Winter 2022

GREENSCAPE 

Ensuring Best Practice for Green Roof & Solar PV Projects MAGAZINE 

WINTER 2022 

Spreading the Word 

Maintenance Tips 

Fire Mythbusters 

Performance 

Academic Corner: Irrigation 

News, Views & Projects 

Plant Selection 

In collaboration with the Green Roof Organisation

Part of the Langley Group 

Bringing living 

roofs back to life 

Is your living roof getting the care it needs? 

Welcome to Eco Green Roofs, the experts in designing, installing and maintaining 

green roofs, to maximise the benefits for people, property and our planet. 

Review, recover, maintain. 

We can restore your living roof, achieving biodiversity 

net gain while enhancing biodiversity on existing 

sites, improving water capture, energy efficiency 

and air quality. We can also provide guidance on Fire 

Regulations and Health & Safety. 

Following our detailed survey to assess your needs, 

we’ll recommend a bespoke maintenance programme 

to protect and extend the life of your roof. 

Opening up the green envelope. 

Part of the Langley group, we are one of the UK leaders in 

green roof technology and green infrastructure, providing 

design, installation and maintenance services for: 

Eco roofs Living walls Biodiverse roofs Blue roofs 

Scan the QR code below to speak 

to one of our eco experts. 

Solar and 

biosolar roofs 

Podium and 

Landscaping 

Planting schemes 

globe 

envelope 

phone 

www.e-egr.co.uk/maintenance 

maintenance@egr.co.uk 

01277 355705 

Part of the Langley Group

GREENSCAPE 

IN THIS ISSUE... 

Matt Downs 

Editorial Director 

mattdowns@media-now.co.uk 

07963 330774 

www.greenscapemag.co.uk 

As we approach the end of another challenging year for construction, one 

positive from 2022 is the increased focus on sustainability and the environment 

from manufacturers of construction materials, the government, and end-users. 

Don’t get me wrong, there’s a long way to go for construction and the built environment 

in this area, but across all the construction titles we publish at Media Now, there’s a clear 

sense that many manufacturers are taking this more seriously and looking at their 

internal processes and the products they produce, as they look to meet the demand of 

their customers and end-users who are increasingly looking for ‘green’ solutions. 

Readers of this magazine and contributors are already well aware of the many positive 

impacts green roofs and associated systems can have on the built environment, but 

it’s clear the goal is to reaffirm this message and take it further afield. With this in 

mind, Maggie Fennell of GRO and Boningale Group has been doing exactly that in 

recent months, and on page 10 she discusses some events where she’s been raising the 

profile of GRO and green roofs to other stakeholders in the supply chain. Discussing the 

importance of networking and creating new relationships, Maggie explains: “We need 

to learn from each other’s experience, otherwise the industry will not develop as fast or 

as effectively as our planet needs it to.” 

But as we know, it’s not just about promoting green roof systems; knowledge around 

correct installation and maintenance is vital to maximise the many environmental 

benefits. As such, this issue features articles on the key steps for maintaining your 

green roof from the experts at Eco Green Roofs (page 20); the team at GRO dispel the 

myth that deeper substrates mean more expense (page 22); plus we talk substrate 

composition with Wallbarn and Sedum Growers (page 24). Enjoy the issue! 

Front cover image courtesy of Wallbarn. Wallbarn discuss 

substrate selection on page 24, and find out more about the 

company at www.wallbarn.com 

GREENSCAPE 

www.greenscapemag.co.uk 

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Mob: 07956 133314 

Email: jakeroxborough@media-now.co.uk 

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

of Greenscape magazine (and website) does not necessarily 

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, 

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Supported by: 

CONTRIBUTORS TO THIS ISSUE... 

This magazine and its packaging can 

be recycled. 

p 10 

Spreading the 

Word 

Maggie Fennell, 

Marketing Chair 

at GRO. 

p 14 

Academic Corner 

Dr Tom 

Young of The 

Environmental 

Partnership. 

p 28 

Solar powers on in 

2022 

Stuart Nicholson, 

Roof Systems 

Director Marley. 

Maggie reports back from recent 

exhibitions which have seen the GRO 

team networking and interacting with 

the supply chain to raise the profile of 

green roofs and associated systems for 

projects. 

P 10 

In part two of his focus on drought 

tolerance of green roofs in a changing 

climate, Dr Tom focuses on the 

importance of irrigation and getting it 

right first time, plus looks at the different 

techniques. 

P 14 

Stuart looks back on what has been a big 

year for the solar PV sector, in no small 

part thanks to the introduction of the 

amendments to Part L, and explains why 

he believes the specification of PV on 

roofscapes will only increase. 

P 28 

www.greenscapemag.co.uk • GREENSCAPE WINTER 2022 3

Contents 

NEWS 

06 Well read: Find out more about 

GRO’s collaboration on Journey to 

the Green Roof, a new book aimed 

at educating children about green 

roofs 

08 Social gains: Sika has donated a 

green roof and other materials to 

a Salford project which is creating 

a safe, indoor space to host events 

and activities to tackle social 

isolation in the area 

GREEN ROOFS 

18 Growing resilience: Dr Elisa Olivares 

Esquivel discusses plant plasticity and 

variation for climate-smart green roofs 

20 Maximising performance: The 

experts at Eco Green Roofs (EGR) 

outline the key maintenance steps that 

will help ensure the performance and 

longevity of your green roof 

24 What lies beneath?: We talk 

substrate composition and 

standards with Wallbarn and partner 

company Sedum Growers 

4 GREENSCAPE WINTER 2022 • www.greenscapemag.co.uk

GREENSCAPE 

SOLAR PV 

28 The year when Part L became 

real!: Marley’s Stuart Nicholson 

looks back on a crucial year for the 

solar PV sector, and outlines why 

he feels this is just the beginning 

for the specification of solar PV on 

roofscapes... 

