I knew we should of checked etsy Frankie! chevron fabric poppyseedfabrics
For insulating behind pretty curtains, i went to Hobby Lobby and bought yards and yard of this stuff call Insul-bright. It's meant to be used when making oven mitts and works great on windows. I just hung it behind our curtains. It's only $2.50 a yard and you can use a 40% off coupon too. Really cheap way to make your curtains insulating ones.