090730_JointFunction_GreenRoofs

7/28/2019 090730_JointFunction_GreenRoofs

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ASHRAE-HKC / CIBSE-HKB / HKIE-BSD

30 Jul 2009 Thu

r. am uDepartment of Mechanical Engineering

e nvers o on onE-mail: [email protected]


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Contents

Brief history of green roofs

Major types of green roofs

Key components

Costs of green roofs


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What are green roofs?

Green Roofs: roofs bearin ve etation FLL

Living vegetation installed on the roofs

egeae roo

Green Roof S stem Definition

A roof area of plantings/landscape installed

level that is separated from the ground beneath it- .

System Manual 2007

er green roo erms: co-roo , v ng roo


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Examples of green roofs in Hong Kong

HK Wetland Park EMSD Headquarters, Kowloon Ba

A school in San Po KwongParklane, Tsimshatsui(Photos taken by Dr Sam C M Hui)


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Examples of green roofs in the world

Solar Campus Jlich, Germany (11 Jul 2001) IBN-DLO Wageningen, the Netherlands (2 Jul 2001)

Beitou Taipei Library, Taiwan (6 Aug 2007)Putrajava Int. Conven. Centre, Malaysia (30 Jun 2006)

(Photos taken by Dr Sam C M Hui)


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Green roof at the Ford Truck Assembly Plant at Dearborn,, , .


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Worlds largest intensive green roof project, , , .


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Innovative and interesting green roof designs

(Source: Havard University)


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Brief history of green roofs

Green roofs are not a new henomenon

Hanging Gardens of Babylon (600 B.C.)

Vikings grass-covered green roofs on residential and farmouses n can nav a . .

Terraced green roofs in Germany & Switzerland (1960s)

Countries with mature green roof markets & policies

Japan: in Tokyo, building > 1,000 sq.m must include a

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The Hanging Gardens of Babylon (an ancient wonder of the world)

(Source: http://weburbanist.com)


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Simple grass-covered green roofs on residential and farm houses



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1963 pre-fab fallout bomb shelter incorporates a green roof



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Goats on a green roof in Wisconsin (USA)


G f i J (1995)G f i G (2000)


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Green roofs in Japan (1995)Green roofs in Germany (2000)



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Modern green roofs in Osaka, Japan (Namba Parks) (2003)

(Source: www.treehugger.com & www.toho-leo.co.jp)


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*

Extensive* Could also be combined

Semi-intensive

as hybrid types

Roof gardens: usually intensive greening with

other features such as potted plants, pond, etc.,

Classif reen roof s stems b basic desi n: Built-in green roofs vs Modular green roofs

bl j f f d h i h i i


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Table 1. Major types of green roofs and their characteristics

Characteristics Extensive Semi-intensive Intensive

ep omaterial

mm or ess ove an eow150 mm

ore an mm

accessible

Full saturated Low 7 -170 Varies 17 -290 Hi h 29 -970weight

kg/m2)

kg/m2)

kg/m2)

Plant diversity Low Greater Greatest

Plant Moss-sedum-herbs Grass-herbs and Lawn or perennials,

Use Ecological Designed green Park like gardenro c on a roo

Cost Low Varies Highest

Maintenance Minimal Varies Highest

Typical structureof extensivegreenroof


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Typical structure of extensive green roof

Vegetation

Filter membrane

Drainage layer

membrane

Thermal insulation

Vapour control

layer

Structural support


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Brown roofs, or biodiverse roofs

Originated in Switzerlan

Replicate the brownfield habitat, e.g. ground-nesting

Local soils & substrate materials are used

The roofs may be seeded like the intensive or

-


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Classif reen roof s stems: Built-in green roofs

Layer by layer

u on s e

Modular green roofsBy modules Interchangeable

Pre- rown

Examplesofgreenroofs inSingapore


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Examples of green roofs in Singapore

Carpark roof of public housing (modular green roof) Carpark roof of housing estate (built-in green roof)

Lawn green roof (Nanyang Techn. Univ.)Carpark roof of public housing (intensive green roof)

