Be concerned! I know a quilter who used to keep her fabrics nicely folded on open shelves. It looked amazing when you went into that room. The shelves did not get any direct sunlight, but the the room was light and airy overall. Some (not all) fabrics faded quite badly on the exposed fold line.
I have posted these before in the forum, but can't remember where and when (I bet Margo can!!). So I'll do it again. I keep my FQs in an open narrow bookcase. I used some scraps and made a simple quilted cover. I used velcro across the top, sticky side on the bookcase and sew-on side on the back of the quilt. When I need access to my FQs I simply rip off the quilt and pop it back on afterwards. I rather the quilt made from leftover fabrics fades then my FQs.
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