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Is a Green Roof Right for You?

If you’ve heard the buzz about green or “living” roofs, you’re probably wondering if this is truly an efficient upgrade. Green roofs may be eco-friendly, but are they difficult to maintain? Are they more or less cost effective than other energy-efficient roofing solutions? Read on to learn whether green roofs are right for your home!

Costs Compared to Other Roofing Systems

According to Green Roof Technology, these systems start at around $15 per square foot for a flat roof. Costs go up based on the slope of your roof, the growing system and the types of plants and their water requirements. In larger installations – above 10,000 square feet – the price of a green roof starts to decrease by as much as 50% per square foot, which makes them more affordable for larger homes and commercial structures.

Compared to metal roofing, however, green roofs come at nearly twice the cost. The average price for a metal roof is between $7.50 and $10 per square foot, while shingle roofs are even less expensive at $5 to $9 per square foot.

Structural Requirements

In many cases, it’s necessary to reinforce existing structures to support the added weight of a green roof. The average green roof – those with a relatively thin layer of growing medium and plants that require little water, weighs up to 50 pounds per square foot, while a conventional roof normally weighs between 10 and 12 pounds per square foot. Rooftop gardens weigh even more – between 80 and 150 pounds per square foot.

If you’re building a home with a green roof in mind, it won’t cost you much more to ensure that the structure will be able to support the weight. If you’re retrofitting an existing structure, however, you may need to install wood or steel supports in the home’s attic or upper story to redistribute the weight more evenly across the roof. In some cases, more supports should also be added to load-bearing walls to support the weight of the roof.

Green Roof Structure | Image from insulationcorp.com

What Kind of Maintenance is Required?

Green roofing is essentially a garden on your rooftop. As such, there are many things that you can do with it. On flat roofs with easy access, some people grow vegetables and ornamental plants. Other green roofs are made with sedum, a low-growing creeping plant that spreads quickly and chokes weeds.

This means that just like a garden, you can expect to put in time weeding and maintaining your roof. Even if you choose sedum for your roof, you’ll need to weed it at least once or twice per year. To keep your roof healthy, you’ll also need to fertilize once a year. You should also inspect the roof several times during the growing season to prevent problems with insects or fungal infections. Sedum is a drought-tolerant plant, so once established, you shouldn’t have to water it unless you live in an exceptionally dry area.

Energy Efficiency

Numerous studies show that green roofs are effective at breaking up the urban heat island effect within cities. However, when it comes to actual energy efficiency, it’s a little more difficult to measure the efficacy of green roofing. Overall, they insulate a home as well as a reflective metal roof. Green roofs do have a slight edge over other roofing types because they don’t transfer as much heat during extreme temperature shifts.

So is the efficiency of a green roof worth the installation and maintenance costs? A study from the Lawrence Berkeley National Laboratory looked at the 50-year cost of green roofing versus reflective white roofs on commercial buildings. Keeping in mind that green roofing is substantially more cost effective for large commercial installations, the researchers found that white roofing was still more economically viable than living roofs.

Green roofing is a great option for large structures or for homeowners that enjoy the look of a living roof. However, for the average homeowner, green roofs don’t yet provide enough of an advantage to outweigh the installation and maintenance costs.