AN EARLY newspaper description of Cooke's Row on Georgetown's Q Street spoke of the "tasty porches."

That seems too mild a word for Joe and Janet Passonneau's favorite place in their Cooke's Row unit - a two-story high (and then some) glass bay that juts out from their kitchen almost into the swimming pool.

The bay is a supersized copy of the 1868 original front windows of the house. The distinctive and graceful windows are arched at the top. The top sash has two arched muntins that divide the glass.

Passonneau's bay is an architectural pun. It is, as he says, a "mannerist" version of the original window. Furthermore, architect Warren Cox also copied the original window, one-story high, for the addition he designed six years ago for David and Helen Kenney, the next-door neighbors in another Cooke's Row duplex.

(The job won Cox and the Kenneys American Institute of Architects Washington Metropolitan Chapter Preservation awards last year. See Living in Style, Oct. 29, 1978.)

"I told Warren I hoped he didn't mind my stealing his idea," said Passonneau, an architect and former dean of Washington University (St. Louis) architecture school. "And Warren said, heck, we both owed Starkweather and Plowman, the original architects."

Any architect touching a fine old house such as Cooke's Row is bound to feel nervous. The houses have been much admired landmarks in Georgetown since they were built.

Today, Starkweather et al. would surely feel comfortable enough with the fronts of the houses. The early architects would, of course condemn the unthinking desecrator who added the strange dormer like a lifted eyebrow on the third floor. The fan light on the Passonneau house is a proper Victorian stained glass; the other a pretty if anacronistic Georgian fan. But the houses look much as they always did.

The four double houses, two each in the Italianate and French taste, all brick, were designed in 1868 for Henry Cooke, the first territorial governor of Washington. (The houses were allegedly built for his 12 children.) The lots are a generous 40 by 140 feet, give or take a few feet. The houses sit up from the street with a lordly air.

But the backs, as with most Victorian structures, were never anything much, being designed to hold mops and pails and be viewed by the horse and the cow. So they have been remodeled many times. The original kitchens were, as suited the time, in the basement. In this century, they moved upstairs, usually in not too elaborate additions. The Passonneau house had had three.

The Passonneau remodeling is instructive as a way to "quote" the original design of the house, while making a drastic change to suit late "70s' ways of living. Most of the rowhouses in Washington are in need of some sort of kitchen and rear updating.

Passonneau, over cold cuts and a bottle of wine at the Eero Saarinen table in the bay, says what he did was to "simplify the additions." The glass wall ("Chevy Chase Glass looked on it as a challenge") extends out 4 feet from the kitchen. It is 20 feet high and 8 feet wide. Arlington Woodworking made the elaborate frame. The careful brickwork around the alcove was the handiwork of William Penn of Alexandria. The bottom sash of the superwindow actually rises like the double hung window he copied. A marvelous brass counter weight, (a device used to raise and lower sails on a boat) was installed by Passonneau himself. He did most of the finish carpentry on the house. Janet Passonneau, a biochemist at the National Institutes of Health, laid the wall tile floor. She also built the wine cellar in the basement out of hollow drain tiles.

The metal kitchen cabinets of a previous remodeling are still there, with stainless steel counters. One of these days, they'll paint the cabinets, but the color isn't decided.

As if the bay isn't surprise enough, on the other side of the kitchen is a 10-by-33-foot slanting glass roof that brings north light to three floors of halls.The effect is dramatic, to say the least. The halls now all are balconies overlooking the kitchen. On the second floor, a wash basin protrudes into the sunlit hall. When you brush your teeth there, you might feel as though you were spotlighted on stage. The glass roof project was under way for three years.

The Passonneaus bought their house in 1969.They've been working on it ever since. Heating and cooling, wiring, plastering, all had to be updated first. Donald Urbis did the plastering, which alone cost $10,000. The heating and cooling of the house usually runs about $2,500 a year for gas and electricity.

Along with the necessary utilities, the first thing the Passonneaus put in was a swimming pool replacing a clothes drying yard. The terrace was raised to meet the house. The 32-by-16 foot oval pool not only pleases the four Passonneau children, but also serves as a reflecting pool for the house. The Passonneaus cook out three or four times a week in good weather. The pool, garden and terrace cost about $15,000.

In the library, Passonneau did a vast amount of carpentry, building in the sound system and bookshelves.

Janet Passonneau likes to say that in another year her husband may have succeeded in eliminating the last closet. In the front hall, he tore out the old closet and set the coat closet into the wall. "I found that the walls in the house are 20 inches thick, three rows of brick and an airspace," said Passonneau. "The walls are hollow, designed to make an airflow up from the basement to the attic, to circulate, cool and heat."

Passonneau has his architectural offices in the tall basement, used by one owner as a bomb shelter. Passonneau cut a sliding glass wall on one side for light. He is currently working on the design of the parkway through Franconia Notch, N.H.

The Passonneaus paid $110,000 for the house in 1969. They figure they've put about $75,000 in it. But a real estate agent wandered by the other day and said if they could ever finish it up, they might get a half million for the house.

But Passonneau has this plan about the cupola. Perhaps a sort of baroque ladder, with a fancy wrought iron gallery.... CAPTION: Picture 1, Joe and Janet Passonneau's Cooke's Row home in Georgetown; Picture 2, At the rear, a glass bay juts out from their kitchen; Picture 3, The bay window is a supersized copy of the 1868 original front windows; Picture 4, Joe Passonneau on the second floor, where there's a handy wash basin. Photos by Douglas Chevalier - The Washington Post.