You may wonder to know this!!! Upgrade the Windows & Doors: If a home is more than 10-12 yrs old, the chances are high that the Doors & windows would have become inefficient. Remember, Windows & doors are passive energy wasters. It is best to have double / tripple pannelled to minimizze the effect on heating & cooling system indoors. Further, new doors are more efficient since they fit better and allow lesser gaps between the seams.