Greenscape Summer 2021


Ensuring Best Practice for Green Roof & Solar PV Projects MAGAZINE


GRO Code in Detail

Blue-Green Roofs

Green Talk: Q&A

Academic Corner: Biosolar

News, Views and Projects

Green Roof Mythbusters

In collaboration with the Green Roof Organisation




Technical advice, the industry quality stamp and fantastic

profile-raising opportunities—for all roofing disciplines

NFRC sets the highest

standards for work across

all roofing and cladding

disciplines. But we’re much

more than the industry’s quality

assurance stamp. Membership

of the trade association offers

contractors and suppliers a

range of powerful technical

and commercial advantages.

These include a profile on our website

and directory listing, making your

business easier for clients to find. Plus

exclusive access to technical support and

updates, an exclusive health and safety

app, and advice on training provision.

For suppliers, key benefits include

numerous opportunities to engage with

roofing contractors all over the country.

And as the voice of the roofing sector,

NFRC makes our members’ views

heard where it matters most. We work

with government, standards bodies

and training providers to promote the

interests of the industry, and of the

construction market as a whole.

3 | Working Towards Zero Avoidable Waste in the Roofing Sector

NFRC trade

membership benefits

NFRC supplier

membership benefits

Call 020 7638 7663 or visit to request our

benefits brochure—and find out more

about what NFRC membership can do

for your business.


Competent Person Scheme:

self-certify roof refurbishment

to Building Regs

Roofing operatives

competency accreditation

UK’s premier event for

the roofing industry

Supporting hardship, training/

upskilling, volunteering

and environment

Contractors with knowledge,

skills and experience of

heritage roofing systems



Matt Downs

Editorial Director

07963 330774

Green roof manufacturers, installers and enthusiasts from around the

world came together to celebrate World Green Roof Day on June 6th 2021.

Building on the success of the launch event in 2020, organisers say the

day attracted greater global involvement, with individuals from as far-afield as

Malaysia, the Faroe Islands and Mumbai getting involved using the #WGRD2021.

Whilst #WGRD2021 still took place largely online, it is hoped that the 2022 event will

involve more face-to-face and live interaction. Organiser Chris Bridgman told us: “We

hope to make next year’s event more interactive, with a range of opportunities for

people to engage with green roofs, from taking part in rooftop tours, to attending

workshops.” Read more on this year’s event on page 12.

World Green Roof Day was the perfect platform for GRO to officially launch the updated

version of the GRO Green Roof Code, and we provide a breakdown of the key points and

additions to the latest version for users to make note of on page 10 of this issue.

Sika Ltd. also used the event to promote its new green roofing range, and in this issue we

take a closer look at the new offering, as well as some key installation tips on page 28.

Elsewhere in this issue, Maggie Fennell of Boningale Ltd. provides planting and

maintenance advice as she dispels our latest green roof myth (page 14); we hear about

Green-tech’s irrigation solution for a London rooftop planting scheme (page 30); and

take a look at Polypipe’s important blue-green roof project in Manchester (page 34).

So read on for all this and much, much more!

Front cover image is courtesy of Sika Ltd. Read

about the manufacturer’s new green roofing

range on page 28



Publishing Director: Andy Dunn

DD: 01892 732 047

Mob: 07963 330777


Commercial Manager: Jake Roxborough

DD: 01892 732 047

Mob: 07956 133314


Brought to you by the publishers of Total Contractor, the content

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reflect the views of the editor or publishers and are the views of

its contributors and advertisers. The digital edition may include

hyperlinks to third-party content, advertising, or websites,

provided for the sake of convenience and interest. The publishers

accept no legal responsibility for loss arising from information in

this publication and do not endorse any advertising or products

available from external sources. No part of this publication may

be reproduced or stored in a retrieval system without the written

consent of the publishers. All rights reserved.

Registered office:

1 Forstal Road, Aylesford,

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Supported by:



Green Talk:


Keith Hills, MD

of ECO Green

Roofs is in the

hot seat!




Dr Tom Young of

STRI Group digs

into the detail of

green systems!


Navigating the

‘solar coaster’


Barnes of

SolarEdge talks

all things solar.

Keith discusses his career so far, past

projects, challenges and opportunities

within green infrastructure, plus why

our reconnection with nature is great

news for the sector.

Find out more on page 18.

In the first instalment of his new,

regular column, Dr Tom looks at

biosolar roofs in more detail, focusing

on their key benefits and installation


Find out more on page 24

Christelle explains why the solar PV

sector of today is drastically different

to that of ten years ago, and why this

presents a number of opportunities for

those who want to do things right.

Find out more on page 40 • GREENSCAPE SUMMER 2021 3



06 Next stop sustainability

Bridgman & Bridgman has installed

green roofs on a number of bus

stop shelters in Milton Keynes

06 The British Association of

Landscape Industries has

launched two new training courses

08 Take a look at GRO’s work

with RBG Kew to help the public

reconnect with nature


10 Cracking the Green Roof Code

We take a closer look at the latest

updates to the GRO Code

12 The increased interaction with

#WGRD2021 is a great sign for the

green roof sector...

22 Dr Anna Zakrisson of Green

Roof Diagnostics talks all things

stormwater management

32 The shape, design and location

of this green roof project produced

a number of challenges for Sika and

Progressive Systems




36 What are the prospects for

the solar PV retrofit market?

Marley’s Stuart Nicholson and Stuart

Elmes of Viridian Solar give their

take on things...

40 Greenscape caught up with

Christelle Barnes, of SolarEdge, to

discuss the ups and downs of the

‘solar coaster’ and why she’s positive

for the sector moving forward


14 Mythbusters Boningale Ltd’s

Maggie Fennell talks planting and

maintenance as she dispels our

latest green roof myth

18 ECO Green Roofs’ Keith Hills

tackles our Q&A and explains why

the public’s reconnection to nature

is a great sign for the sector

24 Dr Tom Young of GRO and STRI

Group looks at biosolar roofs in

more detail in his first Academic

Corner column • GREENSCAPE SUMMER 2021 5




The British Association of Landscape

Industries has launched two new

training courses at Supervisor and

Manager level, to join its popular

Register of Land-based Operations

(ROLO) Operative level course.

It says the new courses will enable

industry Supervisors and Managers

to receive the appropriate level of

health and safety training and apply

for their LISS/CSCS cards.

The Supervisor and Manager level

courses have been developed by

the Association to meet the training

needs of the land-based sector. They

are fully supported and approved by

CITB and Build UK as equivalent to

the CITB SSSTS and SMSTS courses.

Wayne Grills, Chief Executive of the

British Association of Landscape

Industries, said: “Over the years our

provider network has been delivering

ROLO training to the industry, we

have seen standards across sites

consistently improving. In response

to the increasing call for higher level

courses from businesses who are

seeing how useful ROLO training is,

we have developed these two brand

new courses to continue our legacy

of improving standards.”

For more information, please visit


Bridgman & Bridgman, working

with living roof designer Dusty

Gedge of the Green Infrastructure

Consultancy, have installed what

is described as “a pioneering new

green roof system” to 15 bus stop

shelters for Milton Keynes Council.

Considered to be carbon negative,

it is said to be the first time this

approach has been undertaken on

such a scale anywhere in the world.

The size of the shelters in Milton

Keynes range between 8-16m 2 .

Each of the 8m2 bus stop shelter

green roofs is constructed from

312kg of recycled waste plastic – the

equivalent of 18,720 carrier bags

– and delivers 480kg of direct CO 2

emissions savings via the use of endof-life

recycled plastics.

In total, the companies involved

say construction of the new green

roof bus stop shelters has recycled

over 5 tonnes of waste plastic – the

equivalent of 332,280 carrier bags –

and delivered over 8 tonnes of direct

CO 2 emissions savings. The first

green roof on a bus shelter in Milton

Keynes was installed by Bridgman

& Bridgman in 2016 as part of a

Britain in Bloom initiative. Since

then, cities around the world have

been greening bus stop shelters,

including 316 shelters in Utrecht, The

Netherlands. The city of Hamburg,

Germany, has committed to 4,200

greened shelters, sometimes

referred to as Bug or Bee Stops.

UK green roof bus shelter locations

include Manchester, Newcastle,

Leicester and Brighton.

Milton Keynes Council has also

worked with contractor Axiom to

green a further fifteen bus shelter

roofs using a modular green roof

system. Cllr Jenny Wilson-Marklew,

Cabinet Member for Climate and

Sustainability at MK Council, said:

“As well as providing a habitat for

many small pollinating creatures,

and improving biodiversity, the green

roofs will be a great signal for MK’s

green and sustainable ambitions.”






Building on our reputation in roofing, Sika’s complete

green roofing system provides many sustainable

benefits. And on one project, it has even provided

a grazing area for a flock of Dutch Spotted Sheep,

who help reduce maintenance costs.

Sika’s complete green roofs help to manage storm

water, improve the building’s thermal performance

and enhance biodiversity in nature.

SikaRoof ®


Blanket UK

SikaRoof ®


Bio-diverse UK

SikaRoof ®

Rigid Drainage

Layer 20 UK

SikaRoof ®

Protection Fleece

P-225 UK







The Sempergreen Group has

expanded its stock locations with a

UK HUB near Manchester.

