Praising architects, engineers and designers for the beauty they create and the money they can save, President Reagan yesterday presented the first Presidential Awards for Design Excellence to 13 federal projects completed between 1974 and 1984 and selected last fall by a prestigious independent jury.

"It may be true that the federal government is not known first as a world-class designer, but today's awards prove that inspired design . . . is possible from within the federal ranks," Reagan said in a mid-afternoon ceremony held in the elegant Indian Treaty Room of the Old Executive Office Building adjacent to the White House.

"Our award winners have also shown," he continued, "that good design need not be a luxury added onto a project at extra cost. In fact, good design can help us to save money, and you know how much that warms my heart."

The quadrennial awards are the culmination of efforts to enhance government design that began three presidents and 13 years ago with the federal design improvement program initiated and supervised by the National Endowment for the Arts.

The 13 winners, selected from 91 finalists by a jury chaired by I.M. Pei, the renowned American architect whose award-winning buildings include, among many others, the East Building of the National Gallery of Art, represented a wide spectrum of design, from buildings to bridges to signs to an artificial foot.

"It is my hope that the great variety of the 13 awards will help persuade the public that design isn't just buildings or parks and so forth," commented Frank Hodsoll, chairman of the arts endowment. The only building on the awards list directly commissioned by the federal government is, in a sense, a nonbuilding -- architect Robert Venturi's white metal-frame outline of Benjamin Franklin's house (called a "ghost" in the jury citation) in Franklin Court in Philadelphia, a Bicentennial project built under the aegis of the National Park Service.

Three other projects involving buildings -- the Lowertown mixed-use project in St. Paul, Minn.; "The Gardens," a dense, low-rise residential project in San Mateo, Calif.; and scattered-site public housing in Charleston, S.C. -- were produced by local initiatives and funded heavily by the federal Department of Housing and Urban Development.

Among the more spectacular and beautiful award recipients are three engineering projects: the Linn Cove viaduct along the Blue Ridge Parkway in North Carolina, the stunning steel-and-concrete bridge spanning the Columbia River in Washington state between Pasco and Kennewick, and the flood-control dam at the Charles River Basin in Boston, Mass.

Three systematic graphics programs received awards: the "symbol signs" now deployed throughout the country by the Department of Transportation, the "Unigrid Design Program" that governs all visual communications of the National Park Service, and the design standards manual that performs a similar service for the National Aeronautics and Space Administration.

Congress and the Department of the Interior were praised by the jury for enacting and administering, respectively, the historic preservation tax incentives program, credited with saving "more than 9,000 historic buildings nationwide." Another program selected by the panel is the art-in-architecture program of the General Services Administration, which, the jury commented, "has produced salutory results at more than 250 sites" across the country.

Perhaps the most amazing of the award-winners is the "Seattle Foot," a prosthetic device developed by private designers in Seattle under contract to the Veterans Administration. Called "a quantum leap in prosthetics technology," the artificial foot, a realistic-looking mold containing a plastic spring, "duplicates the complex motion and energy of a real foot with just two lightweight parts."

The presidential awards are the belated fruit of the federal design improvement program begun in 1972. Other major initiatives of the program -- to encourage preservation and mixed-use of federal buildings and federally-assisted projects, to overhaul the graphics design in countless federal agencies, and to encourage good design throughout the bureaucracy by means of design competitions and hiring practices stressing design excellence -- were put in place during the 1970s.

"We are greatly encouraged by the reaction to the awards program," commented Adele Chatfield-Taylor, director of the design arts program of the National Endowment for the Arts. "There are a lot of people out there who are proud of their work." More than 50 federal agencies submitted 630 entries to the competition. Photographs of the 13 winning designs, along with those of the 78 other finalists, are on view at the headquarters of the American Institute of Architects, 1735 New York Ave. NW.

Pei, whose name Reagan mispronounced -- "Do I have that name right? Is it Pie?" he asked -- concluded yesterday's ceremony by thanking the president for placing "the essence of design excellence at the highest level of government."