Consider Cambridge physicist David MacKay's Without Hot Air, especially the section "Every Big Helps." http://www.inference.phy.cam.ac.uk/withouthotair/c19/pag

Consider Cambridge physicist David MacKay's Without Hot Air, especially the section "Every Big Helps." http://www.inference.phy.cam.ac.uk/withouthotair/c19/page_114.shtml http://www.inference.phy.cam.ac.uk/withouthotair/c19/page_11... On a related note, I suggest the everyone run Wattzon.org to see where their carbon footprint comes from. I found that while I was a much lower user on everything else, heat accounted for 40% of my entire carbon footprint. Immediately I ran around the house and fixed the duct vents that I could close before, and now I'll have probably halved that, saving me $15 a month, $180 a year, and 20% of my carbon footprint. Seriously! Little fixes can make huge changes.