REGULARS 

10 Spreading the word: Maggie 

Fennell of GRO and the Boningale 

Group reports back from recent 

exhibitions where she’s been helping 

raise the profile of green roofs and 

GRO 

14 Academic Corner: In the second 

part of his focus on drought 

tolerance of green roofs in a 

changing climate, Dr Tom Young 

focuses on irrigation techniques and 

the importance of getting it right 

22 Mythbusters: Our latest column 

dispels the myth that deeper 

substrates mean more expense 


News 

GREENSCAPE 

GRO COLLABORATES ON NEW BOOK TO HELP INTRODUCE 

TOMORROW’S CONSUMERS TO GREEN ROOFING 

LIVING WALL AWARD 

Biotecture is celebrating winning a 

BALI National Landscape Award for 

the Canary Wharf estate Greening 

Phase One. 

The extensive urban greening 

project was selected as a winner in 

the Exterior Living Wall Category 

in what the judges said was a 

‘phenomenally’ high standard of 

entries in this year’s award. 

Biotecture delivered PlantBox living 

walls in prominent locations across 

the Canary Wharf estate in 2021. 

They are now helping to enrich 

the public realm and contribute 

to Canary Wharf Group’s (CWG) 

ambitious sustainability goals. 

The judges commended Biotecture for: 

“A green initiative worthy of support. 

A committed contractor coupled with 

a client willing to experiment.” They 

go on to say: “The modular living wall 

system has some science behind it and 

fulfils the client’s brief”. 

In a nod to the science, the BALI 

judging panel recognised how the 

Biotecture living walls are helping 

to improve air quality, attenuate 

rainwater and increase biodiversity 

for residents, commuters, workers 

and visitors to the area. 

Richard Sabin, MD at Biotecture, said; 

“Winning a National Landscape Award 

is hugely significant because it helps 

us highlight the benefits of adding 

greenery and biodiversity into the 

urban realm. These benefits are hugely 

significant to people living and working 

in the Canary Wharf area, although it is 

the aesthetic appeal of the living walls 

that people notice first!” 

www.biotecture.uk.com 

Angela Lambert, on behalf of GRO, 

discusses Journey to the Green Roof, 

a book for youngsters from GRO and 

Tales from Mother Earth, written by 

Jenny Bailey… 

“The UK Government’s Build Back 

Greener Strategy sets out policies and 

proposals for meeting the country’s 

target of being net zero in 2050. 

I’m in my mid 50’s and there’s no 

guarantee I’ll be around to celebrate 

the achievement. However, by then 

my grandchildren will be in their 30’s 

and 40’s and will likely be in a position 

to not only benefit from the initiatives 

but possibly to influence decisions 

about the built environment. 

“That’s why, when the GRO Marketing 

Team told me about their collaboration 

with Tales from Mother Earth to publish 

a children’s book which highlights the 

benefits of green roofing, I was instantly 

keen to learn more. The new book 

is titled Journey to the Green Roof 

and highlights the benefits of green 

roofing from the perspective of two 

very characterful beneficial insects. I 

won’t give any more away, but I have 

seen the first draft and I can confirm 

that the story is very compelling, highly 

empathetic and absolutely delightful. 

The characterisation puts me in the 

mind of Beatrix Potter – and we know 

how evergreen her stories are. 

“Author Jenny Bailey has successfully 

published three other children’s 

audio story books in the same style 

as Journey to the Green Roof. 

Phoebe the Bee follows the plight 

of a honeybee and helps children to 

understand how crucial biodiversity 

is to the survival of our planet. 

Spike the Hedgehog is an enigmatic 

little character who illustrates the 

challenges for wildlife in gardens and 

Stanley the Water Vole highlights the 

consequences of allowing plastic to 

pollute our environment. 

“Each book includes an audio 

recording, so that children can follow 

the printed words to help develop 

their reading skills. There are also 

puzzles and activities within the book 

to engage little ones further. And in 

Journey to the Green Roof, Dusty 

Gedge has contributed a series of ‘fun 

facts’ to help educate children (and 

adults!) on the practical benefits and 

the charms of living roofs. 

“I urge you to visit Jenny’s website 

to learn more about her books – and 

perhaps purchase one or two for the 

young people in your own life. 

(www.talesfrommotherearth.co.uk) 

“Journey to the Green Roof is on 

track to be launched on World Green 

Roof Day, 6th June 2023, and the 

author, along with GRO, is offering a 

unique opportunity for GRO members 

to get involved. The hope is that 

through members’ sponsorship, GRO 

will be able to offer the book as a free 

giveaway to schools and community 

groups. Participating members 

will have their logo printed on the 

sponsors page in the book and can 

nominate a school or group in their 

area to receive copies. 

“I’m only a humble copywriter with 

a keen interest in green roofing, 

but I can picture myself now, sitting 

with a group of children in my 

granddaughter’s primary school, 

reading the story out loud and 

showing the children some of the 

plants that are mentioned in the 

book. I’d tell them about the green 

roofs to look for in our area, and I’d 

like to think that the youngsters will 

each take a copy of the book home 

to read with family members. I’ll be 

sponsoring some books - will you?” 

