Another little change of design was the addition of a small window in the 'cave' . This space is not supposed to be 'habitable' and is not included in the allowable area of the house as it is only 1m80 high. But it can be used for storage and as this is supposed to be an ecological house, if it did not have a window, then every time one used it, an electric light would have to be turned on. So, I think I'm justified in giving it a little natural daylight to avoid pouring more carbon into the atmosphere !