Leased space in new downtown office buildings now goes for about $19 to $28 a square foot. The maximum, if leasing continues strong through this year and next, is likely to move into the $35 to $40 range before the end of 1982. That would be a 100 percent increase within three years, far above most other price appreciation factors, petroleum products excepted.

An estimated 1.7 million square feet of new downtown space is available for leasing through the end of this year, with only 700,000 feet tentatively committed but unsigned.

Meanwhile, rates for first-class new office space in the attractive but distant Maryland and Virginia suburbs are now in the range of $10 to $14, with the range likely to increase to a maximum of $18 by 1982, unless serious overbuilding develops.

This situation has prompted Thomas G. Owens, a vice president and commercial leasing director of Shannon & Luchs, to speculate in an article to be published in Washington Realtor magazine that future office space users might view the suburban rates as an increasing bargain.

"For a 20,000-square-foot user, that's an additional cost of $20,000 annually for a D.C. image," Owens writes.

Owens adds that prestigious law and accounting firms, which historically are major users of office space here, might continue to pay the high price for District visibility, whereas trade associations, which make up the other third of the Big Three in leasing, may watch their space budgets more closely and follow a trend in which 30 trade and professional groups have located in Reston.

There's plenty of new space being created in suburban areas. It is estimated that nearly 3 million square feet will be completed this year in scores of Northern Virginia buildings, and that more than 2 million square feet will be ready in Maryland -- much of it still unleased.

Other commercial leasing activity:

Dominion Federal Savings & Loan Association has arranged acquisition, renovation and permanent financing of $24 million for the talent group of $24 million for the tenant group acquisition and conversion of the Van Ness East apartments on Connecticut Avenue NW to condo ownership. . . Dominion also arranged $14 million in acquisition-construction financing for the 358-unit Lake Barcroft apartments, in the Falls Church area, where a condominium convesion is under way.