If no attempt is made to control excessive heat loss through glass... a solar house may require as much as 20 percent more fuel than an orthodox house during December and January... Wendell Thomas recognized and solved this problem... by burying the house in the ground, except for the south and east window areas.... at night... windows are covered with from inside by insulation boards and drapes...

The Owner Built Home: A How-to-do-it Book (1972)