Sustainable roofing benefits come from four places: a surface that takes in less of the sun’s heat, a roof that lasts longer so it is torn off less often, old and new materials that can be recycled instead of landfilled, and, on roofs built to carry one, a planted layer that holds back rainwater. How much of each you get depends on the material, your climate, your attic and the roof’s slope. To talk through the options for your roof, call NEMA Roofing at 866-631-3366.
Which benefits does a sustainable roof deliver?
The benefits of green roofing are easier to compare when sorted by what produces them, because two roofs sold as eco-friendly can deliver very different things.
| Benefit | What produces it | What it depends on |
|---|---|---|
| Less heat into the house | High solar reflectance and thermal emittance (a cool roof) | Hot, sunny climate; attic insulation and ducts; keeping the surface clean |
| Fewer replacements over the life of the house | A durable covering, installed and ventilated correctly, then maintained | Installation quality, flashing details, regular inspections |
| Less landfill waste | Recyclable materials (metal, asphalt) and tear-off sent to a recycler | Whether a recycler for that material operates near the job |
| Less stormwater runoff, habitat, cooler air | A vegetated (living) roof | A structure that can carry the weight, irrigation and upkeep |
How much can a reflective roof reduce cooling?
A cool roof reflects more sunlight and sheds the heat it does absorb, so less of it reaches the rooms below. The U.S. Environmental Protection Agency reports that in air-conditioned homes a cool roof can cut peak cooling demand by 11 to 27 percent, and in homes without air conditioning it can lower the hottest indoor temperatures by 2.2 to 5.9 degrees Fahrenheit. The same EPA page notes a trade-off: in cold climates a reflective roof can add some winter heating, which summer savings usually outweigh, and insulation and air sealing get the most out of it.
In much of inland California this benefit is also a code item. The state energy code (Title 24) requires rated cool-roof values when more than half of a steep-slope roof is replaced in climate zones 4 and 8 through 15, with exceptions for well-insulated attics and some other cases. Our cool roofing service covers the rated products and how their values are checked.
Why the longest-lasting roof is often the greenest
The EPA ranks source reduction, using less material and creating less waste to begin with, as its highest priority for solid waste, ahead of reuse and recycling. For a roof, that means the covering you do not have to replace early. A roof that reaches the end of its expected life saves a full tear-off, a load of new material and the trucking both ways.
What shortens that life is usually not the material itself but the details around it: poor attic ventilation that cooks shingles from below, flashing that fails at walls and chimneys, and small leaks left alone until the deck rots. That is why maintenance belongs in any honest list of sustainable roofing benefits; a yearly look through our roof maintenance service catches those problems while they are still small repairs.
What happens to the old roof?
Every replacement starts with waste. The EPA lists asphalt from roofing shingles and metals among the construction materials that can be recycled where markets exist: asphalt into aggregate or new asphalt products, and metals such as steel and copper as valuable commodities. Recycling your tear-off depends on a recycler accepting that material in your area, so ask any contractor where the old roof goes. On the new-material side, metal panels and many membranes can be recycled again at the end of their life.
What a living roof adds
A vegetated roof (plants in a growing medium over waterproofing and drainage layers) brings benefits no reflective surface can. According to the EPA, green roofs reduce and filter stormwater runoff, absorb pollutants and carbon dioxide, provide habitat, and typically have a longer expected life than cool roofs, at a higher first cost. They need a structure that can carry the soil and water, plus irrigation and weeding. For most houses the realistic version is an extensive roof: shallow soil, hardy plants, little maintenance once established. Our guide to green roofs versus cool roofs compares the two in detail.
Which roofing is the greenest?
There is no single greenest roof; the eco-friendly roofing benefits above add up differently on each roof. A few rules of thumb:
- Steep-slope roof in a hot, sunny area: a cool-rated shingle, tile or metal finish gives the largest energy benefit for the money.
- Low-slope or flat roof: a reflective membrane or coating is the usual route; a planted roof is possible only where the structure allows it.
- Roof that still has life left: repair and maintenance beat replacement on every environmental measure.
- Planning solar: choose a covering expected to last at least as long as the panels, so the array does not have to come off for an early reroof.
How to get these benefits on your next roof
- Ask for the product’s rated aged solar reflectance and thermal emittance from the Cool Roof Rating Council directory, not a brochure claim.
- Have the attic checked: insulation, ventilation and any ducts up there change how much a reflective roof helps.
- Ask where the tear-off goes and which parts can be recycled.
- Get a maintenance plan in writing so the roof reaches its full life.
- Check the contractor’s state license; NEMA Roofing holds CSLB license #1083283.
NEMA Roofing has five Google-verified locations, in Santa Barbara, Oxnard, Woodland Hills, Tarzana and Downey, and installs energy-efficient and recyclable roofing throughout Santa Barbara, Ventura, Los Angeles, Riverside and San Bernardino counties; see every area we serve and our green and eco-friendly roofing service. To weigh these benefits for your own roof, call 866-631-3366.
