Insulated window quilts
I love our historic Arts & Crafts house, especially the large banks of windows that let in so much light. But in the winter, the cold seeps through. One of my upcoming projects is to make insulated window quilts for the draftiest windows (which are in the sunroom and the master bedroom). I don't have time to piece actual quilts together, so I will probably sandwich the batting between unbleached muslin or thrift-store sheets. I like the simplicity of these roll-up quilts. If you have more time, you could make Roman shades, balloon shades, hobbled shades, or side-draw shades. The Warm Window company has made a DIY instruction booklet for making these insulated shades.