Contact Chris Bridgman or Maggie 

Fennell from the GRO to find out how 

to sponsor Journey to the Green Roof. 

www.greenrooforganisation.org 


Proud to be 

a member of 

the GRO Code 

The sky’s the limit 

With a Green Roof System from Green-tech 

1 

2 

3 

4 

5 

1. Choice of soft and hard landscaping 

materials available, including: 

• Sedum Matting 

• gtSedum Cassettes 

• John Chambers Wildflower Matting 

• John Chambers Green Roof 

Wildflower Mix 

• Turf 

• Planters 

2. Intensive or Extensive Green-tree 

Roof Garden Substrate 

3. Drainage Board System, including: 

• Filter Membrane 

• Drainage Layer 

• Rootbarrier 

4. Waterproofing Layer 

5. Roof Structure 

This diagram of a typical green roof construction is for illustrative purposes only to demonstrate the range 

and types of products available for a green roof installation. 

Green-tech is a leading supplier 

of landscaping and green roof 

materials. Our products have been 

used in many high profile and 

award-winning green roof projects 

throughout the UK. 

We can provide everything you 

need for a successful installation, 

including technical advice, project 

specifications, CAD drawings and 

of course, a full range of Green 

Roof products. 

For more information, book a 

free Green Roof System CPD 

presentation, to be delivered 

online or in your office. 

T: 01423 332100 

www.green-tech.co.uk 

sales@green-tech.co.uk 

@greentechltd 

@greentechuk 

green-tech-ltd

News 

PV INSTALLS UP IN 2022 

Data from MCS (Microgeneration 

Certification Scheme) for solar panels 

installed on UK homes shows that 

new solar PV installations surpassed 

the total for 2021 just eight months 

into 2022. 

MCS, which defines and maintains 

standards for small-scale domestic 

renewable energy and heating across 

the UK, has recorded all certified 

installations on its central database 

since 2008. 

Figures show that 79,560 solar PV 

installations were completed from 

January – August 2022, a 30% increase 

on the 61,431 installed in the whole of 

2021. There was a 144% increase of 

solar PV installations registered with 

MCS in August 2022 – 12,411, compared 

with 5,082 in August 2021. 

The data combats concerns in 

the renewable energy sector that 

domestic solar PV demand would 

diminish after the Feed-in Tariff (FiT) 

incentive ended in April 2019. 

In all, solar PV installations comprise 

more than 80% of the 1.4 million 

renewable installations so far registered 

with MCS. This takes the total number 

of ‘sunny roofed’ residential properties 

to more than one million. 

In 2021, small-scale solar PV 

installations produced a peak of 

3GW of electricity for the UK grid for 

the first time ever, around the same 

amount of power as the Sizewell C 

nuclear power plant (3.2GW). 

Ian Rippin, CEO of MCS, explained: 

“With UK homeowners quite rightly 

worried about the cost of living amid 

rising energy costs, we are pleased to 

report the installation of solar PV is 

powering on as homeowners look to 

invest in home-grown energy. We are 

seeing more installations registered 

on the MCS database and our certified 

contractor base also continues to grow.” 

www.mcscertified.com 

SIKA DONATES GREEN ROOF TO 

IMPORTANT LOCAL PROJECT 

Leading roofing manufacturer, Sika, 

has donated over £7,000 worth 

of materials to a social enterprise 

in Salford which is creating a safe, 

indoor space to host events and 

activities aimed at tackling 

social isolation. 

Created from two disused 

shipping containers, the new 

building is located at the Cleavley 

Community Forest Garden in Winton, 

which is run by Incredible Education 

CIC, a social enterprise providing 

nature-based services for local 

communities through horticulture and 

forest school activities. 

Having access to the new covered 

space will enable the garden to 

host music events, health activities, 

parent and toddler groups and 

workshops all-year round; all with 

the aim of improving community 

connection. 

The building will primarily provide a 

secure indoor workshop to Salford 

community group, Working in Wood, 

which runs woodwork projects for 

anyone over the age of 18 looking to 

gain skills or meet new people. The 

group, which helps to tackle social 

isolation, has also been involved with 

the construction of the new building, 

having erected the timber frame 

surrounding the containers. 

The two shipping containers were 

combined to form a 20ft x 30ft 

room topped with a Sika Green Roof, 

which blends in with the natural 

surroundings and nods to the land’s 

former use as a plant nursery. 

The system build-up included SikaBit 

VB-724 Air and Vapour Control 

Layer (AVCL) VCL, 100mm Foil-faced 

AL Sikatherm insulation and the 

new, sustainable roof membrane 

Sarnafil Advanced Technology 

(AT) - the UK’s only Cradle to Cradle 

Silver certified single ply 

membrane. The membrane is 

not only independently certified 

in sustainability performance but 

as it contains no plasticisers, oils, 

chlorine or heavy metals it is ideal 

for sustainable construction. Topping 

this, the aluminium edge trim, 

SikaRoof drainage layer, SikaRoof 

Biodiverse substrate and a SikaRoof 

Wildflower Blanket, created a natural 

habitat for flora, fauna and wildlife. 

The wildflower blanket was laid in 

such a way to encourage the roof to 

self-germinate with local seeds blown 

by the wind onto the roof. 

The install took four days and 

was carried out by Sika-approved 

installer, Chorley-based roofing 

contractor, Enviroply Roofing Ltd, 

who donated their time to the project 

free of charge, alongside members 

of the Sika roofing team. 

Ian Bocock, Director and Education 

Manager at Incredible Education 

CIC, commented: “We’re all about 

promoting mental health and 

wellbeing in a green space so to be 

able to host activities year-round 

which build skills and confidence 

is huge. Having the roofing 

materials and labour donated to 

the project was massive because 

our budget was used up on 

groundworks, steelworks, cladding 

and in purchasing the containers. 

