Question

What are the sustainable options for re-roofing our 30-year-old home?

Asked by Jennifer Marks, Tiburon, CA

I want to understand the options for sustainably re-roofing our 30-year-old home. Can you help?

Answer

Cynthia Phakos

Answered by Cynthia Phakos

Los Angeles, CA

Koffka Phakos Design

November 26, 2008

The focus on sustainability in the past few years has yielded many new roofing products.

  • To choose the most sustainable roof for your home, you must consider your specific conditions.
  • Climate is the most important issue.  Because you live near the coast, you'll want to select roofing that will withstand the salt spray and have no wind uplift.
  • The next consideration is to select a "cool roof" that has a high reflectance value to minimize heat gain.

Sheathing and Radiant Barrier

If you are planning to remove the existing roof down to the rafters, my first recommendation would be to use sheathing with a radiant barrier. The radiant barrier is a thin, laminated sheet of aluminum that prevents up to 97 percent of the radiant transfer from the panel into the attic space. This will keep your house significantly cooler in the summer.

  • LP TechShield is a very good product.
  • If possible, select an FSC-certified, no-VOC sheathing.
  • And while you're doing the work, check that your attic insulation meets the R30 value required by California's Title 24.

Roofing Materials

From the brief "tour" I did of Tiburon on the Internet, I would guess that your roof may have a shallow pitch with overhanging eaves. Traditional roofing types that would match the local architecture are:

  • wood
  • metal roof, or
  • asphalt shingles.

Wood shake. EcoStar makes an 80 percent recycled rubber-and-plastic roofing material in the shape of wood shakes and slate tiles. We recently installed EcoStar's Seneca shakes on a traditional home in Los Angeles where we had to meet historic preservation requirements—it's beautiful.

EcoStar's Majestic Slate tiles, made of rubber and plastic, are a fraction of the weight of slate, making them easier to install; they do not require an additional structure for support. EcoStar offers a 50-year warranty on their products and an extended warranty for up to 110 mph winds.

On the negative side, these roofs are expensive (though probably not as costly as a slate roof). Also, there will be more heat absorption with these products than with a cool roof.

Metal roof.  A metal roof ideal for coastal settings is Follansbee's Terne II. Follansbee, a manufacturer in West Virginia, developed a stainless-steel roof coated with a patented zinc-and-tin alloy to withstand corrosive environments. The detail of this roofing maintains the historic metal appearance and finish.

Solar-reflective coatings installed in the factory offer the same benefits as a cool roof. The roof is warrantied for 30 years in a marine environment. (Read the instructions carefully as additional maintenance may be required.)

Asphalt shingles. The most economical choice would be an asphalt-shingle Energy Star Cool Roof.

A product that we are currently using on a craftsman home is the GAF-Elk Timberline Prestique 40 HD Cool Color Series. This, I believe, is the first cool-roof asphalt shingle.

The granules are highly reflective and release absorbed heat. They are rated by the Cool Roof Rating Council (CRRC) and meet Energy Star performance levels. The roof is warrantied for 30 years.

Tagged In: roofing, metal roofing, radiant barrier

Do you have a question about greening your home? GreenHomeGuide invites you to Ask A Pro. Let our network of experienced green building professionals – architects, designers, contractors, electricians, energy experts, landscapers, tile & stone specialists, and more – help you find the right solution.