From this new location, Sempergreen

can deliver its quality vegetation

blankets quickly from local stock, for

both large and small orders.

This location will stock various

vegetation blankets for green roofs,

including the most commonly used

Sedum-mix blanket, but also the

Wildflower blanket for biodiverse roofs.

Sempergreen says opening this new

location fits with its mission and

vision to contribute to a green and

livable world and to counteract the

consequences of climate change

and environmental pollution. To keep

its ecological footprint as small as

possible, Sempergreen operates from

local nurseries as much as possible.

The Sempergreen Sedum blankets

can be applied for both regular

and lightweight roofing solutions.

Sempergreen says it has also

developed the perfect solution

specifically for steeply pitched roofs.

Contact Nicola Leyland (below) via for

further info on Sempergreen products.


Members of the Green Roof

Organisation (GRO) have worked

together to install green roofs on 20

play structures at the Royal Botanic

Gardens (RBG) Kew, which is on

a mission to encourage people to

reconnect with the incredible nature

that surrounds them after over a year

spent largely indoors.

This summer, the leading plant

institute and UNESCO World Heritage

site is delighted to invite visitors on a

journey to uncover the Secret World

of Plants, supported by Starling Bank.

At the heart of the festival are six

‘plantscapes’ – large-scale, immersive

biomes representing contrasting

landscapes found across the UK,

but rarely experienced in such vivid

detail. Each landscape – sand dune;

moorland; marsh and meadow;

hedgerow; woodland; and urban

– is inspired by the UK’s priority

habitats in the Biodiversity Action

Plan: an internationally recognised

programme addressing threatened

species and habitats. Visitors are

invited to literally place themselves

within these monumental landscapes

via playful head-holes, and get a

new, unique glimpse into these

incredible, biodiverse and threatened

UK landscapes designed by Seattlebased

artist Vaughn Bell.

The RBG Kew says it is passionate

about increasing public

understanding of plants and the

important role they play in human

life. With over 350 scientists and

work spanning over 100 countries,

RBG Kew says it is leading the way

in discovering and describing new

plant species, researching their uses,

assessing their risk of extinction,

and conserving them for future

generations. It points out that plants

are our life support – they provide

us with food, materials, medicine,

and more – and RBG Kew has one

of the largest and most important

collections in the world. Contributing

to the ‘plantscapes’, the 20 colourful

structures include several pitched,

sedum and wildflower, biodiverse,

edible and turf roofs that enable

children to discover that rooftops of

any size can be living and encourage

more greening in urban environments.

Through initial contact from RBG Kew

with GRO member Bauder, the project

was led by Mike Cottage of The Urban

Greening Company with materials

generously supplied by Bauder,

Harrowden Turf, Sempergreen and

Optigrun. Representatives from GRO

member organisations then came

together, including Radmat, Pritchard

& Pritchard, Eco Green Roofs, The

Urban Greening Company and

Bridgman & Bridgman to install the

green roofs over three days.





Solar Energy UK has praised the

Climate Change Committee’s call for

“long-term ambition” around solar

and other renewables, as a means to

reducing greenhouse gas emissions

in line with the Government’s

commitment to achieving a net zero

economy by 2050.

The trade association says the

report points to analysis from the

International Renewable Energy

Agency that highlights some

solar generation sources as now

producing the cheapest electricity

in history, and draws parallels with

the International Energy Agency’s

recommendation for a rapid buildout

of renewables, particularly solar

and wind, in order to deliver a net

zero power sector by 2035. The

CCC’s recommendations specify that

renewables need to meet 70% of the

UK’s electricity demand by 2035.

Chris Hewett (below), Solar Energy

UK Chief Executive, said: “Green

NGOs, energy trade bodies, and now

the Climate Change Committee are

all calling for the Government to

be ambitious around solar energy.

We need to deploy this affordable,

proven technology as fast as possible

to ensure we can meet the clean

power needs of a net zero economy.

We will go faster with some timely

interventions from Government.”


Flex-R is celebrating after its award-winning project Cwm Mawr came out top in the

‘Best Sustainability’ category at the 2021 SPRA Awards.

Flex-R received the award for its work with contractor Randell and Janes Roofing on a

distinctive project which sits in an area designed as an SSSI (Site of Special Scientific

Interest). Cwm Mawr, in the heart of the Welsh National Park, has been designed by

architects Kinver Kreations as a low impact dwelling that blends seamlessly within its

surroundings. The roof features a large, curved form to echo the surrounding hillside

which has been completed with a green roof. Large windows have also been added to

capture the stunning coastal views.

Requiring a membrane which would be buried beneath a green roof, the architects

needed assurances that the installation would be professional, accurate and backed

by robust warranties.

Tom Kinver, owner of Kinver Kreations, explained: “We have worked with Flex-R

and Randell and Janes Roofing on previous projects and having them again on this

difficult project was so important to us. The experience of the contractors, their

extensive knowledge of the product and the support from Flex-R made every stage of

the project so easy for us.

“Flex-R’s specification team worked closely with us and the roofing contractor

throughout the project. They advised on the correct specification during the tender

stage and recommended their RubberBond FleeceBack EPDM which offers superior

protection and long-term durability. Most importantly for this project, it has been BBA

certified as a waterproofing membrane suitable for green roofs and resistant to root


Due to the sensitivity of the site, which contains rare plants and flowers of particular

interest to science, Flex-R worked with the roofing contractors to carefully plan the

installation and overcome any challenges. This even meant that no heavy machinery

was allowed on the build and all the materials had to be carried by hand down a quarter

of a mile narrow track! Danny Cole, Sales Director at Flex-R, said: “I am immensely proud

of the hard work by our contractor Randell and Janes Roofing and the team at Flex-R

on this project. Cwm Mawr, with its unique RubberBond FleeceBack EPDM membrane

topped with a green roof, is a great achievement by everyone involved.” • GREENSCAPE SUMMER 2021 9




The 2021 edition of the GRO Green Roof Code of Best Practice

continues to hold true to its original values, but also includes

guidance on blue roofs, biosolar roofs and modular green

roofs. Below, the experts at GRO explain more about this

important document…

To find out more about

joining GRO email:


Tweet: @RoofGro

The latest instalment of the GRO

Code was launched on 10th June

2021. It’s the third edition and a

special anniversary edition of the GRO

Green Roof Code of Best Practice, which

was first published in 2011 by the then

newly established GRO ‘Green Roof


GRO and the Code have gone from

strength to strength since its beginnings

as a voluntary organisation of a few

enthusiastic contributors under the

keen eye of former NFRC CEO Ray

Horwood, and GRO is now a Trade

Association registered with Companies


The 10 year Anniversary edition of

the GRO Code continues to hold

true to the original values of making

green roof technology accessible and

guiding best practice. The original

Code was the result of an EU funded

project at the Green Roof Centre,

University of Sheffield. As a result it was

always going to be free to access and

therefore would never be a Standard.

The Green Roof Centre took advice

from and all the other

GRO members to create a document

that demystified and established

performance criteria to specify, design,

install and maintain natural-based living


The 2021 edition of the Code has

welcomed the inclusion of the

increasingly popular and rapidly

developing technology of blue roofs,

biosolar roofs and modular green roofs.

Who is the GRO

Code for?

Green roofs are not ‘rocket

science’ but they are easy

to get wrong in a surprising

number of ways! Therefore,

the language of the Code,

and the comprehensive

glossary, are intended to

make the technology of

green roofs as accessible

as possible. The guidance

held within the Code is

as applicable to an Architect planning

a 10,000m 2 accommodation block,

to a homeowner considering a 20m 2

extension or garden office.

When should you use the

GRO Code?

It is best to consult the Code at the

earliest possible stage in a design or

project plan. Green roofs may be the

last part of the external structure to be

applied, but they have an impact on the

very structure of the building and even

the foundations. The benefits of green

roofs can be found in the Code, these

highlight where costs gained for the extra

loading can be offset by water retention

and biodiversity net gain calculations.

It is also necessary to consider

ongoing green roof maintenance at

the earliest stage. A green roof is an

investment, but it will only perform

to its full potential if it is correctly

maintained. For example, a newly

installed green roof with pre-grown

flowering turf will

need watering for

the first few weeks

and after prolonged

dry spells. With this

in mind, is there a

water supply? Does

it have any pressure?

These things are

easy to change on

paper, but difficult and

potentially expensive

during construction.

Where should the GRO Code

be used?

The UK has a unique and sometimes

frustrating climate. For such a small

country it has a peculiar range of very

dry areas, very wet areas, very windy

areas and lots of areas that have a

blend of these conditions. The Code has

drawn from the vast experience of its

members to produce guidelines that will

perform well in most of the regions of

the UK. If the site you are considering

has additional special environmental

conditions, a green roof specialist should

be consulted. The Anniversary GRO

Code is free and available to everyone

in the UK and beyond, although it is not

specifically designed for climates outside

the UK and Ireland.

Further updates and extensions to the

Code will be developed by the GRO

board and membership, led by the

Technical Committee.


Beneath your green roof you need waterproofing

and thermal insulation that are BBA certified for

the application.