To receive those donations was 

fantastic and we’re thrilled with our 

new green roof, which fits so well 

within the garden.” 

www.sika.co.uk/roofing 


GREENSCAPE 

Above: Alice, Georgia, Emily and Mark from 

Green-tech Specifier 

NEW WEBSITE LAUNCHED BY 

GREEN-TECH SPECIFIER 

Green-tech Specifier has launched its 

new and improved website 

www.gtspecifier.co.uk 

Green-tech Specifier is the 

specification team of leading 

landscape supplier Green-tech. The 

team was established to meet the 

growing demand of Landscape 

Architects, Garden Designers and 

Contractors who required assistance 

at the specification, estimating and 

drawing stages of their projects. 

The new and improved Green-tech 

Specifier website addresses the needs 

of Landscape Architects, Contractors, 

and Garden Designers and showcases 

the latest solutions and products for 

urban regeneration and landscaping 

projects, including a number of 

solutions to address climate control, 

flooding and biodiversity challenges. 

Visitors will find a host of resources 

to help support landscape design 

projects, including: 

• Resource library; 

• Product calculators; 

• Event calendar; 

• Project assistance; 

• CPD seminars; 

• Past webinars; 

• News articles & videos 

Green-tech Specifier is a team of seven 

that has the product knowledge and 

technical expertise to provide advice, 

guidance, and recommendations for 

bringing landscape designs to fruition. 

www.gtspecifier.co.uk 

MCS PROVIDES ACCESS TO REAL- 

TIME RENEWABLES DATA WITH NEW 

DATA DASHBOARD ONLINE TOOL 

MCS (Microgeneration Certification 

Scheme), the standards organisation for 

small-scale domestic renewable energy 

and heating across the UK, has announced 

the launch of its brand-new, interactive 

online Data Dashboard to provide a 

detailed analysis of the volume of domestic 

renewable energy installations in the UK. 

The MCS Installations Database (MID) 

holds the details of every MCS certified, 

small-scale renewable energy installation 

in the UK since 2008, making it the most 

comprehensive reference for small scale, 

renewable energy installations in the UK. 

The organisation says the abundance 

of information in the MID puts MCS in a 

unique position to share data-driven insights 

to help manage the net zero transition. 

MCS says Industry, Ofgem and BEIS (the 

Department for Business, Energy and 

Industrial Strategy) have long used the 

MID as a single reference point to help 

inform policy development, but this data 

will now be made publicly available for the 

first time. MCS says the new MCS Data 

Dashboard will provide near-real-time 

updates on MID data, tracking the adoption 

of small-scale renewable installations across 

the UK. Given the UK’s legally binding netzero 

targets, MCS says the platform will 

monitor the current uptake of small-scale 

renewables, highlight current and past 

trends, and identify opportunities for further 

development and growth. The organisation 

points out already this year, it has recorded 

continued growth in solar PV installations, 

with the number of installations recorded in 

the first eight months of this year exceeding 

the total number of installations in 2021 

(see page 8). 

By creating dynamic visualisations, MCS 

says users of the Data Dashboard will be 

able to view the uptake and distribution 

of small-scale renewable installations 

across the UK in near-real-time. MCS 

points out data is updated every 24 hours, 

instantaneously providing the most 

accurate picture of home-grown energy 

available across the industry. The platform 

is also said to provide insights into the MCS 

certified contractor community, identifying 

growth and opportunities in green jobs 

as the volume of low carbon installations 

continues t to increase. 

The MCS Dashboard is said to be divided 

into two sections: Installation Insights 

and Scheme Insights; the Installation 

Insights section showcases the uptake and 

geographical distribution of renewables, 

where they’re used successfully and 

where opportunities for growth are, whilst 

Scheme Insights enables users to compare 

the growth of different technology types 

and shines a light on the contractor base 

installing them. MCS says both can be 

filtered by year, location, technology and 

installation type, with image and data 

exports available to download. 

Ian Rippin, CEO of MCS, said: “Robust data is 

the essence of strong decision-making. Our 

Data Dashboard has been a long time in the 

making and our efforts have paid off as we 

roll out our invaluable data via a real-time 

platform that will be a useful tool for several 

audiences. We believe this data will be 

important to people working on renewable 

installations and those who influence the 

policies for our low carbon future. 

“This is why we believe it is important 

to make our data freely available and 

we encourage anyone in the domestic 

renewable energy sector or working on 

energy system modelling to use it to their 

advantage. The MCS Data Dashboard will 

continue to evolve, and as we look to build 

its capabilities out even further we seek 

honest and constructive feedback from 

users.” 

mcscertified.com/about-the-mcs-datadashboard/ 


EXHIBITIONS & NETWORKING 

RAISING AWARENESS & BUILDING 

BUSINESSES THROUGH NETWORKING 

Maggie Fennell, Marketing Chair for GRO and board member 

representing Boningale Group, reports back from recent 

exhibitions which have seen GRO interacting with the supply 

chain and raising the profile of green roofs through interaction 

with key stakeholders... 

GRO members are making 

the most of trade shows and 

exhibitions in order to meet with 

and create relationships with industry 

experts, manufacturers, growers, 

specifiers, planners and potential 

clients. 

Maggie Fennell, Marketing Chair for 

GRO and board member representing 

Boningale Group, recently represented 

GRO at the Landscape Show, in 

Birmingham, where she says she was 

kept on her toes by a constant stream 

of visitors wanting to learn about green 

roofing. The audience consisted largely 

of garden designers and landscapers 

who wanted a greater understanding of 

domestic green roofing. 

Building on the success of the 

Landscape Show, GRO says it is 

planning to visit Futurebuild at London 

ExCeL in March 2023. A very different 

audience, but with a similar objective 

– to create links within the industry 

so that expertise can be shared and 

opportunities created. 

