Sustainable Green Roofs

1
SustainableGreen Roofs

• A Presentation
• By
• Mr. Jones Wong General Manager
• KEYTECH
• Yr 2008

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Order of Presentation

• Green roofs in Singapore
• Traditional green roof
• Classification of green roofs
• Design factors
• Green technology
• Substrate technology
• Selection criteria
• Green roof Mistakes Solutions
• Case study 1 Extensive green roof
• Case study 2 Intensive green roof

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Order of Presentation

• Green Roofs in Singapore
• Traditional Green Roof
• Classification of Green Roofs
• Design Factors
• Green Technology
• Substrate Technology
• Green Roof Mistakes Solutions
• Climate vs Maintenance

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Green Roofs

• Which of these 21 spots are green roofs?

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Definition

• .....Nature on Superstructure.......

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Green Roofs in Singapore

• Intensive green roofs or roof gardens in public
  housing
• The Singapore way

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Green Roofs in Singapore

• Future plans
• The Singapore way

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Traditional Green Roof (Soil-based)

• Typical components
• Vegetation

• Substrate Top soil, sand, etc

• Sand layer

• Filter layer

• Drainage layer

• Waterproofing layer

• Other possible add-on components
• Protection screed
• Vapour barrier
• Thermal insulation

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Traditional Green Roof (Soil-based)

• The shortcomings
• Consolidation

Then there are pests!

• Settlement of fine particles

When is aeration going to take place?

• Drainage impediment

• Harden surface

• Ponding

• Filter layer deteriorates

• Root penetration

• Thick heavy

Within 12 - 18 months upon installation
After 2 yrs
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Classification of Green Roofs
Intensive roof garden
Semi-intensive roof garden
Extensive roof garden
Extensive roof garden
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Design Factors to Consider

• Premise - Shape, location, height, surroundings,
  full sun, shaded area, etc

• Type of green roof Intensive or Extensive
  Vegetation

Main Objective To have an active green roof to
complement life of the building ( also to
prevent green roof failure!)

• Irrigation use of water

• Type of roof - Inverted roof, warm roof, cold roof

• Wind up-lift sweeping

• Load bearing capacity

• Architectural details - Upstand and parapet
  details, Roof penetrations eg. Air con vents,
  water pipes, etc

• Fire personal safety

• Waterproofing

• Drainage, slope fall

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A Good Green Roof

• A good well-performing green roof needs at
  least 1 - 2 years in the tropics to exhibit its
  true performance level.

or like this
It can look like this
Original
Settlement
Now
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Green Technology
Irrigation
Moisture
Water

• Mode Capilliary action vs Evaporation

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Green Technology
Water storage
Water
Water

• Where and how much water is stored?
• Bathub vs Cups concept

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Green Technology
Drainage
Water
Water
Surface runoff
Erosion risk
Uplifting risk
Drainage

• Proper drainage without risk of erosion or
  uplifting

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Substrate technology
Extensive vs Intensive
Grain size
Water retention
Air volume
Nutrient reserves
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Substrate technology

• Possible minerals
• Gravel
• Lava
• Expanded clay
• Expanded shale
• Brick chips
• Slag
• Sand

• Possible material
• Peat moss
• Coco peat
• Composted wood chips

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Substrate technology
Organic vs Inorganic content

• Good growth
• Consolidation
• Ave to high cost initially
• Ave maint cost

• Slow growth
• Minimal consolidation
• Costly initially
• Low maint

• Good initial growth
• Consolidation
• Ave initial cost
• High maint

• Performance vs Maintenance issue

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Green Roof System Selection Principles

• From the Plants perspective

• The green roof system needs to
• Allow sufficient root space
• Provide sufficient quality water for irrigation
• Provide proper mode of water storage
• Provide nutrients for long and short-term
• Support long term behaviour of plant growth
• Sustainable with the maintenance given

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Green Roof System Selection Principles

• From the Building Owners perspective

• The green roof system needs to
• Be well suited for the roof.
• Guarantee permanent and appropriate drainage,
  even when under pressure.
• Ensure well balance supply of air and water.
• Integrate with the form of vegetation
• Allow for minimal maintenance.
• Enhance the life expectancy of the waterproofing.

