Business Articles - Specialty and Trade

Choosing Green: Flat, Foam, or Single Ply Roofing

Roofs rank near the top of the list when it comes to commonplace home improvements that can benefit big from going green. After all, your roof's exposure to heat, cold, and sunlight make it an excellent candidate to be a major player in improving your home's overall energy efficiency. And since your roof is also your home's most important line of defense when it comes to protecting you and yours from the elements, it's easy to see why homeowners across the country are drawn to the quality workmanship and high expectations that come with green remodeling.

Embracing Possibility: Green Flat Roofing
To be honest, flat roofing is one of the most paradoxical roofing systems in the green roofing world. On one hand, they can be about as un-green as roofing gets. Most flat roofing products are petroleum based, require a lot of energy to manufacture and install, and they have a relatively short life span. Add to that the fact that flat roofing materials are known for off-gassing potentially harmful volatile organic compounds (VOCs), and that their poor drainage often leads to leaks, water damage, mold growth, and subsequent health issues, and it's easy to see why flat roofs aren't generally considered to be the greenest roofs around.

On the other hand, the development of true green roofs, roofs that are comprised of living vegetation, means that flat roofs have the potential to be the greenest roofs around. The question is whether you're willing to make that leap— and if you're not, what else is you can do to help turn a traditional flat roof into a brighter shade of green.

Green Roofing with David Johnston
The man with the answers to those questions is David Johnston, founder of the green consulting firm What's Working, Inc., author of the Nautilus Award winning book Green Remodeling: Changing the World One Room at a Time, and ServiceMagic's most trusted adviser on all things green. Here's Johnston's take on the flat roof dilemma, and what you can do to make sure your flat roof installation is as green as possible.

Why a Living Roof is the Greenest, and Best, Roof Around
Let's start by going as green as it gets. A green roof (also called a living roof), is a roof that consists of a protective membrane and insulation with soil and plants all installed on top of it. According to Johnston, these roofs have a huge upside, including the following:

  • Reduced Runoff—Since the soil traps water and the plants drink it up, green roofs produce substantially less runoff than other flat roof alternatives. That can be a big plus in urban areas where runoff places high demands on sewer systems and municipal waste-water facilities.
  • Green Roofs are Cool Roofs—Because they're so thick compared to other roofing systems, green roofs provide an excellent barrier against solar heat, reducing your home's cooling needs. And because living roofs tend to absorb the heat rather than reflect it back into the environment, they also reduce the urban heat island effect.
  • Fight Global Warming—Because a green roof is comprised of living vegetation, it actually absorbs carbon dioxide and emits oxygen. That makes it a small step in the right direction when it comes to fighting the effects of global warming.
  • Gardening Anyone?—As a side benefit, green roofs can be landscaped to provide garden areas or food for residents. What could be greener than that?

Potential Pitfalls of a Living Roof
While green roofs do have almost unlimited potential from a green standpoint for low slope and flat roofs, Johnston is quick to point out that they don't come without a few drawbacks— the biggest of which is their weight.

  • Special Engineering Required—The combination of insulation, drainage, geo textiles, soil, and vegetation places a significant burden on the structure of any building. Factor in the added weight that comes with absorbing up to half of the normal runoff during any given rainfall, and it's clear why a green roof must be specially engineered to accommodate the weight of the roof, accumulated water, and any people (gardeners, repairmen, etc.) that may be walking around up top.

If a Living Roof Isn't for You
Of course, not all homeowners are ready for the major investment in both time and money that installing a living roof requires. If that's the case for you, here are some other flat roofing suggestions from Johnston to help you paint your traditional flat roofing installation a brighter shade of green.

  • Reduce Energy Costs with Light Colored Roofing—Light colored roofing or roof coatings can make a huge difference in flat roofed structures, since it reflects, rather than absorbs, heat from the sun. The result is a cooler home and reduced cooling bills (especially if you have air conditioning ductwork in the attic). It also makes for a longer lasting roof, thanks to the fact that a lighter roof will experience less contraction and expansion over its lifetime than a dark one.
  • Reduce Cooling Needs with Radiant Heat Barriers—Radiant heat barriers are a thin layer of metal insulation (usually tin foil with a paper backing or a metalized mylar sheeting) that can reduce radiant heat transfer into your attic by as much as 95 percent when installed to the underside of your roof.
  • Minimize Waste & Recycle Materials—Measure your roof and order roofing materials carefully to minimize waste. Also, remember that 85 to 90 percent of construction waste is recyclable, either by reusing it or disposing of it at facilities that will recycle the materials. Talk to your contractor about whether your roofing project qualifies.
  • Increase the Pitch on Your Roof—If you're considering building a home with a flat roof, or are going to perform a major remodel on a flat-roofed home, keep in mind that a roof with a steeper pitch discourages standing water, leakage, and other water damage. That means less chance of moisture penetration, and a reduced risk of water damage and potentially dangerous mold growth.
  • Monitor For Leaks—Poorly constructed flat roofs (really flat) can lead to pooling and lingering water and eventually leaks and moisture problems inside your home. Flat roofs should have a slight pitch that ensures water runoff. The resulting water damage, rot, and mold can seriously compromise your home's indoor air quality. To avoid these problems, install better drainage systems on your flat roof, monitor your roof to make sure it's in tip top condition, and be sure to hire a contractor experienced in working with flat roofs to ensure your roof will live up to your expectations.
  • Be Aware of Indoor Air Quality Issues—In addition to mold caused by moisture problems, flat roofing materials like asphalt and tar off-gas a number of volatile organic compounds (VOCs) that can be harmful to your health, including benzene, plynuclear aromatics, toluene, and xylene. These VOCs are the worst as the roof is being installed, and for a few weeks afterward (keep the windows shut!), but will continue to off-gas in warm and hot weather. Be sure to monitor your indoor air quality and take measures to improve it if necessary.

Calculating the True Value of Going Green with Your Roof
What's it going to cost you if you go green with your flat roofing project? If you install a living roof, your initial cost is going to be substantial. If you're not ready to make that leap, but are still interested in taking smaller steps in a green direction, your costs shouldn't vary too much from an average installation. Whichever direction you decide to go, try not to get wrapped up in the investment/return side of green remodeling too much. As David Johnston is fond of pointing out, going green is worth a lot more than a person can measure in dollars and cents. Green roofs are healthier, longer lasting, more maintenance free roofing solutions. And when you figure in that you're making a commitment to passing on a better, more environmentally responsible world to your children and grandchildren, it's easy to see what Johnston means when he says that it's tough to put a price tag on the true value of going green.

If you think green is the right choice for you, be sure to talk to your contractor about adopting a green building philosophy, find a contractor who specializes in green building and remodeling, or seek out the services of a green consulting firm to help you plan and design the best, and greenest, roof you possibly can.

David Johnston
We are proud to partner with David Johnston, internationally recognized green building expert, to provide our homeowners and service professionals with the information necessary to "green" their projects.
• To learn more about David Johnston, click here.
• To learn more about Green Certification training, click here.

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