During the heat of summer, a non-reflective rooftop is one of the hottest places out there — far hotter than the surrounding air. Even with good insulation, that heat penetrates roofs and warms up attics and top floors, forcing air conditioners to work overtime just to keep up. The key to avoiding this expensive problem is to replace or treat those roofs with reflective, cool roofing materials.
Replacing an existing roof is often costly, but if your current roof is your home’s biggest energy efficiency weak spot, a new cool roof may pay for itself over time. And if you’re not financially prepared for such a big job, you may be able to achieve similar results by applying energy-efficient roof coatings at a fraction of the cost.
ENERGY STAR Roofing
Homeowners have a helping hand in choosing energy-efficient roofing materials thanks to the federal ENERGY STAR program. The same ENERGY STAR labels you see on the most efficient appliances also apply to shingles, roofing panels, energy efficient roof coatings and other related materials.
The roofing materials that have earned the ENERGY STAR label have a high degree of solar reflectance, which means that they reflect more of the sun’s heat than other materials. These materials can lower the surface temperature of a roof by as much as 50 F, and can reduce peak demand on air conditioners by up to 15 percent.
Roof Color and Energy Efficiency
Since the biggest concern with roofing energy efficiency is unwanted heat, you might assume that a lighter colored roof is always better than a darker roof. But the reality isn’t quite as straightforward.
While lighter colors are inherently more heat reflective, roofing materials have a much larger impact on roofing energy efficiency than their colors do. A darker ENERGY STAR-rated roof will usually outperform a lighter roof that isn’t designed with efficiency in mind.
Another factor is climate; while lighter roofs can be a clear choice in the warmest climates, homes in cooler climates are often better suited by a darker roof that can absorb a little free heat from the sun during winter.
No matter what type of roofing material you ultimately choose, you’re likely to find a variety of colors within that range. It’s usually best to choose your material first and your color later.
What Roofing Material is Most Energy Efficient?
Among residential homes, asphalt shingles are the most commonly used roofing material due to their low cost and ease of installation. Unfortunately, asphalt shingles are great at absorbing heat and poor at reflecting it, even when they’re lighter in color. If you want to save more money later, it’s worth springing for a more expensive but efficient roofing material now.
Many of the energy saving roofing systems that qualify for the ENERGY STAR label are made from metal. Even though metal gets very hot in the sun, this is because it’s highly reflective, so most of that heat is redirected away from the home below. Metal roofs can be designed as a series of panels or more traditional looking shingles, and they’re also relatively easy to install.
Another good choice for energy efficient roofing is a tile roof. Tiles can be made from slate, clay or concrete, the latter of which is exceptionally durable. Many tile roofing materials are pre-treated to maximize heat reflectivity, but these types of roofs are also easy to treat with reflective coatings after they’ve been installed.
As for those coatings, while they can be applied to a range of roofing materials, they work least well with asphalt roofs. Most coatings also change the color or physical appearance of the roof, and the most reflective coatings may not be a good aesthetic match for your home’s exterior colors. But there are also pigmented coatings which, while less effective than their white counterparts, still add a reflectivity boost to any roof.
Finally, if you happen to have a flat roof, you could always consider a green roof. Not a roof that is painted green, but rather a rooftop garden. Designing and installing one of these properly is often a major undertaking and expense, but a good green roof is a great thing. It’s not only energy efficient, it creates a whimsical environment in a previously unused space, and it can even be used to feed your family.
Insulate for Added Energy Efficiency
An energy efficient roof makes a huge difference, but it can’t do all the work. If the insulation in your attic or under your roof is not up to snuff, you’re still likely to have a problem with unwanted heat. Installing attic fans and rafters can also encourage air circulation in a way that will bring down temperatures beneath your roof. If you’re considering energy efficiency upgrades for your roof, you should think of upgrading your attic as part of a package deal.
Don’t let a dark asphalt roof absorb heat into your home summer after summer. Start thinking about your new roof today, and choose energy efficient roofing materials to help it pay for itself.