To protect your fabric from the sun, you could make 'curtains' for the book cases.

I like the idea of the design wall to cover bookcase. I have most of my stash behind doors. The rest is in those cloth cube storage bins. I try to keep blinds closed over windows when not in room. but I love a sunny room to sew in.
Denise

Most window film will cut out over 98% of UV light which is partly to blame for fading (around 40%). other causes are visible light, another 25%, heat another 25% and miscellaneous causes around 10%. So the best thing for fabrics is to keep them dark and cool.
I have window tinting and I would never draw the curtains during the day, I love a sunny room. I try to keep my very meager stash in a wardrobe to keep in in the dark as much as possible:)

I love the idea of using flannel. The sun here in AZ is unforgivable as you can imagine. We do have 90% sunscreens but it still shines brightly into the room.

Fabric can definitely fade along the fold lines - even in what I thought were protected areas - blues seemed to be most vulnerable. Definitely get something in front of the fabric to protect it.

Actually, some of the Jinny Beyer fabrics for RJR seemed to be more prone to damage than some other lines.

You definitely need to do something to protect it, but I don't have any fancy ideas. I have most of my fabric in 2 wardrobes in plastic boxes.

Great idea Kat Sews.

Wow!!! what an AWESOME idea!!! I was thinking of using a bookcase but do no like the open look when I am not sewing...this is perfect!!! Thanks...love this board!!

They sell insulation fabric at JoAnn's for drapes which would probably help and although your windows sound huge, perhaps some of the plastic that adheres to your windows to shade you. It's not dark enough so you can't see out, but it does stop some of the heat and UV from coming in. You can get it at most RV stores in varying sizes. We used some because the bird ate our blinds and he's right in front of the window. It does a pretty good job and you can't see it unless you miss a spot!

One of my first wall hanging s was a school house quilt,the east sun got it!!!! Now the navy blue is ruined on it, it faded so badly. I now make sure my quilts and fabric are covered or put in dark containers.