If Rozansky & Kay Construction Co. does indeed wind up taking title to the 25-acre Foxhall Road estate of Nelson Rockefeller, there is considerable speculation as to what will happen to the property.

Potential builders understand that about 130 single-family houses can be built under current zoning there, but there is also reluctance to seek any zoning variance because of the potential of neighborhood opposition in that exclusive area. However, a planned unit development with the same number of clustered dwelling units would probably be more prudent for the billy site. Developers who looked at the property figured that to make economic sense, lots would cost about $80,000 and houses would have to be priced in the $300,000 range.

There is also some doubt about the strength of the market for such houses.

Meanwhile, there are reports that the contract to buy the entire plot is already being offered quietly, even though Rozanzky-Kay has not yet gone to settlement The Town and Country agent handling the projected transaction here is a one-name person called "Basheyba." who wouldn't discuss it. The Rockefeller property is being listed by the William Yates real estate firm in Briarcliff Manor. N.Y.

Garth Marston, former chairman and now member of the Federal Home Loan Bank Board (and a Capital Hill resident), is being rumored to succeed Olvier H. Jones as executive vice president of the Mortgage Bankers Association of America. Jones will be honored at the MBA convention in New York City in late October but it is remembered that his resignation (effective the end of October) was triggered by interference in his domain by elected officers, Jones and his wife are living in their new contemporary house in the mountains near Bedford. Pa.

Thermography is the "science of detecting and measuring infra-red heat (or cooling) loss in homes, buildings and electrical equipment," according to Larry Wasson, president of Energy Conservation Consulting Service, Inc., 4711 Chesapeake St. NW. While admitting that a 20-degree difference between inside and outside temperatures is needed to make an effective analysis. Wasson contends that the service can detect heating and cooling losses and pintpoint them to enable building or house owners to take corrective or house owners to take corrective measures. The minimum fee for a report from the camera with infra-red detectors is about $50.

Real estate and politics seem to run in the family of George Shafran, chairman of Better Homes Realty. Son Tom, who is president of BHR. is candidate for the Virginia legislature, where his father formerly served. And youngest son, Jack, a sophomore at James Madison University in Harrisonburg. Va., got the idea for the family to buy the town house in which he and colleagues are residing. The likely appreciation of the dwelling during his tenure at Madison will probably be enough to pay for the collegian's education.

All of the 418 town houses and apartments at the Pembrooke of Loudoun condo concersion at Sterling Park have been sold, according to Steven G. Yeonas, who was a coredeveloper with Walter J. Hodges. That was accomplished in about six months, proving - according to Yeonas - that's there's a strong market for ownership in the $20,000 and $30,000 range in this area.

A recent edition of Forbes magazine quotes Benjamin Franklin Kahn. president of Washington Real Estate Investment Trust and lecturer at the University of Pennsylvania's Wharton School, thus: "I guess I'm just a sissy. I'm afraid to take much risk. Other people can make money faster than us (WRIT) but over the long run we should do just about as well." Another quote in the Washington native's profile: "Real estate is still very much a backyard horse-trading business. I grew up here and that gives me an advantage over any outsider.

Over in Ocean City, Md., the 50-room Stephen Decatur Hotel, which dates from the 1930s, is being readied for razing. Some folks in the Atlantic resort are reluctant to see the landmark white frame building go down. Developer Angelo Puglisi and his partners have a razing permit and plan to rebuilt on the site - 19-unit masonry apartment building with space for six stores on the boardwalk location at 12th Street.

Joint Chiefs of Staff Chairman George S. Brown, whose controversial public statements sometimes make headings, has to be the highest ranking military officer among the preponderance of the gold braid set who are owner-occupants of those expensive Forest Hills town homes near Shirley Highway, opposite Army-Navy County Club. Another resident is developer Albert Van Metre, a former Navy officer who now wins sailing honors with his sleek, big vessel.

Walter E. Ekblaw, newly elected chairman of the National Association of Home Manufacturers, is convinced that the NAHM must take the leadership in forming an all-building industry group to prevent the proliferation of conflicting codes and standards for energy conservation in new housing and buildings. "I believe that we must impress on the new Department of Energy that this problem deserves top priority. We must have a national and I repeat, national standard," he told a recent NAHM convention here.