After weeks of learning how to winterize our homes, we've reached our last installment of the Weekend Winterizing Challenge, in which my eco-partner in crime, Susanna Donato, explores how to seal up your mail slots and old milk doors using simple blocks of Styrofoam. With the temperatures plummeting this weekend, it's a great time to plug up any chilly drafts sneaking into your house. The mail slot: Donato doesn't use her mail slot, but we use ours. When I sit on the side of the couch closest to it, I usually have to wrap myself in a blanket, Snuggie-style. Donato keeps air from sneaking through her unused mail slot using a trick I think I can also adopt. She found an old block of Styrofoam in her recycling pile and sized it to fit the mail-slot opening. She then wrapped the block with duct tape (to keep it from falling apart) and made a handle. Thanks to the portability of this solution, I can use this in my working mail slot. Not only can I easily pop in the foam block overnight, but since I work from home, I can leave it there all morning and just pop it out when the mailman comes during the noon hour. The milk door: Donato has an old milk door in her kitchen (which opens both into the home and to the outside) that had been filled with unmortared bricks. She removed the loose bricks for a warmer option. Again, she used various pieces of Styrofoam to create a different kind of insulator. She wrapped the whole thing in plastic bags and duct tape and used Great Stuff insulation to keep it in place. While she admits it's not the prettiest solution (I love how polite her insulation looks from the outside door), you can't see it when the door is shut, and she finds that the door is actually warmer than the walls around it.