Green Roof Guide v2

8/8/2019 Green Roof Guide v2

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Guide to Green Roofs

Visit us at: 11 – 12 FEBRUARY MANCHESTER CENTRAL

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SCHOOLSEXHIBITION & CONFERENCE

09

03 - 05 march 2009, earls court, london



Contents

What is a Green Roof? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

ABG and Green Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

The History of Green Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Types & Terminology - Extensive . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Types & Terminology - Intensive . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Types & Terminology - Brown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Types & Terminology cont. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Components cont. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

Extensive Green Roof Drainage - Finesse Roofdrain . . . . . . . . . . . .10

SUDS and Rainwater Attenuation . . . . . . . . . . . . . . . . . . . . . . . . . . .11

Intensive Green Roof Drainage - Finesse Deckdrain . . . . . . . . . . .12

Benefits of Green Roofs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Benefits of Green Roofs cont. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

Barriers & Myths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Barriers & Myths cont. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Design Considerations cont. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

The Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

ABG Ltd E7 Meltham Mills Road Meltham West Yorkshire UK Tel: 01484 852096 Email: [email protected]



Definition:

“A Green Roof is an intentionally Vegetated roof”

Sounds simple and in essence it is,provided you seek expert guidance

along the way. Finding the rightcompany to assist you at each stage of

the process is the difference betweenthe success and failure of the project.

This brochure is designed to be asimple introduction to Green Roofs andwill hopefully be of great use as a pointof reference.

For project specific advice please

contact our experienced andknowledgeable team direct;

Tel: 01484 852096

Email: [email protected]

Web: www.abgltd.com

1. What is a Green Roof?




2. ABG and Green Roofs

ABG Ltd are a UK based

manufacturer and supplier of specialist geosynthetic materials,offering an extensive range of

geocomposite drainage products,geotextiles, geomembranes, andseveral specialist SUDS related

systems.

We first became involved in Green Roof projects approximately 20 years ago

when developing and launching ourown range of products specifically withGreen Roofs in mind. Since this timewe have supplied products to projects

throughout the UK, Ireland & mainlandEurope. Products supplied includeover 1,000,000 m² of geocomposite

drainage for both extensive & intensiveGreen Roofing projects.

Over the years we have developed a

number of long term relationships withfellow suppliers and installers which inturn has enabled us to offer a complete

ABG Green Roof package specifically

tailored to the needs of the client.

We pride ourselves on being a pioneerand innovator of environmentalsolutions. This includes being a

contributor to CIRIA C644 'BuildingGreener Guidance' which focuses onthe use of Green Roofs.

ABG are working to develop a UK

specific Green Roof which is tailored tothe geographical location and climaticconditions for the UK. We have

established development partnershipswith the University of Sheffield, TheUniversity of East London and

Groundwork UK. These partnershipswill investigate and develop theenvironmental benefits of Green Roofsand provide guidelines and training on

best practice. We will also develop aUK system with native plants toencourage local biodiversity with focus

on sustainable drainage systems.These will consider the hydrology andmaximise the attenuation of water to

encourage plant survival and growth

whilst alleviating storm water run off.




3. The History of Green Roofs


When hearing the term 'Green Roof'people quite often assume that

this is a relatively new concept aimedat helping to counter the effects of

climate change. You may be surprisedto know that the concept of GreenRoofs date back as far as the 6thcentury BC (as depicted below).

More recently, the 20th century saw anincrease in the number of flat roof areas. This was partly due to theutilization of concrete in buildings.The knock-on effect was an increase inthe number of terraced roof gardens.

The 1950's saw the first real period of development in Green Roof technology.This development continuedthroughout the 60's and 70's, meaning

that by the 1980's any technicaldifficulties had been overcome and theGreen Roof as we know it was born.

As our counterparts in mainlandEurope and America have continued toincrease the number of Green Roofsthrough legislation and incentives, theUK has fallen behind. This isbeginning to change.

