The most attractive building in the exhibition of New Zealand architecture, which opened here last week, is the New Zealand Embassy that houses it.

The exhibition, to judge from rather small, crowded and mostly unrevealing photographs, shows an architecture that is no more indigenous than New Zealand's culture in general. The native Maori tribes had little or no influence on the British colonists.

What the settlers built follows changing European styles, with, lately, a heavy infusion of American fads, notable wild and colorful conceits in the latest Post-Modernist manner.

The only reminder of New Zealand we get in this medley of provincial Modern architecture are a few pictures of breathtaking flora, mountains and fiords.

The new embassy building, however, in whose great hall this well-meant exhibit is mounted, is anything but provincial. It was designed by New Zealand architect Miles Warren in association with the local firm of Faulkner, Fryer and Vanderpool. It is located somewhat hidden away at the end of Observatory Circle behind the British Embassy and across from the vice presidential mansion.

I find the building most handsome with its simple rhythm of brick arches that seem to grow out of the earth like trees. I also find it quite sophisticated in its simplicity, a simplicity which unself-consciously overcomes the cliches of Modernism without straining for new modes. Miles Warren was not trying to be original. He was just trying to build a good building.

But what, in these confused and confusing times, is good architecture?

In previous periods there used to be agreement on that. At times the agreement lasted several generations. The Greeks, quite universally, I assume, liked Greek architecture, as it evolved. The Romans liked Roman. The Goths would no doubt have liked Gothic had it existed in their time. And the Victorians were amused by Victorian.

But when we come to the Moderns, the majority does not like Modern at all. As Peter Blake, the new architecture dean at Catholic University, was among the first to complain, Modern form followed not function but fiasco. And it is rather ironic that the first architectural style in history which was deliberately created to uplift the common people, a.k.a. "the masses," depresses them fearfully. Despite two generations of Modern formgivers and taste makers, they still want Late Sears Roebuck stable lamps.

That, of course, is hardly news any more. That is why International Style Modern is being replaced by "Post-Modern," which, as noted above, has already spread as far as New Zealand. But that does not make it any more promising. Or anything more than a fad.

The capriciously eclectic juggling of machine age and historic forms into deliberately irrational collages -- and that's what Post-Modernism seems to add up to -- may or may not be witty. A basis for a new, humanistic architecture in the coming age of energy conservation it is not.

It only compounds the basic mistakes of International Style Modernism in that it is an abstract, esoteric, cerebral affair. For all its playful assembly of historic bits and pieces, the Post-Modernists deliberately flaunt our common esthetic heritage and our common and irrepressible notions of what is appropriate and beautiful.

But if these architectural puns are not good architecture, what is?

In the distressing absence of an accepted and acceptable style of our time, of any valid artistic expression of the present Zeitgeist , the best we can hope for in buildings, is the best we can hope for in people.

That is, first of all, that buildings, like people, ought to be polite and accommodating. Modern psychiatry has proclaimed conformity a crime and noisy self-expression a virtue. It is not. This incessant me-me-me leads to chaos in architecture and society.

Other criteria of good, i.e., well-mannered architecture are modesty, honesty and spirit, or call it character and distinction.

Miles Warren and his associates have succeeded in bringing all these attributes to their building.

The New Zealand Embassy is, to begin with, polite to the point of gallantry in the way in which it gets along with its neighbors and sylvan setting.

To accomodate itself to the other houses on Observatory Circle -- they are pleasant enough, but architecturally slightly retarded Phony-Colonial -- Warren has broken up what might have been a sizable office building into three pavilions. These are separated by the clearly but modestly stated entrance and a large hall. They are almost casually grouped along Observatory Circle.

To accomodate the building to Sir Edwin Lutyen's British Embassy, a jubilant tour-de-force, Warren used a nicely patterned brick and a symphony of gentle arches. The effect is that of an old English country house in the backwoods of Lutyen's palace.

The new embassy is modest in that it does nothing to call undue attention to itself. Warren used a minimum of materials and shapes for his pleasing composition. He saved his dramatic flair for the interior hall, a large all-purpose space roofed by an interesting timber structure and adorned by colorful banners.

All this is honest in that there are no frills and embellishments. Every detail of the building has its necessary job. The building is spirited with its clear-cut forms and rich textures of brick and wood.

An embassy is, of course, basically an office building. And even though most of us spend more of our waking hours in offices than we do in our homes, office buildings are the most neglected building type in Modern architecture.Even offices with attractive exteriors are generally no more inspiring to work in than the cotton mills of 150 years ago.

In the New Zealand Embassy most architectural features combine into an animated work atmosphere. There is nothing institutional about it. All of the roughly 80 staff members have access to pleasant public spaces, terraces, pleasant views and natural light. Impressive examples of New Zealand art and crafts are displayed all over the premises.

The people of New Zealand can be proud to be so handsomely represented. The people of this city can be glad to have such a pleasant new building in our midst. Its official opening will take place next Wednesday in the presence of R. D. Muldoon, New Zealand's prime minister, and Vice President Walter F. Mondale.