Last weekend, I figured out how to build an inexpensive "storm" window - those clear plastic panels that fit snugly inside your existing windows, reducing heat loss to the great outdoors. My existing windows are circa 1961, so you can imagine how efficient they are. Using $3 worth of wood, some double-sided tape and 2 sheets of shrink wrap plastic, I got one built in about two hours. Found the instructions on youtube. It took me awhile because I have very little practice doing "handy" sorts of things! The resulting insert is a little rough around the edges, but it's not terrible - and it clearly works. My office is warmer for sure. Next weekend, I plan to make 4 more to go in my bedrooms! And I think I can cut my time in half, now that I have some practice.