My summer quilt has Hobbs poly down in it. While most people claim it doesn't breath because it is a synthetic, I find mine very light weight and not too hot for the summer and this summer has been as hot and humid as Galvestine in the northeast this year (many days in the 90's with 70% plus humidity, ugh!). I do have a window AC unit, couldn't sleep without it but just this quilt as a cover is fine and when I have the ceiling fan on high with the AC I can actually feel the breeze in places. And it is a LC with loads of seam allowances. Another thing that will help keep the quilt not so hot is denser quilting. It keeps the batting from forming the air pockets that hold in heat.