(Photos taken by Dr Sam C M Hui, 29 May & 1 Jun 2009)

Examplesofgreenwalls (Singapore)


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Examples of green walls (Singapore)

D.I.Y. vertical garden (Albert Quek) Vertical greening (panel type)

Various types of vertical greeningVertical greening (net & pack type)

(Photos taken by Dr Sam C M Hui, 1 Jun 2009)


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Built-in reen roofs

Installed in layers for the roof surface

Time needed for on-site installation & growing

Excess weight (180 to 450 kg/m2)

Complexity of maintenance

Modular green roofs- , - ,

Sub-divided into standard interchangeable parts


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T es of modular reen roofs Mat system

, - ,

Very light weight and thin (45 mm)

ray systemMost commonly found nowadays

Tray containers (e.g. plastic) filled with all elements Sack s stem

Sack paks easily conformed to irregular areas


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. .

Tra s stem (www.liveroof.com)

Sack system (www.greenpaks.com)

Major characteristics of the 3 modular green roof systems


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Mat System (Source: Elevated Landscape Technologies, www.elteasygreen.com)

Size : 1 m2/module (vegetated area)

Saturated weight : 39 - 73 kg/m2

(soil depth 40 mm)

a er a s : g ens y po ye y ene pos - n us r a recyc e ma er a s

Handling : Modules must be installed within two days after being palletized

Installation : Interlocking panels are placed on top of root barrier. Overlap two pockets on thepanel and fasten by polyethylene rivets.

Tray System (Source: LiveRoof, www.liveroof.com)

Size : 0.18 m2/ module 0.3 m x 0.6 m

Saturated weight : 73 - 130 kg/m2

(soil depth = 75-100 mm)

Materials : 100% post-industrial recycled polypropylene

Handling : 18 modules/pallet, 54 pallets/truck

Installation : Ergonomically designed modules can be installed by just one person. They areplaced on root barrier and needs to be watered immediately after installation.

Sack System (Source: Green Paks, www.greenpaks.com)

Size : 0.48 m2/module

2 .

Materials : Woven fabric knitted of high density polyethylene

Handling : 42 modules/pallet, 20 pallets/truck

Installation : Modules can be stored prior to installation. They are placed on root barrier and cutslits in the fabric module to insert plant plugs or seeds.

Construction process of modular green roofs


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p g

Waterproofing Roof barrier layer Drainage layer

Install modules Fix modules (if needed) Completed

(Source: www.tajima-roof.jp)


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Key components

Vegetation (plants)

Growing medium or soil (substrate)

Drainage/storage layer

Moisture mat

Waterproof layer

Greenroof systemsfromGermany(left) andJapan(right)


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Green roof systems from Germany (left) and Japan (right)

Typical setupof greenroof systems(extensive)


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Typical set up of green roof systems (extensive)

Green Roof Structure


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Green Roof StructureVegetation/Plant level

Growing medium

Filter sheet

Drainage/storage layer

Moisture mat

oot arr er

Waterproofing

Concrete roof top

(Source: www.zinco.de)

HowDoesTheSystemWork (1) ?


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How Does The System Work (1) ?

It retains water...




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... drains well ...




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... and ventilates.



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Key components

Ve etation lants

Vital & beautiful components of green roofs

an e perennas, ennas or annuasExtensive systems: mostly perennials

Intensive systems: use full plant palette, suitable toclimate and other design features

Functions:Aesthetic benefits, insulation, stormwater management,

biodiversity protection, fire retardant potential, filteringair pollution, shading, transpiration, absorb CO2,

u x , w u u


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Infrared hotofor assessin thermal effect

Typical hardy plants (sedums) used for green roofs


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Key components Growin medium or soil substrate

Utilize mixture of organic & inorganic matter

Inorganic matter used includes: perlite, zeolite,

, , , ,sands, pumice stone & rock wool

Critical to plant survival, stormwater retention, thermal, ,

Important for weight, evaporation & drainage

rov e re ressance, nsua on pro ecwaterproofing


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Key components

Non-woven & non-biodegradable geotextile fabricma e o non-rottng, po ypropy ene ers