• Extensive sedum, wildflower

and biodiverse green roofs

• Blue roofs

• Thermal insulation




• Waterproofing

Tel: 01858 410372 Email:




With ministers and government bodies getting involved,

increased interaction and some big announcements from those

operating in the industry, #WGRD2021 highlighted a better

understanding of green roofs and a bright future for the sector.

Building on the success of its

launch in 2020, the organisers

of Word Green Roof Day have

announced this year’s event was bigger

and better, with even more engagement

from new countries, including

Argentina, Ghana, Nigeria, Malaysia,

Singapore, Vietnam, Kuwait, Lithuania

and Albania. The event also even

welcomed interaction and green roofs

from Mumbai and the Faroe Islands!

Using #WGRD2021, companies and

individuals shared images and videos of

green roofs and rooftop gardens from

around the globe. Standout interaction

included Emporio Armani celebrating

funding a green roof on a children’s

hospice in the UK, new telephone

booths with green roofs being launched

in Austria, and an open rooftop tour

was hosted in Rotterdam!

In addition to celebrating green roofs,

some used this dedicated occasion

to officially launch new products

and initiatives, including the 2021

Anniversary Edition of the GRO Code

in the UK; Sika launching a brand-new

green roof product range (see page

28); and a new eLearning Green Roof

training course from Lantra (UK)


Future plans, some of them extremely

grand and highlighting the scale of

potential projects within the green

infrastructure sector, were also revealed

on the day, with The Netherlands

announcing plans to build accessible

roof gardens at high altitude, connected

by air bridges, by 2025! Announcing

this huge project, a statement was

released on #WGRD2021 explaining that

the organisations ROEF and Rooftop

Revolution signed a “green alliance

on top of a sustainable roof”, with the

“roof activists” aiming to “strengthen

each other in making even more green

metres on our roofs”. Alexander van der

Meer, co-founder ROEF explained: “We

want to launch bigger initiatives with

lasting impact, such as the creation of a

roof park. For this we need an activating

knowledge partner, and that is Rooftop


Jan Henk Tigelaar, Director of

Rooftop Revolution, also touched on

the importance of collaboration and

“joining hands”, when discussing the

huge rooftop park at high altitude

project: “ROEF’s experience and

network gives us the space to push our

boundaries in the field of awareness

and activation.”

Further evidence of the impact of

#WGRD2021 and the increased focus on

greening within cities was highlighted

by the news that the global event was

endorsed by the Austrian Environment

Minister and the Welsh Government

Minister for Climate Change; organisers

say it also received the support of the

United States Environmental Protection


Further evidence was provided by the

news that in the days following the

event, the city of Milan, Italy, announced

it will map all of its existing green roofs

and walls.

Chris Bridgman, of Bridgman &

Bridgman, who launched World


Green Roof Day alongside Green

Infrastructure Professional and

Founder of, Dusty

Gedge, explained that the increased

reach and support of this year’s event

was clear evidence of the greater

understanding of the important role

of green roofs, and the impact they

will have on the built environment

moving forward: “The wider reach

of this year’s World Green Roof Day

in terms of global engagement and

variety of support far exceeded our

expectations. There is growing support

and understanding of the green roof

sector and this was particularly evident

when the Day received endorsement

from Environment and Climate Change

Ministers, as well as government


Chris is also pleased with the way

#WGRD2021 has established itself as a

key date for those within the industry,

and explained that plans are well

underway for more live interaction with

green roofs – alongside online activity

– for #WGRD2022, as Covid

restrictions are hopefully

relaxed: “Within the

sector, World Green

Roof Day has become

a key focal point for

suppliers and related

organisations to

come together to

promote the benefits

of green roofs and

celebrate exemplar


“We hope to make next year’s event

more interactive, with a range of

opportunities for people to engage with

green roofs – from taking part in rooftop

tours, to attending workshops. We’ve

been able to cultivate a strong following

online and we are confident that we

can capitalise on this as economies, and

countries, open up again.”

Find out more about

World Green Roof Day


Images top to bottom. Jan Henk Tigelaar,

Director of Rooftop Revolution (left)

and Alexander van der Meer, co-founder

ROEF, signed a “green alliance on top

of a sustainable roof”; @urbanscapes -

Amsterdam; Sika launched a new green roof

range on #WGRD2021 – find out more on

page 28. Further images from #WGRD2021

available at • GREENSCAPE SUMMER 2021 13




Maggie Fennell, of Boningale Ltd, gives her thoughts on this misplaced belief regarding planting

on extensive green roofs, and outlines some of the different species which can be used, as well

as the maintenance considerations which must be taken into account...

Extensive green roofs are

traditionally dominated by

sedums for their extreme

drought tolerance, or wildflowers

chosen for biodiversity support and

preference for low nutrient substrate.

These survival skills make them natural

candidates to cope with extreme

weather conditions and the harsh

growing environment of a rooftop.

Low-growing sedums are often chosen

to survive on shallow substrate depths

and can provide fairly uniform winter

cover. Wildflowers are mostly deciduous

and create big bursts of flowers and a

longer display of colour, with greater

provision of nectar and some reaching

a height of half a metre or more. This

variety of plant forms and

flower types is great for

wildlife, and even once

they have finished

flowering and died

back they provide

valuable resource

to insects and the

local ecosystem.

The removal of dead

material should be

considered at an early

stage of development to

ensure there is adequate access

to bring excess biomass down from the

roof, and scheduled in accordance with

biodiversity objectives – refer to section

5 of the GRO code for more details.

However, dispelling the myth mentioned

earlier, there are many more plant

communities that can thrive in these

conditions, particularly when you have

the full 150mm substrate depth to

allow for extra

root growth

and storage of

water that will be

accessible to the

plants. These may

be particularly useful

to consider for extensive

roofs that are overlooked, or

those with challenging limitations

for removing excess plant material

but requiring a varied plant range for

biodiversity and aesthetic performance.

Coastal, alpine and steppe/prairie

ranges that can offer a variety of lowgrowing,

evergreen or semi-evergreen

plants with a wide variety of forms and

flowering seasons would fit the bill – as

long as they are hardy, drought-tolerant

and happy with low nutrient availability.

Look for plants with silvery, hairy or

waxy leaves, dwarf cultivars and a long

flowering season. Low-growing varieties

might provide great pollinator support

with less requirement for material

removal and maintenance, and plants

such as small ferns could be helpful

in shady areas. The RHS gives further

guidance on optimising biodiversity

support when using non-native plants,

such as avoiding double flower forms.

Bulbs can also be a great, economical

way to extend the flowering season.

Continued on page 16 >>>






M-Tray ®

The green roof that allows

quick roof deck inspection

0208 916 2222 •


>>> Continued from page 14

When putting together a plant mix,

think about how the community might

develop over time. A range of different

plants will react differently to extreme

weather conditions providing greater

resilience. It is also possible for some

species to gradually disappear over

time or be crowded out by vigorous

neighbours, which may only become

apparent over several years.

The maintenance planning should

consider whether the emerging plant

community is still robust enough to

withstand next year’s unknown weather

cocktail, or if it has become dominated

by one or two species that could

become vulnerable and die back – as

can be the case when invasive grasses

take over.

There are further important practical

considerations for your plant palette

including the lead times, growing

season and commercial availability of

material. A large range of perennials

may be commercially available

as 9cm pots rather than plugs –

although plugs can also be available

and are advantageous for quick

root establishment. If 9cm (P9)

plants are used there may be more

displacement of substrate depending

on planting density.

Plants should be grown in a peat-free

medium which supports the root

integration into the substrate, as well

as the wider responsibly-sourced

growing media agenda.

Many species can be requested to be

grown to order in the required size in

season from March – July.

My ‘top tip’ for successful planting is

to be clear on what performance you

want and design accordingly. Readily

available wildflowers and sedums

could actually provide a more resilient

community when combined rather

than used separately. As we have ever

greater need for clever optimisation

of space and thrifty use of resources,

we can employ the wide diversity of

beautiful, multi-functional plant life to

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Keith Hills, Managing Director of Eco Green Roofs, discusses his

path into the green roof industry, his perspective on how the sector

is performing, projects he’s been involved with, the challenges and

opportunities on the horizon, and why our reconnection with nature

is good news for the industry…

GM: What was your path into

construction and to your current


KH: Initially, before entering the

construction industry, I worked as

a volatility market maker options

and futures trader within the

stock market for 12 years. After

successfully supporting investment

strategies for investors, I was dealt

an opportunity within the green

roof market. I have always been

conscious of my impact on the

environment and wanted to do

something different.

Understanding the environmental

benefits green roofs can offer in

mitigating urbanised flooding,

alongside air purification and

reducing urban heat island effect,

to name a few, I made the decision

to leave the commercially driven

financial sector behind for a

more environmentally focused

opportunity. It has been the best

career move I could have made.

That move has resulted in the

creation of Eco Green Roofs (EGR),

which continues to grow year on

year. Starting with a green roof

offering, there has been further

integration of sustainable solutions

including blue roofs, solar, biosolar

and recreational podiums/

roof gardens. I have

been the Managing

Director of the

business since its

creation in 2010.

Tell us a bit about

Eco Green Roofs...

