‘A Concise Guide to Rooftop Greening’ was jointly prepared by National Parks Board and The Centre for Urban Ecology and Greenery (CUGE).

Contributors:

Ng Cheow KhengNur Faezah Mohd SanifPeter HuntPoh Choon HockShirley LingSimon Longman

We would like to thank the following organisations for their contribution:

Bedok Reservoir – Punggol Harmony Resident’s CommitteeCity Developments LimitedElmich Pte LtdFar East OrganizationFrasers Centrepoint LimitedGarden and Landscape Centre Pte LtdHitchins (FE) Marketing Pte Ltd Housing Development BoardKhoo Teck Puat Hospital National Archives of SingaporeShaw OrganisationSingapore Botanic GardensSurbana International Consultants Pte LtdUniseal Waterproofing Pte LtdZinco Singapore Pte Ltd

All rights reserved. No part of this work may be reproduced or copied in any form or by any means, electronic or mechanical, including photocopying, without the prior permission of the copyright owner.

©National Parks Board, 2010

introduction

benefits of rooftop greenery

i . . . good for the environment

ii . . . brings economic rewards

ii . . . ideal for social interaction

ii . . . enhances a building’s aesthetic appeal

types of rooftop greenery

green roofs

roof gardens

a selection of rooftop greenery in singapore

ready for rooftop greenery?

i . . . provision of rooftop greenery to new building

ii . . . provision of rooftop greenery to existing building

faqs

CONTENTS

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INTRODUCTIONHave you ever thought about greening your building’s rooftop? Well, the art of rooftop greenery is fast becoming very popular in Singapore. Over the past few years, more and more buildings, both private and public, have decided to go green over their roofs. You will find some interesting rooftop greenery along the shopping belt in Orchard Road and many others in the heartlands of Punggol, Queensway and Woodlands.

If you are keen to find out more about rooftop greenery, this concise guide will provide you with useful information and guidelines for this green journey.

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One of the many benefits of greening your rooftop is that a green roof will last longer than a conventional one. It looks more attractive and it also helps reduce the urban heat island effect that is currently affecting many urbanised cities like Singapore.

But that’s not all. Rooftop greenery is also...

BENEFITS OF ROOFTOP GREENERY

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...GOOD FOR THE ENVIRONMENT

Improve air quality

Rooftop vegetation improves the air quality directly by filtering airborne particles in their leaves and branches.

Through photosynthesis, plants on green roofs contribute to maintaining the stability of the atmosphere’s composition.

Better acoustic insulation

Rooftop greenery can reduce noise levels by up to 50 dB.

Bare rooftops and concrete surfaces act as heat sinks, making Singapore’s urban areas 3 C hotter than the rural ones. Rooftop greenery shields bare surfaces from the harsh tropical sun, cooling the urban environment. Are you staying in one of these hotspots?

o

Study of Urban Heat Island in Singapore - Dr Wong Nyuk Hien, 2004

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Conventional RoofHigher surface temperature

Higher indoor air temperature

Higher waterproofing damage

…compared to green roofs.

Green RoofReduces surface temperature

Reduces room temperature

Reduces carbon emission

Reduces rain water discharge

…for cooler and cleaner environment.

Conventional Roof vs Green Roof

Improve rainwater retention

Rooftop greenery improves rainwater retention to help storm drains cope with severe downpour, reducing flash floods.

Rooftop greenery can filter heavy metals and nutrients present in rainwater, keeping our reservoirs clean and vibrant.

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...BRINGS ECONOMIC REWARDS

Create more usable space

In urban areas, rooftop greenery can be used to reclaim lost space and create lush green views.

Reduce cooling resources through better insulation

Rooftop greenery serves as insulation, cooling buildings and leading to savings of up to 15% from improved energy efficiency of air conditioning.

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Provide savings in drainage infrastructure

The ability of green roofs to retain rainwater and to lower peak runoff can aid in reducing the extent of stormwater drainage infrastructure.

Provide space to cultivate vegetables

and food

In urban areas where high-rise dwellers lack space for a garden, rooftop greenery helps to facilitate agricultural production.

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Foster community interaction

Roof gardens atop high-rise residences or office buildings can provide an alternative relaxing setting for neighbours and colleagues to mingle.

Therapeutic effects and improve health of its users

Plants can have a restorative effect, which leads to decreased stress, improved patient recovery rates, and a higher resistance to illnesses.

Facilitate recreational and leisure activities

As there is a high premium for land at street level in the cities, rooftop gardens provide less crowded, less polluted and less noisy spaces for informal recreation.