T ical materials are white li htwei ht waterresistant, chemically & biologically neutral

Prevent fine sediments from growing media fromaccumuat ng on t e ayer eow & c oggng rans

May help prevent roots from working their way toward

the membrane


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Key components

Draina e/stora e la er

Egg-crate plastic, porous mats or granular media

plants; modular system may have built-in drainage

transported to pipes and downspouts; some also allowwater to remain on the roof for irri ation

Functions:

discharge stormwater; may provide root repellency,

insulation & water stora e benefit


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Key components

A geotextile fabric mat, manufactured fromrecyc e po ypropy ene, an s o ten grey rown

in colour It is non-rotting, bitumen compatible, and

Functions:For use as a moisture/nutrient retention and protection

layer under extensive and intensive green roof


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Key components

An root resistant sheet made of polyethylene, ands ac n co ou

It is non-rotting and bitumen compatibleMetal lining (e.g. copper) or impregnated with

chemical-based root re ellin a ents ma also be use

Function: reven unwane pans rom compromsn e

waterproofing, especially species with aggressive root


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Key components

Water roof la er

Modified bitumen reinforced with non-woven

Impervious concrete

Membranes may be liquid applied, speciallydesigned single-ply sheet or a built-up roof system

20 year warranty recommended

Prevent water from entering the building; facilitate

Green roof on steel deck structure


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(Source: www.alumasc-exteriors.co.uk)

Green roof on concrete structure


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(Source: www.alumasc-exteriors.co.uk)


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Key components

Other com onents of reen roofs:

Insulation

Leak detection system

Ponds and pools

Irrigation system

Walkways

Railings

n

(Source: www.tajima-roof.jp)

Examples of green roof details


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FZ-Schiene + Clamping profile EP 150

Upstands

Roof Perimeters

ca. 150 mm

Gutter System SR 75 Siraset

ca. 100 mm

Inspection chamber KS 8 ca. 300 mm

oo ou e w

inspection chamber



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Key components

Insulation

May be made of foams or fibres,

foam, phenolic foam; Fibres: vegetable or glass

Reduce heat transfer to and from the building

In t e w nter, prevent mo sture trappe n t e su strate

from removing heat from the building ro ec pan roos rom reeze aw cyc e

May protect waterproofing in inverted system

nsua on a ove e waerproo n


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Key components

Cold roof: insulation layer beneath the roof deck.e. on top o t e ce ng

Warm roof: insulation la er above the roof decRoof structure temperature is close to the interior

Weight/Load resistance required for the insulation

Inverted warm roof: insulation above thewater roof la er rather than below

Three types of roof construction,


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drainage

waterproof

insulation

roof deck

(Source: Planting Green Roofs and Living Walls)


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Key components

Protective non-woven fabrics, boards and sheetingt at are g tweg t an water resstant

Relativel inex ensive non-woven and non-biogradable landscape fabric

Protect waterproof membrane from construction stressan nsta at on of t e ranage ayer, f requre

K


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Key components

Electronic field vector mapping (EFVM) useseectr ca ow to pnpo nt t e ocat on o ea s as

small as a pin hole 48 hours or longer flood test prior to installation

Ensure quality of waterproofing, e.g. on sloped roofsw ere water tests are mpractca

Used to locate leaks

K t


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Key components

Water features e.g. waterfalls, fountains & pondscan e ncorporate nto green roo esgn

Se arate water roofin membranes ma be use Precast fiberglass shells may be used for ponds

Funct ons:

Aesthetic use primarily and psychological benefits

May include stormwater management feature

K t


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Key components

Overhead or spray, surface or near surface driprr gat on, cap ary rr gat on, an ase r p or

trickle irrigationExtensive systems may function without this

Ensure plant survival initially & ongoing healthTemporary rr gat on requre to ep pant esta s

Ongoing irrigation for intensive systems fairly standard

K t


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Key components

Precast concrete pavers, natural stone, gravel,woo , ergass roc s, recyc e past c ec ng

