Best Types of Attic Insulation

Reflective Insulation and Radiant Barrier

Adding attic insulation is paramount to creating a more comfortable and energy efficient home, keeping you cooler in summer and warmer in winter. By properly installing a radiant barrier in your attic, you can lower your air conditioning and heating bills and can potentially extend the life of your equipment.

The attic insulation material should be a reflective insulation is an absolute must in warmer climates. The aluminum foil material used in reflective attic insulation reduces radiant heat transfer through the attic by 97%. Installing an attic radiant barrier in the attic ceiling means that the heat of the sun will be reflected back out of your attic instead of crossing the airspace to be absorbed by the insulation on the attic floor and then radiated down into your home below. Similarly, adding an attic radiant barrier can reducing the loss of heat from the attic floor to the roof sheathing in cold weather by reflecting attic heat downward.
 
Attic Radiant Barrier Installed During New Construction

Attic radiant barriers are not affected by moisture and can completely replace older insulation materials in warmer climates. Reflective insulation can also be used effectively in conjunction with other bulk insulation materials in colder climates.
In a typical home, up to 30 percent of heat is lost through the roof. Adding attic insulation is an easy upgrade in comparison to insulating walls, floor or the roof deck in an existing building. Adding a radiant barrier is the most common home insulation retrofit project. Reflective insulation used as a radiant barrier can be easily added to an existing attic as it hangs below the rafters.

Energy Savings

Attic insulation also gives the fastest time to payback. The cost of insulation is usually measured as the time to payback the initial cost of installation through energy savings. Payback is calculated by dividing the initial cost of the insulation by the annual amount of savings in energy costs. Most agencies and manufacturers report the payback time on any insulation job as 5-6 years. Heavily insulating the attic is usually seen as a worthwhile investment as an average home will stand for 100 years or more.

Economic gains from installing reflective insulation as a radiant barrier in the attic are well documented. Estimates are that insulating an un-insulated attic saves 25 percent on heating costs in cold climates while adding a radiant barrier to an insulated attic saves 12 percent in warm climates. The Oxford City Council has estimated that the cost to add extra insulation to an attic will pay back in 5-7 years while installing insulation in an un-insulated attic will pay back in 2 years.
 
Attic Radiant Insulation Retrofit

Research conducted by the Florida Solar Energy Center (FSEC) has shown that the installation of a radiant barrier can generate significant financial savings. About 22 percent of the heat gain in a typical Florida house comes in through the attic. Installing an attic radiant barrier reduces heat gain through the roof by about 40 percent. This equates to a savings of 8 to 12 percent on the annual electricity costs for air conditioning in a typical Florida home. The summer peak energy use savings was as much as 27 percent. This study also showed that the average peak reduction from the radiant barrier system was three times as great as the savings produced by adding more fiberglass insulation (a change from R-13 to R-19).
Whole house tests run by the Mineral Insulation Manufacturers Association and the Oak Ridge National Laboratory show the average reductions in ceiling heat flow from the addition of a radiant barrier stapled under the rafters between 24 and 30 percent compared with R 19 attic floor insulation and no attic radiant barrier insulation. The U.S Department of Energy Attic Radiant Barrier Fact Sheet (DOE/CE-0335P) states that reductions in the cost of cooling can reach up to 17% by proper installation of an attic radiant barrier.

Installation

Radiant barrier attic insulation is easy to install. It can be incorporated into new building construction on top of the rafters before adding the roof decking or on the bottom of the roof truss chords or rafters. In existing homes, a radiant barrier can be easily added to your attic by attaching it to the bottom of the roof trusses. It is important that the reflective side of the insulation face the airspace of the attic if using a single sided reflective insulation product.
 
Installation Options

Reflective insulation used as an attic radiant barrier is the most effective when there is at least a 3/4" airspace between the insulation and any adjacent material. Furring strips can be added to create additional airspace if needed. Reflective insulation can rest directly against some other insulation materials like fiberglass insulation and still maintain ample airspace as the fiberglass batt is primarily composed of airspace. Drywall can also be directly installed over reflective insulation. Reflective insulation attaches with tape, glue, nails and staples noting that tape doesn't adhere well to either concrete or wood. After installation, all seams must be sealed with reflective tape.
In high moisture content homes, a perforated reflective insulation product would be preferable if for use stapled on top of existing attic floor