Biodiversity has played a huge part

in the direction EGR has taken as a

business. We offer a comprehensive

biodiverse roof offering to suit

specification whether it be

meeting planning requirements

or recommendation through an

ecological report, to meet the

environmental needs for each

individual project. With mandatory

requirements likely to be on the

horizon from the Government,

it was, and is, important both

environmentally and with the

potential compliance to regulation,

that we offer a service from

design and install to aftercare and


From this, and resulting

from further governmental

commitments made, we have

created a biosolar offering,

featuring all the benefits of a

green and biodiverse roof, with

the inclusion of PV panels, thereby

cutting emissions and

potentially contributing

to zero carbon in new


EGR provides a

complete design and

collaborative project

partnership through to

after-care, including maintenance

solutions for green envelope

systems, green and biodiverse

roofs, biosolar & PV, blue roofs,

recreational podium/roof garden.

With regards to green roofing,

how is the sector performing?

Due to the ongoing lobbying

around the environmental benefits

gained from green roofs, the sector

continues to perform well, with

green roofs being a mainstream

option for creating healthy and

more sustainable communities.

On April 20th this year, the UK

government set the world’s most

ambitious climate change target into

law; to reduce emissions by 78% by

2035 compared to 1990 levels.

Green roofs in particular contribute

to atmospheric carbon dioxide

reduction through their beneficial

impact on energy consumption

of buildings and sequestration of


carbon in plants and substrates.

A study by Bianchini and Hewage

indicated that the annual air

pollution reduction from a green

roof will offset the emissions

associated with its production

after 13 to 32 years.

What more should

the government

be doing to


green roofs

in towns and


Now, more than ever,

designers/specifiers will

seek support in creating green

envelope buildings, to help contribute

to a reduction in carbon emissions,

of which green roofs and other

sustainable roof solutions will play

an integral part. The Government is

looking at how it can place a price on

carbon, as part of a ‘green recovery’

from the coronavirus pandemic.

The Zero Carbon Campaign by

Opinium has estimated that a

carbon tax could raise £27bn a

year by 2030, and could work by

replacing or simplifying existing

green levies on the industry.

From an educational point of

view, more could be done from

thought-leaders within government,

particularly community driven

strategies, in educating decision

makers of the benefits gained

from incorporating green roofs.

From an environmental point of

view including water attenuation,

air quality and biodiversity, it is the

beneficial impact on people’s health

and wellbeing. Research confirms

Images show the Chimes Project in Westminster which EGR worked on.

green open for sustainable roof solutions to

space aids ensure that NBS specifications


are suitable for the changing

mental and technologies of systems and

physical health, products for those specifying.

of which green

The third key issue being discussed

roofs/podiums can

at GRO is the hierarchy risks when

offer a solution, especially

designing green roofs, to help better

in urbanised areas where green

inform those developing/creating

open spaces are limited.


You recently Chaired your first

What are some of the more

GRO Technical Meeting, what are

common mistakes designers and

some of the key issues you’re

installers make when it comes to

looking to tackle?

green roof projects?

The Building Safety Bill, with its

From a design point of view, not

purpose of putting in place new

utilising a roof area to its maximum

and enhanced regulatory regimes

potential, in particular the inclusion

for building safety, inclusive of

of biodiverse enhancements. This

enhancing fire safety. Fire continues

is where a roof can incorporate

to be pivotal in our discussions

components such as log and sand

at GRO, looking at each aspect

piles, animal boxes and ephemeral

including design, supply, install and

pools to support biodiversity net gain.

maintenance thereafter.

A key consideration in installing a

EGR has recently undergone fire

green roof is maintenance, this is

testing of its green and biodiverse

not always factored into the design

roof systems inclusive of a

of a building, such as water outlets

waterproofing build-up scenario,

for irrigation systems. This is where

offering Broof(t4) classification in

it is important that designers look to

line with Building Regulations, and

the expertise of those that design,

continues to endeavour to ensure

supply and install green roofs at

safe, sustainable solutions are

early design stage.

specified for the built environment.

Continued on page 20 >>>

We are also looking at NBS clause/s • GREENSCAPE SUMMER 2021 19


>>> Continued from page 19

Installation wise, it is not necessarily

a mistake, but often logistical

challenges are faced when it

comes to installing green roofs,

in particular when materials need

to be lifted to roof level. It is of

paramount importance that teams

are sequencing with other trades

to ensure use of cranes and other

machinery to safely deliver the

green roof system components on

to the roof, whilst meeting strict

programme deadlines.

If there was one roof that you

could green anywhere in the UK,

which one would it be?

Emirates Stadium – Being an

Arsenal fan I really wanted them to

take this on. I visited the stadium,

provided a quotation but they said

they didn’t have the budget and

ended up buying Granit Xhaka a

week later…!

Tell us about a project you’re

proud to have been involved with…

Tough one; from a prestige project

point of view, Battersea Power

Station. That being said, from an

environmentally friendly feat,

Chimes in Westminster was a

fantastic project; not only did we

install sedum roofs offering air

purification, water attenuation

(sedums have high water capacity)

and natural habitats, these roofs

could be overlooked by residents

from the landscaped podium

area with planters and evergreen

shrubbery, supporting health and

wellbeing. The project also included

a blue roof system, to further

support the mitigation of urbanised

flooding by attenuating water,

reducing the impact on the old

London drainage system. Further

greenery was incorporated

within the communal courtyard,

again giving residents an access

to nature. This project should

be considered a benchmark in

which other projects in our inner

cities should look to as a hybrid


What’s the biggest issue affecting

the supply chain currently?

The main issue affecting the

supply chain is the lack of trained

operatives to install the green roofs

and other sustainable roof level

system components, therefore

impacting all those involved within

the supply chain. It is not only the

green roof industry, the roofing

sector as a whole faces challenges

with an ever-growing skills gap

and shortage. An NFRC survey has

shown that labour shortages was

the second highest area of concern

for roofing and cladding contractors

in 2021.

After what’s been a particularly

challenging year, are there

reasons to be positive within the

green roof sector and the wider

construction industry?

Lockdown, for many of us, has

facilitated a stronger connection

with nature, due to not working

in offices, venturing outside on

work breaks and more time

in evenings through the

removal of commuting.

In May 2020, 36% of

people responding

to the People and

Nature Survey by Natural England

said they were spending more time

outside during the pandemic than

before. This rose to 46% in July


Research carried out by Naturescot

demonstrated the increase of those

reacquainting themselves with

nature, with many reporting that

after spending time outdoors they

felt that they had gained health and

wellbeing benefits. It’s never been

more important for not only the

environment but also us as people

to ensure there is no devastating

loss to biodiversity, to ensure our

natural world thrives alongside us,

for us to enjoy.

Green and biodiverse roofs

will continue to thrive through

the reconnection to nature,

Government mandates for

biodiversity, net zero carbon targets

and reducing the impact of climate



Eco Green Roofs:

Tel: 01277 355705

Tweet: @EcoGreenRoofs

With regard to the construction

industry, many companies

have thrived in the pandemic

due to funding placed via

the Government to support

stability in the UK’s economy.

The construction industry has

demonstrated resilience alongside

being compliant to safe practices.

It will continue to grow and

shape, though with a heavier

focus on sustainability as part of

a green recovery from the


The full version of our

interview with Keith

is available at www.


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Dr. Anna Zakrisson (below), of Green Roof Diagnostics, explains

the difference between two of the industry’s most hotly

debated concepts, with comment from Mike Wharton

(inset right), of Complete Roofing Systems, on the importance

of green and blue roofing.

Traditional green roofs

and retention

Green roofs are

excellent at

reducing annual

stormwater volumes.

Up to around 60% of

the annual precipitation

can be retained by a highretention

traditional green roof. This

means that approximately 60% of the

yearly rainfall never becomes runoff

and never enters the canalisation. This

water will never have to be cleared by

a sewage treatment plant, a process

requiring a lot of energy; this water also

cools the cities through the process of


This 60% represents retained

water and leaves the roof through

evapotranspiration: the combined

processes of evaporation and

transpiration. Retention is excellent at

managing small storms: the 60% of

the volume representing 80-

90% of the total number

of storm events.

But what happens

to the remaining

40% of the volume

representing 10-20%

of the storm events?

This is coincidentally

the 40% that causes

most damage to a city;

intense and multiple-day

rain events resulting in flooding

and erosion. If you manage to slow

down the outflow rates of the runoff,

this damage will be prevented.

Maximum allowable runoff


Stormwater management

can be summarised as such:

“provide methods that

reduce runoff rates from

your property predictably

and reliably to meet the

maximum allowable rates set

by the municipality.” Often these

maximum allowable runoff rates

are in the ballpark of 1-10L/s/ha for

most European urban areas. Another

commonly used term for this delay is

“stormwater detention.”

Many different types of at- and belowgrade

stormwater tools can lower

runoff rates by delaying the outflow of

water e.g., stormwater tanks, cisterns,

rain gardens, perforated pipes and

many more. These methods are all

space constraining and may thus

cause some headaches for planners

in many urban areas. However, you

are required to show that the

building is adequately

protected against

severe storm events,

which is especially

important now as a

climate adaptation


The maximum

allowable outflow

rates must also be met

under certain pre-defined

conditions often referred to as

a “design storm.” These statistical

storms have a specific shape, describe

a volume, and have a time factor.