A combination of progressiveurbanisation and climate change,resulting in more intense rainfall hasincreased the volume of rapid run-off

from hard surfaces. This has beenhighlighted by the recent floodingwhich devastated the South Yorkshireand Humberside areas during 2007(see adjacent picture). Green Roofshave an important role in mitigatingthese effects by forming a sustainable

drainage system (SUDS).



4. Types & Terminology - Extensive

Y ou are no doubt aware that there

are various types of Green Roofsand a number of terms commonly usedto describe them. But what do they

actually mean?

CharacteristicsExtensive Green Roofs are probably

the most common type of Green Roof. An extensive roof consists of a shallowlayer of substrate, typically 20mm to

200mm deep and a variety of droughttolerant hardy plants/vegetation.

Also referred to as a turf roof or sedum

roof

MaintenanceExtensive roofs are relatively self-

sufficient and are not designed andconstructed with the intention of beingtrafficked by pedestrians. Thereforeaccess to the roof tends to be limited

other than for occasional maintenance.Vegetation should be selected with thisin mind.


VegetationMosses, herbaceous plants,sedums and grass.

Waterproofing & root

barrier

Vapour barrier(Optional)

Leak detection layer(Optional)

Roofdrain 25Stores and drains water,incorporates Geotextile filtertop and attenuation &

protection blanket bottom.

20-200mm substrate0-200mm substrate

LightweightRoofdeck

Insulation



Unlike extensive Green Roofs an

intensive Green Roof can be assimplistic or as complex as the clientdesires.

CharacteristicsIntensive roofs consist of a deep soillayer, typically 150mm to 1500mm.

Due to this soil layer there is greaterscope when it comes to planting. Theroof can be viewed very much like atraditional garden area and within

reason can be landscaped accordinglyto include trees, lawns, flower bedsand paved areas.

Also referred to as a roof garden or

living roof.

MaintenanceGenerally speaking when it comes tomaintenance an intensive Green Roof requires the same level of care and

attention as any traditional garden.

5. Types & Terminology - Intensive


150-1500mm substrate50-1500mm substrate

Roofdeck

Insulation

Vegetation A range of plants includingtrees and bushes.

Waterproofing & root

barrier

Vapour barrier(Optional)

Leak detection layer(Optional)

Deckdrain 25Drains water, incorporatesGeotextile filter top.




The term Brown Roof is commonlyused to refer to a roof where the

vegetation is intended to replicate theexisting brownfield habitat.

With an increasing number of

developments being undertaken onbrownfield land, Brown Roofs canpartly mitigate this loss of habitat.

CharacteristicsThis type of roof can be seeded like

the intensive or extensive roofs or self colonised. Please note that seedingdoes increase the biodiversity potentialof the roof in the short term.

Also referred to as a biodiverse or

rubble roof.

MaintenanceSimilar to that of an extensive Green

Roof. Minimal maintenance isrequired. Aggregate & vegetationwould be determined by the

biodiversity objective the client would

like to achieve.

6. Types & Terminology - Brown



Semi intensive/amenity

There are many projects where theGreen Roof does not fit neatly intoeither an extensive or intensive

category. These include some of thecharacteristics of each type and aretermed semi intensive or amenity roofs,

as they are usually intended forrecreational purposes.

The roof can include hard and softlandscaping which can have a variable

depth and type of substrate. Trees andshrubs that require deeper soil can beaccommodated in planted or raised

beds.

An amenity roof often includes watermanagement by means of SUDS,

attenuation, drainage layers, rainwaterharvesting and irrigation.

This can and should be designed with

the geographic location andattenuation requirements tocomplement the UK's environmental

needs.

Podium Decks

Many modern developmentsincorporate landscaped roofs, atterrestrial level, for example above

basement areas and shoppingprecincts. These areas are commonlyreferred to as a podium decks.

The deck areas themselves help createadditional usable space in populoustowns and cities, as car parks orrecreational parks. Whether the

intension is to create a hard or soft

landscaped area it is important to

consider the design implications of thedeck. Key considerations include:protection of the waterproofing,

drainage, water retention, outlets anddesign loads.

