I was wanting to get a bunch of batting to have on hand "just in case " LOL
Then I go to thinking about using a flat flannel sheet I know some of yall do that and also use it for the backing.
My question is how warm would one with a flannel sheets for both batting & backing be? I am talking warm enough for Idaho winter? NW Texas winter?
If not then what batting would you suggest for use with a flannel backing?

I am not sure how warm it would be. I did a flannel backing on a small lap quilt because the fabric had dogs on it. But I did use regular Warm and Natural batting. To answer your question, actually I can't answer your question. Hope someone more experienced than me can.....

I often use flannel as the middle of my rag quilts. I think it makes a great quilt for watching tv or taking in the car (keeps the air conditioner from making my knees stiff). It would not be warm enough for a blanket to use on a cold winters night, in my opinion. In that case, I would use the flannel for the backing and a nice batting for middle.. I like Warm and Natural.

I often us flannel for the backing because it's soft and snuggly....but I always use some type of batting, usually warm and natural. I just gives it a little more warmth.

I use lots and lots of flannel for backing. Have never used flannel for batting, but a backing is one of my fav's.