How to keep that precious heat inside your home

In an ever more energy-conscious world, these scientists seem almost un-American. They say wood stoves are a waste of effort - and they don't put much stock in solar water heaters or triple-paned windows.

These energy revolutionaries at Princeton University and the Lawrence-Berkeley Laboratory in California say energy conservation in the United States puts the cart before the horse: It focuses on fuel-thrifty ways to generate energy and puts too little emphasis on the ability of homes to retain heat.

Their answer to America's energy woes is ''house doctoring,'' - an energy ''checkup'' that searches for leaks and holes through which precious heat slips out of even moderately well-insulated homes. After the search, the technician outfits the home with some intitial, low-cost conservation devices.

Most houses are mazes of air ''bypasses,'' says Dr. Gautam Dutt, the Princeton professor who inspired the first systematic study of air movement and heat loss in the home.

The most common bypasses occur where plumbing and wiring pass through walls and the attic floor; in spaces above drop ceilings and staircases; where ceilings and interior walls meet; in hollow masonry basement walls; and around chimneys, which are often surrounded by an air shaft that is open from basement to attic.

''These leaks in one- and two-story wood-frame houses alone result in the waste of almost 20 percent of all the home-heating energy . . . used in the United States,'' Dr. Dutt says in a study co-written by Dr. Lawrence J. Becker, an environmental psychologist.

A house doctor's equipment includes a device called a ''blower door'' (only a few of which have been built so far in the US), which fits tightly into the front-door frame and blows up the house like a balloon. Once pressurized, the house is checked for leaks with an infrared scanner.

One of the nation's few commercial house-doctor businesses, Potential Energy Inc. in Chicago, guarantees a 10 percent permanent minimum reduction in home fuel costs - regardless of what other energy improvements have or have not been done to the home - for a average fee of $450.

But the house-doctor concept has special significance for poor urban areas with huge numbers of old, leaky single-family homes, and where residents cannot afford the latest, expensive energy-saving devices. Neighborhood groups can do a retrofit (with free labor and at-cost materials) for $50 to $100 per house. If the homeowner can later afford more improvements, a few groups help locate reputable contractors.

Advocates of the house-doctor concept say it can be more effective than the usual question-and-answer energy audit. Instead of giving homeowners a list of recommended energy improvements - which often gathers dust - the house doctor actually does a partial retrofit while the blower door is in place and leaks are easily detectable.

Doors and windows are weatherstripped and caulked, a some insulation is applied to bypasses, and the hot water temperature is set back to 50 degrees C., if it is too warm. Insulating gaskets are placed behind wall outlets and switches. Furnaces can be checked for efficiency and adjusted.

The blower door can also be used to see if a house has been made too airtight - a condition that can create a kind of indoor air pollution. Heat exchangers can be installed to circulate fresh air while retaining up to 80 percent of the heat in the process.

Princeton's Center for Energy and Environmental Studies began a successful house-doctor program in New Jersey in 1978. Minneapolis has one of the most ambitious programs in the country so far. The city's goal is ''to reduce (residential energy) consumption . . . by 30 percent by the end of the decade,'' says Robert Henderson, of the Minneapolis Energy Coordination Office.

Yet ''virtually no one (else) is practicing house doctoring,'' Dr. Dutt says.

Why? Because ''the cheap things that will really make the difference don't have any advocates,'' says Harvard University Prof. Daniel Yergin. Says Princeton Prof. Robert Socolow, who helped design the house-doctor concept: ''We're spending a great deal on fuel assistance and almost nothing on fixing up those old homes so they'll be better on fuel next year.''