For large areas such as car parks or

recreational spaces it is imperative thatconsideration is given to provision of adequate subsurface drainage below

the topsoil layer and paving. In manycases a geocomposite drainage layerprovides subsurface drainage andprotection to the waterproofing.

7. Types & Terminology cont.





8. Components

Waterproofing & InsulationSelecting an appropriate waterproofing

and insulation system is acheived on aproject specific basis. For reference,

virtually any type of roof structure andwaterproofing is suitable to have aGreen Roof including new build andretro-fit. Please contact ABG direct for

further assistance.

The U Values for Green Roofs is, at the

moment, under detailed study andcomprehensive tests have not yet beenestablished. Green Roofs are proven tohave a cooling effect in summer andwe are currently working to determine

whether they assist the insulationagainst heat loss in winter. Until the

findings are published Green Roofs stillrely on the usual insulating layer tomeet specification.

Plants/Vegetation

Plants are selected on a projectspecific basis. Plant choice shouldreflect air pollution, location, building

height, shade, weight limitations, levelsof maintenance etc. The choice is also

dependent upon what the client wantsto achieve, i.e. does it need to be green

from day one?

For intensive roofs there are fewlimitations. For extensive roofs thereare 4 main options when it comes to

vegetation & planting:

Pre-grown Mat - a vegetation mat where the

material is grown to maturity, rolled up and supplied in the form of a mat. This can be

either sedum, turf or meadow plants to

create an instant green effect.

Plug Planting - ideal for smaller projects.

This involves planting species such as

sedum, typically 20 per square metre. For a

fuller cover you can incorporate cuttings or simply increase the number of individual

sedums per square metre.

Brown roof vegetation - replicating the

existing site conditions on the roof.

Hydro seeding - the process of spraying a

specially mixed slurry comprising of water,

seed, mulch & fertiliser directly on to the substrate. It typically takes 12-18 months for

full coverage.



Substrate

The substrate used in Green Roof projects can be designed specifically tosuit each project and this can be varied

to meet the requirements of thevegetation and surrounding ecosystem.

The substrate can range from low

nutrient site specific medium such as alimestone mix for calcareous grassesand plants, to a composted nutrientmix to support geophytes such as

snow drops or daffodils and a range of herbacious plants and other nativeperennials.

The most common mix for extensiveGreen Roofs is a free drainingformulated layer consisting of organic,

inorganic, mineral and recycledcomponents, sometimes sintered clayor slate is added to aid the absorption

of rainwater, the material is lightweightand helps minimise weight on the roof structure.

The most common mix for intensive

Green Roofs uses a denser and slowerdraining substrate. This consists of both organic and synthetic materials to

simulate a topsoil type material whichcan support a wider variety of vegetation.

Edging DetailWhilst Green Roofs are accepted as fireresistant, additional fire preventionmethods, such as a firebreak, should

be taken in to consideration at thedesign stage. The need becomesmore prevalent in the case of extensive

roofs, primarily due to their shallowlayer of substrate and general lack of irrigation.

A typical firebreak would consist of a300mm wide layer of 20-40mmrounded stone or decorative gravel.

This layer should be equal to the depthof the build up and run parallel with theperimeter of the roof.

9. Components cont.


Roofdeck

Insulation

Firebreak

300mm typical



10. Extensive Green Roof Drainage - Finesse Roofdrain

ABG Ltd E7 Meltham Mills Road Meltham West Yorkshire UK Tel:+44(0)1484 851 562

Drainage and water storage areparticularly important components

in any Green Roof project. As amanufacturer and supplier we have

developed drainage and filter productsto suit both intensive and extensiveroofs.

Extensive Green Roofs consist of a thin

substrate growing layer. During dryspells this substrate would dry out

quickly, impacting upon the plantsthemselves.

Finesse Roofdrain is a lightweightwater storage geocomposite primarilyintended to solve this problem. In

addition to providing drainage theperforated Roofdrain core (see

adjacent picture) provides a waterreservoir for plant roots, storingbetween 4 and 20 litres per m² and inturn aiding sustained growth during dry

spells.

