insulation

While learning about insulation technologies from various chaps, I wondered why curtains weren't much mentioned. Curtains seem to be thought of as some kind of household accessory - something to accent a room (the curtains that were here when we moved in certainly lent moods to the rooms). But no one we spoke to seemed to rate curtains as insulation. This struck me as odd, as I know the importance my mother placed on well-lined curtains in the house I grew up in. We drew the curtains as soon as dusk fell, and we were told that this 'kept the heat in'. So off I went