ENERGY INDEPENDENCE: Green Roofs

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ENERGY INDEPENDENCEGreen Roofs Implementation
and Feasibility

• Chris Gardino

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History of Green Roofs

• Originated in ancient Mesopotamia
• Viking sod roofs in Scandinavia
• Sod roofs in Africa

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Green Roofs Generally

• Growing medium is part of the roof
• Layers of a contemporary green roof

Cross Section of a Green Roof
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Decking

• Can be constructed from wood, metal concrete,
  plastic, gypsum, or composite
• Concrete decking will provide the most sound
  structural support

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Waterproofing Layer

• Very important to make sure that there is an
  effective seal
• There are four different methods of waterproofing
• - Built up roof
• - Modified Bitumen roof
• - Single Ply membrane
• - Liquid applied membrane

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Insulation

• Proper insulation will promote the energy saving
  advantages of green roofs
• Insulation can either be placed above or below
  the waterproof membrane

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Protection and Storage Layer

• Must be placed above the waterproof membrane
• Usually constructed with PVC or HDPE sheets

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Drainage Layer

• Drainage layer is critical to the health of the
  plants and the roof system
• Drainage systems are very site specific

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Filter Layer

• Root permeable
• Basically separates the medium from the drainage
  layer to avoid clogging
• Could be a filter cloth or some other
  semi-permeable fabric

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Growing Medium

• Green roof plants need to grow in a medium that
  is porous
• Ideal mixture is about 75 to 90 percent inorganic
  material with the remainder consisting of compost
• Depth of medium will vary with the type of roof

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Extensive Green Roofs

• Typically less than 6 inches of soil
• Usually not open to public
• Low plant diversity
• Minimal cost to maintain

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Intensive Green Roofs

• Deeper and more organic soils
• Often open to the public
• More plant diversity
• Higher maintenance costs

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Semi-Intensive Green Roofs

• Between intensive and extensive green roofs
  regarding maintenance and support capacity
• Semi-public purpose

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Plant Selection

• Will be extremely site specific
• Generally Green Roof plants will be tougher and
  less nutrient reliant than plants found in ground
  gardens
• Elevation will carry certain dangers not found on
  the ground

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Annuals

• Annuals are plants that grow, flower and seed in
  one season
• Should not be dominant in green roofs used more
  as an accent

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Herbaceous Perennials

• Herbaceous perennials are some of the most
  desirable green roof plants
• Advantages aesthetically pleasing, lots of
  variety
• Disadvantages Most have limited drought
  tolerance, will require deeper substrate, biomass
  accumulates as they grow, very few are evergreen

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Some Well Suited Herbaceous Perennials
Phlox
Dianthus
Campanula
Petrorhagia
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Hardy Succulents

• Hardy Succulents are the best suited plants for
  green roofs
• Advantages can survive drought/ wind/
  temperature extremes, store water for extended
  periods, shallow root systems
• Only viable option for certain shallow soil
  extensive roofs

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Sedums

• Nearly 600 species available
• Found in well drained areas
• Long life span and self-propagating
• Change color with the seasons

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Other Hearty Succulents
Talinum
Delosperma
Sempervivum
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Grasses

• Grasses can add texture and habitat
• Require deeper medium for root systems and larger
  biomass

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Herbs

• Herbs can be very tolerant once established
• May require deeper substrate for less ground
  cover
• Added culinary and olfactory perks

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Groundcovers

• Groundcover plants provide dense soil cover,
  retard weed growth, and prevent soil erosion
• Most of the plants on a green roof should be low
  density ground covers
• Allow for rapid and reliable growth at a
  reasonable price

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Accents

• Accent plants may not live over five years and
  will require more care and maintenance
• Many of the aforementioned annuals make for
  viable options as accent plants

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Natives

• Native plants often function in an ecological
  system which makes their inclusion in green roofs
  somewhat difficult
• Advantages already adapted to local weather
  conditions, resistance to local pests etc.

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Cost!!!!

• The cost for implementing a green roof in the
  United States is about 15-20/sq ft
• The price of a conventional roof runs about
  8-10/sq ft
• The price of a green roof is offset by long term
  cost saving

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Energy Independence

• Heating/cooling energy
• Green roofs can reduce heat consumption during
  the winter months
• Green roofs will keep air conditioner use down in
  the summer months
• Will also keep surrounding areas cooler in the
  summer months

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Urban Heat Island

• Most suburbs and city roofs are made in shades of
  gray and black which tend to soak up heat and UV
• This contributes to the phenomenon known as the
  urban heat island effect

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Urban Heat Island
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Carbon Dioxide and Other Particulate Matter

• Green roofs will naturally absorb excess CO2
  through photosynthesis
• Green roof plants can also remove harmful or
  unwanted particulate matter (dust)

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Water Run-Off

• Excess runoff is costly
• About 75 of rainwater in urban areas becomes
  surface runoff
• Green roofs can mitigate surface water runoff

ABOUT 1.5 OF THE UNITED STATES IS COVERED IN
IMPERVIOUS SURFACES AN AREA ABOUT THE SIZE OF
OHIO
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Other Benefits

• Habitat
• Aesthetics
• Worker Productivity
• Sound Insulation

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Green Roofs and the Law Incentives and Mandates

• Most contemporary legislation relating to green
  roofs is based upon incentives
• Germany offers individuals 15 euros per square
  meter of green roof
• Switzerland requires that 25 percent of new
  commercial development be greened

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Domestic Green Roof Incentives

• Chicago is at the forefront
• Tax incentives
• Water run-off credits
• Open Space Requirements

South Loop Target Store
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CONCLUSION

• Green roofs provide an opportunity to use
  otherwise wasted space in a way that promotes
  energy independence
• Legislators should follow the lead of European
  countries in promoting the development of green
  roofs to offset the loss of open spaces through
  incentives and mandates