Should my curtains or Roman shades be lined?
In general, simple curtains do not need to be lined, and sheer fabrics like handky linen and gauze should never be lined. However, lining does prolong the life of your shades or curtains by protecting them from sunlight. If your windows face west into direct sunlight, you might consider lining them. We particularly recommend lining richly colored curtains as the colors are more subject to fading. Custom dyed linen will also do better with a lining. We use a cotton fabric made for drapery lining and treated to resist water marking.
For a particularly sunny room, consider interlining. We sew an inner layer of baby flannel between the lining and the face fabric for extra insulation or light blocking
Unlined curtains in heavier linens are opaque enough for most situations. Lining will provide more shade in a bedroom. Black out lining with a polymer coating is available as well and provides more shade but does not completely black out a room.