...IDEAL FOR SOCIAL INTERACTION

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Improve aesthetic appeal

Landscaping has often been used to improve the appearance of the urban environment. Greenery provides visual contrast to the highly built-up city environment and relief for tired eyes.

Hide unsightly rooftop services

Residents and workers in high-rise developments often look down on large expanses of ugly asphalt, tiles, slates and flat roofs. Rooftop greenery provides a cover and creates better visual interest for rooftops.

Integrate well with buildings

A layer of plants can enhance good design or disguise bad design in building developments. Plants add visual interest to plain walls and roofs and soften the ‘straight edged’ features of industrial and commercial properties.

...ENHANCES A BUILDING’S AESTHETIC APPEAL

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TYPES OF ROOFTOP GREENERY

Green Roofs Hybrid Gardens Roof Gardens

Plant Group Grasses and/or groundcovers

Grasses and/or groundcovers and low shrubs

Grasses, groundcovers, shrubs and trees

System build-up height

up to 150 mm up to 250 mm up to 1500 mm

System build-up weight

≤ 150 kg/m2 ≤ 300 kg/m2 ≤ 500 kg/m2

Maintenance Low Periodic High

The above values are estimates. It is advisable to consult a Professional Engineer and landscape experts for the calculation of loads.

There are three types of rooftop greenery - Green Roofs, Hybrid Gardens & Roof Gardens. The basic layers remain the same although designs may differ.

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Green roofs are not designed for public access. They are mainly developed for their aesthetic and ecological benefits.

With their thinner vegetation support layer, green roofs are lighter compared to the heavier roof gardens. They also support a limited range of vegetation species – with preference for drought-tolerant vegetation with shallow roots.

Requiring minimal maintenance, green roofs are potential value-adding features to both existing rooftops and new buildings. Access to green roofs is limited to periodic maintenance.

GREEN ROOFS

Do not be unduly worried if your green roof looks a little unkempt with overgrown weeds and shrubs - it is part of the natural green roof look.

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There are many ways in which green roofs can be landscaped and set up. Here are the two popular models:

Blanket Model / In situ Green Roof Model

Involves the in situ assembly of green roof components in sheet layers, directly across the roof

Allows lateral migration of water and roots

Has a seamless look

Is customised to fit roof site area

Modular Model

Involves the modularisation of green roof components into standard small trays that are assembled and planted ex situ, and later installed on the roof

Each tray is equipped with a filter layer, drainage and storage cells to hold the substrate media for the plants

Has the appearance of a grid

Vegetation

Growing Medium

Drainage Layer / Water Reservoir

Insulation (optional)

Membrane protection & Root barrier

Roofing Membrane

Structural Support

Typical Cross Section of agreen roof system

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Roof gardens are developed to be accessible for use. They usually incorporate areas of paving and seating. With potentially deeper soil depths to support a wide range of plant species, roof gardens are more suitable for new buildings where the building structure can be appropriately designed to cater for the higher overall loading.

Regular garden maintenance such as mowing, fertilising, watering and weeding is required for such intensive landscaping.

ROOF GARDENS

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A SELECTION OF ROOFTOP GREENERY IN SINGAPORE

Singapore Botanic Gardens HDB Carpark Roof @ 180 Edgefield Plains

Singapore Flyer School of Art, Design and Media, Nanyang Technological University

People’s Association Headquarters Khoo Teck Puat Hospital

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READY FOR ROOFTOP GREENERY?

PROVISION OF ROOFTOP GREENERY TO NEW CONSTRUCTION

Incorporating rooftop greenery into the original design of a new construction will save you time and money. But before deciding on one, do consult the architects to develop a detailed plan for your rooftop greenery.

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Load-bearing capacity

The weight of most green roof systems is between 50 to 150 kg/m2.

Check the current load for the existing roof

The roof’s load bearing capacity is usually found in building’s floor plans

Existing rooftop surface

Ensure that the roof surface is made good prior to installation of any rooftop greenery.

Roof must be smooth and even

Roof must have minimal or zero cracks

Roof must be adequately sloped to fall

The approach for greening an existing rooftop should be a holistic one. Here are some of the considerations you have to take into account prior to installation:

PROVISION OF ROOFTOP GREENERY TO EXISTING BUILDING

Existing waterproofing of the roof

Installing a green roof over a waterproof membrane significantly extends the life of the waterproof membrane and the life cycle of the roof.

Ensure water-tightness on the rooftop before installing any rooftop greenery

Drainage

Blockage of drainage leads to the continuous contact of roof surfaces with water or wet soil. It also leads to unwanted stagnant water which can be a fertile ground for breeding mosquitoes.

