Thermally efficient window shade construction

A thermal isolating shade assembly comprising in combination, a header box, a roller shade member mounted in said box, for movement between extended and convoluted positions, said shade being normally urged to said convoluted position, an access slot formed in the bottom of said box, said shade projecting downwardly through said slot, a shutter blade mounted to said box, said blade extending a transverse distance substantially coextensive with the width of said shade, and including a seal surface movable toward and away from said slot, spring means yieldingly urging said blade toward said slot to thereby clamp substantially the entirety of the width of said shade between a wall defining said slot and said seal surface to define a transverse seal area with said shade and clamp said shade against movement from said extended to said convoluted position, and release means operatively connected to said shutter manually actuable to shift said shutter away from said slot to thereby release said shade for return movement to said convoluted condition.