Here’s Maggie’s report from the 

Landscape Show and her thoughts on 

Networking: 

“In an industry which relies on the 

successful cooperation of many 

disciplines, networking is key to growing 

the marketplace and offering a wide 

variety of green roofing solutions. 

Although the word ‘networking’ 

conjures up the worst kind of images 

of ‘beige’ buffets and small talk, I am 

Above: Maggie Fennell presenting on behalf of GRO at a recent industry trade show. 

happy to report that this has not been 

our experience at all. 

“One of the core benefits the Green 

Roof Organisation offers to members is 

that kind of networking that builds trust 

and confidence. We need to learn from 

each other’s experience, otherwise the 

industry will not develop as fast or as 

effectively as our planet needs it to. 

“The Landscape Show in September 

provided a great opportunity to connect 

with domestic green roof installers and 

designers and – just as importantly – 

with many prospective and fledgling 

green roofers who are at the very 

beginning of their journey towards 

including living roofs into landscaping 

projects. 

“In a targeted trade show like 

Continued on page 12 >>> 


EXHIBITIONS & NETWORKING 

See GRO at 

Futurebuild 

7-9th March 2023, 

ExCeL London 

Book tickets at: 

www.futurebuild.co.uk 

GRO has enjoyed success at recent exhibitions, creating good relationships and educating the supply chain on the benefits of green roofs 

>>> Continued from page 10 

Landscape, there are rarely huge 

volumes of traffic, which means more 

time to spend with individuals. In that 

way, each conversation is more detailed, 

more specific and more personal. GRO’s 

objective for this event was to reassure 

new entrants to the industry that they 

will be welcomed and supported at 

every step of the way. I came away from 

the two-day event feeling confident that 

we had achieved just that. 

“NEC Birmingham provided an ideal 

venue for this show. Its central location 

is easily accessible and we saw visitors 

from all over the UK. The show 

organisers did a fantastic job of turning 

the cavernous, industrial hall into a light, 

bright meeting space with four seminar 

theatres, several demonstration areas 

and a central cafe area with superb 

flapjacks! The presence of plants on 

every other stand certainly helped 

create a good ambience too. 

“On day one of the show I teamed up 

with Kay Davies from Oxford Green 

Roofs to give a presentation entitled 

‘How To Get Going In Green Roofing’. 

The attendees responded well to our 

mix of technical background, varied 

case studies and signposting towards 

resources that will help businesses take 

the next step towards green roof design 

and installation. 

“Kay has been helping to advise GRO 

on further support needed by domestic 

green roofers. As a starting point, our 

organisation has set up a Facebook 

Group to encourage communication, 

support and cross referrals. Join 

‘GreenRoofOrganisation GRO Official’ 

on Facebook to share your thoughts, 

ask questions and tell us more about 

your work in the green roof industry.” 

Looking ahead 

“Looking ahead to next year, GRO has 

been in talks with Futurebuild about 

providing our members with the 

opportunity to engage face to face 

with policy makers, planners, landscape 

architects and architects. Plans are 

very much in their infancy but we 

hope to provide GRO Members with 

opportunities to come together with 

stands and interactive demonstration 

spaces that provide a great educational 

experience for visitors. 

“Green roofs lend themselves to visual, 

practical, and tactile displays which can 

include different plant types, colours 

and textures. These conversation 

starters are a great lead-in to explain 

the benefits of green roofs and how 

following the GRO Code of Best Practice 

will optimise their performance. 

“If you’d like to be involved, please get 

in touch with one of the GRO board 

members.” 

Sign up for GRO updates to keep in 

touch with the organisation’s news, 

views and activities. 

Simply email: membership@ 

greenrooforganisation.org and the 

team will do the rest. 


SAVVY SHOPPER 

THIS AWARD IS PRESENTED TO THE: 

Laura Crombie 

Brand Director 

Real Homes 

M-Tray®: modular, instant green roofs 

EASY ON EASY OFF 

The great outdoors 

WALLBARN M-TRAY 

M-Tray 

installed by 

YMCA 

students on 

the awardwinning 

Green Roof 

Project, 

Milton 

Keynes. 

www.wallbarn.com 0208 916 2222 

has your green roof been physically 

FIRE TESTED? 

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British grown - quick delivery - easy installation - all-year vegetation

ACADEMIC CORNER 

DROUGHT TOLERANCE FOR A CHANGING 

CLIMATE – PART 2 

By Dr Tom Young, Blue-Green Infrastructure Associate at TEP. 

When I spoke about water 

on green roofs in my last 

article, I mentioned in passing 

the role of irrigation on green roofs. 

However, it really deserves a full article 

to itself. Irrigation can be a contentious 

issue on green roofs, but very often 

it is not thought through properly. 

In many situations irrigation may 

not be appropriate for a green roof. 

However, due to our changing climate 

some form of irrigation, either as a 

backup or an establishment method, 

is recommended in some situations. 

As a caveat, this article is designed to 

speak to a UK design audience. 

Other countries have much 

more extreme climates than 

us and therefore irrigation 

requirements are very 

different. 

When and how to irrigate 

You need to be very careful 

when deciding to specify an 

irrigation system on a green 

roof. An irrigation system shouldn’t 

be used to make up for a poor or 

inadequate design. It should be used as 

a backup system to cope with extreme 

events. With extreme events becoming 

more common, the need for additional 

irrigation is likely to increase in the 

future. However, green roof design 

should also adapt to changing climate 

i.e. different plant species, landscape 

design or substrate depth. 

