I have fashioned a curtain out of heavy duty plastic with Velcro on all 4 sides. Just measure the window/sliding door, purchase a heavy duty plastic (most of the fumes from the plastic - if any - will go outside) and then add the Velcro to the curtain and to the frame around the door. I have also just made a curtain with Velcro on just 3 sides so that I can be removed easier when the days are not quite so cold. I live in Indiana and the weather here can be harsh and I found that purchasing something "ready made" either was too expensive or just didn't fit right. I have also used several colors of Sharpie pens to personalize the curtain with drawings that really look cool when the sun shines through. If you don't feel you are artistic enough, you can always trace from a coloring book and then color it yourself with the Sharpies.

In response to the insulated curtain dilemma, I am in the same boat. JC Penney has cotton sailcloth curtains, but the backing is acrylic foam. We have a family bed with an 11 month-old sleeping just below this window. I found a site, "rawganique" that sells organic hemp curtains which they claim insulate well. I like the idea of sewing or velcro-ing in a quilte liner. Would recycled fleece also work? Or would the plastic content in this be harmful? And do hemp curtains really insluate?