Radiant Barrier

Radiant barrier is a product that is put in your attic that reduces the temperature drastically thereby keeping your air conditioning ducts cooler and operating more efficiently. By reducing the attic temperature you are also eliminating the heat transference into your actual living space. That’s where the right amount of insulation is important, usually one to two feet of blown in insulation is recommended. There are three types of radiant barrier available.

  • The first is manufactured with the foil directly on the underside of the roof decking and is most commonly used in new construction. If you are now in the process of building your new home, this is a must have in my opinion. In order to use this type on existing homes, the whole roof must be torn off and is not cost prohibitive.
  • The second comes in large rolls of foil that is unrolled and stapled directly to the underside of the roof  joists. This type is difficult to install because you need more access area in the attic and some attics are very small. The coverage area may be compromised and there is more potential for gaps and energy leaks. It can also block the proper air flow  to roof vents if not properly installed. Another potential problem with the foil type is the durability. It can tear away from the joists leaving your attic unprotected in some spots decreasing its effectiveness.
  • Lastly, there is the type that I prefer which is a thick silver paint like product called Heat Bloc Ultra  that is sprayed directly to the underside of your roof decking and is easier to install and has more complete coverage than the foil type. Once installed it is permanent and won’t degrade over time. It won’t block any ridge vents or attic fans either.

By applying a radiant barrier in your attic area and replacing your old windows and doors, you will greatly reduce the heat that is constantly trying to seep into your home during the summer. Energy bills will be reduced thereby saving you money.


  • Lowers summertime cooling costs
  • Increases comfort level in the home
  • Keeps duct work cooler, delivering cooler air
  • Makes insulation perform better
  • Environmentally friendly, very low odor
  • Lowest e-value: 0.19 (stops 81% of potential heat)
  • Does not block antenna, dish, or cell phone signals like foil.

Common Questions and Answers

How does Heat Bloc Ultra work?

Unlike mass insulation which only slows down or resists heat transfer, radiant barrier reflects heat. Heat naturally turns cold so the problem is to keep the heat in during the winter and out during the summer.

There are three ways in which heat transfers from warm space to cold space:

  • Conduction – direct heat flow through a solid object like a wall or ceiling
  • Convectionheat movement through air occurring when air is warmed. Warm air expands and becomes less dense and rises.
  • Radiation – movement of heat rays across air spaces from one warm object to another cooler one. The heat we feel from a wood stove or space heater is an example of radiant heat.

All objects and bodies give off radiant heat! Even the insulation in your attic gives off radiant heat to the cold attic space in winter and to the living space in the summer. Regular insulation won’t stop radiant heat loss. It must be reflected with a radiant barrier.

How can Heat Bloc Ultra keep me warmer in the winter?

Just like wrapping a baked potato in aluminum foil keeps it warmer longer by holding in the heat, covering your attic decking with radiant barrier holds holds the heat in the house. Another analogy would be that in winter radiant barrier works just like a space blanket, which, although very thin and lightweight, holds in your body heat. A thin space blanket can keep you warmer than several heavy blankets.

How does Heat Bloc Ultra keep heat out in the summer?

Like a space suit, radiant barrier reflects the sun’s heat before it can warm up the insulation in your attic. When the insulation stays cooler, your house will too. The reflective surface inhibits radiant heat transfer. This is also effective in keeping your air ducts cooler thereby increasing the efficiency of your air conditioning unit.

Will the roof be hotter with Heat Bloc Ultra?

No. Field tests in the south where radiant barrier is used extensively, shows no difference in roof temperature.

Does the old insulation have to be removed to install Heat Bloc Ultra?

No. Radiant barrier actually makes your present insulation more effective. We have to get up in the attic space so if it is cluttered with items though, they must be removed  by you prior to installation.

I already have plenty of insulation in my attic. Do I really need Heat Bloc Ultra?

Regardless of how much insulation you have in your attic, adding Heat Bloc Ultra will save on heating and cooling expense and keep you much more comfortable. Energy savings for heating and cooling can vary from 10% to 25% depending upon a number of factors including climate, materials used, site, building configuration, family size, and lifestyle.

Comments are closed.