A Truth Window (or truth wall) is an opening in a wall surface, created to reveal the layers or components within the wall. In an eco built strawbale house, a truth window is often used to show that the walls are actually made from straw bales. A small section of a wall is left unplastered on the interior, and a frame is used to create a window which shows only straw, which makes up the inside of the wall.

Many designs exist for truth windows, they have become quite a novelty for sustainably built homes. Glass may be placed over the window, or an openable wooden panel, or it may be a simple framed opening.

More Truth Windows at this Flickr search.

Photo via Intscher