Curtains are manufactured from a variety of thick fabrics, each with a differing degree of light absorption and heat insulating qualities. For maximum temperature control, the curtain gap to the window should be small, with minimum convection drafts below or above the curtain. Various architectural structures around the curtain can minimize these air drafts, but usually they are just used for decoration and make rooms feel more cozy.
A sheer or net curtain is one that is made from translucent fabric, such as a loosely woven polyester voile or a cotton lace. Sheer curtains allow a majority of light to be transmitted through the fabric, with the fabric weave providing a basic level of UV protection while retaining maximum visibility outward through the curtain.