Thanks a to combination of Carter administration cool, now-popular energy conservation, and relaxed dress styles, 1978 could be the least-binding summer ever for Washington's 172,000 male bureaucrats.

It is becoming downright partiotic not to wear a necktie during the capital's hot or humid summer months.

Over the past couple of years a number of federal agencies have quietly put out the work that male - and female - employes should dress more comfortably. The bureaucracy was slow to react. But now, thanks to higher indoor temperatures and the open-neck look at the White House, ties are being put in mothballs all over the city.

Thanks to a national energy conservation program, temperatures in federal buildings here will be kept between 78 and 80 degress this year. The idea is to save fuel by cutting back on the use of air conditions.

The heat wave hasn't hit Washington yet. But when it does, various federal agencies are prepared to advise workers to dress lightly because it will be almost as unpleasant inside as it is outside.

Earlier this month civilian workers at the Forrestal Building (sometimes called the little Pentagon) were told that they could follow the lead of military personnel who have switched to summer - no necktie - work uniforms.

"During this period," the edict said, "which encompasses the summer uniform code for military personnel, Defense civilian employes in the national capital region may wish to make some similar adjustment in normal and customary clothing attire by, for example, eliminating coats and ties."

The escape clause, which is obligatory in any government memo ro directive, added, ". . . Naturally, there will be occasions when during the course of the day coats and ties would be appropriate an should be worn. However, it must be understood that, based upon the nature of individual duties being performed by employes, informal attire may not be appropriate."

What that means, a federal official translated, is that people who normally "don't meet the public regularly should dress to suit the weather. That, of course, doesn't mean anybody should come in in a tank top or T-shirt. What we are hoping people will do is to use common sense." He agreed that was easier hoped than done.

At the Civil Service Commission, the trend-setter for federal administrative matters, employes dress according to Letter A-386, which says in part:

". . . During the summer, open-neck, short-sleeve dress shirts should be considered an appropriate substitute (for coat and tie). Of course there will still be occasions when coat and tie would be more appropriate and should be worn. Similarly, female employes should feel free to wear neat, comfortable clothes . . . clothes made for the beach are not suitable for the office."

The CSC memo, which many agencies will copy, points out that relaxed dress "does not diminish ever an employe's responsibility to dress in a manner that is considerate of federal employes and suitable for a government office." It finishes with the warning that a slovenly or offensive appearance has never been appropriate."

Everybody take it from there.