The D.C. housing department issued new regulations yesterday that could permit the owners and developers of many large apartment buildings to convert their rental units to condominiums despite a moratorium passed last week.

Reacting to lobbying by tenant groups worried that the rapid escalation of conversations would displace them from their apartments, the City Council approved last week a temporary halt to conversions of condominiums and cooperatives.

The emergency, 90-day legislation also authorized Mayor Marion Barry to allow exemptions from the moratorium. Yesterday, the housing department released regulations detailing those exemptions.

A key element of those new regulations allows any owner or contract purchaser of a building with 20 or more units who already has invested more than $20,000 to go ahead with plans to convert rental apartments to condominiums. A project with less than 20 units and an investment of $1,000 per unit also can qualify.

Developers contacted yesterday who already held certificated to convert said they fell the various exemptions will enable them to proceed. It appears that owners or persons with contracts to purchase buildings who had taken even initial steps toward conversion before May 22 probably will be able to continue with their projects.

Condominium specialist G.V.(Mike) Brenneman said yesterday he was aware of several sections of the regulations but had not read the guidelines. Nevertheless, he said, "I had one building that I thought might be affected [by the moratorium], and I'm breathing easier on that one now. It looks as if we're safe."

Brenneman added that he had hoped the city would consider as substantial financial investment as less that $20,000. I think that's rather high," he said. "the great preponderance of condominium conversions have been relatively small jobs, with 20, 30, or 40 unit. For those, $20,000 is a lot of money . . . It really depends on what stage the conversion is in.

The council passed the moratorium May 22. It allowed the mayor to exempt any project that was purchased on or before May 22 in contemplation of conversion, any project in which an intent to convert on or before May 22, any project where the conversion is agreed to by the tenants, and any project in which there was a substantial financial investment on or before May 22.

Those exemptions could be allowed only after regulations were issued by the mayor's staff.

The question or "substantial investment" puzzled many people. Yesterdayhs regulations provided the city's answer.

Building owners who believe they qualify for an exemption from the moratorium must apply to the city housing department. The special assistant to the city housing director then has 10 days in which to approve or reject the application. The applicant can appeal a rejection to the director.

Developers will have to submit affidavits documenting their investment, and they must notify their tenants of a request for an exemption. A notice of the request also has to be posted in such places as elevators and laundryrooms and on trash room doors, according to the regulations.

Mark Looney, a spokesman for the Emergency Committee to Save rental Housing, a coalition of about 50 tenant and community groups that pushed for a stong condominium moratorium, said yesterday his organization considers the regulations weak and is disappointed.

"They would allow for most buildings with certificates to be converted," Looney said.

Looney said the organization is particularly displeased that contract purchasers can obtain exemptions. and that members feel that the dollar amounts necessary to prove finiancial commitment are too low.

Last week , the city released a list of 26 projects containing nearly 2,000 units that are excluded from the moratorium because their owners already had received notice that their condominium registration documents had been filed. Information from the city shows that between 9,000 to 10,000 units whose owners have received a certificate to convert could potentially be affected by the moratorium.