Let's Save Energy - 'R' Values...What They Mean

We have all heard about insulation R values right?  R11 vs. R19 vs. R30….what does that all mean?    Before we go into that, let’s first review basic heat transfer out of your home.

We have discussed previously the very basic thermodynamics (basically energy transfer physics) principle which is that heat energy always flows from warm towards cold…like higher pressure towards lower pressure.  Think of a balloon filled with air…the air inside the balloon is under pressure from the balloon pressing on it….if you open the balloon, the air rushes out….the air goes from higher pressure inside the balloon to lower pressure outside the balloon.  Heat acts the same way.

Inside your home, the warmer air is higher pressure air, and wants to move, or transfer to lower pressure, cooler air outside.  Insulation in your walls and ceilings slows down this heat transfer.  Any good insulation material, such as  fiberglass, foam board, spray foam, etc., all act to slow down heat transfer out of your home. There is a direct relationship between the amount of insulation and the amount of heat transfer. The bigger the R value, the better the insulation is at slowing down the heat transfer.  So R19 is better insulation than R13, and R30 is better than R19.  The larger the R value, the better the insulation value.  

Most older homes have walls built with 2x4’s.  The depth of the 2x4 is 3.5 inches, which will accommodate R11 or R13 insulation.  New homes with 2x6 walls will accommodate R19 or R21 insulation.  In attics, we should use additional layers of insulation up to about R50 or so.  This means you could use R38 insulation, and then add another layer of R13, for a total of R51….again, the higher the better.    

Bottom line:  insulation slows down the heat transfer out of your home in the winter, and into your home in the summer.  The more insulation you have, the better you maintain your desired temperature.  For more information about your home and insulation, please see my website at www.saveenergyusa.com

Energy Saving Tip of the Week:  The next time you are in your attic, check how much insulation you have in your ceilings.  You can either read it from the paper backing, or measure the thickness.  You need a minimum of R38 (10 inches) for our climate.  R50 (13 inches) is even better.