Greenroof:

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Greenroof

• A Cost-Benefit Analysis of the Urban Ecology of
  Rooftop Gardens
• Courtney Szper, Barnard College
• Research Advisor Stephanie Pfirman of Barnard
  College
• Research Mentor Colin Cheney of Earth Pledge

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Greenroof History

• Original idea for contemporary greenroof from
  Iceland.
• Sod roofs and walls used based on available
  supplies.
• Modern Greenroof technology from Europe (decades
  old).

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Extensive vs. Intensive Greenroofs

• Extensive
• Thin layer of drought tolerant self-seeding
  vegetated roof covers.
• Lightweight
• Roofs with slopes up to 33.
• Uses sedums, grasses, mosses, and meadow flowers.
• Utilizes existing structures/little to no
  modification.
• Less Costly.
• Requires little to no irrigation, fertilization,
  or maintenance.

• Intensive
• More elaborate roof landscape
• Significantly heavier
• Flat roof surfaces or mild slope (up to 3).
• Can include many plants, shrubs, trees, and
  agriculture.
• Engineering required to conform to building
  standards.
• More expensive
• Demands irrigation, fertilization and
  maintenance, and is intended for human interaction

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Advantages Benefits

• Ecological
• -Urban Heat Island Effect Alleviation
• -Storm water Mitigation
• Economic
• -Insulation for the Buildings (temperature and
  sound)
• -Prolonged Roof Life
• Aesthetic
• Psychological

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Ecological Benefits Reduction of the Urban Heat
Island Effect

• What is an Urban Heat Islands?
• - Vegetative canopy biomass greatly lowers air
  temperatures.
• - Artificial/altered surfaces increase air
  temperature.
• New York City is an estimated 6-8F hotter than
  surrounding suburbs.
• Greenroofs can reduce air temperatures and
  increase humidity levels.

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Ecological Benefits Stormwater Mitigation

• Replaces impervious cover.
• Can absorb up to 90 (average 50-90 depending on
  soil depth, soil composition, and plants).
• Returns water to the atmosphere
• Alleviates combine sewage overflow.
• Reduces loads on storm water treatment centers.
• Vegetation absorbs pollutants from rainwater
  (over 95 cadmium, copper, and lead and 16 of
  zinc can be taken out of rainwater.1)

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Test Site Hamilton Ecoroof in Portland Oregon

• Ten story building located downtown.
• Total area of roof 8,711 ft2
• 60 is covered with an ecoroof, 40 covered by
  impervious roofing surface.
• To study, ecoroof divided into two parts West
  4-5 depth East 2-3 depth
• Same vegetation, different soil and soil depths.

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Economic Benefits

• Greenroof installed in place of conventional
  storm water practices.
• Doubles/Triples the life of roof (also saves
  disposal costs of old roof material).
• Overall building energy costs can be reduced.
• Acoustic insulation.
• Previously wasted space now utilized.

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Aesthetic Psychological Advantages

• Ecological designs can foster community and
  health.
• Greenroofs help visually ease the stress caused
  by lack of green space.
• Psychological studies have elaborated on the link
  between quality of life and natural green space.
• Sense of community through a shared community
  garden.

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Potential Problems

• Waterproofing Integrity
• Roof Weight Bearing Capacity
• Access Problems
• Environmentally Sound Irrigation
• Price

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Case Study A New York City Garden in the Sky

• The Earth Pledge Foundation completed the over
  700 square feet semi-intensive greenroof.
• 3-12 of engineered soil mix.
• Herbs mint, basil, tarragon, catmint, thyme,
  rosemary, and sage.
• Vegetables squash, lettuces, tomatoes, peppers,
  zucchini, and eggplant.
• Flowers lavender, bee balm, verbena, and
  daylilies.
• Fertilizer cold-pressed fish waste emulsion
  applied monthly.
• Water drip irrigation used in times of drought.

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Earthpledge Greenroof Manhattan
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Greening New York City

• 33 of Manhattan is rooftop.
• Estimate cost of greening a roof 4-25/square
  foot.
• Estimated that NYC is 6-8F hotter than
  surrounding suburbs.
• Heating and cooling costs could be cut by as much
  as 50, reducing energy demands.
• Estimated that NYC could save as much as 16
  million annually in energy costs alone.
• A reduction in temperature can translate into a
  reduction in ozone and a reduction in heat
  related deaths and illness.
• One square meter of greenroof can remove 0.2kg
  of air born particles from the air annually.
• Greenroofs can retain up to 90 of storm water.

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Funding and Incentives

• Germany and other European countries implement
  mitigation requirements and incentive programs.
• US can use tax money from saved construction and
  maintenance of storm water treatment plants.
• Funding can be obtained through EPAs Clean Water
  Act Section 319 (non-point source pollution)
  grant program.
• Incentives from sewer and power companies (reduce
  maintenance and blackouts).

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Greening Manhattan

• A greener Manhattan could benefit and
  ameliorate problems including
• Ecological Problems
• Urban Aesthetics
• Psychological and Health Problems
• This is proving to be economically beneficial, in
  spite of high initial costs.

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Thank you!