Harvesting greenroof runoff and more

Unfortunately, the time to put together thoughful comments on articles continues to elude me... but this bit about rainwater harvesting from greenroofs.com is worth reading, if only for the linked resources...

I hope that I'll have time to post more in-depth ideas/photos/research/etc. soon!

Greenroofs, PV panels, and green building

A couple of tidbits for your Monday AM:

An interesting article about the symbiosis between greenroofs/white roofs and PV panels...

And a very cool building planned for Portland, OR.

And last, but not least, the Wall Street Journal did a short overview of stormwater management in big -- and biggish -- American cities.

Greenroofs in the news

Three interesting articles today:

1. NPR outlines the benefits of green- and cool roofs.

2. Another rooftop farm in NYC, started by one of the people that developed the one in Greenpoint.

3. Systems for making sure your greenroof doesn't leak.

Sustainable roofs and EPA news

First, a couple of great ideas for rooftops from some smart high school students...

Second, last week we approved New York's 2010 303(d) list of impaired waters and released information to generate public interest and involvement.

Galactic gardening in NYC

No need to consider soil fertility with these hydroponic greenhouse pods. Very interesting... but they presumably offer no water retention or insulation...

Rooftop soil fertility

A very interesting article on fertility problems associated with Uncommon Ground's intensive greenroof/garden roof soil.

Inspiration on a rainy city day

Some green roof eye candy, from NYC...

Green roofs and walls

I've made a couple of cool discoveries over the past couple of days and wanted to share them.

First, in our quest to find the perfect wedding venue, my fiancee and I took to Durham, NC. While we didn't find a spot for vows, we did find a new parking garage at Duke -- complete with greenroofs and walls. A couple of photos, and a couple of links:

Here's some information and a few graphics that picture areas that I couldn't capture.

The garage follows tenets outlined in the New Campus Master Plan (essentially, the redevelopment of the old Central Campus).

Second, I got a note from a client yesterday with images of a greenroof we installed at the end of last summer (see below). So far, so good! The sedum should fill in the gaps this summer.



Last, but not least: Columbia and Con Ed have teamed to assess the insulating and cooling capacities of cool roofs (white roofs and greenroofs) vs. conventional black roofs (tar beaches!). In a very interesting study released last week, the group found that green and white roofs perform roughly equally in preventing heat island effect (through evapotranspiration and albedo, respectively) and that each limited temperature variability enough to produce modest energy savings. There is concern, however, that the performance of older white roofs may suffer since the reflectance of these roofs declines as they age. White roofs also lack the ability to moderate water flow, improve air and water quality, provide habitat and recreation space, and improve aesthetics for nearby neighbors, six of the primary motivators for greenroof installation. A very interesting study and I look forward to reading future research findings...

Chicago's Comer Youth Center green roof wins ASLA award

I've got this fantasy about starting a network of agriculture-supporting green roofs, akin to the one at Rooftop Farms in Brooklyn. Seems as though I'm onto something. Much more here.

Greenroofs for Redstarts

In another success story for urban wildlife, green roof professionals in Sheffield, England have replicated habitat favored by the Black Redstart to the degree that the birds now appear to inhabit the roofs.

Also, there's an audio slideshow of a "greenroof safari" here. The narration explains some of the benefits of green roofs and depicts a variety of those found in Sheffield (actually, the show provides a good sense of the different intents and designs associated with greenroofs, from recreation areas to those made to mimic habitat). Our intrepid narrator gets inexplicably and disconcertingly winded at the end... perhaps an issue with heights?

In Brooklyn, Lettuce, Not Steel, Scrapes the Sky

Today the Atlantic published an inspiring piece by Annie Novak of Rooftop Farms. Check it out: In Brooklyn, Lettuce, Not Steel, Scrapes the Sky.

It's blocking my sunlight!

An interesting bit about rooftop agriculture (and highlighting Rooftop Farms) in the Detroit News.

Rooftop Farms

So, I finally made it to Rooftop Farms in Greenpoint yesterday to scope out what they're up to and how they've managed to grow vegetables and fruits atop the City That Never Sleeps. I must say, it's a great space albeit smaller than I had envisioned.

They had what looked to be a decent year despite the bad weather. Lots of healthy looking tomatoes, chard, kale, cilantro, lettuce, winter squash, beans, eggplants, peppers, etc.

Unfortunately, I wasn't able to get details on the technical considerations, since apparently Goode Green did the design and installation of the greenroof without involving the farmers themselves.

Nevertheless, I got some cool shots on my phone and will return (next week, assuming I get all my fall seeds planted on Friday or Saturday) to help and -- hopefully -- learn something about composting sans worms.

