How Does a Radiant Barrier Work?

   One of the most important things to consider in Phoenix when weatherizing your home and becoming more energy efficient is your attic. The summers in Phoenix get very hot and attics are almost always problematic areas. One way to improve upon your attic is through the use of a radiant barrier in combination with solar attic fans and insulation upgrades. A radiant barrier by itself is only one part of the total solution needed to get your attic tempatures under control and cooled down. It's the process of combining the radiant barrier with additional insulation and solar attic fans that completes the process. Depending on what part of the country you live in, the Zero Energy Team in Phoenix recommends either using a paint based spray-on Radiant Barrier or the traditional foil based product that can be stapled in place.  A Radiant Barrier reduces summer heat gain and winter heat loss, which dramatically helps lower heating and cooling costs. The barriers consist of a highly reflective material that reflects radiant heat rather than absorbing it. They don't, however, reduce heat conduction like thermal insulation materials.



   Naturally we know heat travels from a warm area to a cool area by a combination of conduction, convection, and radiation. Heat flows by conduction from a hotter location within a material or building to a colder location. Heat transfer by convection occurs when a liquid or gas is heated by a surface, becomes less dense, and rises, or when a moving stream of air absorbs heat from a warmer surface (forced convection). Radiant heat travels in a straight line away from any surface and heats anything solid that absorbs the incident energy. Radiant heat transfer occurs because warmer surfaces emit more radiation than cooler surfaces.



   When the sun heats a roof, it's primarily the sun's radiant energy that makes the roof hot. A large portion of this heat travels by conduction through the roofing materials to the attic side of the roof. The hot roof material then radiates its gained heat energy onto the cooler attic surfaces, including the air ducts and the attic floor. A radiant barrier reduces the radiant heat transfer from the underside of the roof to the other surfaces in the attic. This is where having a radiant barrier in place under the roof can reflect a large portion of the radiant heat that has made it through the roof's materials. The little heat that does make it through into the attic can then be slowed and deflected from entering into the living space of the home by increasing the R-Value of the home's insulation with a product like blow-in insulation.  While the increased insulation slows the heat from entering the home, properly placed and installed solar attic fans can quickly remove that heat from the attic completing the heat exchange cycle. The combination of a Radiant Barrier, Insulation and one or more Solar Attic Fans can keep the temperatures in your attic between 30 to 50 degrees cooler, which ultimately keeps your living areas cooler and most importantly, your A/C units running less, which simply put, SAVES ENERGY!

The Radiant Barrier Hot Box Test - The Proof is In the Numbers!

   The hot box above is a representation of an attic with a radiant barrier foil installed.  The hot box shows the temperature difference between a homes attic with and without radiant barrier, using infra-red heat lamps.

Left Side: The left side shows a laid down radiant barrier with unfaced R-19 fiberglass insulation.  The thermometer reads 93.2 degrees F.

Right Side:  The right side shows unfaced R-19 fiberglass insulation only.  Its thermometer reads 152.5 degrees F.  

   There is a difference of 59.3 degrees F between the two sides.  This difference is due to the radiant barrier's ability to reflect radiant heat away from the insulation. The numbers were read after a six hour period with an ambient air temperature average of 84 degrees. NOTE: Both sides reached their steady state after only one half hour.  

What Is a difference between Radiant Barrier Spray and Radiant Barrier Foil?

   Both the newer spray and the foil "Reflect" radiant heat. Simply put the foil can reflect more heat than the spray can. Sprays reflect up to 81% and the foil will reflect about 97%. Spray-On Radiant Heat Barrier is essentially a "liquid foil". We all know that foil is a heat barrier. There are many brands of foils and paints which all have different performance characteristics. However, foil is indisputable for out performing radiant barrier spray paint, it just costs much more to install since it is a labor intensive process verses the spray-on application. The Zero Energy Team has all found that when our Radiant Barrier paints are properly installed with adequate insulation and attic ventilation, the spray-on application performs as well as the foil application under the same attic conditions. The key to having a Radiant Barrier perform properly is understanding the entire attic situation and by ensuring that there is ample insulation and ventilation available to complement the Radiant Barrier paints or foils.
                            

   The Zero Energy Team in Phoenix Arizona is your Radiant Barrier specialist. Whether you are looking to simply buy our Heatblock Radiant Barrier Paints or Radiant Barrier Foils for the do-it-yourself application, or if you want one of our Zero Energy Team members to install and apply the Radiant Barrier for you, the Zero Energy Team in Phoenix Arizona is here to help every step of the way!