Commonly, your project must be able

to deal with a so-called 100-year storm,

or in more sensible terminology: a

design storm that has a 1% probability

of occurring in any given year based on

past events.

Available green roof detention

(delay) solutions

The outflow delay factor varies in a

traditional green roof – for a dry roof

it is several hours, worst case when it

rained yesterday and today once again,

we are talking about minutes, which is

not nearly sufficient to meet the max.

allowable outflow rates of a 100-year


In a typical green roof profile, the

macropores never fill up to full capacity.

Water simply falls out of these pores

as they are too big to hold onto the

water through capillary forces. Also,

the drainage layer is an optimised

water facilitator, not a restrictor, which

is why traditional green roofs are not

considered stormwater management

tools in its fullest sense. However, there

are several interesting detention/delay

solutions on the market.

With some blue-green roofs, you can

circumvent the issue largely by simply

storing most storms on the roof and

using this water to irrigate the plants:

little outflow and little water to slow

down, ergo little detention. But even

blue-green roofs release water when it

rains 2-5 days in a row. Nonetheless, if

you want to use it as a stormwater tool,

it still needs to meet the requirement

of managing the 100-year design


Mike Wharton, Chief Executive, Complete Roofing

Systems: “As the call for net zero carbon 2050 starts to

get louder, we’re seeing more and more clients enquiring

about green and blue roofs, as well as improved insulation.

The ability to detain water is coming up more frequently

as a client request too, and the constant improvement in

technology will also help both the installation side and the

ability for the industry to continue to push the agenda.”

Complete Roofing Systems is a commercial roofing and cladding contractor.

Find out more:

storm. Some types of blue-green roofs

use orifice restrictions to release

water at predictable outflow rates.

For blue-green systems, you need

a flat roof. Other solutions include

Purple-Roof compliant systems that

use a drainage fabric with internal

turbulence to achieve reduced and

predictable outflow rates also on

sloped roofs.

Sadly, it is a frequent misconception

by many stormwater engineers that

green roofs cannot be solid and reliable

stormwater tools. Possibly because of

a confusion of terminology between

the green roof industry and the civil

engineering world combined with a lack

of solid stormwater modelling studies

for green roofs.

Many of the mathematical methods

currently used in the industry are rough

ballpark figures covering extremely

narrow conditions that won’t satisfy

stormwater engineers. This has most

likely led to several great opportunities

having been missed.


Contact Green

Roof Diagnostics

Tweet: @GRD_Research

Retention cools our cities and

reduces annual loads on our sewage

treatment plants, and keeps our

cities beautiful and green. Detention

(delay) saves us from flooding

damages and prevents horrible

things like combined sewer overflows.

Both processes are important

and serve different purposes, and

the latest blue-green and purple

concepts can deliver both. • GREENSCAPE SUMMER2021 23




In the first instalment of his new, regular column, Dr Tom Young, GRO Board Member and

Environment Systems Manager at STRI Group, looks at biosolar roofs in more detail...


huge amount of relevant

research into green roofs

has been conducted over the

last 20 years. However, an issue with

academic research is that it often does

not filter through into the industry

to help with improving design and

maintenance of green roofs. In this

regular column, I hope to provide easy

to read summaries of hot topics in

the green roof academic sector, and

introduce readers to some academic

research which is available.

A common statement that everyone

who has worked with green roofs has

heard is: “I want a green roof, but I can’t

have one as I want solar panels/

PV”. Now, having either of

these technologies is

commendable and

will improve the



of a building.

However, the

answer back

should always

be: “well, why

don’t you have

both then?” Not

only do you gain the

benefits of both, but

the two systems can actually

complement and improve one another.

Known as biosolar roofs, developers

are increasingly becoming aware of

the benefits of combining these two


One of the first major studies into this

area was conducted by Manfred Kohler

in 2007 (Kohler 2007) which looked at

two rooftop solar farms in Berlin; one

with a bitumen roof and

the other with a Sedum

extensive green roof.

This study provided

initial results into

an 8-year study and

suggested a number of

positive feedbacks from

the two systems which

have since been investigated

by others in much more detail.

Standard PV (photovoltaic or solar

panels) panels appeared to produce

1-15 % less electrical energy during

the study period compared to green

roof PV panels, and lead to an increase

in plant diversity across the green

roof. This was linked to the

increase in ecological

niches provided by

the solar panels,

with a decrease

in surface air


by the green

roof increasing

PV panel



studies have

clarified the

mechanisms described

in the Kohler 2007 paper

and helped to optimise the

design of biosolar roofs:


Increased PV output

Key mechanisms

Reduced air temperature on roof

caused by evapotranspiration of

vegetation, substrate heat sink, and

Left: Dr Tom Young. Below:

biosolar roof installation

courtesy of Bauder.

reduced albedo, leads

to cooler PV panels.

PV panels function

more effectively at a

lower temperature and

therefore produce more


General power output improvements

ranged between 1-8 %, with an average

of 1-3 %. Some studies show negligible

improvements (0.08-0.5%), due to

position of solar panel, vegetation type

and climate.


Decreased air and roof temperature

Key mechanisms

Reduced air and roof temperature can

reduce requirement of air conditioning

within building. Therefore, building

energy requirements are reduced,

allowing a greater amount of electricity

to be used for other purposes or

exported to the grid.

Energy savings of 0-11 % have been

modelled and observed for European

green roofs, and up to 79% for roofs in



Improved plant diversity and resilience

Key mechanisms

Increased range of shade patterns,

which in turn causes range of

Continued on page 26 >>>


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>>> Continued from page 24

temperatures across roof surface.

Uneven distribution of rainfall across

the roof from solar panels, leading to

wetter and dryer areas.

Some plants enjoy different

temperatures, and substrate moisture

compared to others and thus

differential plant communities start

to form. Kohler 2007 observed an

increase in plant diversity of 24 % on a

PV roof compared to non PV roof.

As a word of caution, some studies

have found little impact upon species

diversity (Schlinder 2018), although

this may be due to the harsher

Mediterranean climate the study roof

was in.

Most studies show that additional cost

of green roof to a PV system has a

rough payback period of between 10-20

years depending on the climate and

type of installation. More research is

still needed to fully quantify pay back

periods in different regions, in order

to help prove the case for developers

and building owners. In addition, more

research is needed to understand

the optimum design of biosolar roofs

with key areas including vegetation

composition and height

of PV panel above


There is still

no hard and

fast rule for


biosolar roofs,

but some

general design

pointers are listed


• May need additional

walkways and access routes

around PV panels

• Green roof substrate can be used

as ballast for the panel arrays. Panels

can also be attached directly to

drainage layers to prevent piercing the

waterproof layer of the roof.

• Vegetation maintenance is as

important as ever, as uncontrolled

growth can result in shading of panels.

• Species selection during design stage

is critical to ensure that correct types

are selected.

• Vegetation design can be much more

ambitious, as PV panels

provide multiple

habitats across the

roof in terms of

shade, wind and

water flow.

• Correct

height of PV

panel above

the roof is key

to ensure cooling

benefits are


GRO has recognised the

increased need for guidance in

this area, and has included biosolar

general design points in the latest GRO

Code. These will be built upon in further

editions and as knowledge in this area


References available on request, or

view at


STRI Group

Tel: 01274 565131


Tweet: @striturf_tomy /


Images show biosolar roof projects.

Courtesy of: Top Optigrun; Left Bauder;

Centre two Bridgman & Bridgman;

Above Optigrun.





With Sika having recently launched a new range of green roof

systems, Richard Aldred MSc (pic right), UK Roofing Market

Manager at Sika, offers advice on installation methodology and

design considerations in this informative step-by-step guide.

Presenting a myriad of benefits,

green roofs are becoming ever

more popular among specifiers

looking to build for a sustainable future.

In support of that, we’re thrilled to have

recently launched our new Sika Green

Roof systems.

It’s a total package that allows specifiers

to choose from a range of highperformance

waterproofing systems

that best fits their project’s needs

– whether that’s hot melt structural

waterproofing, reinforced bituminous

membranes, single ply or cold-applied

liquid membranes – all of which are

compatible with Sika’s Green Roof


If you’re considering a green roof

addition, but unsure about what’s

involved from an installation

perspective, read this six-step guide to

installing a Sika Green Roof (applies to

Sika’s standard products)

Step 1 – Roof waterproofing and

site checks

Firstly, ensure the roof is complete and

watertight. Check that the roof is a safe

working environment (edge protection/

scaffold or mansafe system is in place)

and have lifting equipment ready to

lift materials to the roof securely. It is

essential to ensure all other trades have

finished working on the roof before

starting, especially if the roof is a new

build, making sure the roof is fully clear,

as a loose screw or site debris can

cause problems further down the line

and mechanical damage normally isn’t

covered under any roofing warranty.

Step 2 – Protection fleece and

Riverstone application

Place the protection fleece roll onto the

roof and lay over the waterproof layer in

strips from one side to the other, ensuring

there is an overlap of at least 100 mm for

each strip of protection fleece, to prevent

any gaps in the fleecing that may expose

part of the waterproofing, and may risk

subsequent damage to the waterproofing

during the installation of the green roof.

