If I had a project that was going to be in one spot for a long time I would just cover it with a blanket or something. Otherwise I don't worry much about sunlight ruining anything.

I have a wall of windows, with my working wall on the opposite side of the room. I sometimes have projects on the wall for months while I think and rethink, move bits around, and ponder.

That said, take a strong colored piece of fabric, cut two decent sized pieces, and take one to the window. check it against the 2nd piece once a month for a year. Then you'll know. We can't say, in your situation because age of windows can have much to do with the results. I doubt with my new windows there will be any fading in my house, but the wall of 40 year old windows in my liviing room caused my carpet on that side of the room to fade. .. over 25 years.

Interesting question. In a lqs, I purchased a fabric that was a good 20' from the windows. As the fabric was unrolled to cut, I noticed a faded part at the same spot - so about every 10 - 12 inches or so - with each unfolding. It took about 4 'unrolls' to reach the part of the fabric that was not exposed to daylight while sitting on the shelf. The fabric did not get direct sunlight.

It is possible that at one time it was closer to the front of the store, though. Even so, the fading had penetrated farther than I ever imagined it would.

I have two goodsized windows that face north with an substantial overhang. Most of my fabric is in draws. I have not noticed any sign of fading.

I also was looking at fabric from a store that had no windows and the fabric had faded just from the fluorescent overhead lights.
I bought some very dark room darkening curtains and covered all of my fabric on shelves with them. Hangs from a curtain rod above the shelf works really well.

I'm lucky to quilt in a basement with a large picture window on the northeast wall. No direct sunlight comes in, but I have nature light. This has been my quilting room for the last 24 years, I have quilts hung on two walls and my fabric stored on open bookcases. I have not noticed any fading on the fabrics.

That should say Tape one of the two pieces to the window ;) duh..

I think I'm ok. Most of my fabric is in a walk-in windowless closet, and the rest is in a room on the North side of the house. The house has Bee Windows which are supposed to exclude harmful rays.

My sewing room is in the basement so no direct light coming in. And all my fabric is in closets with doors, and all precuts are in file drawers. I recently bought a piece of fabric that has a fade line. I was using it as borders, so I just cut that narrow section out and resewed the pieces together. Any unfinished projects are put in tinted artbins. The lighting in the room, if strong, can fade as much as sunlight or bright outside light.

We live in a very sunny climate and have a very bright and sunny house. We had UV coating put on all of our main floor windows to protect the furniture and carpeting. We purchased UV film from Lowe's and installed it on the two garden level windows in my sewing room which is a walk-out area of the basement. It was not difficult to do. We had it installed on the main level because of high windows and the need for tall ladders. In the past, in another house, we experienced sun fading. We had a sun room in a house we bought that had sun faded carpet. We re-dyed the carpet and had the windows professionally coated. We lived in the house 15 years and never had the carpet fade again. However, I made a quilt for the bedroom and it faded (and rotted) where the sun hit it.