I have used the Quilter's Dream cotton batting in the thinnest loft, and it is VERY thin. I think it's just what you want, if you don't want Thermore (polyester, but really nice and light), or a flannel sheet, etc. Just be careful not to tear it when smoothing it out over your backing--it's that thin. I actually prefer the next thickness in Quilter's Dream cotton batting, but I'm not in a hot climate. You can even order just one batting directly from Quilter's Dream and they'll ship it to you (from North Carolina, if my memory is correct).