Curtain - Light Control and Insulation

Light Control and Insulation

Curtains can be made from varying thicknesses of fabric, 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. Sheer curtains are sometimes referred to as privacy curtains in reference to their screening abilities; during the day most sheer fabrics will allow people inside the home to see the outside view whilst preventing people outside the home from seeing directly into the home. Due to the loose weave in sheer fabrics, these types of curtains offer very little in the way of heat insulation.

Uncoated fabrics provide the next level of heat insulation and light absorption. Uncoated fabrics constitute the vast majority of fabrics used in curtains, and are composed of a tightly woven fabric, most typically a cotton/polyester blend, which is mostly opaque when viewed in ambient light. Uncoated fabrics provide a reasonable level of heat insulation due to the tight weave of the fabric, however the fabric itself is typically not thick enough to completely absorb strong light sources. As a result, when curtains made from uncoated fabrics are closed in an attempt to block out direct sunlight, light will still be visible through the curtain.

Coated fabrics consist of a standard uncoated fabric with an opaque rubber backing applied to the rear of the fabric to provide improved light absorption. To create a coated fabric a liquefied rubber polymer is applied in a single coat to an uncoated fabric and subsequently fused dry by means of a heated roller, in much the same way that a laser printer applies toner to a sheet of paper before fusing it dry. A fabric that has been through the coating process once is considered a 1 pass coated fabric, anecdotally referred to as dim-out or blackout because of the fabric's ability to absorb approximately 50-70% of a direct light source. To improve the light absorption of a fabric it is possible to re-coat a fabric up to a maximum of 3 pass coated, which is considered sufficient to block out 100% of a direct light source, hence such fabrics are referred to as blockout coated.

Maximum light absorption and heat insulation in a curtain is created through a lined curtain, which typically consists of an uncoated fabric at the front to provide the look and feel of the curtain, with a separate coated fabric attached at the rear to provide the insulative qualities. The coated fabric is typically referred to as a lining, which simply refers to a coated fabric that does not have any particular color or pattern.

Curtains may be held back with tie-backs or may be closed and opened with sticks called draw-pulls or curtain rods which are attached either to the runner or to the first hook. On some curtain rails/poles, there is a pulley system for opening and closing called corded curtain tracks. The knobs at the end of these cords are called cord pulls or acorns. A roll-down or drop-down curtain has its fabric rolled around the curtain rod and is lowered down from above by a separate device (such as pictured at right) or by pulling the fabric itself, with curtains using the latter mechanism being called pull-down curtains.

A curtain hook stopper is a device used to stop the curtain from falling off the end of the curtain rail.