Tenants in Arlington's Clarendon House apartments, some in their 80s and 90s, have been notified by the building's new owner that their units will be converted to condominiums during the next year.

Announcement of the conversion three weeks ago has troubled county officials and a number of the building's elderly tenants, many of whom do not expect to be able to buy their units, because of the shortage of affordable rental units elsewhere in the county. Arlington currently has a vacancy rate of 1.4 percent, making the prospect of finding an apartment difficult for the elderly, who may not have the strength for an exhaustive apartment hunt.

Wentworth Associates, a corporation headed by John Eames and his wife Mary Walker Eames, bought Clarendon House for $3.1 million on Oct. 31 from Michael Abrams. John Eames plans to begin renovation of the five-story building, at 3515 Washington Blvd., starting next week. The project should be completed in a year, he said.

Arlington County officials have expressed concern about the relocation of Clarendon House's elderly tenants. About 39 of the 100 tenants are over age 65, and at least five are in their 90s, according to Fran Lunney of the county's housing section.

"Conversion impacts more greatly on the elderly than on young families. Peoples' support network may be broken down. They won't be able to relocate" to the same area, she said.

A memorandum from county manager Larry J. Brown says that Eames plans to provide some continuing rental units at prices comparable to current rents. The monthly rents for an efficiency start at $385, and a one-bedroom apartment starts at $475.

County ordinances governing condominium conversions require that a developer make provisions for 20 percent of the condominiums to be kept as rental units with three-year leases. Eames said he expects to sell about 16 of the 78 apartments to investors willing to lease to elderly tenants at rents near the current rate.

Eames will pay $500 to help each tenant relocate, exceeding the county's requirement of $440. Although Eames has no formal program to help older tenants relocate, he said that his office will accommodate those who ask for help.

Since 1972, the county has lost 12,000 apartments, roughly 30 percent of its stock, to condominium and cooperative conversions.