Ma be set on edestals to allow unim eded drain Functions:

es e c ene ; access o mec anca equpmen

other roofing features requiring maintenanceControl movement of people (keep them from walking

on plants)

Separate or isolate sections to prevent spread of fires

K t


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Key components

Precast concrete curbs, aluminum edging, timberor ers, panter oxes, recyc e cur pro ucts

Ma be set on edestals to allow unim eded drain Function

es e c ene s

Separates vegetation areas from structural roofcomponents e.g. parapet walls, drains & skylights

May be used to separate vegetation components and

provide a fire break or protection from wind uplift

K t


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Key components

Wide range of railing technologies

Worker safety anchor systems should be

considered durin reen roof installation Functions:

ro ec peope rom a ng o e roo

May also perform an aesthetic function

Limit the access of people to the entire roof, areas ofwhich may be support an intensive system or live loads

Key components


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Key components

Wide range landscape lighting

Functions:

AestheticbenefitNight time use and possible security functions

Benefits of green roofs


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building owners and the society Some benefits of green roofs will only be apparent

if roof reenin is on a lar e scale; others canoperate on a much smaller scale

roofs, but many are project design specific

Table 1. Public and private benefits of green roof systems


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Public benefits: Private benefits:

- Mitigate urban heat island - Increase roof life expectancy

- Reduce dust and pollutant levels - Reduce noise levels

- Stormwater retention - Enhanced thermal insulation

- Natural habitat for animals/plants - Heat shield

- Cities and landscapes - Better use of space

- Nature look (aesthetic) - Reduced risk of glare for


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(Source: www.g-sky.com)



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.

1.1 Biodiversity and wildlife value

1.2 Stormwater management

. 1.4 Air pollution mitigation

1.5 Carbon sinks (sequestration)

.

1.7 Control of noise pollution



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1.1 Biodiversit and wildlife value

As a habitat to support life (plants, birds, insects) reae n s con nu y or green space

1.2 Stormwater mana emen Rainwater retention

1.3 Rainwater runoff quality Improve water quality; reduce nutrient loading;

neutralize acid rain



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Stormwater runoffs causes flooding & otherpro ems; resu tant costs are orne y t ecommunity as a whole

Increased frequency of severe rainstorms

, . .

detention pools, green roofs A key point to translate green roof benefits into

im rovements in immediate cash flow

Rainstorm flooding problems in Hong Kong (2008)


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(Source: www.accuweather.com)



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Effects of reen roofs on water runoff

Water can be absorbed into pore spaces in the

Water taken up by the plants (stored in plant

ssues or ranspre ac o e amosp ere ;lodged on plant surfaces & evaporate away

evapo- ranspra on

Water stored and retained by drainage system

Reduce actual runoff and act as a buffer

,

Green roof hydrograph comparisonGreen Roof H dro ra h Com arison 12-2-05

4 50


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4.50

3.50

4.00

3.00

2.00

2.50

low[

L/min]

Green RoofHydrograph

1.50 Control RoofHydro-graph

0.50

1.00

0.00

.

0 5 10 15 20 25 30 35

(Source: Stormwater Academy, University of Central Florida)

Time [min]



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Greatest contribution is in low-intensity tomo erate storms

Once the roofs are saturated their effect lessens When combined with other sustainable drainage

,

Possibilit of inte ratin rainwater orgreywater recycling systems



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.

Filter out fine airborne particles

Foliage can absorb gaseous pollutants

1.5 Carbon sinks (sequestration)

Little evidence now to quantify the benefits



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1.6 Miti ation of urban heat island

Urban heat island (UHI): elevated urban

Large number of built structures absorb/release heat

e uc on n evapora n sur acesLack of vegetation cover, shading and evaporation

aste eat rom u ngs ve c es

Less cooling from wind because of shelter of buildings Urban air temperatures significantly higher than in

the surrounding countryside

Urban heat island in Hong Kong


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(Source: SCMP and Lawrence Berkeley National Lab)



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.

