OK.. here's an old time answer.. My grandmother made quilts out of cotton. When there were old suits, woolen clothing, corduroy, etc.. she would make "comforts". She usually did "postcard" or "brick" comforts.. the blocks were cut the size of a postcard and laid out in stairsteps. They had fluffy quilt bats and were tied as they were too fat to quilt. The backing was usually flannel. These were used on the beds, on top of 2 or 3 cotton quilts, usually the beds with the featherbeds on them, and the farthest from the furnace or space heater. Let me tell you, when you were put to bed in one of those beds.. you stayed till morning.. too hard to get in and out...lol. but oh, so cozy on frosty winter mornings. I don't remember being concerned about them shrinking.. and they were only cleaned once a winter.. at the end of it before being put away for the next year.

I am a manic "pre-washer"....mainly because I use lots of vintage and op-shop purchased fabric and wools. I even prewash new fabric, just to test shrinkage, colourfastness and to remove any chemicals from the dyeing process.

I agree with Butterflywing, do a test piece first, that way you will avoid disaster. Maybe you could back it with a really light-weight woollen blanket? Anyway, I think it sounds a wonderful project and it would be nice to see it when it is finished. I am sure the recipient will find lots of comfort in it.

I have some very old wool quilts from grandmother, they all have flannel on the back.they are at least 75 yrs old.

I would not risk putting an entire quilt together with unwashed wool of an unknown source in the top! Definitely create a test piece and wash it first.

Wool fibers have little "hooks" on the end. That is why wool will "felt" when subjected to agitation in water (as in a washing machine) and then subjected to heat (as in a dryer). More and more of the little hooks snag each other, tightening up the weave. Felting can make wool very soft and wonderful. Mittens and hats made out of felted wool are luxurious. Unfortunately, the felting process results in a lot of shrinkage. That's why felted wool items are always made after the wool has been felted. Many of us have accidentally "felted" a wool sweater with machine washing and drying. The one I remember came out about the right size for a toddler.

If you absolutely have to use unwashed felt in a quilt, my suggestion is to quilt it very heavily. Quilting is your best bet for preventing uncontrolled shrinkage.

Never ever put a wool quilt in hot (or warm) water, or the dryer. Never ever!