If you’ve ever been up on your roof or even touched the roofing’s surface on a warm, bright day you understand how hot it can get. The more the roof is exposed to the sun and the darker its color, the hotter it becomes.
For a lot of traditional roof materials, that heat is moved to the sheathing listed below and into the attic. From there it can penetrate into your home depending upon the condition of the insulation. As your home heats up, it puts a higher need on the cooling system.
Energy efficient roofing materials decrease that “heat-soak” result, reducing the quantity of heat that’s passed into your home. That suggests that it does not take as much a/c effort to keep your house comfy.
It’s Everything about Reflectance And Emittance
Energy efficient roofing takes advantage of 2 residential or commercial properties called reflectance and emittance. In a nutshell, cool roof materials have better reflectance and emittance worths than non-cool roofing materials.
Reflectance is the ability of a product to show the energy from the sun back into the atmosphere rather than absorbing it. It’s determined on a scale from 0 to 1 with 1 being the highest level of reflectivity.
When you look for cool roof products, you should search for the term “solar reflectance” on the product’s specification sheet. It’ll most likely be a decimal number like 0.76. You can use that number to compare numerous cool roof items.
If there’s a down-side to a roofing’s solar reflectance property, it’s that it can change gradually. Dirt build-up and typical wear and tear of the roof material will tend to reduce its capability to deflect the sun’s energy. That’s why you’ll see requirements and rankings for cool roofing products based on efficiency after three years of service.
Emittance represents a material’s capability to “shed” or produce heat rather than maintain it. Like reflectance, it’s determined on a 0-to-1 scale with 1 being a higher (better) worth. Emittance is likewise noted in the specifications for energy efficient roofing products as a decimal like 0.90 and is usually designated as “thermal emittance.”
ENERGY STAR Roof
Much like your dishwasher or fridge, energy efficient roofing products can make the ENERGY STAR label, officially designating them as meeting a pre-set requirement for energy efficiency.
To be certified as an ENERGY STAR roofing the material should fulfill the following minimum requirements:
- Preliminary Solar Reflectance – greater than or equal to 0.25
- Reflectance After 3 Years – greater than or equal to 0.15
These certifications are for steep-pitch roofing systems or roofs that have a rise-to-run ratio greater than 2-in-12. This represents most of residential roofing system styles.
Roofing systems with a lower pitch are essentially flat roofs and have to fulfill reflectance certifications of 0.65 and 0.50 for preliminary and maintenance values respectively.
These are the minimum requirements to meet ENERGY STAR accreditation. Other states, regional areas or municipalities may enact more stringent requirements for defining cool roofs. For example, California’s Title 24 Structure Standards Code states more strict requirements for cool roofing.
The advantage of the ENERGY STAR labeling system is that it supplies you with a way to determine precisely what roof items fulfill higher energy efficiency standards and in the end, provide much better energy-related options for your house (not to mention the environment).