A $30 investment in quality caulking and weather-stripping materials is one of the best energy-saving moves a homeowner can make, says one civil engineer who has spent the past two years developing conservation guidelines for new houses.

As director of technical services for the National Association of Home Builders, Alan R. Trellis has helped raise the energy-saving consciousness of many builders. His technical guidelines spell out conservation measures that will pay for themselves in seven years, taking into account a 10 per cent price increase each year energy and 9.7 per cent annual financing costs.

Trellis, a homeowner in Columbia who has experience in building, recommends that builders use such materials as polysulfide, polyurethane, silicone, latex, acrylic, butyl rubber and cholor-sulfonated polyethylene caulking.Simply buying the cheapest brand of caulking won't do, he says.

People who already own houses can make certain their attic floors have at least six inches of insulation, he said, adding that 10 inches is preferable.

But if a house already has six inches of attic insulation, he advises, "I'd look elsewhere to spend money. The efficiency of heating and air conditioning equipment is significant. So are storm doors and windows, if you're not over-paying for a quality product."

If you're looking at new houses, Trellis recommends that you buy from a builder in whom you have substantial confidence. Most are now offering "energy-conserving packages," he notes. If it's an electrically heated house, as most new dwellings are in this area, Trellis says to make certain that the system includes a heat pump from a reputable manufacturer.

"No doubt about it, heat pump systems save money," he said. "The average $300 extra for the heat pump is paid back in three to five years."

But Trellis and new home builders are aware that heat pumps have operating warranties and require warranties; good maintenance is a necessity. He also said that it is better to have a furnace and an air cooling system that are not oversized for the dwelling.

"It is more costly to have the capacity for ultimate heating or cooling on the hottest and coldest days. It is less costly to have a unit sized to heat and cool comfortably on most days," he noted.

In addition to being satisfied that the builder of a new house cares about energy conservation, the prospective buyer should check to see that attic floor insulation is six to nine inches deep and that the walls have at least 3 1/2 inches of insulation. Trellis recommends the use of double-glazed, insulated windows. Check windows for labels of approval from the Architectural Aluminium Manufacturers Association or the National Woodworking Manufacturers Association, he said.

"Once the house is under construction, the buyer can visit and get visual assurance that cracks are stuffed with insulation before the drywalls are in place. That goes for caulking too," he said.

Trellis added that some builders now assign a person to check all weather-stripping, cracks and spaces around windows and between joists before drywalls are placed.

In terms of home equipment, the water heater is a major energy user. In addition to making certain that the unit is efficient, Trellis recommends that builders install the heater as near as possible to the point of greatest use. The temperature setting need be no more than 125 degree Fahrenheit, he said.

In addition to providing heat pumps, which are designed to extract heat from the outside on moderately cold days, builders now are taking a hard look at the installation of solar hot water heating systems.

For instance, National Homes Corp., which manufactures package houses in Lafayette, Ind., and markets them to builders in many areas including Washington, is selling a solar-assisted system is says requires only a small area of roof-top collectors but saves up to 72 percent of the average hot water heating bill.

But Trellis and most housing industry sources regard total solar heating as now impractical in this area.

Manufacturers of insulation materials have been plagued by shortages since the advent of high heating and cooling bills and the promise of a possible tax credit of up to $400 for money spent to conserve energy in the home. Many firms have been expanding their production; 3.9 million homes had attic insulation upgraded in 1977 compared with 1.7 million in 1976.

For instance, CertainTeed Corp., based in Valley Forge, Pa., has been operating its four insulation plants 24 hours a day, seven days a week. And it is building a new manufacturing plant at Chowchilla, Calif.

At the recent NAHB convention in Dalls, where many energy-conserving products were displayed, CertainTeed vice president George Hoffman said that the shortage of insulation materials is expected to continue into 1979. He also warned that "the current production lag has created some unique marketing opportunities for a few obscure, unethical suppliers. Hasty action by homeowners in purchasing insulation materials could result in the purchase of an inferior product."

At recent mid-winter meetings of the National Association of Realtors in Atlanta, a professor of real estate and urban development of the University of Georgia pointed out that about 27.8 per cent of the toral U.S. fuel use occurs in the home.

The professor, William M. Shenkel, said that realtors have a responsibility to demonstrate the benefits of buying a more energy efficient house when a potential buyer is making a choice.

Adding too much insulation is a waste of money, however, a point NAHB engineer Trellis continues to make with home builders. The Consumers Union warned recently that an owner could "insulate a house to a point where the money spent on insulation far exceeds the money saved on fuel."

CU spokesman Ira Furman's view coincides with that of engineer Trellis. They insist that much of the money spent on ineffective, additional insulation could be better spent on storm windows, exterior caulking, weather-stripping and energy-saving thermostats.

In the meantime, a booklet on "Making Most of Your Energy Dollars" has become a government best-seller. Prepared by the National Bureau of Standards, it is available for 70 cents by check or money order from Superintendent of Documents, U.S. Government Printing Office, D.C. 20402. Specify stock order No. 003-003-01446-0.