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Green Roof Mistakes Solutions
What are the common mistakes?

• Water stagnation
• Compacted substrate
• Wind sweep uplift
• Topple effect
• Poor plant growth
• Neglect

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Green Roof Mistakes Solutions
Water stagnation

• Common causes
• Insufficient fall
• Inadequate or no drainage layer
• Insufficient drainage outlets

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Green Roof Mistakes Solutions
Water stagnation

• Common solutions
• Fall 1 80 1 120
• Install suitable drainage layer
• Vert drainage outlets at 1 pc of 100 mm Ø per 100
  sqm to cater for tropical storms of 330 mm/hr
  rainfall

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Green Roof Mistakes Solutions
Compacted substrate

• Common causes
• Grain size distribution having excessive fines
• Excessive clay material
• Excessive organic content

Poor plant growth
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Green Roof Mistakes Solutions
Compacted substrate

• Common solutions
• Grain size distribution FLL Guidelines
• Remove fines (lt0.063 mmØ) as much as possible
• Limit organic content
• (mm vs )

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Green Roof Mistakes Solutions
Wind sweep uplift

• Common causes
• Substrate overly lightweight
• Insufficient vegetation cover
• Improper installation at the prone areas eg edges
  corners
• Design oversight

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Green Roof Mistakes Solutions
Wind sweep uplift

• Common solutions
• Ballast to weigh down at prone areas
• Use of pre-cultivated vegetation mats
• Use of anti-erosion nettings

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Green Roof Mistakes Solutions
Topple effect by winds

• Common causes
• Poor plant choice Sail effect in high wind
  environment
• Improper or no anchorage
• Insufficient substrate depth

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Green Roof Mistakes Solutions
Topple effect

• Common solutions
• Plant choice Advice from Specialist
• Substrate depth Advice from Specialist
• Design proper anchorage

Volume of substrate becomes ballast weight for
the tree.
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Special Details on Tree Anchorage

• Tree anchorage
• Type 2 using concrete ballasts

Slab-shape concrete ballast that uses the weight
of overlying substrate as dead weight
U-shape concrete ballast
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Green Roof Mistakes Solutions
Poor plant growth

• Common causes
• Poor plant choice
• Plants and system not integrated
• Unsuitable substrate
• Lack of proper maintenance

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Green Roof Mistakes Solutions
Poor plant growth

• Common solutions
• System selection
• Improve substrate quality eg with organic
  content, nutrients, etc
• Improve maintenance
• Re-planting

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Green Roof Mistakes Solutions
Neglect

• Common causes
• Lack of maintenance

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Green Roof Mistakes Solutions
Neglect

• Common solutions
• Upkeep maintenance

• Intensive green roofs -
• Weekly programme as per traditional roof garden

• Extensive green roofs -
• Once every 2 to 4 months to focus on weeding,
  pruning fertiliser.
• Watering during drought periods.

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Climate vs Maintenance
Climatic factors temp rainfall
SINGAPORE
Ave day temp is 31 deg C
Ave night temp is 24 deg C
Ave rainfall is 180 mm per mth
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Climate vs Maintenance
Climatic factors temp rainfall
Prolific growth

• Maintenance issues during growth period
• - Coverage vs pruning
• - Nutrients vs insecticides
• - Weeds

Dull growth
Dull growth

• Maintenance issues during dull period
• - Coverage vs weeds
• Fire safety
• Wind sweep

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Green Roofs

• Which of these 21 spots are green roofs?

12 are not green roofs
8 are green roofs
1 is debatable
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What is a Sustainable Green Roof ?
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Thank you very much!