Finesse Roofdrain attenuates the

rainfall run off and is therefore an active

SUDS system. This ability to controlthe discharge rate is a key criteria in

overcoming planning constraints.



As much as 95% of rainfall onundeveloped land is naturally absorbedinto the vegetated surface only 5%becomes run off. Within a catchmentarea the streams and rivers haveevolved in response to this minimaldischarge from the land. Urbanisationand development of land creates hardimpervious surfaces that absorb only5% of the rainfall, a huge 95% of therainfall becomes run off. The streamsand rivers cannot accomodate thishuge influx and the result is severeflooding and erosion.

The only viable solution botheconomically and ecologically, is toensure that the built environment has asimilar rainfall response to the natural

land. One method is to build SUDStanks below ground to store excesswater until the rainfall has abated. Theother method is to construct GreenRoofs so that the building directlyreplicates the land on which it is builtand discharge is reduced to less than5% as run off.

A Green Roof is the natural way toattenuate rainfall it can also be incertain situations the most economicalmethod in addition a Green Roof willfunction in areas where a SUDS tankwill perform poorly e.g clay,contaminated land, aquefious etc...

For a Green Roof to provide a SUDSsolution the geocomposite, waterattenuation and substrate layers arespecifically designed wih enhanced

water storage capacity. Storage

capacities approaching 100l per m2can be acheived this way. This storedwater can be released slowly or usedas grey water or irrigation for thevegetation.

A Green Roof provides ecologicalbenefits to the local flora and fauna thata SUDS tank cannot.

11. SUDS and Rainwater Attenuation




12. Intensive Green Roof Drainage - Finesse Deckdrain

As intensive Green Roofs have a far

greater depth of soil this layer isless likely to dry out but requires gooddrainage to ensure that the roof does

not become water logged.In this instance we offer FinesseDeckdrain. This product consists of a

combination of either a 12 or 25mmthick cuspated core with a geotextilefleece bonded to the upper face.

Finesse Deckdrain provides excellentdrainage over the whole base area of the soil layer in addition to providingadditional waterproofing protection.

Please note: both Deckdrain &Roofdrain incorporate a filter fleece and

can be rolled out during installation asan all in one layer.

The deck drain product is alsoenvironmentally friendly and can be

made of 95% recycled material, therebyhelping reduce the carbon footprint.

Also in house manufacturing enables a

range of different role sizes and widthswhich reduces waste and makes theproduct very cost effective.





Stormwater ManagementIts design works by retaining water, insome cases as much as 90%, therebysignificantly reducing storm water run

off and playing an important role inreducing the risk of flash flooding.

Added protection for thewaterproofing layerThe build up above the waterproofingmembrane is proven to greatlyincrease its life expectancy. The build

up helps reduce the impact of temperature fluctuations, therebyreducing thermal stress. Anotherbenefit of Green Roofs is that severalwaterproofing companies have realisedthat a Green Roof actually protects thewaterproofing from thermal differences

in temperature and in turn, stoppingexpansion and contraction whilst alsoprotecting the waterproofing fromharmful UV rays. This prolongs the lifeof the waterproofing and many partnerwaterproofing companies haveextended their warranties when a

Green Roof is installed.

Extracts pollutants

The vegetation & plants filter dust andpollution from the air and water thusreducing the amount of chemicals and

pollutants that reach the river networks.

Aid planning consent Although there are no regulations inplace with regards to Green Roofs,many local authorities favour proposals

that incorporate sustainable drainagesystems.

13. Benefits of Green Roofs




Mitigating the Urban Heat

Island effectCity centres are known to have highertemperatures than surrounding rural

areas. This is due to a number of factors, many of which are linked to thespecific heat and impervious nature of

city surfaces such as concrete, tarmacand traditional membrane roofs. Thisis known as the Urban Heat IslandEffect.

