As I was listening to the evening news recently, the home improvement "specialist" said something like this: "Want to save energy? Seal up that home! Install new windows, caulk around the foundation and sill plate, add weather stripping, install backdraft dampers on the exhaust fans and clothes dryer, and seal any other openings that will allow air to infiltrate your home's structure. Put plastic over windows and consider installing storm doors and windows. Energy costs will soar this year, and you don't want to pay to heat the outdoors!"
It's true that heating costs probably will go up again this year. People will want to conserve as much as possible. However, if homes are sealed up so tightly that their combustion appliances don't have enough ventilation/combustion air, it can lead to dire health risks.