An unassuming building topped by a very cool roof.

Park Slope green roof pt. 2

I would be remiss if I didn't add some imagery from the tail end of the Park Slope green roof install I worked on with EcoBrooklyn last week.

Unfortunately, I didn't get to see the end result since I had friends in town and couldn't help on the planting and last-minute touches. In any case, I've got some photos of drainage, soil, plants, personalities, and improv. supplies.

Hopefully at some point I'll get back on the roof and see how it all turned out. Come to think of it, though, I chatted with the neighbor while we were hoisting soil and she was very interested in having her roof greened. I'm going to head back on behalf of EcoBrooklyn next week and try to make her an offer she can't refuse, so perhaps I'll see the roof soon...

We had four 1.5 cu. yd. bags of Gaia Soil delievered and didn't have a crane, so Nash and I spent a full day bagging and lifting the soil onto the roof. It went off without a hitch, if you don't count my near-decapitation when the plywood/2x4 structure we used to protect the roof membrane fell three stories and landed next to my head.


Gennaro found some old drink racks and thought that they could double for these, to hold soil and plants in place on the sloped portion of the roof.

The perimeter and skylight boxes installed, ready for greenroof add-ons.


Drainage layer/water retention mat installed and ready for Gaia Soil. The layer we used is made by Colbond and incorporates a pretty impressive water retention mat. We dumped half of a 12 oz. bottle of seltzer on a 2-in. square sample and lost virtually none of it. Its drainage mesh is made from 40% post-industrial recycled polypropylene, to boot.

Nash is excited to plant. We got 20 lbs. of sedum clippings from Motherplants to encourage a mixture of species, rather than a monoculture plug-farm look.

Future Green Brownstone

I was poking around the net yesterday, searching for info. on greenroofs in NYC and Brooklyn and happened upon a series of posts on Brownstoner that I found totally fascinating. They're by a landscape architect/greenroofer named David Seiter who's got a firm in Brooklyn called Future Green Studio.

Apparently, Mr. Seiter was tapped to work on a greenroof for his co-op building in Park Slope, Brooklyn and decided to offer a glimpse into the development of the roof to the general public on Brownstoner. Check the site for some images of the Park Slope roof and some pretty neat images of other ideas/projects.

Park Slope green roof

We started the green roof that I spoke about in my last post this weekend. We decided to use EPDM, a Colbond drainage product (recycled polypropylene mesh topped with a highly absorbant water retention textile), Gaia soil, and 20 lbs. of mixed sedum clippings. We're also planning to experiment on a steeper (30 degrees-ish) portion of the roof that we had previously thought about leaving bare, to see if we can put together a system that could be implemented on a larger scale in future work. I took some pics of the work this weekend with my phone:

The old roof(s) -- gravel overlaid with asphalt

A roll of EPDM roofing. This stuff is heavy

Cutting the EPDM, being taunted for taking photos

A truckload of dumpster-salvaged EPS insulation



The remnants of a tin roof from the turn of the 20th c.(?)

Insulation on the roof, and the front of the roof where we may try the green roof on a slope

After laying the insulation



Jack laying the EPDM adhesive

The Gaia soil should arrive tomorrow, and the drainage and sedum on Wednesday. Should be installed by next weekend. More to come...

A couple of new things

1. I'm working on an extensive green roof now that we should be installing over the next couple of weeks. (Unless it gets delayed -- then it'll be October sometime). I've sourced all the materials and put together an idea for the roof, will help to clear the roof of its existing tar and begin EPDM installation this weekend. I'll post pictures of the wknd's activities and the install as soon as these things happen.

2. I got a note from a colleague today re: a USGS study on mercury contamination in freshwater fish in the U.S. I've put the intro. blurb and link below. If you look at anything in the report, check out Figure 21 (pp. 36-9) for a number of interesting relationships between environmental variables and Hg levels.

The USGS released a study today that assesses mercury contamination in fish, bed sediment, and water from 291 streams across the nation, sampled from 1998 to 2005.

The report, along with a press release, podcast, and summary of major findings can be accessed at http://water.usgs.gov/nawqa/mercury/.

Scientists detected mercury contamination in every fish sampled in every stream. About a quarter of these fish were found to contain mercury at levels exceeding the criterion for the protection of people who consume average amounts of fish, established by the U.S. Environmental Protection Agency (EPA). More than two-thirds of the fish exceeded the EPA level of concern for fish-eating mammals.

Atmospheric mercury is the main source to most of these streams — coal-fired power plants are the largest source of mercury emissions in the United States — but 59 of the streams also were potentially affected by gold and mercury mining. Since USGS studies targeted specific sites and fish species, the findings may not be representative of mercury levels in all types of freshwater environments across the United States.