Other advantagesGreen Roofs help create a living habitatfor small wildlife & a wide variety of

plant species; create more accessiblespace in densely populated areas;more aesthetically pleasing than a

traditional roof.Noise reduction

A Green Roof is also very good at

reducing low frequency sounds, anextensive Green Roof can insulate upto 40dB and an intensive Green Roof can insulate up to 50dB which can

make a noticable difference especially

near airports.

Reduced air conditioning loadGreen Roofs cool in the summer thus

reducing the energy consumption of the building and decreasing carbonemissions. This helps to reduce the

urban heat island effect.

A study in Toronto estimated that directenergy savings through city wide

greening would result in a reduction inpeak demand and result in a saving of approximately 55,000 metric tones of fossil fuels per year.

BREEAMBy improving the energy performance

of buildings and embracing GreenRoofs not only does it help to meetstandards such as the code forsustainable homes and BREEAM, it

also helps to meet planningrequirements and the revisions to PartL Building Regulations. A development

which incorporates a Green Roof can

earn up 6.2 points on an Eco Homes

score. A Green Roof also contributes tosustainability and enhances local

biodiversity. This provides a solution toenvironmental policy issues whichsaves the developer time and money.

14. Benefits of Green Roofs cont.




15. Barriers & Myths

“Green Roofs are expensive to

maintain”Even though extensive Green Roofs arerelatively self-sustaining, they still

require some form of maintenance. ABG recommend this should be dealtwith in the form of a maintenance

contract. Maintenance for extensiveroofs will typically be required twice inthe first 12 months, then once annuallythereafter. Therefore the overall cost of

maintaining a Green Roof can berelatively minimal.

“Green Roofs cost more”

In terms of initial outlay Green Roofsare generally more expensive thanconventional roofs. However when

taking into account factors such as thewhole life cost of the building, thereduction in other infrastructure such

as stormwater tanks, and the extensionin the life of waterproofing membranesthis additional cost can be easily offset.

Until UK legislation arrives, cost will

inevitably be a determining factor as towhether the Green Roof project goesahead or it doesn't. At ABG we work

with a varied network of specialistsuppliers enabling us to provide eachcomponent of the Green Roof. As

opposed to having a 'one system fitsall' approach, our supply chain enablesus to put forward bespoke systems to

meet the needs of the client, on timeand within budget.

Please contact us for advice onsystems to fit your budget.




“Green Roofs are susceptible to

fire” A fire is actually 20% more likely tooccur on a bitumen exposed roof. In

addition to this Sedums used on mostextensive Green Roofs are succulentswhich do not burn easily. Another

important element is to include forshingle fire breaks around theperimeter of the roof.

“A Green Roof will leak”

On the contrary, a Green Roof willactually help protect the membranefrom the weather, whilst the root barrier

will prevent any damage to thewaterproofing caused by plantintrusion.

Please ensure the waterproofing is leaktested prior to installation of the greencomponents. Contact ABG for advice

prior to installation.

16. Barriers & Myths cont.




17. Design Considerations

There are a number of important

issues to consider when planningand designing a Green Roof.

Structural Loadings

The introduction of a Green Roof willhave loading implications for thebuilding. It is vital to consult a

structural engineer at an early stage.This will enable you to determine anyconstraints you may be under and inturn help decide which type of Green

Roof system to implement.

Example:Saturated

Type Weight (Kg/m²)

Extensive 60-150

Intensive 200-500

Compressive strength A factor which is commonlymisinterpreted is the structural

requirements for the drainage layer anddescriptions such as 1000 kPa are

sometimes mentioned.

This is significantly above the

requirements of the roof and indeedmost roofs do not need anything above150kPa. From the diagram to the right,

which is from independent test data, itshows the pressure exerted by a fullyloaded construction vehicle. As you

can see the actual loads exerted forGreen Roofs and podium decks areactually quite low.

The chart shows the compressive

strength of a 500kPa product and inparticular that a product designated as500kPa working load, actually has a

peak compressive strength of 1200kPa.This means that a 500kPa product canaccommodate high short term

construction loads and will also providelong term performance under designloads without danger of collapse.