There should be a hierarchy of water 

sources used for any irrigation system. 

Potable mains water should always be 

used as a last resort as there are plenty 

of more sustainable – and cheaper in 

the long term – sources of water. This 

list provides a rough water source 

hierarchy that should be followed: 

Left: Dr Tom Young. Above: Figure 1 – Illustration shows a potential fog net and 

solar panel dew harvesting green roof. See Fog water section on next page. 

1. Rainwater direct or 

reuse (this could also 

include fog/dew water) 

2. Recycled greywater or 

air-conditioning condensate 

3. Treated wastewater (hopefully to be 

made more available in the UK in the 

future) 

4. Saline water (very much location 

dependent) 

5. Potable water. 

Rainwater harvesting 

The most obvious way of irrigating a 

green roof is to collect all the water 

that falls on it. A degree of water is 

retained anyway but green roofs will 

drain like a normal roof when at field 

capacity. A variety of methods exist to 

capture drainage water. These range 

from large tanks at ground level, to 

more innovative blue-green roofs which 

store water on the roof (see subsurface 

irrigation section). Water can then be 

moved from these storage areas with 

either pumps, or passively wicked into 

the substrate on demand. 

Air conditioning condensate 

Air conditioning (AC) units produce 

condensate water as part of their 

mechanical process. In UK cities 

the use of air conditioning units is 

becoming much more prevalent. An 

AC unit designed for a single room or 

apartment on a green roof in Beirut 

provided between 0.2-1.2 l hour -1 

depending on the humidity 

(Sisco et al. 2017). 

This wouldn’t be enough to support a 

large green roof but could be used to 

help supplement other water sources. 

The advantage of this water source 

is that as temperatures increase and 

water demand rises, the amount of AC 

water available is also likely to increase. 


Greywater 

Greywater can be defined as 

wastewater from domestic and 

industrial uses. The easiest and safer 

to use sources of greywater include 

kitchen drains, hand washing from sinks 

and domestic clothes washing. This can 

be reused on green roofs with minimal 

treatment, with the green roof actually 

providing the treatment in some cases. 

Due to its regular production, large 

amounts of storage are not needed as it 

is a very predictable supply 

(Mahmoudi et al. 2021). 

Fog water 

In coastal or humid environments, a 

surprising amount of water can be 

collected from fog/dew. Fog collectors 

can range from giant vertical mesh 

nets which capture fog, to adapted 

solar panels which collect dew. A study 

of different warm climates found that 

between 1.2-15.6 l m -2 day -1 could be 

harvested from fog water and 0.2- 

0.7 l m -2 day -1 from dew. This could 

potentially supply 100% of the irrigation 

need of green roofs in these climates 

(Pirouz et al. 2021). Figure 1 (left) 

shows a potential fog net and solar 

panel dew harvesting green roof by 

Pirouz et al. 2021. 

Saline water 

Saline water is another option to 

use on green roofs. Saline water can 

come directly from the sea, or even 

from brackish groundwater or treated 

wastewater. In an extreme example, 

Ntoulas & Varsamos 2021 irrigated 

warm season turfgrass in a green roof 

setting with seawater from Athens’s 

harbour. The idea was to see if the 

turfgrass could be kept alive under 

extreme conditions i.e. during a long 

summer drought when no other 

water was available. They showed that 

although turf quality declined during 

the irrigation period, turf still survived. 

An effective method was to over 

irrigate with salty water in order to 

Above: Figure 2 shows an inappropriate irrigation system on a green roof in the UK. 

prevent salt build-up in the substrate. 

The extra water, despite being salty 

helped to keep salt in solution and 

pass out of the substrate as the excess 

drained (Ntoulas & Varsamos 2021). 

Benefits of irrigation 

It sounds obvious, but in the harsh 

green roof environment a small 

amount of extra water, specifically 

during extended dry spells, can 

significantly increase plant survival. 

This is particularly true in the first few 

establishment years of a green roof. It 

also applies to green roofs that have a 

wider range of plants other than very 

hardy succulents. Irrigation provides 

a greater amount of plant available 

water which prevents plant death, 

lowers substrate temperature, and 

reduces stress on plants. A study in the 

US showed that irrigating green roof 

modules could reduce their average 

summer substrate temperature by 

between 2-4ºC, as well as reducing the 

level of extreme substrate temperatures 

(Guckenberger et al. 2011). This can 

also then result in greater ecosystem 

service benefits, for example a 

greater cooling effect on the urban 

environment (Van Mechelen 2015). 

Reduced plant mortality also works out 

to be much cheaper in the long term 

as plants do not need to be regularly 

replaced! 

Negatives of irrigation 

Irrigation, when used carefully, is very 

effective at helping plants establish and 

survive extended dry spells. However, 

when used excessively, irrigation 

can lead to poor quality green roofs. 

Green roofs are designed to be harsh 

environments to prevent excessive 

plant growth and ingress of weed 

species. Excessive irrigation leads to 

certain plant species (grasses, tree 

seedlings) dominating and pushing 

other more desirable species out. See 

Figure 2 (above) for an example of an 

inappropriate irrigation system on a 

green roof in the UK. This system was 

too small to cover the whole roof and 

was set on a regular timer, which had 

over-irrigated the roof for a number 

of months. Species diversity was 

significantly less in this area and had 



ACADEMIC CORNER 


promoted a much less species-diverse 

habitat. 

Another example is provided in Figure 3 

(right) which shows the massive effect a 

dripping pipe can have on vegetation. In 

this instance a tap had been leaking for 

a couple of years on an extensive roof, 

leading to a very different vegetation 

composition in this area. 