Step 3 – Aluminium edging


The aluminium edging should be

installed on roofs with a pitch to

help retain the system on the roof.

It is not required on flat roofs but is

recommended for an aesthetic finish.

The aluminium edging is placed

underneath the Riverstone border – the

weight of the Riverstone will hold the

aluminium edging in place. Ensure that

there are gaps in the aluminium to

allow for drainage of excess water in the

system. Retention edges can be glued

together using a special aluminium

adhesive. Make sure there is an overlap

when adhering to avoid gaps in which

the Riverstone and other parts of the

border could fall off the roof.

If a Riverstone border has been

requested, place the sacks along the

roof perimeter with a general spacing of

1 bag per 800 mm. Slit bags open and

hand place the pebbles evenly along

the border at a width of 300 mm (or

otherwise specified at the site location).

Step 4.1 – Drainage board with

filter fleece

Sika’s drainage boards come in two

varieties. A drainage sheet with a filter

fleece already attached, and drainage

rolls that require a separate roll of filter


For the drainage sheets with filter

fleece already attached, place the

sheets across the roof surface with an

overlap of at least 100mm where the

excess filter fleece is located. This will

prevent exposure of the waterproofing

membrane and reduce the risk of

any damage to it. Cut the sheets that

overlap the 300mm Riverstone border,

as well as around any protruding units

attached to the roof to form neat

edges. The adhered filter fleece is built

to overlap to ensure substrate does not

get into the drainage cups.

Step 4.2 – Drainage board and

separate filter fleece installation

Roll out the drainage board onto the

roof, creating a continuous drainage

layer, cut the drainage board along the

perimeter edges of the roof neatly.

Leave a 300mm spacing between the

drainage board and the edge of the roof

for the Riverstone border. Where there

are protruding skylights or other roof

components, cut the drainage board up

to and around the object to form a neat

edge. Be careful not to damage the

waterproofing layer.

To apply with the filter fleece, follow the

same method as the protection fleece.

Allow for a minimum 100mm overlap to


prevent the drainage board protection

from being filled with substrate.

Find out more about

Sika’s green roof offering:

Tel: 01707 394444


Step 5 – Substrate installation

Place substrate bags onto the roof over

the filter fleece. This will prevent the

fleece from being lifted by the wind and

maximise homogeneity of the substrate

depth across the roof. Cut the edge of

the bags and spill the substrate evenly

over the filter fleece. Use a rake to

create an even spread of the substrate.

Measure the depth of the substrate to

check that the substrate is at a minimum

depth of 50mm for sedum blanket

and 100mm for wildflower blanket (if a

deeper substrate is specified, measure to

the indicated depth).

If bulk bags are being used, lifting

equipment will be needed to hang the

bulk bags over the roof. You can either

slit the bottom of the bag or shovel the

material from the bag onto the roof

evenly to the depth specified by the

project. Great care must be considered

when emptying bulk bags to prevent

excessive loads of substrate onto one

point of the roof, which could lead to

damage to the roof systems if the weight

exceeds the restrictions of the roof.

Step 6 – vegetation installation

Unroll the blankets on top of the

substrate, butting each roll close to the

other. Cut rolls at the roof perimeter

and use extra pieces to complete the

roof. Also cut parts where skylights

protrude from the roof. Excess debris

blanket and/or soil left after installation

can be used to fill in any bare patches

where the blanket system has

deteriorated during transportation.


Green roof systems include living

products which must be installed

on the day of delivery and watered

immediately upon installation and

for the first 12 weeks in situ. This is

especially important during the Spring

and Autumn period each year. For

pitched roofs over 7.5 degrees, an

irrigation system is recommended to be

installed with the roof. • GREENSCAPE SUMMER 2021 29






Tel: 01423 332100

Tweet: @Greentechltd

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and is on track to achieve LEED 2009

Gold, meaning that this cutting-edge

building is expected to consume 25%

less energy, and generate 34% lower

greenhouse gas emissions than the

average commercial building. This

impressive green performance is

achieved whilst retaining much of the

existing structure and facades and

combining it with new.

One of the main goals for MAKE

Architects, the building’s designers, was

to engender a strong sense of wellbeing

for the office workers, residents and

public that use it. As part of this

commitment, the design allowed the

inclusion of numerous roof terraces,

both private and shared for the offices

and residents, offering dramatic views

over Fitzrovia including the BT Tower.

Green-tech were contacted by Barton

Willmore landscape architects, with whom

they have a long working relationship

going back nearly ten years, to quote for

irrigation for the many planters that were

required on two of the external terraces;

part of a design developed by Piercy &

Company Architects for a specific highend

tenant fit-out.

The most effective solution was to use

Green-tech’s Mona tank system. This

subterranean reservoir system irrigates

the soil through capillary action,

reducing watering frequency whilst at

the same time aerating the soil.

With sizes from 3 to 24 litres, the Mona

tanks can either be used individually

or linked together in line, for beds and

longer runs. Each tank has two capillary

legs that are back-filled with soil and

reach down into the water inside the

reservoir. Once filled via the filler pipe the

tanks act as a reservoir, supplying water

to the rooting soil via capillary action.

As the water is taken up, the empty space

is replaced by air through the filler pipe,

acting as both irrigation and aeration. If

the surrounding soil is damp, the tanks

do nothing and the water is stored – once

the soil dries out, the water is taken up

by capillary action into the soil, keeping it


Over 200 tanks were

supplied to the


Contractor Oasis

Plants for the

terrace planters,

ensuring that the

plants are kept

well irrigated all

year round.

Commenting on

landscape supplier

Green-tech, a spokesperson

from Barton Willmore Landscape

Architects explained: “We have worked

with Green-tech for many years now,

and they can always be relied on not

only to help out at the front end with

specification and cost proposals, but also

provide a reliable service when it comes

to supply.”

Planting at the

Charlotte Street roof

garden courtesy of

Barton Willmore.

Green-tech’s Specification

Advisor Alasdair Innes added:

“We have a great relationship with

Barton Willmore, and it is particularly

exciting to be involved on a project with

such impressive green credentials. The

Mona tanks do their job so well, I have

no doubt that they will keep the terraces

green and healthy for many years to



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We take a look at the roofing element of The Liner luxury

apartment project, where the shape and exposed location

posed some interesting challenges for Sika’s technical team

and contractor Progressive Systems...

The Liner, a nautical-inspired

£35m residential new-build

in Falmouth, presented a

compelling roofing challenge. Exeterbased

roofing contractor, Progressive

Systems, assisted by Sika, took on

the task, installing a roof to withstand

the harsh seaside conditions with an

immaculate finish.

Boasting panoramic views of

Gyllyngvase Beach, this latest

development by Acorn Blue consisting

of 52 luxury residential apartments was

designed by Poynton Bradbury Wynter

Cole Architects. Far from a conventional

footprint and façade, the six-storey ‘V’

shaped building echoes the bow and

upper decks of an ocean liner, with a

‘bridge’ containing penthouses on the top.

The curved roofline is designed to

resemble the ocean waves. A podium

component comprising additional

residential apartments, commercial and

retail spaces was also required.

Progressive Systems and Sika were

selected for the job thanks to their

outstanding work on The Dunes in

Perranporth, a prior beachfront project

with Acorn Blue. Testament to this,

said project won the Single Ply Roofing

category in 2019’s NFRC UK Roofing


Project details:

The Liner, Falmouth

Contractor: Progressive Systems

Roofing client: Acorn Blue (part of

Acorn Property Group)

Size: 2300m 2

Products: Sika Sarnafil G410 18EL

PVC Single Ply Waterproofing

Membrane, Sarnavap 5000E SA

Vapour Control Layer, Sarnafil

Primer 610, Sarnatherm ‘G’

insulation, Sikalastic 625, Sarnafil

G445-13 PVC Protection Sheet, Sika

Green Roof System.

Range of roofs

The scope of the roofing works included

the penthouse roof and balconies,

winged roofs, garden apartments,

roofs for the commercial units, plant

room, paddleboard store and podium

roof, totalling an area of approximately

2,300m 2 .




Tel: 01707 394444


Tweet: @SikaLimited

As the building would be exposed to

the coastal elements, Acorn Blue was

looking for a robust roofing system that

would withstand the Cornish winters.

Sika’s technical experts helped to create

a robust specification using a range of

durable roofing systems, guaranteed to

stand the test of time.

This included a fully adhered single ply

membrane Sika Sarnafil G410 18ELF,

Sika Liquid Plastics Sikalastic 625 for

the balconies and podium, and a Sika

Green Roof system, to best suit the

various requirements of each area.

Sika conducted thorough wind uplift

calculations to reassure the architect

and client that this type of system

would withstand the high winds.

On top of this, Progressive designed a

bespoke galvanised “c” channel detail to

match the sweeping curvature of the roof

design. A time-consuming challenge, but

one that ensured that no direct winds

would impact on the edges of the roofing

system, giving further peace of mind.

