We have vinyl windows (mostly double-paned) and live in a shady greenbelt in Seattle (i.e. wet and dark). We don't have much severe weather to worry about, just a pervasive damp cold that settles in and makes our extremely inefficient remodeled money pit cost a fortune to heat.

I've looked at rolls of plastic for window sealing at Home Depot and Lowe's and have been surprised at the cost, considering it's just a roll of plastic. Is this the most efficient option? Are there ways to winterize that involve materials that could be re-used next winter?

Any advice appreciated!