Inspect drainage on rooftops and ensure drainage routes are not blocked

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If plants are exposed to a prolonged period of drought, will they grow back subsequently?

It depends on your choice of plants, which should be hardy and drought-tolerant.

What is the average weight of a green roof system? The average weight of green roof system ranges from 50-150 kg/m2.

It is advisable to consult a certified Professional Engineer on the load bearing capacity of the roof structure, regardless of whether you are working with a new or existing building.

Is an irrigation system required?

Green roofs are intended to be non-irrigated. Usually, the drainage layer comes incorporated with an integrated water reservoir. However, green roofs with integrated irrigation are not uncommon.

If you are considering installing irrigation for your green roof, drip-irrigation is the preferred choice. Sub-surface drip irrigation optimises the use of water by directly dampening the substrate.

What is the lifespan of green roof? The lifespan of a green roof is about 20 years. It can last longer when well maintained. The conventional exposed roofs need maintenance every five to ten years.

FREQUENTLY ASKED QUESTIONS (FAQs)

Will a green roof affect my waterproofing?

Correct installation of a green roof will not have any adverse affect on the waterproofing. The additional layers of a green roof can protect the roofing membrane from UV rays, extreme temperature fluctuations and puncture. The reduced stress can double the waterproofing’s serviceable life. Is rooftop greenery expensive to maintain? Maintenance costs vary. You can work with your contractor to design a solution to fit within your budget. For the lowest cost, consider a sustainable green roof where plants are allowed to flourish together as nature intends. Maintenance is infrequent and this is the best choice to achieve biodiverse, environmentally friendly rooftop greenery.

CUGE STANDARDSThe CUGE Standards is a set of written guidelines for voluntary adoption in the landscape and horticulture industry. They are written through a formal process that involves consultation with relevant bodies and reaching consensus across all interested parties so that the final document meets the needs of business and industry. All standards take the form of either specifications, methods, vocabularies, codes of practices or guides.

CS E 01: 2010 - Guidelines on Design Loads for Rooftop Greenery

The Guidelines On Design Loads for Rooftop Greenery includes suggested landscape materials and their appropriate placement. A useful reference for designers and installers of rooftop gardens.

ISBN 978-981-08-5231-3

CS E 02:2010 - Guidelines on Design for Safety on Rooftop Greenery

The Guidelines on Design for Safety on Rooftop Greenery highlights safety considerations during the design, installation and maintenance phases. A useful reference for designers and installers of rooftop gardens.

ISBN 978-981-08-5232-0

CS E03:2010 - Guidelines on Substrate Layer for Rooftop Greenery

The Guidelines on Substrate Layer for Rooftop Greenery is intended to provide an understanding of the constituting substrate-components, their respective Technical Properties & recommended Performance Criteria, for effective monitoring of the substrate’s overall performance and quality control.

ISBN 978-981-08-7203-8

CS E04:2010 - Guidelines on Filter, Drainage and Root Penetration Barrier Layers for Rooftop Greenery

The Guidelines on Filter, Drainage and Root Penetration Barrier Layers for Rooftop Greenery is intended to provide an understanding of the filter layer, the drainage layer, the root penetration barrier layer and their respective constituting materials. The guidelines will also provide the recommended Technical Properties and Performance Criteria for the effective monitoring of the layers’ overall performance, design and installation considerations.

ISBN 978-981-08-7206-9

SUGGESTED READING

PUBLICATIONS

Selection of Plants for Green Roofs in Singapore (2nd Edition)Editors: Tan Puay Yok & Angelia Sia

This handbook presents a selection of over seventy plants that are suitable for green roofs in Singapore.

ISBN 978-981-07-0052-2

Introduction to Vertical GreeneryEditors: Derek Chan & Kelly Chiang

An introduction to vertical greenery systems, some basic principles for set-up, a quick look at classification of systems, and largely with details on the vertical green systems at Hortpark.

ISBN 978-981-08-1623-0

Vertical Greenery for the TropicsEditors: Kelly Chiang & Alex Tan

This publication outlines the benefits, technical know-how, and considerations for design and maintenance in the implementation of vertical greenery in Singapore and it will serve as a useful resource for policy makers, city planners, developers, students and professionals in the architecture, landscape and horticulture industries, who will be able to glean a greater understanding of current trends, technical and design considerations as well as the advantages of vertical greenery.

ISBN 978-981-08-3973-4

National Parks Board Headquarters Singapore Botanic Gardens 1 Cluny Road, Singapore 259569 Tel: (65) 64717808, Fax: (65) 67621383 Email: skyrisegreenery@nparks.gov.sg

www.nparks.gov.sg/skyrisegreenery