Working Insulation vs. Inefficient Insulation

Wasted Energy and How Science can help you improve Efficiency


Why do down (goose feathered) jacket keep you warm on a very cold day? The feathers are not heavy, so what makes them keep you war. The answer lies in the very small pockets of air that is created between the feathers. Air can insulate very well.

The way insulation works is slowing down the process of heat transfer.  When heat moves from one place to another, it does through first conduction, second convection and third radiation. For example in a goose down jacket, the heat moves through conduction. This take place by moving through each of the feathers (fibers) that are touching one another. While conduction is through solids such as feathers or fibers, convection happens in the air.  All of the air pockets between the fibers  add up to a large volume. Radiation is also a slower process because each fiber has to radiate its own heat.


Knowing about insulation can help you pinpoint inefficient energy performance in your home.


If you understand home insulation better, you can figure out what is wrong and help find the solution. These are the things that cause problems:


  • Voids- Void are places where insulation is missing. There are many reasons for voids: accidents, poor quality insulation, but sometimes voids come about because of safety requirements. A good examples would be for recessed lighting.  These lights are not rated for insulation.  Regardless, the void creates convection and radiation. Home energy scientists have concluded that a small 4% void in insulation can create a 50% loss in effectiveness.
  • Compression – The effectiveness of insulation is significantly reduces by compression. This is because all of the air pockets that create insulation are now squeezed out.
  • Movement of air through insulation- Air moving through insulation reduces the effectiveness of the insulation. Why? The reason for this is because the amount of convective heat loss is increased. In order for the transfer of heat to be slowed down, the insulations air pockets have to be dormant.

Moisture- R-value can also be very greatly reduced by moisture. This is because the insulation becomes more conductive. Also compression takes place, voids open up and settling occurs.  The ability to slow down heat transfer plays just as an important role in hot weather than in winter months or cold climates.  The same concepts are true in hot weather.




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