Sika Green Roof was specified for the

garden apartments, commercial units

and first floor podium roof. These

roofs are the most bespoke part of the

building because of the curvature and

multiple pitches that were built on each

individual roof (created in structural

steel with timber joists and a multi-cross

weaved layered plywood deck). Due

to the exposed coastal environment,

specific coastal plants were chosen

to withstand the conditions, increase

biodiversity and give a stunning visual


Creating the paddleboard shape for

the penthouse roof took time and

expertise. Close attention had to be

paid to ensure the correct curvature

was being created. However, despite the

irregular shapes, all roof junctions and

upstand details were kept as simple as

possible to reduce the potential for any

further issues. Keeping these “typical”

details simple was key to the project

running smoothly.

Images show work by Progressive Systems

and Sika at The Liner, a nautical-inspired

residential new-build project in Flamouth.

Steve Kerswell, from Progressive

Systems, said: “From inception through

to project completion, Sika was in close

contact with us. They were always

happy to discuss and resolve any design

and specification queries. We found

the field technicians’ weekly site visit

both useful and informative for both

us and our client, who took confidence

that another set of eyes were checking

the quality of the roofs’ install and


Thanks to the impressive workmanship

of Progressive and the high quality

finish of the Sika roofing systems, the

final result is worthy of topping the very

best in contemporary coastal living.

Following the successful completion of

The Liner project, Progressive and Sika

have been invited to tender on further

upcoming coastal projects. • GREENSCAPE SUMMER 2021 33




Polypipe Civils & Green Urbanisation’s blue-green roof

installation at Bloc is said to be “a perfect example of the

future workspaces of tomorrow, today”, with the innovative

roof set to provide a climate resilient vision for Manchester.

Work has been completed on

the installation of a groundbreaking

climate and water

resilience research roof in the heart of


Sited on Bloc – a city centre workspace

that has been transformed by

Bruntwood Works as part of its £50m

Pioneer redevelopment programme

– the blue-green roof from Polypipe

Civils & Green Urbanisation will help to

develop a greater understanding of how

new construction and data technologies

can help cities and urban developments

to mitigate the impact of climate

change and population growth, while

enhancing biodiversity.

Over the next two years, the ‘smart’

blue-green roof, designed by

environment management consultants

EPG, part of the STRI Group, will allow

United Utilities – which co-funded the

development at Bloc – to assess how

storing and re-using rainwater at roof

level can reduce the volume of surface

run-off entering its sewer network. As

a result, it will help to lower the flood

risk associated with the prolonged

high-intensity storm events that are

becoming increasingly frequent as the

climate changes.

Unlike conventional green roofs, which

use a drainage layer to simply remove

rainwater, the 525 sq m blue-green

structure retrofitted to Bloc’s flat roof

stores rainwater beneath the planted

surface where it lands. Advanced

passive irrigation components within

the attenuation layer draw water up

through the structure to the underside

of the green roof substrate to support

surface planting.

The breakthrough technology protects

green areas during periods of drought,

reduces potable water demand during

hot weather and enhances biodiversity

by maintaining flora in optimum

growing conditions. In the case of Bloc,

planting has been specially selected

by partners of the project, STRI, from

local varieties to help attract pollinators

and a particularly rare butterfly, the

Manchester Argus.

This net-zero re-use of water to sustain

surface planting is a new approach to

water management known as green

urbanisation, and represents the next

generation of sustainable drainage

systems (SuDS).

Nicholas Wright, Specification Business

Development Director at Polypipe

Civils & Green Urbanisation, said: “The

two-year roof research programme at

Bloc will demonstrate the full creative

and multifunctional potential of green

urbanisation, which represents the next

generation of sustainable drainage


“By introducing integrated natural

habitats across the urban landscape,

we create healthier, more resilient

communities that are highly carbon and

energy efficient.”

Sophie Tucker, United Utilities’ Area

Engineering Manager, said: “As a

company, we continue to explore

innovative ways on how things can


Contact Polypipe Civils

& Green Urbanisation


Tweet: @PolypipeCivilGU

be done differently, as we look at

alternative methods to increase

resilience in our sewer systems, away

from simply building underground.

As such, we’re heavily invested in

learning more about urban assets

that can deliver surface water

separation and sustainable solutions

which can make our regions more

resilient to the long-term impact of

climate change.”

Bruntwood Works’ re-imagining of

the 16-storey office block on Marble

Street has introduced a raft of new

workspaces, amenities and technology,

and has a focus on biophilia to help

improve wellbeing. As well as a twostorey

living wall that provides oxygen

and helps reduce noise levels, Polypipe

Civils & Green Urbanisation’s blue-green

roof installation has made Bloc the

home of Manchester’s first wildflower


Andrew Cooke, Strategic Director at

Bruntwood Works, added: “At Bloc, the

latest project in our £50m Pioneer

programme, we’ve transformed a

traditional corporate office building

into an innovative and futureproof

workspace that’s at the cutting-edge of


“With its potential to mitigate the

impact of climate change while

promoting health, wellbeing and

biodiversity, Polypipe’s blue-green

roof is a perfect example of the future

workspaces of tomorrow, today.

“The purpose of workspaces is evolving,

and it just goes to show the integral

role buildings such as Bloc will play

in shaping communities and urban

landscapes of the future.”

Polypipe Civils & Green Urbanisation’s

Permavoid solution has been used at

Bloc to create the innovative bluegreen

roof structure. The shallow subbase

attenuation system, which is made

from 100% recycled polymer, manages

rainfall at source.

This collected surface water is then

either retained for re-use or gradually

released to help prevent flooding ahead

of periods of extreme weather. • GREENSCAPE SUMMER 2021 35




With predictions of soaring demand for solar PV in new build

housing, what are the prospects for the retrofit market? We

asked Stuart Nicholson, Roof Systems Director at Marley and

Stuart Elmes, CEO of Viridian Solar, for their views.

With a 31% carbon reduction

target, the proposed changes

to Part L in 2022 could

lead to a five-fold increase in the

number of new homes built with solar

technologies, according to Solar Energy

UK. But how is the retrofit market being

affected by the UK’s drive towards

net zero carbon emissions?

Market drivers

Stuart Elmes, CEO

of Viridian Solar

(right), which is

now part of Marley,

explains: “The

retrofit market for

solar has historically

been driven by the Feed-in

Tariff scheme, which produced

successive boom and bust cycles as

consumers rushed to install solar PV

before the next drop in subsidy. When

the scheme finally ended in April

2019, it caused the retrofit market to

scale back to a model based on home

improvement and reducing energy use

and carbon emissions.

“Now, in 2021, we are seeing a new

set of market drivers, this time driven

by government regulation rather

than government hand-outs. This

should create a more steady and

sustainable retrofit market, without

the highs and lows associated with

some subsidy schemes. In England

and Wales, there are already statutory

minimum efficiency levels for private

rented property and in Scotland,

similar regulations are aimed at social

housing. The required energy levels

(EPC ratings) are readily achievable

for all but the poorest performing

properties. However, the intention is

that these regulations will become

tougher over time, to align with national

environmental standards.

“Solar PV is a very convenient way to

meet regulations like these because

it requires relatively low

disruption to the property

and residents. The industry

is already seeing large

contracts for retrofit solar

PV on social housing in

Scotland, as a result of

the Energy Efficiency in

Scottish Social Housing

regulations (EESSH).

“Indeed, social housing providers

across the whole of the UK are

increasingly referring to ‘No Regrets

Refurbishment’, which means avoiding

doing things and then having to come

back and do more work to meet new

energy efficiency targets. A classic

example of this is roofing replacement.

If a housing association is

going to refurbish the

roofs of properties and

they need to engage

tenants, appoint


and incur the

expense of

scaffolding, then

why wouldn’t

they install solar

PV at the same

time? We are seeing

more and more social


housing providers looking to combine

low carbon retrofits into their asset

management programmes.”

Purchasing influencers

When it comes to private

homeowners and

occupiers, Stuart

Nicholson, from Marley

(left), says that many of

the factors influencing

new build buyers to

choose properties with

solar panels, are the same

for those looking to retrofit

solar PV: “People have become

much more conscious about reducing

their own impacts on the environment,

alongside the need to reduce high

energy bills and this is a driver in the

private retrofit market. However, an

even more significant factor is going

to be the Government’s ban on all

new diesel and petrol cars from 2030.

This will represent a huge increase in

demand for electricity for charging

vehicles at home over the coming

years. Electricity is expensive, so onsite

electricity generation will become

increasingly appealing to home owners,

as well as social housing providers.

“In addition, the cost to install solar

panels has reduced dramatically over

the past ten years, making it much

more affordable and the potential

savings and return on investment are

very good. Prices are now around 75%

cheaper than they were back in 2010,

and the cost of battery storage is also

becoming much cheaper, due to the

automotive sector creating volume

demand for use in electric vehicles.

“New integrated systems, like Marley

SolarTile, also make retrofitting very

easy because they simply replace

a section of roof tiles and have an

easy push together design. Whereas

previously consumers may have been

put off by bulky on-roof systems,

Continued on page 38 >>>

Images show solar

PV installations, all

courtesy of Marley

and Viridian Solar. • GREENSCAPE SUMMER 2021 37


>>> Continued from page 37

these discreet, integrated panels are

incorporated into the roof surface,

acting as an MCS 012 approved building

material and becoming a seamless part

of the roof design. This makes it easier

to pass difficult planning conditions

and they have even been approved for

use on heritage sites and conservation


Indeed, integrated systems are

becoming more widely used on retrofit

projects, particularly among local

authorities and this is expected to

follow suit in the private homes market,

as the aesthetic, maintenance and

installation benefits are realised.