Roofdeck

5T wheelLoad HGV

150m

Deckdrain

1200

1400

1000 m ² )

600

800

s s ( k N /

200

400 S t r e

0

0% 10% 20% 30% 40% 50% 0%0% 10% 20% 30% 40%

Strain

Compression of Deckdrain 1250S drainage core




Access & Maintenance

Even extensive roofs need occasionalmaintenance. Provisions must bemade for this. The BRITISH STANDARDS

INSTITUTION state that all new buildsmust provide access to the roof area toenable a minimum of 2 inspections per

year. The installation of a Green Roof does not change this, but if there is noedge protection on the building, healthand safety regulations require anyone

within 2m of the edge to wear a safetyharness.

Drainage & Water Retention

Drainage and water retention are keyelements to consider when designing aGreen Roof. The specific type is

entirely dependent upon the proposedlandscaping element. Ensuringadequate water retention requirements

are met will aid the long term survivalof the vegetation whilst adequatedrainage provisions will prevent poolingand in turn prevent the plants

becoming saturated.

Please note: Irrigation will be required

immediately after installation. Forfurther information please contact ABGdirect.

Geographical LocationGeographical location and orientationare also an important part of designing

the roof. Which area of the country andthe amount of average rainfall in thatarea determines the type of uses andneeds for the Green Roof. Biodiversity

and drainage are then designed intothe roof from these requirements. Thedirection in which the roof faces and

amount of sunlight the roof receiveshelps to determine the types of vegetation for a sucessfull roof.

18. Design Considerations cont.




19. The Future

As the world begins to understandclimate change is happening and

something needs to be done theawareness and understanding of Green

Roofs is increasing. This is helped byevents including "World Green Roof Congress", the development of GreenRoof organisations such as "Living

Roofs" and research centres likeSheffield University who are developingGreen Roof exhibition centres and

forums.

Unlike our counterparts in Canada, America and mainland Europe theGreen Roof policy is not part of our

legislation yet but it is coming!

New reports that have recently been

released have announced that by 2015there has to be a zero storm water runoff rate for all new buildings.

There are Local authorities and

developers in the UK who recognisethe importance of the Green Roof

system in the fight against climate

change and the need for sustainableurban drainage systems, they are

proposing Eco friendly plans to putGreen Roof into policy.

Sheffield development framework (partof the Sheffield city council) havealready consulted on "Emergingoptions" for new policies and are now

consulting on preferred options.

Option 1 Green Roofs will be required

only on medium or large developmentswithin 100mtrs of the green belt, greennetwork, waterways, parks and openspaces greater than 1 hectare.

(Medium or large = Non residential developments

over1000sq meters and residential over 10 dwellings.)

Option 2 Green Roofs will be required

on all medium and large developments.

Option 3 Green Roofs will be requiredon all developments.

As all parties ranging from

manufacturers and suppliers to local

authorities and developers continue to

work in conjunction with one another,the future expansion of Green Roofs

within the UK is inevitable.




Overall Green Roofs offer a wide

range of social, economic andenvironmental benefits. These rangefrom significant ecological issues, such

as helping to mitigate climate change,whole-life cost benefits or somethingeven simpler, such as "It looks nicer

than a traditional roof". Whatever thekey influences are, it looks like GreenRoofs within the UK are set for asustained period of growth.

Going forward Green Roofs will not justlook to attenuate water but to reduceflooding and erosion. These will

provide an alternative beneficialsolution to SUDS tanks.

The purpose of this booklet is to help

give you an overview of key factors totake in to account when proposing,designing or specifying a Green Roof.

Seeking advice from the experts isessential to the projects success.Therefore next time you are thinking of incorporating a Green Roof system in

to a new or existing development don't

hesitate to contact ABG direct and letus assist you through every stage of the process from design through to

installation.

20. Summary




Think Green Roofs...

...Think ABG




Sustainable Roofing Solutions

Working in partnership with;

Green Roof Guide v2

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