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By Glen Anderson,2014-04-18 02:35
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constprodconsultshomesteadcom

Overview of Green Roofs Topics:

    Learning Objectives

     To learn the importance of the benefits of the greenroof system To understand the function of each component in a greenroof system To understand stormwater management relative to greenroofs

    Environmental Concerns

    ; Stormwater

    ; Impaired Waterbodies

     Air Pollution ;

    ; Urban Heat Island Effect

    Definition

     A green roof is a roof of a building that is partially or completely covered with vegetation and soil, or a

    growing medium, planted over a waterproofing membrane. This does not refer to roofs which are merely

    colored green, as with green shingles. It may also include additional layers such as a root barrier and drainage

    and irrigation systems. Container gardens on roofs, where plants are maintained in pots, are not generally

    considered to be true green roofs, although this is an area of debate.

     Environmental Economic

     Improved stormwater management ? Decreased building energy

     Improved air quality ? Increased roof life

     Reduction of urban heat island ? Increased building space

     Reduced noise ? Increased property value

     Wildlife habitat ? Tax benefits/incentives

     Improved water quality

     Reclaims lost landscape

     Utilization of recycled materials

     Recycling of nutrients

    Types

     Extensive

     Little to no maintenance

     Plant characteristics

     Minimal burden on growing media

     Minimal maintenance

     High draught tolerance

     Typically a diffuse root system

     Shallow growing media depth

     Intensive

     Requires maintenance

     Plant characteristics

     Require maintenance

     Watering

     Fertilizing

     Pruning

     Increased demand on growing media

     May have tap root

     Deeper growing media depth

    Components Waterproofing through plants

    Plants Dictate greenroof component requirements.

     Introduced into greenroof

     Vegetated mats

     Transplants

     Plugs

     cuttings

     Seeding/hydro-seeding

     combination of above

     some types of plants may not be practical to introduce as a seed such as trees or shrubs

    Growing Media Not Dirt!

    Growing Media

     Lightweight

     Aggregates

     Organics/compost

     USGA grade sand

     Uniform distribution

     Consistent

     Color

     Aeration

     Permeability

    Dirt

     Heavy

     Minerals

     Organic matter

     Unwanted pathogens, pesticides & herbicides

     Random distribution

     Inconsistent

     Color

     Aeration

     Permeability

     pH - pondus hydrogenii

     Acidity or alkalinity 5.5 to 8.0

     Nitrification allowing bacteria to decompose organics oxidizing ammonia into nitrates

     Irrigation increase 0.5 to 1.0

Major nutrients

     Carbon backbone of biomolecules photosynthesis

     Hydrogen builds sugars air/water

     Oxygen cellular reproduction air

     Phosphorus converts light energy to chemical energy root system

     Potassium regulates stoma (leaf) controlling air/CO root system 2

     Nitrogen essential to protein root system

     Sulphur essential to amino acids root system

     Calcium cell walls root system

     Magnesium coordinates chlorophyll root system Minor nutrients root system

     Iron enzyme cofactor photosynthesis

     Molybdenum enzyme cofactor amino acids

     Boron sugar transport & cell division

     Copper builds chlorophyll

     Manganese builds chloroplasts

     Zinc builds enzymes for DNA transcription

     Chlorine cofactor production of oxygen

    Filter Fabric Provides separation between growing media and drainage layers

    Drainage Holds additional water

     Aquifer

     Two types

     3-D board

     Aggregate

     Free flow permeable

    Protection/Retention Protects root barrier

     Point load of 3-D drain board

     Aggregate drainage

     From potential puncture of tools Retains additional water

    Root Barrier Prevents root penetration to waterproofing layer

     Roots seek nutrients

     Membrane

     Treated with copper hydroxide

     Thermoplastic

     Seams typically sealed

    Waterproofing Hot-Applied Rubberized Asphalt - PMR Single Ply

     TPO

     PVC

     EPDM

     BUR asphalt

    Stormwater Management Rain falls

     Soaks into growing media

     Passes through filter fabric

     Fill drainage layer

     Overflows to protection retention layer Slowly flows to drain

     How much stormwater actually stays in the green roof?

     What is the quality of the stormwater going down the drain?

     Plants retain water…

     Difficult to calculate

     Evapotranspiration loss up to 90%

     10% atmospheric moisture from plants

     Typical plants for green roof are 85% to 95% water by weight.

     Typical growing media can absorb about 33% water by weight.

     Example

     2”/hour rainfall

     4” deep growing media

     64% volume stormwater retention in growing media

     Typical filter fabric

     Negligible volume

     Typical 3-D drain board

     1.25” top of cup diameter

     0.5” bottom of cup diameter

     1” cup height

     33 cups/sq-ft

     About 0.76 gal/sq-ft

     Typical protection mat

     1/8” to 5/16” thick

     Hold about 95% volume in water

     5/16” mat holds about 0.185 gal/sq-ft.

     Compressed less volume

     Quantity

     Growing media

     Drainage

     Protection mat

     Quality?

    Quality Why?

     Growing media

     Too much organics

     Too shallow limits performance

     Extensive minimal fertilizer to establish

     Stormwater runoff keep stormwater in greenroof

     Earth greater depths for filtering

     Greenroof shallower depths flow to drains

    Greenroofs

    Alternate Designs…

    Definition

     A green roof is a roof of a building that is partially or completely covered with vegetation and soil, or a

    growing medium, planted over a waterproofing membrane. This does not refer to roofs which are merely

    colored green, as with green shingles. It may also include additional layers such as a root barrier and drainage

    and irrigation systems. Container gardens on roofs, where plants are maintained in pots, are not generally

    considered to be true green roofs, although this is an area of debate.

    Alternate Designs - Trays Easier access to roof membrane for repairs

     Where do removed trays store during repairs?

     Electronic Field Vector Mapping

     Save money

     Tray is only part of system

     Waterproofing system?

     Single source warranty?

     Compare apples to apples

     Engineered system

     All greenroofs engineered

     Limited performance

     Provide flexibility

     For what?

     Conventional built in place greenroofs allow greater designs

     Easily removed without disrupting greenroof

     Why remove?

     Repairs EFVM

     Flexibility of design successful design?

     Require non-skilled labor to install

     Single ply claim

     Poor quality seam weld resulted in leaks

     Now require skilled labor factory trained

     Do not provide the full extent of greenroof benefits

     Too shallow

     Limited to extensive designs

     Minimize plant spreading cannot jump containers

    Greenroofs

    Additional Thoughts…

    Building Considerations Weight/dead load limitations of structure Exposure to sun/shade throughout year Hydrological conditions

     Roof slope and drainage

     Access for maintenance

     Staging of components during installation Height of roof and wind uplift

    Maintenance

     All greenroofs require maintenance Extensive vs. Intensive

     Removing unwanted seeds dropped by birds

     Weeding

     Removing dead plants

     Establishment

     Irrigation

     Fertilization

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