The Arlington County Board revised the county's housing grants program yesterday to assist more low-income elderly, disabled and needy residents following decreases in funds from federal housing assistance programs.

The unanimous vote came after an 18-month study by the county's housing commission. It constitutes the first major revision of the program, which provides funds to subsidize rent payments for eligible residents, since it began in the early 1970s.

The program, board member Albert C. Eisenberg said, "is one of the most important tools we have to deal with the problem of housing affordability."

The board boosted the county's current budget of $625,000 for housing grants by $209,000 and adopted policy changes that Fran Lunney, a member of the county's housing staff, said would make between 40 and 100 additional households eligible for the program, which now assists 631 county households.

"The emphasis is to get as much as possible to people paying a large part of their income for rent," Lunney said. "The [housing] commission found that 12 percent of the elderly households were paying over 80 percent of their income for rent even after getting the grant. Four percent of the [nonelderly] families were paying over 80 percent of their income for rent after the grant."

Part of the new grant formula the board adopted yesterday assures that none of those eligible for the program will have to pay more than 70 percent of their income for rent. The county will pick up the remainder.

The board increased the income eligibility ceilings by about $2,000 in various household-size categories and added a category for families of four or more with a maximum yearly income of $20,850.

The maximum allowable monthly rents were increased to match the fair-market rates set by the U.S. Department of Housing and Urban Development for the federal Section 8 rent subsidy program.

Also, the board changed the way the county calculates its subsidy to eligible residents. The formula now calls for the county to pay half the amount by which a person's rent exceeds 30 percent of his or her income.

The old formula set a 24 percent rent-to-income standard. Those currently receiving the county's housing grants will still fall under the old standard while newcomers to the program will come under the 30 percent standard.

"As the federal government's contributions decrease, local commitment will have to increase and the state will have to enter the picture much more," Eisenberg said in an interview.

He announced that he has met with officials from Alexandria and Fairfax County to discuss the formation of a Northern Virginia coalition of governments to lobby the state government for more housing funds.

"We're kidding ourselves if we think people are somehow going to be able to get by with the costs which exist in this area," Eisenberg said.