Reflective Roofing Products & Energy Star
Amongst the lesser known energy facts is just how much money the sun costs the average homeowner in air conditioning bills. Summer rays striking the roof of a home or residence can send attic temperatures skyrocketing well into the triple digits, driving heated air downward into the cool comfort of your home envelope. Most people don't even realize that a good portion of their air conditioning bills are wasted - instead of cooling the home this effort goes toward combating the radiant effects of the sun.
And heat's not the only problem, either. High temperatures caused by a buildup of heat inside of your roof can delaminate plywood, warp studs, and cause extensive damage over time. With heat comes moisture, and this could wreak further havoc in the form of water damage and swelling, depending upon the humidity of the climate. Luckily, reflective roofing products are sold these days to cool things down up there and keep the sun from unnecessarily inflating your air conditioning costs.
The EPA's Energy Star program recognizes qualified roofing materials that reflect the sun's rays away from a home or structure. Sustainable design products such as a reflective roof coating or reflective paint can help lower outside roof temperatures by over a hundred degrees or more! Energy Star also gives their blue star of approval to select roofing materials and shingles that meet rigid insulation standards. These products may fall outside the scope of reflectivity, but will have a specific roof insulation value (measured as an R-value). The higher the R-value, the greater the level of insulation for that particular roofing product. However, Energy Star's criteria for roofing differs slightly than normal in that different R-values are required for different climates in order to achieve the Energy Star logo.
|An Energy Star Fact: Fully 1/6th of all electricity generated in the US is spent on air conditioning, amounting to $40 billion dollars each year.|
There are a few different categories of reflective roofing materials available today, and each can be used for a different purpose. In general though, the lighter the color of the roofing material the more light will be reflected from its surface, thus making for a cooler rooftop overall. Emissive reflectivity and conductive factors need also be taken into account, but the general types of available reflective roofing are listed below.
Reflective Metal Roofing
Perhaps not common or suitable for a home residence, metal roofing is an acceptable standard for commercial or industrial type buildings. Until recently, structures sporting a metal roof were subject to high temperatures from the radiant heat emitting from roof's hot metal surface. New alloys of metal however, allow for less emissive heat transfer. 'Cool metal' roofing is now sold with highly reflective surfaces that bounce away much of the solar radiation that would normally be passed into the structure. Reflective metal roof options should certainly be considered when undergoing new construction in sunny regions.
Reflective Metal Shingles & Tiles
Providing the same energy efficiency as reflective metal roofing, the latest in metal shingle products now have the look and even the feel of asphalt roof shingles. At the same time, they still reflect solar rays and keep up a waterproof, moisture-resistant barrier between the inside and outside of a home. Some of these 'cool roofing shingles' can reflect as much as 70% of the sun's light energy.
Re-Emissive Metal Roof Surfaces
This type of roofing acts much the same as any reflective metal roof product by deflecting solar energy away from its surface. However, re-emissive metal rooftops have the added advantage of built-in pigments that re-emit surface heat. Any heat distributed over the surface of the roof is subject to the pigment's re-emissive properties, further reducing the temperature of the roof itself.
Reflective Roof Coatings
An easy option to green roofing would be the application of a reflective surface coating. White wash and other coatings contain tiny microscopic reflective surfaces within the paint that are designed to reflect solar energy and keep the treated surface several degrees cooler than normal. It should be noted however that the lighter the color of a surface, the higher its attraction of UV rays will be. It's therefore important to choose a reflective coating with some sort of UV protection built into it, to protect the roofing surface from harm.
Made from strengthened, flexible waterproof materials, modern roofing membranes can be installed beneath roof shingles or tiles to create an energy-saving heat and moisture barrier. Even better, some roofing membranes are incorporated right into the construction of the shingles themselves, embedded in the actual roofing product. Check the specifics of whatever roofing material you are considering for your project, and remember to look for the Energy Star logo to maximize efficiency and environmental benefits.