Can You Put New Insulation on Top of Old Insulation?

Homeowners sometimes ask if one application of a particular type of insulation provides energy savings, will “doubling up” with twice as much insulation produce even more energy savings?  

The simple answer is that more insulation can produce more energy savings.  But other factors enter into the picture, such as type of insulation you are using, where the insulation is being installed, etc.  For instance, if you are using batt (roll) insulation with a paper vapor barrier on one side, most professionals would agree that having two vapor barriers is not a good idea.  If you are using blown in insulation or spray foam insulation, it may be easiest to consult a professional to determine the optimal amount of insulation needed for different areas of your home.  A professional can help you determine the proper amount of insulation needed, balancing your desired energy savings within your budget.  
Fiberglass Insulation Danger