A congenial atmosphere includes protection from too much sunlight.

Sunlight streaming through a window directly onto a rug is virtually guaranteed to harm it, whether morning or afternoon, southern or western light. Naturally dyed rugs and synthetically dyes rug suffer equally. Colors fade unevenly and wool and cotton dry out and become brittle.

You can prevent the problem by keeping the curtains closed or by having your windows professionally covered with mylar.

Mylar is a film which can be applied to your windows and filters harmful ultraviolet light. It does not impart a noticeable tint to windows. Mylar has the secondary effect of taking a couple of degrees of heat off hot summer sun and softening glare through a window. Most damage is caused by light shining through a window, of course, but often enough rugs are faded by sunlight streaming through a skylight.

Sometimes people have no idea that this is happening because it occurs at a time of day when they are not at home.

If your rug has already suffered fading by the sun, there is still hope that it can be improved. If the fading is merely on the very tips of the pile, then washing the rug may help the problem by simply abrading the faded tips of the wool. More sever fading can sometimes be improved by professional clipping of the entire pile.

Occasionally a rug is so faded that neither of those methods work, and then one must decide whether to accept the rug as it is, or to attempt to fade the entire rug evenly. This involves covering parts of the rug that are faded and leaving the unfaded portions exposed to the sun.

Source: Oriental Rugs Today By Emmet Eiland