Hard surfaces of urban areas tend to reflect soundrat er t an a sor

Green roofs can absorb sound and reduce noiseReduce sound transmission into buildings

Usually very effective for metal roofs



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g

Extends roof life

Reduces air conditioning & heating costs (energy

and maintenance Reduces capital costs for equipment and

,

Reduces water and sewerage charges

Attracts buyers and tenants

rac s an reans empoyees



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g

.

Exposed roofsExperience higher temperature than that of green roofs

Daily temperature fluctuations create thermal stresses

Roofing materials & membranes are degraded

Moderate the daily temperature fluctuationsProtect the roof system from heat, UV radiation & other

mechanical damages: the roof will last longer



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g

2.2 Coolin insulation and ener efficienc

Thermal properties of green roofs

Evaporative cooling from the plants & substrate

ona nsua on rom e pans su s raeThermal mass effects of the growing medium

Summer reduction in cooling energy requirements

Possible winter insulation effect

To maximize the cooling potential, a healthy &com lete lant cover is im ortan

Thermal properties of green roofs


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Evapo-transpiration

Insulating

property

Roof slab

n oor


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Green roof evaluation in Singapore


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(Source: Wong, Tan and Chen, 2007)



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Affect mainly upper floors of a building

Saving in annual and peak energy consumption

continuous evapotranspiration and by circulating

Thermal modelling of green roofs

Evaporationransp ra onRadiation


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n

ducti

Co

" TwC

n - sa a on:

)( mie hrr

vapo- ranspra on:

totalssq 21Conduction:

Green roof research at a construction site office (contd)


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Infrared pictures:

Green roof Conventional roof



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.

Green roofs can gain points in some greenu ng rat ng sc emes, e.g. n

1) Reduced site disturbance, protect/restore open space

2) Water efficiency

4) Materials and resources n oor env ronmena qua

6) Innovation in design

Up to 15 LEED credit points may be available



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.

Promote green image of a building/organisation

Public relations (PR) and marketing value

- May increase rental income & uptake rate

Can have direct financial benefit



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.

Aesthetically pleasing, useful space If roof loading is sufficient, green roofs can be planned

for amenity and recreational use

Food production

A range of marketable products (vegetable, fruit) oca o creat on rect an n rect

On green roof maintenance, urban agriculture, etc.



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Urban farming(e.g. growing vegetables, herbs)Make best use of roof space; may be organic

Education environmental scientific liberal stud Integrated with school curriculum

ommun y an soc a unc ons

Exercises & hobbies for children, adults & elderly

Healing landscape(e.g. horticultural therapy)

,


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social functionsUrban farming & education



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Unattractive view of bare roofs (dark asphalt) Green roofs are more pleasant to be looked at

Im roveem lo ee roductivitTherapeutic effects

tress re uct on

Lower blood pressureRelieve muscle tension

Increase ositive feelin

Nanyang Technological University, Singapore


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(Source: www.inhabitat.com)



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Extensive green roofs: HK$400 to 1,000 per sq.maverage per sq.m

Intensive reen roofs: HK 1000 to 5000 ersq.m, (average HK$2,000 per sq.m)

ypca recurren manenance coss

Extensive reen roofs: HK 0.8 to 2.2/s .m/ ea

Intensive green roofs: HK$6.5 to $44/sq.m/year

.(Source: ArchSD - Study on Green Roof Application in Hong Kong Final Report)

Capital cost rang comparison of extensive green roof


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(Source: ArchSD - Study on Green Roof Application in Hong Kong Final Report)



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Cost breakdown of t ical extensive reenroof

(example from www.greenrooftops.com)

Plant materials (31%)

Root barrier & waterproofing (16%)

Planning and funding of green roofs requiresan un ersan ng o e-cyc e coss From cradle to rave; environmental benefits

Green roof research and urban farming


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Urban farming on green roofs


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Farming on the roof Vegetables and herbal plants

Green beansWater melon(Photos taken by Dr Sam C M Hui; Acknowledgement: St. Bonaventure Catholic Primary School )

The reen roof volunteers in Hon Kon


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The reen roof volunteers in Hon Kon

(Our green roof research information can be found at: www.hku.hk/bse/greenroof/)

Documents

090730_JointFunction_GreenRoofs