Methods of irrigation 

Water can be applied in a number of 

ways to a green roof. A number of 

these were compared in an excellent 

trial by Rowe et al. 2014. The authors 

compared overhead sprinklers, drip 

lines and sub-surface emitters in a 

variety of green roof settings. In this 

trial, overhead irrigation seemed to be 

the most effective at encouraging plant 

growth. Due to the coarse nature of 

green roof substrate, the wetting front 

of sub-surface and surface drip lines 

did not cover the whole green roof, 

resulting in patchy growth. However, 

the addition of a water retentive fabric 

did help to improve the effectiveness of 

both sub-surface and surface drip lines 

by retaining more water and helping to 

more evenly distribute it 

(Rowe et al. 2014). 

Blue-green roof subsurface 

A more efficient sub-surface irrigation 

method combines the drainage layer of 

a green roof and the water storage of 

a blue roof. This means that drainage 

water from the green roof is retained 

and can be easily reused. An additional 

benefit is the much greater amount 

of stormwater retention, reducing 

potential flooding downstream. 

Generally, this involves passive capillary 

wicking of water from the storage tank 

into the substrate via a water retentive 

fabric which helps to evenly distribute 

water. This type of system has been 

shown to be very effective at irrigating 

extensive green roofs, allowing a 

reduced substrate depth and providing 

Above: Figure 3 shows the huge impact a dripping pipe can have on vegetation. 

large amounts of evapotranspiration, 

without the need to use additional 

water sources (Cirkel et al. 2018), 

although this type of system can also be 

topped up with other water sources if 

captured rainwater runs out. 

Smart systems 

Irrigation controls are also becoming 

much smarter. There are plenty of 

systems now that irrigate according 

to weather conditions, predicted 

evapotranspiration and green roof 

moisture levels (Bandara et al. 2016). 

Care still needs to be taken when 

using these to ensure they are set up 

correctly and calibrated on a regular 

basis. I have seen plenty of examples 

where they have gone rogue and 

irrigated nonstop for months on end! 

Conclusions 

• Irrigation is sometimes required on 

green roofs in the UK. 

• Requirement is likely to increase in 

some areas due to climate change. 

• Requirement can be reduced by good 

green roof design (substrate depth, 

type, drainage layer, moisture retention) 

and appropriate plant selection. 

• Irrigation system is important – some 

are much more efficient at providing 

irrigation direct to plant, reducing 

losses. 

• Water source should always be 

considered. Use non potable, captured 

or recycled water when possible. 

• Excessive irrigation should be avoided 

at all costs. Irrigation should be viewed 

as a backup and only used to keep 

roofs alive. This advice is specific to UK 

climate. 

• Irrigation system can be combined 

with stormwater storage and passively 

used to irrigate the roof. 

• The green roof system needs to be 

thought of carefully as a whole system. 

Irrigation should not be considered at 

the end as a passing thought to tack 

onto the design. 

Contact 

Dr Tom Young 

E: tomyoung@tep.uk.com 

Tweet: @DrGreenRoof 


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ROOFING TILES

GREEN ROOFS PLANT SELECTION 

GROWING RESILIENCE: 

PLANT PLASTICITY AND VARIATION FOR 

CLIMATE-SMART GREEN ROOFS 

By Dr. Elisa Olivares Esquivel, Lecturer in Planting Design, Department of 

Landscape Architecture, at the University of Sheffield. 

In the autumn issue of Greenscape, 

Dr. Tom Young wrote the first part of 

a very insightful article about green 

roof challenges in the face of climate 

change and the different elements 

that can be tuned to achieve resilient 

systems. 

Plant selection is one of these elements 

that goes a long way to future-proofing 

the roof and a critical process that is 

worthy of far more research. There 

are plenty of green roof mixes on the 

market, with plants suitable for many 

different types of roof. However, with 

the impact of climate change, some of 

the species that work today may not be 

optimal in the future. 

Broader plant palettes 

These days we often hear that we 

need to work not only with broader 

plant palettes of species, but also more 

diverse plant material with greater 

plasticity. These sources of natural 

variation (and artificial selection) could 

be obtained either by responsibly 

and sustainably collecting plant 

material from the wild, especially from 

distinct populations, or by breeding 

drought resistant plants, for example. 

Nevertheless, before starting with these 

endeavours we need to understand 

what these terms mean and their 

implications for climate resilience and 

adaptation. Plasticity can have different 

meanings depending on the discipline 

or the context in which we are studying 

the plants, for example ecology or 

molecular biology. 

The concept of plasticity 

To clarify the concept of plasticity, Rob 

Brooker and his team (2022) explained 

how the concept can be applied in crop 

breeding. This can be applied to plant 

breeding as a whole or plant hunting 

and screening for green roofs and / or 

green infrastructure. 

Brooker explains that one of the most 

often applied forms of the term is 

phenotypic plasticity, which often refers 

to “changes to phenotype in response 

to changes in environmental conditions” 

(2022). Phenotype, according to 

Scitable by Nature Education (2022), 

“refers to the observable physical 

properties of an organism; these 

include the organism’s appearance, 

development, and behaviour.” 

This means that a plant with a high 

phenotypic plasticity could respond 

to drought by changing the size of 

its leaves, reducing the number of 

stomata, and generating a greater 

number of offshoots for vegetative 

propagation, for example. The plant 

can adapt appropriately for its survival. 

Phenotypic plasticity can be expressed 

in a lower or higher degree in traits, 

i.e. “a morphological, physiological, or 

phenological feature of an individual 

plant that is measurable” (Brooker 

et al. 2022) in plants from particular 

locations. 