Stuart Nicholson adds: “As well as the

aesthetic benefits, integrated systems

offer some significant advantages,

including much easier maintenance.

Unlike on-roof systems, both tiles and

PV are installed together, which means

there is no modification to the roof tiles,

securing the manufacturer warranty

and reducing the risk of breakages or

cracks. Our integrated solar panels also

prevent the problem of bird infestation

and provide excellent weathertightness,

wind and fire resistance.”

Contact Marley

and Viridian Solar

Tweet: @MarleyLtd /






The solar PV sector of today is drastically different to that of

ten years ago. Christelle Barnes (below), Country Manager

UK at SolarEdge, discusses riding the ‘solar coaster’ and

navigating the industry’s ever-changing landscape, but also

explains why things are looking positive moving forward.

The UK solar PV industry is no

stranger to turbulence. The

twists and turns of the wild ‘solar

coaster’ ride, set in motion following

the launch of the government’s Feed-in

Tariff scheme back in 2010, have

transformed the sector to something

very different to what it was ten years


“Previously, there were a lot of

companies that just did electrical

work, and then they’d start adding a

little bit of solar,” explained Christelle,

who is well placed to comment on

developments within the market. “Or

they just did roofing and started adding

a little bit of solar, and then they found

that it wasn’t sustainable for them to

continue. So now it’s more dedicated PV


“The PV industry of 2021 is very

different to the PV industry of 2010,

when it really took off in the UK. We

have a lot more solar installed now, so

there are more challenges on the grid.

We have a more sophisticated buyer, so

our installers need to be at the top of

their game.

“And we have a lot of different sectors

that are using solar. Now we have the

local authorities making decisions for

housing association portfolios. We have

the new-build market and housing

developers having to tick boxes, and

then we have private homeowners and

the whole commercial sector as well.

So, there’s a lot of different elements

to it…”

Founded in 2006 with a focus on

module-level power electronics, global

company SolarEdge set out to change

the way solar power is harvested and

managed in the PV system, and to

address “shortcomings” with the PV

technologies of the time.

The traditional string inverter lacked

what Christelle describes as “enhanced

digitalisation or cleverness”, and was

limited by a ‘domino effect’

which meant that the underperformance

of a single

solar panel would reduce

the efficiency of all the

other panels on the same


Christelle explains: “With

the traditional inverter, the

whole system is connected

together on one string. This

basically means that if one panel is

shaded, the performance of all the

other panels on that string is impacted

– so if a bird lands on one module for

five minutes, the power from every

module in that string drops down to the

same level as the one with the bird on.

“There are no electronics up on the

roof so the inverter doesn’t know

that there’s something wrong with

one panel. It just sees a reduction of

performance coming from the whole


Looking to address these issues, the

SolarEdge system features a Power

Optimizer which allows each panel to

work individually at its maximum power

point, ensuring that

unlike traditional

systems, if one

‘domino’ falls, the rest

of the system continues

to operate at maximum

capacity. It also gathers all of the

information about system performance

at a panel level, which can then be

sent directly to the system owner or

maintenance team via SolarEdge’s

cloud-based monitoring platform.

The SolarEdge product was launched

in 2010 and “I think it’s fair to say that

the response was quite positive,” says

Christelle, “because we’re now the

biggest inverter manufacturer in the


In what Christelle describes as a “very

up and down kind of 12 months” for

most in construction, SolarEdge has

seen different sectors strengthening


and weakening on a quarterly basis:

“Through the first lockdown a year ago,

the residential market really was very

quiet, with everyone trying to figure out

how to work in this pandemic, whereas

the commercial market did continue,”

she says. “There was obviously a little

bit of confusion at one point about

whether construction sites were

allowed to remain open or not… then

we found that the commercial market

became more cautious.”

Fast forward to 2021, and it’s the

commercial sector, which includes

large-scale public sector projects as well

as businesses, that’s showing signs of

strong growth, with the Public Sector

Decarbonisation Scheme Funding

expected to bring a ‘huge pipeline’ of

projects to fruition.

“I believe that in 2021, we’ll likely

see the strength in the commercial

market, in particular, through public

sector projects,” says Christelle.

“Residential is not doing badly, but

it’s been challenging, I think, through

this pandemic for a lot of companies.

Looking ahead, our focus is providing

solar installers with the tools to boost

their businesses.”

With the bulk of its UK business in the

retrofit sector, SolarEdge maintains a

strong commitment to training in the

UK, reinforced by the requirement for

companies here to be MCS approved.

“I think especially in the UK,” says

Christelle, “because of MCS there’s

been a focus on training from the very

beginning – and on having accredited

installation companies. So, we’ve always

been very committed to the UK market

and making sure that our installers

have all of the tools that they need

to operate to the best of their ability.

We’ve always had a training programme

on offer and we’ve expanded that out,

through the last 12 months, to include a

big focus on the Edge Academy.”

Described by Christelle as the “next

step” for committed professional PV

installers who already understand the

basics of the PV, the Edge Academy

caters for those seeking to “evolve in

knowledge” and become a specialist in

their chosen PV technology.

“It’s a place where our installers can go

to really excel… to make sure that they

are offering the best solution for their

customers because they have the full

knowledge about the product range.

“And when they’re installing a

SolarEdge PV system, it’s with absolute

confidence that they’re doing it in the

most efficient way. So, it’s a course,

that’s really focused on our products…

it’s continually evolving and there’s lots

of nice plans for the Edge Academy this

year, with new courses being added.”

Looking to the future, Christelle

acknowledges the changing motivations

of the consumer, pointing out how

the financial incentive for consumers,

initially driven by the government’s

Feed-in Tariff, has given way to those

who choose solar because they

care about their carbon footprint,

about tracking expenditure, reducing

electricity consumption and doing so “in

the most easy to use way.”

“And that’s where solar has really risen

in popularity, because it’s relatively

easy for people to install. It’s a

straightforward technology,” she says.

“I think the persona of the buying

profile has changed a lot over the last

couple of years, which has probably

been partly driven by the pandemic

and the shift to working from home,

as well as the big increase in electric

vehicles, all of which need to be charged

at home. Electricity consumption is

Main pic: Rooftop solar

install. Inset: Christelle

Barnes, Country Manager

UK at SolarEdge.

Continued on page 42 >>> • GREENSCAPE SUMMER 2021 41


>>> Continued from page 41

increasing and people don’t like that.

They don’t like having to pay more

on their direct debit every month. So,

they’re looking for ways to reduce that

and they’re choosing technologies that

are smarter… it’s a really interesting

transition of the market and it applies to

the commercial sector as well.”

So what’s next for the solar PV


“We’re still learning about the Future

Homes Standard and reading about

what it means for us as a manufacturer

and what our customers are going to be

looking for from us in the coming years.

But I think that the market and the

industry are going to continue to evolve.

I’m sure there’ll be new challenges that

crop up along the way that we haven’t

thought of yet…

“I don’t know what’s going to happen

in a year or two years, three years

from now, but I know that our team

will continue to introduce innovative

solutions to any issues that arise.”

While Christelle, doesn’t have a crystal

Advancements in safety will be important

for the sector moving forward.

ball, she thinks there might be more

focus on the invisible components of

PV systems that affect things like safety

standards. “The industry already ticks a

lot of boxes when it comes to things like

safety features,” she says, “but I think

we’ll continue to set new benchmarks

when it comes to technology

advancements for higher levels of

safety, offering further cost- and timeeffective

benefits. … There’s a lot of

focus also on those really important

features that are absolutely critical to

the success of the industry.”

The last year has been tough for

everyone but according to Christelle,

there are plenty of reasons to be

cheerful thanks to a strong commercial

market. “We’re seeing our installers are

super busy and reporting really strong

pipelines,” she says, “and there’s a

general positive feeling in the industry,

so I think we are looking forward to a

positive year ahead.

“As an industry, we’ve got through

Brexit and we’ve got through a

pandemic. We’ve taken another loop of

the ‘solar coaster’ and we’re still here.”


SolarEdge UK

Tweet: @SolarEdgePV


Green Roof Code of Best Practice

incorporating Blue Roofs and

BioSolar Applications

Anniversary Edition 2021

Photo: ABG Limited




Green Roof


BioSolar Ap


Photo ©ABG Ltd

The Green Roof Organisation (GRO) represents companies, organisations and

people involved in, or interested in, nature-based roof solutions that help our

towns and cities mitigate and adapt to the effects of climate change whilst

making them nicer, healthier places to live.

GRO members positively contribute to the delivery of living green and blue roofs

that support nature, provide amenity, attenuate rainwater and generate solar

energy, helping ensure no roof goes unused.

Whether you are active in ecology, design, specification, installation or the

maintenance of green and blue roofs, join GRO and help make where we

live and work greener.

Further information:






W: :




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