Deep inside the magnificent Pension Building in Washington, Isabel Lowry was pasting large Helvetica cutout letters on a door. They spelled "National Building Museum."

Her husband, Bates Lowry, is the newly elected director of the phantom museum. The new president is Albert Bush-Brown, chancellor of Long Island University.

Right here, you should know that in 1977, I took a year's leave of absence from this newspaper to help plan a national center for exhibiting, documenting and discussing the drama of building America.

The idea was, and is, to stimulate informed public interest in the quality, beauty and livability of our buildings, neighborhoods, towns, suburbs and cities -- our "built environment," as the jargon has it.

Our proposal to convert the Pension Building into a museum of the building arts was titled "The Building Building."

Some months ago, in the face of tenacious amateurism, I resigned from the committee which pursued the proposal. I now feel free to discuss and, I hope, promote it in this space.

One architecture critic fussed a little when the pamphlet on the "Building Building" was first published in January 1978. Architects and engineers, builders and preservers, however, warmed the air with applause for the idea. And Congress passed a Joint Resolution calling on the Smithsonian Institution, the National Endowment for the Arts and the General Services Administration to recommend what should be done.

The Smithsonian passed politely.It was, at the time, criticized on the hill for building more than enough museum buildings. The art endownment, which also funded the proposal, along with the Department of Housing and Urban Development, the Atlantic Richfield Foundation and others, renewed its full support.

Last week the GSA announced -- with undisguised enthusiasm and in a heavy, two-volume study -- that the Pension Building should be a "Building Building."

The GSA team, headed by architect Richard T. Broderick, concluded in the first volume that this "exceptional Amercian landmark" is basically in good condition and can be restored to its former glory relatively easily.

The second volume discusses the best use of this glory. At present it serves as a depository for miscellaneous bureaucrats. The great inner court -- where presidents danced on their inaugurations -- sporadically houses exhibits and social events. Defiled by litter, the wrong color paint and dirty carpet, this wonderful space looks almost as abused as the grand concourse of Union Station now that it is a visitors' center.

Restoration for nothing more inspired than that, says GSA, makes no sense. Restoration would cost about $15 million. Conversion to a museum, as outlined in "The Building Building" proposal, would cost only half a million more.

The Pension Building, says GSA, "will most definitely prove to be an ideal host for the activities of a National Museum of the Building Arts. The exterior and interior of this remarkable structure is a tribute to American architectural and engineering expertise and innovation. Its large site provides ample space for extensive exterior displays and imaginative site development." The first major reform of the landmark historic preservation act of 1966, introduced by Rep. John F. Seiberling (D.-Ohio), also endorses the building museum as proposed. It would be placed under a triumvirate of the Interior Department, GSA and the non-government committee which started the whole idea.

The Seiberling bill, which will come before the House Interior and Insular Affairs Committee next week and is essentially approved by the Senate, would also make authorized historic preservation funds available for renovation fo the Pension Building. That might solve the $2 million problem of fixing the roof that GSA has no money for.

In view of these auspicious developments in government, it is now vital that the private sector get organized. Congress, when it comes down to appropriating money, will surely insist on substantial financial support by the public and the building industry. Foundations, building material manufacturers, building trade unions, developers, contractors, builders and designers, in turn, will insist on a fairly detained, plausible program before they pull out their checkbooks.

That is why, scared, as it were, by its own success, the original "Committee for a National Museum of the Building Arts" has finally reorganized.

It changed its name to the more appealing "National Building Museum."

It enlarged the board of directors to add two labor leaders and two business executives to the original group of architects, architectural historians and well-wishers. On the other hand, it received the resignation of James W. Rouse, the developer of Columbia and Faneuil Hall Marketplace and the country's leader in the business of building a better environment.

(The labor leaders are Robert A. Georgine, president of the AFL-CIO building trades department, and John T. Joyce, president of the bricklayers; the business leaders are William B. Moore Jr. of Reynolds Metal and David S. Miller, a management consultant.)

The committee's legal and legislative affairs are now handled by the American Institute of Architects, whose executive vice president, David O. Meeker Jr., a former assistant secretary of HUD, has labored for the museum from the start.

The new director, Bates Lowry, is a professor of art history with museum experience. For a year, he directed the Museum of Modern Art in New York and, in 1966, organized the rescue of Italian art after the disastrous flood of Venice, 1966. He presides over the Dunlap Society which promotes the study of American art and architecture.

The as-yet-unsalaried Lowry, his wife and two volunteers were exhausted from cleaning and repainting their office in the Pension Building when I called on them. He hopes to make the museum national by starting right now to spread educational and inspirational materials around the country. But there is as yet no money.

He hopes to start right now to attract luncheon crowds to the Pension Building with audio-visual shows about building activities of all kinds. But there is as yet no money.

Yes, he hopes to start right now to raise money. But it takes money to raise money.

There are two basic questions. The first is whether any such ambitious undertaking can succeed without critical mass, without some need money for a professional office, a professional staff, a professional program and design. Is it perhaps counterproductive to start with little amateur slide shows that bore and discourage everyone before you even get started.

The second, more basic question is whether the apathetic and fragmented building industry can be roused to this challenge of serving the public. And if so, can architects and historians do it?

A decade ago, it was still necessary to put all emphasis on historic continuity. The time has come, it seems to me, to balance concern for the past with concern for the future.

The new president of the museum, Albert Bush-Brown, also a noted art historian, seems to see this.

He knows about architecture and design, having served on the architecture faculty of MIT and the as president of the Rhode Island School of Design. He knows about administration and fundraising, serving as chancellor of Long Island University for the past nine years. He is on the board of Barclays Bank and a fund-raisers' headache, the Metropolitan Opera Association.

"The American achievement in building is celebrated throughout the world," Bush-Brown stated. "Yet, the very nation that threw bridges across rivers, touched the sky with towers, tunneled through rock, laid rails across a continent and designed the comeliest shelters for family, school and work, has not itself hymned its architecture and engineering enterprises.

"The new National Building Museum will exhibit the skills of our building industry in construction, manufacture and design. But it will do more. It will become an educational force for alerting the American future to new possibilities of a noble environment."

A "hymned" Amen.