by on-site inspections.

The Carter administration has suggested that a corps of young people be trained to make housing inspections to show owners how they could save energy. This idea was greeted by complaints that the government wanted to train a bunch of snoopers to spy in people's homes. The Princeton study, however, shows the value of such house-by-house inspection.

The researchers found the furnaces in their study houses provided only 60 per cent of the space heat. The balance was made up by appliances (20 per cent), body heat from occupants (5 per cent), and the sun (15 per cent). They determined that if the appliances were redesigned specifically to capture waste heat, they could supply as much as 40 per cent of the heat for the house.

By enlarging the windows that face south, more heat could be provided by the sun. Of course, this has the same effect in the summer when lower temperatures, not heat, is desired. This problem can be taken care of, however, by the use of shutters or making other structural changes.

The study found that over a year more money was spent on water heating than on space heating. Yet just insulating the hot water tank reduced the energy used by more than 10 per cent and paid for itself in less than a year.

Another goal of the Princeton study was to find out how important differences among people are in their energy consumption. The researchers report: "The observed variation in energy consumption for space heating is primarily assignable to the resident." Supporting their statement, they found that when a new family occupied a house, their energy use was not related to that of the previous occupants.

They were unable to find out the characteristics of people who are high-or low-energy users.