For more information, contact Barbara Scudder, bscudder@usgs.gov , (608) 821-3832 or Mark Brigham, mbrigham@usgs.gov , (763) 783-3274.

A video on the Vancouver Convention Center's green (living) roof

This video's pretty cool as long as you can stand the melodramatic soundtrack. Makes me think that my growing medium idea is totally reasonable... though lava might be less carbon intensive than calcined clay, depending on the sources.

Vancouver's 6 Acre Living Roof from Dave Budge on Vimeo.

Making green roof substrate

Just posted an entry to ecobrooklyn.com on making green roof substrate ourselves, rather than paying for commercial blends. Check it out here or below.

Green roofs use an engineered substrate, rather than natural soil, to support plant growth. There are a number of commercial varieties available, but these are often shipped considerable distances from supplier to consumer and can be expensive. To reduce the cost of our roofs, it would be best if we could produce our own green roof soil. In this post I will examine information available from a variety of roof soil producers and independent studies to explore the feasibility of making our own green roof substrate. (n.b. Substrate formula differs based on the type of roof being installed (i.e. extensive vs. intensive); since Eco Brooklyn focuses mainly on extensive roofs, I will concentrate on soil formulas for extensive roofs only.)

The planting substrate used in a green roof installation is crucial to the success and longevity of the roof itself. If the soil mixture does not support plant growth while simultaneoulsy allowing the roof to function as a traditional roof would (i.e. shedding water), then the installation will fail. Therefore, the standards to which green roof soil will be held are extremely high, and we need to do our best to get the formula right!

Steve Skinner, a green roof products manager with American Hydrotech and soil scientist, writes that the most important green roof substrate considerations include:

• grain size distribution

• density

• water & air management

• pH, lime & salt content

• organics

• nutrients

• cation exchange capacity (CEC)

Since the modern green roof movement began in Germany, the Germans have a head-start on establishing standards for successful green roofs. The FLL is held as the authority on green roof planning, execution, and upkeep, and has established guidelines for individual components, including substrate; these guidelines can be downloaded here.

Before we dive into FLL guidelines, let's check out some of the commercial soils and identify relevant attributes.

In our most recent green roof installation, we used Gaia Soil for Green Roofs, a locally-produced, lightweight (10 lbs./cu. ft. dry, 30 lbs./cu. ft. saturated) substrate made from expanded polystyrene (modified to improve water-holding and cation-exchange capacities), clay, and finshed compost. We liked that it was made close to New York City, that it was light, that it retained water well (200% of dry weight!), and that it uses recycled content. However, the soil was expensive and tricky to pick up and transport.

The makers of Live Roof, a modular green roof system, have developed their own brand of green roof substrate which aims to increase soil lifespan and reduce substrate shrinkage by incorporating a high percentage of inorganic material (94+%) and avoiding the use of peat moss, compost, and perlite, all of which can break down and erode after exposure to the elements. In addition, the system uses clay to bind nutrients, a buffering agent to reduce the impact of acid rain, and a disease-supressing organic element.

G-Sky produces two blends of Roof Soil from pumice, well graded sand, and aged bark mulch compost. The manufacturers claim that, given appropriate installation, these soils can be used with little or no structural support on roof slopes of up to 35 degrees.

Rooflite Extensive MC uses a blend of mineral lightweight aggregates like HydRocks, a calcined clay, and organic components to achieve FLL certification. Detailed specifications for the product can be found here.

The most important commonality among these substrates is that they include a high percentage of low-density inorganic particles. These elements, whether pectin-coated expanded polystyrene, pumice, or calcined clay, play an important role in air and water management: they allow the soil to drain quickly during heavy rains and, because they do not break down, maintain interstitial space over the long-term. Each blend also incorporates an organic element to absorb water and provide a nutrient reservoir. The organic component within roof soils, however, typically represents a lower proportion of the soil mass than would be found in a natural system and CEC (and nutrient availability) suffers as a result. Some companies, therefore, use calcined clay or add clay to their soils to increase CEC and bind essential plant nutrients like potassium, calcium, magnesium, and ammonium.

Independent studies are a good source for information on substrate formula, as well.

A recent Michigan State University study looked at the ability of a variety of substrates to support Sedum and native plant growth on rooftops in Michigan. In their study, Rowe et al. found that at a depth of 10 cm., a soil mixture of 80% heat-expanded slate (PermaTill, from Carolina Stalite), plus USGA grade sand, aged compost, and peat, amended by approximately 50 grams of controlled-release fertilizer per sq. m per year enabled a Sedum community to establish itself (in about a year) and thrive with minimal decomposition of organic material and nutrient-laden runoff.

