The Cool Roofing Option17 February
Looking for a new roof? Whether you’re updating an existing one or in need of a new roof for an upcoming structure, a cool roof might just be the perfect option. So, what exactly are they? If you haven’t heard of them before, they are an energy efficient option with benefits for the environment as well as your wallet. Consider this your ultimate guide when making the decision for your building.
A More Detailed Explanation
The word “cool” has two meanings here. First, it means the color of the roof itself is lighter. Second, that color means a cooler temperature overall. It’s the same concept as wearing lighter clothing in the summertime. A white t-shirt is going to keep your body a lot cooler than a black one would. That’s the most basic explanation.
Getting more into how they work, the surface is designed to reflect sunlight and emit thermal heat more efficiently. A dark or hot roof can absorb 90% or more of incoming solar energy, making their surface an average of 150 degrees on a summer day. That means increased heat being absorbed into your home, causing your AC to work harder than it has to, but we’ll get into heating and cooling benefits later.
The fraction of sunlight a surface reflects is called solar reflectance. Any light not reflected becomes absorbed as heat. How efficiently a surface cools itself by emitting thermal radiation is measured by thermal emittance. Knowing the definition of these two lets us determine the SRI, or solar reflectance index, and gives us a good comparison between roofing options.
The solar reflectance Index takes solar reflectance and thermal emittance values to determine how cool the roof will be. An SRI of 100 would completely reflect all rays and warmth, while an SRI of 0 would absorb every last bit of heat. Traditional roofing lands at around a 20 or less on the scale as they only reflect about 20% of incoming sunlight. These lighter roofs can reflect 55 to 90%, depending on style and model, which is a major improvement. A good way to think about it when food is wrapped in foil. The foil keeps the warmth in, which is great when you need to keep a meal hot, but certainly not ideal for your home.
Know What to Look For
So, a roof can be defined as “cool” when it meets or exceeds the SRI standards set by the Department of Energy or US Green Building Council’s LEED (Leadership in Energy and Environmental Design) program. If you’re looking at a product that qualifies for LEED certification, you’re on the right track. Typically, these roofs are going to feature a low slope with a pitch of 9.5 degrees or less. That’s 2:12 rise over run. For those looking to meet building codes or rebate program requirements, always be sure find the appropriate cool roof definition from your local agencies. For us consumers, let’s take a look at the label.
Check for a CRRC label, that will mean the material has passed the appropriate evaluation system. They’ll tell you the solar reflectance and thermal emittance rating both now and an approximated three years later from weathering. They will also contain a rated product ID number, license seller ID number, and classification. Also, you won’t only be looking at white color options. Many of the sun’s rays are invisible to the human eye, making any roof than can reflect them while meeting the standard SRI a good choice. There are plenty of “cool dark color” options that look just like any other roof you may have owned from black to terracotta and even chocolate. You won’t have to sacrifice your home’s good looks to go green.
Heating and Cooling
When your home experiences too much heat gain, or loss, your AC and heating unit have to work overtime to keep your house at a comfortable level. We all know how much these appliances can run us in a year, but a cooler roofing option can help save you hard earned cash by reducing the excess absorption of heat in the summer. While you’ll need to use a little more heat in the winter, the money you’ve saved in electricity from not running the AC drastically outweighs the increased heating bill. Those that live in hot climates will benefit the most, but even those that experience harsh winters can expect to see year-round savings. If your home is equipped with thermal insulation, those savings will only increase.
For those not looking to purchase an entire new unit, look into the coating options that can make your existing roof into a cool one. Find yours and learn how to make it cool right here. For those looking to build it new, you’ll be able to choose from shingled, tile, and metal options. Always look into building codes before deciding a course of action. Here is a list of state codes, industry standards, and voluntary programs to look at before getting started.
Roof Economics 101
This is a big purchase, and it’s important to know if it will benefit you in the long run. Compare the upfront cost to the amount of savings on utilities in the future, and also consider the lifetime of the roof, any maintenance it may require, it’s durability, installation cost, any rebates you may receive, possible HVAC downsizing, and any increase in the cost to heat your home during winter months. When it comes to the upfront price, you should be looking at around the same cost as a traditional roof, and labor is labor anyway you look at it. Those looking to simply coat their roof will have to take other factors into consideration such as the quality of the existing surface, and the amount of surface area.
To calculate energy cost and savings, click here.
After taking into account the cost and the savings, get out there and find the best deal you can. It doesn’t have to break the bank, it just has to get the job done and get it done right. On average, new “cool” materials will cost under $1 extra per square foot, while coating your existing roof can cost between an extra $0.80 and $2.75 a square foot. That’s compared to non-cool options. Some prices may be lower or higher, but you’ll have to decide what the best deal is for yourself.
When it comes to maintenance, you won’t be doing anything differently than you already are. A recommendation is to clean it once a year to take full advantage of saving on the AC bill.
That’s One Cool Roof
Hopefully this guide has given you a better understanding of what a cool roof is, and given you the tools to determine if it’s the right choice for your house. When selecting an energy efficient option, you have a lot of choices. It might not be Top Gun or Fonzie cool, but it holds a lot of benefits for your home and your wallet, and is worth looking into.