The best way to think of your home is like a giant refrigerator. It makes sense that if you have two identical refrigerators and put one in the sun and one in the shade that the refrigerator in the sun will use more energy, right?
Why is this? First consider that the air temperature is exactly the same whether you are in the shade or the sun. However the surface temperatures are very different; the refrigerator in the sun will be hotter to the touch (surface) because it is directly absorbing radiant heat from the sun. It may be only 70ºF outside, but the outside surface of the refrigerator could easily be 120ºF. As far as the refrigerator is concerned it is 120ºF.
The same thing occurs in your attic. It may relatively cool (70ºF outside) but if it's sunny, the roof will heat up and then radiate heat down towards the insulation. The result is that the top surface temperature of the insulation can easily be OVER 100ºF (without a radiant barrier it is very typical for the top of the attic insulation to be 20-40 degrees hotter than the outside air temperature) even with GREAT attic ventilation the AIR inside the attic may be close to the outside temperature, but the attic insulation STILL heats up due to radiant heat coming from the roof. This is one reason why we may need to run our air conditioners on a 60 degree sunny day. The top of the insulation could easily be heated to close to 100 degrees and that heat will pass through the insulation and into the home.
Radiant barriers act like shade. Using the refrigerator example, if we wrapped the refrigerator with radiant barrier foil and put it in the sun the surface temperature would only go up a few degrees compared to the refrigerator without radiant barrier that might be 20ºF- 40ºF warmer on the surface. Do you see how adding a radiant barrier mimics the same effect as putting something in the shade (shade from the HEAT, not the light)? Ultimately it's all about surface temperatures. The larger the difference between the inside and outside surface temperature, the more heat will flow in or out.
Buy Radiant Barrier Foil for your home today.
Attic insulation & Radiant Barrier work together in both hot and cold climates to make homes more energy efficient. Attic insulation will reduce CONDUCTIVE heat flow and radiant barrier will reduce RADIANT heat flow.
|Types of Installation|
Installation methods are not based solely on where you are located; there are several factors that determine the best installation method for your home. Every home is different, so while there are general recommendations for certain climates, sometimes one method is best for a particular home.
Generally hot climates like Arizona, Texas, Louisiana, and Florida use the Open-Ridge (or Flat-Top) Method because of the primary concern with summer cooling costs. Additionally these climates oftentimes have air handlers, duct work, or both, up in the attic space which makes cooling that space a priority.
The Over-Insulation Method works very well in ALL climates and is generally easier to install. If you don't have ductwork in your attic, then this is a good method that will provide very good refection of radiant heat in the summer and help reduce radiant heat loss in the winter.
It is worth mentioning that we know of many people who have the time and energy to do both methods and they have seen good results year round.
There is a lot of debate on which method is the best installation method in warmer climates. See our article on the Best Radiant Barrier Installation Method for our full analysis of the debate and what we think.
You might also be interested in our radiant barrier supplies page.