Insulating a building's walls to R-11 saves energy, but insulating to R-14 will save even more. Installing a solar water heater can cut fuel bills, but so will wrapping the water tank with a fiber glass batt. Energy also can be saved by rearranging the floor area and judicious placement of windows.

Most builders know all of this, but few can say which choice will pay off the best or by how much; calculations like these require a computer and sophisticated software.

But now help could be coming from a long-slumbering program mandated by Congress seven years ago and being revived by the Department of Energy. Its sponsors say that, best of all for builders, no expensive computers will be needed for choosing the most effective conservation options.

Once known as Building Energy Performance Standards, or BEPS, the program originally was conceived as a way of forcing energy consciousness into all building designs. However, a not-surprising outcry from the construction industry quickly buried that notion.

John Rivera of the Washington-based National Institute of Building Sciences remarked recently: "I hate to tell you this, but BEPS is dead. It had cancer, and every day someone puts flowers on its grave like Joe DiMaggio did for Marilyn Monroe."

But while there may not be life after death in government programs, there is certainly reincarnation. BEPS is being transformed into Energy Performance Standards for New Buildings (but still usually "BEPS" for short), and will be mandatory only for federal buildings.

It also will be available on a voluntary basis for mobile-home dealers and manufacturers, homebuilders, and commercial-building designers. For the first two, it will come as a set of technical reports and guidelines; for the third group, it will be presented as an update to the commercial buildings portion of Standard 90A-1980 of the American Society of Heating, Refrigeration and Air Conditioning Engineers.

Using extensive data gathered by government laboratories and contractors, along with a computer program set up by DOE for estimating effects of energy conservation in various climatic zones in the country, BEPS will present simple "slide rule" cards and worksheets along with guidebooks.

By adjusting the tabs of the slide rule to mark off the appropriate figures for ceiling and wall insulation, floor area, and window characteristics, a few minutes of caculations will yield a gauge of expected energy consumption by fuel type. Then, with the accompanying worksheets, a builder can list and compare a number of options in a design for each type of house being planned in each location.

These options would include design changes such as moveable insulation for the windows, solar domestic water heaters, flow restrictors in faucets, water tank insulation and more efficient appliances. The data for dishwashers, clothes washers and dryers, refrigerators and stoves were obtained from the government's separate appliance-labeling program.

With the slide rule card and worksheets, for example, a builder might decide to trade off a more efficient and expensive refrigerator for added ceiling insulation, or a solar water heater for a water-tank insulating blanket. Meanwhile, cash-flow calculations, described in the guidebooks, are intended to enable builders to estimate first-year energy savings, mortgage cost changes and down payments. While the present plans do not call for the calculations to include fuel-cost escalation, that could come later.

Says Emanuel Levy of Steven Winter and Associates, which provided technical support along with DOE's Lawrence Berkeley Laboratory to the American Institute of Architects for the mobile-home and residential standards, the guides will create a priority list for energy improvements. The builder even could use them to try to get a lender to change his terms, he suggested. As the first energy-saving item is selected--by the builder's own choice, not statutory requirement--the priority-list changes also can be shown. So far, only the mobile-home guidebooks are nearing completion, says Levy. They are being aimed at generally accepted practices rather than at encouraging innovative designs. Options such as solar water heaters are included but passive solar designs are not, even though a number of manufactured-home companies are offering solar greenhouses now. Guidebooks for residential buildings such as ranch houses, split levels, town houses, two-story houses, quadruplexes and eight-plexes will come out later. They will include passive solar and other innovative designs.

Ray Reilly of DOE's Pacific Northwest Laboratories notes that the commercial guidelines, still further off this year, will cover small, medium and large office buildings, warehouses, schools, churches, high-rise apartments, shopping centers, convention centers, and other building types.

Although the most objectionable aspect of the program--mandatory standards--has been all but eliminated, there are still some disputes. George Barney of the Portland Cement Association remains concerned. He claims that buildings made by his members need less insulation because of the "thermal mass" effect that allows the temperature of a building's interior to lag behind the changing outside temperature. He says this lets the rooms stay cooler in summer and warmer in winter.

But the interim standards will not recognize thermal effect. Requiring masonry buildings to have the same insulation levels as wood-frame structures will tend to price them out of the market, Barney contends.