How roofing insulation improves home energy efficiency

Roofing insulation prevents the movement of heat to colder areas, whether that's keeping a home warm during the winter or keeping the heat out during the summer. But that's not all it does.

Insulation can reduce the risk of ice dams, muffle noise from vehicle or air traffic, and even extend the life span of the roof. But for many homeowners, insulation's greatest appeal comes from the way it can increase a home's energy efficiency and reduce monthly utility bills.

How Insulation Works

Before we understand how insulation can trim a homeowner's energy bills, we first need to consider how insulation works.

Insulation interrupts the flow of heat, whether through conduction, convection or radiation.

The US Department of Energy has a succinct explanation of these three types of heat transfer:

• Conduction is the way heat moves through materials in direct contact. This is how a stovetop can move heat from burner to pan to food.
• Convection is the way heat circulates through liquids and gases. This is how warm air rises and, in a poorly insulated house, moves directly outside.
• Radiant heat is caused by electromagnetic radiation, such as the sun's rays.

Common types of residential roofing insulation include batts of fiberglass insulation, rigid foam insulation and spray foam insulation. All of these reduce conduction and convection by creating tiny pockets of air that act as barriers between the exterior surface of your home and the comfortable interior. The effectiveness of a given insulation is measured in a rating called the "R-value." The more effective the insulation is, the higher its R-value.

Radiant insulation packages, such as HeatBloc Ultra from Roof Guardian Technologies, are most often used in hot, sunny climates to interrupt radiant heat transfer. They can be used alone but are often packaged with other types of insulation such as foam or fiberglass.

Insulation and Energy Efficiency

Proper roofing insulation creates a buffer zone between the exterior and interior of a home. But many homes don't have proper insulation, and that buffer is damaged and easily penetrable. In fact, according to EnergyStar, a shocking 9 in 10 homes are underinsulated.

Insulation in key areas such as a roof slows the inevitable loss of conditioned air to the outside. As a result, the mechanical systems work less to maintain a comfortable indoor temperature. That results in lower fuel usage as well as less strain on the home's heating and cooling systems, potentially meaning fewer maintenance calls and longer life spans. It also decreases the home's carbon footprint.

Roof Ventilation and Sealing

Ventilation and sealing describe two different types of airflow in a home.

"Sealing" refers to preventing air from flowing through the many small holes in the walls and ceilings. "Ventilation" refers to the practice of drawing outside air into the attic and passing it along the back of the roof.

In a drafty home, conditioned air passes from the living areas into unconditioned spaces such as an unfinished attic. This is why sealing off attic penetrations is typically part of the insulation process. However, because of condensation, a roof also needs some air movement behind it.

If you've ever held a cold beverage on a hot summer day, you've seen water droplets form on the cold surface. That same moisture can form on the interior of a roof. And when the wood framing of a home gets wet repeatedly, it can weaken or begin to form mold and mildew. That's where ventilation comes in.

Ventilation is intentionally drawing air from outside a home, across the back of the roof, and allowing it to escape through a second vent. This air movement prevents moisture from building up enough to create condensation and reduces the expansion and contraction of the roof.

Proper Insulation Means Lower Utility Payments

With great energy efficiency comes great savings! According to the Environmental Protection Agency, proper sealing and insulation can save typical homeowners up to 15% on their energy bills every year. But that's just the average — a large home, a home with extensive Southern exposure, or a home that is seriously lacking in insulation or sealing might benefit even more dramatically.

Insulation can also extend the life of the roof itself. All the parts of a roof are exposed to the elements, from the hottest sun-baked summer temperatures to the coldest snowy winter days. And with that exposure comes continual expansion and contraction. That movement can cause materials to fail and push nails and other fasteners loose. Proper insulation and ventilation keeps the expansion and contraction within tolerance, literally adding years to the life span of a roof.