go green on your roof

I recently was hired to work on a residential project in Pawling, NY. It is on a gorgeous piece of land that overlooks a pond, and the view is extraordinary. The house was existing, and was skillfully renovated by the Architects Khanna-Schultz. The Client wanted to build an extension (for an indoor pool) which resulted in a pretty big tar roof extending beyond the deck. Not ideal for taking in such a view...so when the Client mentioned she wanted a Greenroof, we were thrilled.

Robert Schultz had been in touch with a few companies and finally found a great one, called Eco Roofs.

 

Before...

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...and after.

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Green Roof Basics:

Greenroofs are basically roofs that are partially or completely covered with vegetation. They look incredible and they have strengths that go beyond pure aesthetics: They 1. Cool the atmosphere by absorbing heat 2. Absorb rainwater 3. Add insulation to your home, reducing the need for heat and cost associated, and 4. They provide wildlife habitat and. 5. They actually extend the life of your roof, protecting the membrane from the weather and wear. They come in two different forms: extensive and intensive. Intensive greenroofs have a greater soil depth (6"+) which means you can accommodate a greater mix and diversity of plants, perennials and grasses, but they are heavier in weight and require more maintenance. Extensive roofs have a shallow soil depth (1"-5"), are much lighter in weight, and require less maintenance. The one photographed above is an extensive greenroof.

The Eco- roof system was exactly what this project needed. We needed a green roof system that was very lightweight, easy to implement, and low maintenance. Eco-Roofs is a grower and supplier of an extensive system pre-grown green roof trays in southwest Michigan, (their parent company Twixwood Nursery is a family owned groundcover and perennial nursery with almost 50 years of horticulture experience). They provide sedum mats, plants and plugs, and they can ship to you directly.  They have been in this business for a long time--50 years--and have developed a variety of products in that time. The one we ordered for this particular project was sedum planted in trays that form a grid can be placed side by side on a roof. When pushed together, the trays appear pretty seamless, like a green shag carpet (maybe not quite so 70's). Sedum are extremely drought tolerant and hardy, so unlike an extensive system, they require very little maintenance (maybe some watering and fertilizer occasionally). Their trays are a a stunning mosaic of color and texture, all sedum(they grow about 12 different varieties and can tailor the mix to your specific requirements based on where you are). I loved how it connected the architecture to the surrounding landscape. 

questions you should ask beforehand: 

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does my roof have a waterproof membrane?

Most roofs already have a waterproof membrane, but if you are starting from scratch, this is a must. Better to ask and make sure. This system is compatible with most waterproof membranes. Ask what type of waterproof membrane you have, and if you don't have one, opt to have one installed that is of a higher quality if you are planning to have a green roof installed.

 

 

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how much weight can my roof handle?

I always recommend having an engineer weigh in on load, no pun intended. These sedum trays are lightweight, but they're not nothing, and with the weight of say, a big snowstorm, the pounds can add up. Better to be safe than sorry when it comes to the structural integrity of your home.

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When the trays arrived, we lined them up on the ground below the pool house. You can see the stairs to the deck which were used and then carried onto the roof. We gave them good watering beforehand as they had been in transit for a couple of days.

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It's all about the trays:

Depth: 3.3″ Weight: Maximum, fully saturated weight with mature plant foliage: 23 pounds per square foot. (average dry weight 18lbs/sf)

Material: 100% recycled high density polyethylene (HDPE) plastic trays

Wall Thickness: 150 mil (more than 1/4″). No lip allows flush fit.

Color: Black for enhanced UV resistance.

Handles: Molded into the tray on both ends for safe, convenient carrying.

Drainage: 46 hole (3/8″) in the lowest points of the tray and edges; Bidirectional drainage channels molded into the bottom of the tray.

Water Reservoirs: Minimal to avoid root rot.

Media: Engineered growing media meets German FLL guidelines.

Plant Types: Standard Sedum; Can be grown to full established (95%+ coverage) with enough lead time. Other approved plants may be possible.

Eco-Mat Pre-Vegetated Sedum MatSedum cuttings rooted into a coir blanket designed to reinforce soil and roots for green roof vegetation. The mats are pre-grown on speculation with a standard mix of at least 8 varieties of performance proven Sedum species. Full Brochure available here.

Size: 10″ x 20″ (1.3 square feet) standard

Depth: Approximately 1″ soil/stabilizer depth

Place on 3″ or more of green roof media above filtration, drainage and protection  fabrics.

Weight: 5-7 pounds per square fot (average dry weight 4lbs/sf)

Plus the weight of the media and layers placed under the Eco-Mat and any potentially retained water by those components. Typical installation with 3″ of media and minimal water retention reservoirs will be 25-35lbs/sf for full system when fully saturated.

Plant Types: Standard Sedum; Can be grown to full establishment (95%+ coverage) with enough lead time.

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They are very carpet-like...compact with efficient root systems.

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and so beautiful close-up, too.

 

For more about Green roofs:

Visit Eco-Roofs to find out more about this wonderful product and company.

Brooklyn Greenroof  installs Green roofs in Brooklyn

For information about different systems and the benefits of Green roofs, visit Green Roofs for Healthy Cities

Nigel Dunnett is an incredible Greenroof Designer in the UK, creating beautiful landscapes including many green roof parks, some atop parking structures in the middle of cities...you wouldn't even know they are green-roofs unless someone told you.