The type of roofing material used on a home or building, whether for a roofing replacement or a new roof, is an important variable when obtaining the best thermal efficiency is a goal. Different materials have different emissivity properties, which is important when choosing the most efficient material for a roofing installation. To understand the value of emissivity, and help homeowners understand what they are buying when searching for the best residential roofing services, following is a brief explanation of roof emissivity and thermal function, and how it can help or hinder home efficiency.
What Is Thermal Emissivity?
Emissivity is a material’s ability to absorb and release thermal energy or heat. This is an important factor in terms of the roof on a home or building, because roof emissivity is part of what makes a building more or less energy efficient. Materials with lower emissivity are most efficient for roofs, as they do not absorb as much heat, nor do they release it against decking layers, which is how heat enters a building, through its roof. Highly emissive materials absorb more heat, which then radiates against whatever other surfaces are nearby, such as wooden roof decking, which is also highly emissive. This allows the heat to eventually make its way into the attic space, reducing home cooling efficiency.
What is Solar Reflectivity?
Reflectivity is a material’s ability to reflect thermal energy, rather than absorb it. Since materials that are highly reflective are also less emissive, they are preferred when reducing thermal absorption is important for increased roof efficiency. Reflective materials work very efficiently to help prevent heat from a more emissive material from passing through a roof, heating up a home’s interior.
Cool Roofing and Energy Efficiency
A cool roof is one that does not allow the passage of radiant heat from the roof’s surface to the interior of a home. Reducing cooling energy costs requires cool roofing, as it helps homes stay cooler, more naturally. Therefore, the goal of cool roofing is to choose materials that either by themselves or in combination, have the least emissivity and highest reflectivity, lessening the need for artificial cooling due to heat absorption.
Emissivity and Reflectivity Working Together
The coolest, most reflective roofs are light-colored and made of metal, ceramic, and other non-conductive materials. Yet these materials are not always recommended for all climates. When specific roofing challenges require a roof to be made of more durable or cost-effective materials but emissivity is high, adding a reflective surface against the underside of decking can greatly reduce the effect of emissivity. Radiant heat barriers on the outside decking surface reflect the thermal energy passing through roofing material, preventing it from passing into a home. When radiant barriers are installed on the underside, interior surface of the roof decking, it also acts to aid insulation, preventing home heating from escaping through the roof.
Based on local climate and specific home efficiency goals, homeowners must choose the right material for their replacement roof. This material must provide the best emissivity and reflectivity rating to achieve these goals. Lower utility bills means installation of right roofing materials, and working with the best residential roofing services who understand how to manipulate emissivity and reflectivity to gain them the best possible results!