Green Architecture: Design for an Energy-Conscious Future by Brenda and Robert Vale (Bullfinch Press/Little, Brown & Co., 1991; 800/759-0190). Hardcover, 81/2x11, 192 pages. $40. Brenda and Robert Vale, the British architects who designed the largest superinsulated structure in the United Kingdom, have turned their expertise to the emerging practice of "sustainable" architecture. In Green Architecture, the Vales peer into the future and show us what designers and builders must do to help the planet and its inhabitants survive the increasing stresses on the environment. Drawings and photos are plentiful, including brilliant color shots of buildings that illustrate points made in the text. To help describe sustainable architecture, the Vales use the elemental symbolism of earth, air, fire, and water. Buildings, they declare, are poised among these elements and interact with them. The first chapter