a double - glazed window apparatus for use at a sloped angle is disclosed having an insulating roller shade assembly extendable between the glazings in a u - shaped loop for insulating or shading . the apparatus includes supports for holding the sheet in spaced relation to the glazing and maintaining defined air spaces for insulation . a lower portion of the sheet is supported by stationary supports while an upper portion is supported by cross bars attached to the sheet and riding on slideways along both side edges thereof .