Another study by Oberndorfer et al. suggests that organic components typically comprise about 10% (by weight) of green roof substrate and notes that crushed brick can be substituted for expanded (calcined) clay, depending on the load-bearing capacity of the roof.

In his 2007 dissertation for Ohio State University's Horticulture and Crop Science program, Reid Coffman notes that that extensive green roof soil is typically engineered to be 75% inorganic and 25% organic and closely mimics the conditions found within the rock outcrop ecosystem. In a 2006 article, Lundholm notes that the most popular plants used in green roofs are naturally found in these outcrop systems. Though I will not do so in this post, study of productive rock outcrop ecosystem soil may provide additional insight into optimal green roof substrate composition.

Lastly, Skinner's article provides very helpful information on green roof substrate composition. He notes that extensive green roof soils are typically between 3% and 6% organic by mass, but that additional organic matter can be added initially to help to establish young plants. The organic component, however, should have a low carbon to nitrogen ratio (i.e. be highly decomposed) so that plants can easily extract nutrients and to prevent the severe shrinkage and accumulation of toxic compounds that can accompany rapid decomposition. Humus made from composted straw, sawdust, wood, leaves, grass clippings, agricultural waste, biosolids, and/or animal carcasses, separately or in combination, could be used as the organic component in green roof media and will initialy provide the macro- and micronutrients necessary for plant growth, though later it may be necessary to amend the soil with fertilizer. The inorganic component, Skinner states, could be comprised of synthetic expanded slate, clay, or shale or of natural materials like pumice. Sand, perlite, scoria, or pumice fines are often used as secondary inorganic components. Skinner advises that soil pH be maintained between 6 and 7.5 and that the substrate contain carbonate levels sufficient for plants to readily absorb nutrients and water (though architect Allan Wingfield suggests that carbonate levels be kept in check since high levels (above 6 grams/liter) can lead to corrosion of roof drains and outlet pipes).

Based on the general formulas outlined here, it seems reasonable for us to develop our own Eco Brooklyn substrate blend for our extensive roof installations. The next step would be to source materials, mix a trial batch and, if we choose to try to meet FLL guidelines, perform an empirical comparison to the FLL figures. For example, FLL places emphasis on grain size, organic content, permeability, water storage, air content, pH, and salt and nutrient content, and all of these parameters must be within a specific range for the soil to be certified FLL compliant. Most of these characteristics could be easily measured, and our formula tweaked to ensure compatibility with the FLL guide.

Without undertaking an effort to guarantee FLL certification, however, I believe that it is possible to mix a good quality green roof substrate. To begin, I would advocate the use of calcined clay or expanded slate as our primary inorganic substance, as both have reasonably high CEC. Pumice, repurposed polystyrene, and lava rock (with some clay mixed in) would work as well, and might lower the embodied energy of our substrate mix (although calcined clay is produced as a byproduct of cement production in Brazil). Depending on the load-bearing capacity of the roof, crushed brick could be added to the mix, too. Cost will be a major factor in determining our ultimate formula. To the clay/slate/etc., I would recommend adding well graded sand and finished compost or humus. I would aim for 10% organic material initially, with the expectation that the percentage will fall to closer to 5%. I would plan to amend the substrate with fertilizer annually, and water the roof if it has not received precipitation for two weeks.

In an ideal world, we would work to get our soil to FLL spec, and periodically test the product to ensure that it is appropriately mixed. For now, however, the time that it would take to test and reformulate the soil is not a luxury that we have. Still, based on my analysis of the green roof studies and substrate formulas available, I feel reasonably confident that my recommendations will produce a soil that will green a roof and support plant growth for years to come.

White light/white heat

The New York Times featured a story today on the energy benefits of white roofs. The article speaks to the savings that white roofs produce in hot climates, while acknowledging that they are not a panacea; in cities like Minneapolis and Detroit, scientists suggest that white roofs can actually lead to increased energy bills since they reflect light (and heat) during cold winter months.

While I can't refute evidence on the suitability of white roofs in northern climes, I certainly can speak to the benefit of green roofs. The beauty of the green roof is that it buffers temperature extremes, whether hot or cold. If you're skeptical, plug "green roof energy savings" into Google Scholar and see what comes up. (Start with these: "Analysis of the green roof thermal properties and investigation of its energy performance" by Niachou et al. and "The effects of rooftop garden on energy consumption of a commercial building in Singapore" by Wong et al.).

I'm not sure why the author didn't think it appropriate to include green roof information in the article, but I sure wish that there were a comment section on this one...