The value of new second mortgages and home-equity loans will increase this year to more than $150 billion, according to U.S. Housing Markets, a research survey published by Lomas & Nettleton, the Dallas mortgage banking and financial services firm.

Home equity loans totaled $30 billion in 1981, according to the report, but topped $50 billion by 1984 and will rise to between $150 billion and $200 billion this year.

The report said a conservative estimate is that Americans have $1.4 trillion in unpledged home equity available for financing. U.S. Housing Markets estimates that one-fourth to one-third of the money being borrowed against home equity is being used to upgrade the borrower's own property.

In an effort to increase home ownership, the Department of Housing and Urban Development is now permitting up to a 2 percent interest rate reduction for qualifying home buyers in its Federal Housing Administration mortgage insurance program.

Such reductions occur through buydowns, in which a seller pays a portion of the home buyer's mortgage for a period of time. In a typical example, a buyer with a long-term 11 percent interest rate would only make payments for the first year equivalent to those with a 9 percent rate and for the second year at a 10 percent rate.

HUD said it would qualify borrowers at the initial, lower rates in hopes of increasing home ownership opportunities for more first-time and low- and moderate-income buyers.

Downtown office vacancies nationwide declined slightly to 16.2 percent in the third quarter, while suburban office vacancies rose to 23 percent, according to a new survey by the Coldwell Banker Commercial Group.

The highest rates of downtown office vacancies in the 43-city survey were in Austin (35.8 percent), Oklahoma City (33.3 percent) and Denver (30.3 percent), while the lowest were in Hartford, Conn. (5 percent), midtown Manhattan (7.6 percent), Charlotte, N.C. (7.7 percent) and Sacramento, Calif. (8 percent).

Several surveys have shown that Washington's downtown office vacancy rate is about 10 percent, while Coldwell Banker said the suburban vacancy rate is 17.4 percent.

Analyst Raymond Torto said that nationally "the suburban market remains overbuilt, and the average level of absorption in the quarter was inadequate to offset the level of new space completed."

IN THE BUSINESS ... Edward E. Pagett, owner and president of the real estate firm that bears his name, has been elected 1988 president of the Northern Virginia Board of Realtors ... Architect William F. Vosbeck has started a new firm, called Vosbeck Associates Inc., specializing in improving land and building assets ... Fortress Co. has started construction on Old Ferry Business Park on Old Alexandria Ferry Road in Clinton ... Battery Development Corp., a joint venture of Miller, Mattheeussen & Long Inc. and Marcus Corp., has started work on Madison Park, a 10-story condominium building at 5000 Battery La. in Bethesda ... McShea & Co. Inc. has started construction on the $30 million, 300,000-square-foot North Amber Business Park in Frederick ... The National Association of Industrial and Office Parks has selected its Northern Virginia chapter as one of five winners of its Chapter of the Year Award ... Associated Cos. have acquired 12 1/2 acres from Prudential for construction of a 131-unit town house community at Waters Landing in Germantown ... Stanley Martin Cos. Inc. are building 119 town houses at Bull Run, a Manassas development ... the F.W. Dodge Division of McGraw-Hill Information Systems Co. reported that construction contracts in the Washington area are up 6 percent through the first nine months of the year over the January-to-September period last year, from nearly $5 billion to $5.3 billion ... cpl, a Reston-based design and building firm, is building 21 homes at Riverbend Knolls near Great Falls.

PERSONNEL FILE ... Nancy K. Card, formerly development officer for Cadillac Fairview Urban Development Inc., has joined the Mason Hirst Cos. as vice president of the newly formed development department ... Roger W. Snyder, Prince William County's planning director, has been named chief executive officer of the Northern Virginia Building Industry Association, replacing Michael Forbes, who recently resigned ... Warren J. Dunn, formerly senior staff vice president of communications for the Mortgage Bankers Association of America, has been appointed the first general manager and senior vice president of Mortgage Banking Service Co., a subsidiary of MBA that will manage ECHO 1, the trade group's electronic communications system ... Herbert A. (Tony) Slunt has been named vice president for construction of CMC, a real estate management and development firm ... Corby-Lynn Real Estate Co. Inc. has promoted Kenneth E. Miller to vice president for property management.