Your Guide to Curtains and Window Treatments
By SARAH STEBBINS
Where Do I Start? Set aside style considerations for a moment; function comes first and will limit your curtain choices, in a good way. If you want treatments that provide privacy or total darkness, you need lined curtains. If you’re OK with light filtering through or if your curtains are simply decorative, unlined will work. Lining is more expensive but has other advantages: It can shield fabric from sun damage.
Image: Metropolitan Curtain systems from JAB Anstoetz
Source: Guide to Curtains and Window Treatments | Real Simple