In research exploring the plasticity of 

Fragaria vesca to drought, clones of 

material from different locations of 

the French Pyrenees and Alps were 

tested in different moisture regimes. It 

was found that flowering and runner 

production from plants from south 

facing slopes were maintained in low 

moisture conditions in comparison 

with material from north facing slopes, 

which had reduced or no capacity for 

producing them (De Kort, 2020). This 

is found in a higher degree according 

to gradient and aspect, more than 

to elevation. There is tremendous 

variation within species dependent on 

a plant’s origins and this can be utilised 

for resilient plant selection. 

Building-in resilience 

The take-home message here is that for 

our urban green spaces to survive the 

onslaughts of extreme weather events 

brought about by the climate crisis, we 

need to build-in resilience to our plant 

selection now. That resilience comes 

from diversity: in the number of plant 

species and within-species varieties, 

such as ecotype. As with our food 

systems, reliance on the same small 

number of species and cultivars makes 

us increasingly vulnerable to the effects 

of climate change and the pests and 

diseases that come with it. 

Contact Dr Elisa Olivares 

Esquivel 

Email: 

elisa.olivares@sheffield.ac.uk 


Updated GRO Code 

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01_GS0421 1 16/04/2021 17:07 

From the publishers of

GREEN ROOFS MAINTENANCE 

GAINING THROUGH 

MAINTAINING 

The experts at Eco Green Roofs (EGR) outline the important 

maintenance steps you should take to maximise the 

performance and ensure the longevity of your green roof. 

To ensure their aesthetic 

appearance, design 

functionality and 

environmental benefits are 

maintained, it is important that 

regular maintenance of green 

roof systems is undertaken. 

At Eco Green Roofs, we 

recommend that regular 

maintenance be carried out at 

intervals appropriate for the 

type of living roof; generally 

twice per annum for sedum and 

biodiverse roofs, and between 

3 and 6 times per annum for 

fully developed wildflower blankets. 

Given the investment made in the 

design and installation of a green 

roof, it is important that the system 

delivers its full life-cycle potential of 

both commercial and environmental 

benefits. A well-managed and regular 

maintenance programme will ensure 

longevity of performance and an 

economic and environmental/social 

return. 

The main considerations to ensure the 

ongoing performance of a living roof 

are: 

• Free flowing and unrestricted roof 

drainage 

Regular maintenance of roof outlets 

and drainage inspection chambers will 

ensure free flowing and unrestricted 

roof drainage. It is vital that an excess 

build-up of rainwater is not retained on 

the roof to harm the living roof. Excess 

water will weaken root systems and 

allow invasive species to take over. 

• An adequate amount of nutrients 

The correct amount of nutrients in a 

living roof is important to help maintain 

strong and consistent vegetation 

growth and coverage across the 

whole roof area. A lack of nutrients 

will eventually result in bare patches 

across the roof and will limit the 

species capable of living in the system. 

Conversely, if it’s too nutrient rich, it will 

encourage excessive vegetation growth 

which will require trimming and cutting 

back to acceptable levels. 

• Control of all spent vegetation, and 

undesirable and potentially invasive 

species 

To maintain the balance of both species 

and nutrients it is important to monitor 

development of the plants. This involves 

controlling excess growth and regularly 

removing dead material and excess 

vegetation to avoid impeding drainage 

and leaving excess biomass on the roof 

which can upset the nutrient levels in 

the substrate and spoil the aesthetic 

look and design performance. 

At this time of year it’s 

particularly important to pay 

attention to these elements. 

Leaves are falling and although 

some sedum and late flowering 

wildflowers are still in bloom, 

there will also be many deadheads. 

All of this excess 

vegetation should be removed 

from the living roof areas. Any 

spent vegetation left over the 

winter can add unwanted biomass 

to the roof as it rots down, 

causing nutrient levels to become 

too high. This is particularly 

important to avoid on biodiverse roofs 

which need low nutrient systems. If leaf 

guards or inspection chambers are not 

in place over outlets, these need to be 

checked before the winter to make sure 

they are not blocked with leaf litter, 

which could cause leaks. It’s also the 

time of year when permanent irrigation 

systems need to be drained down, so 

that there is no water left in external 

pipework over the winter – otherwise 

this could freeze and burst. 

If you don’t already have a maintenance 

contract in place, now is a perfect 

time to have your green roof tidied 

and its condition checked, and a plan 

put in place for when the roof starts 

its growth again in the spring. Regular 

maintenance visits really can make a 

difference to the year-round health and 

appearance of your living roof. 

Scan the QR code to speak 

to one of our Eco experts 


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NFRC sets the highest 

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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 

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MYTHBUSTERS 

MYTH: DEEPER SUBSTRATE MEANS 

MORE EXPENSE 

Fact: Optimising substrate depth leads to enhanced benefits and greater sustainability. The experts 

at GRO explain more... 

When designing any structure, 

build costs will always need 

to be a consideration. But 

rather than think in terms of initial 

expenditure, think about lifetime value 

for money. The purpose of this article 

is to encourage you to think about 

future proofing the green roofs you are 

designing, installing and maintaining, 

rather than viewing them as a boxticking 

exercise. 

Let’s start by reviewing the functions of 

the substrate layer on a green roof. The 

most obvious is, of course, to sustain 

life and give the plants somewhere to 

grow whilst also providing a home for 

nature. The substrate is also an intrinsic 

factor in stormwater management, 

thermal performance, protecting the 

waterproofing from UV and mechanical 

damage, fire protection and creating 

wildlife habitat. 

Substrate installation. 

Image courtesy of 

Bridgman & Bridgman 

On a less positive note, some green roof 

designers are tempted to skimp on the 

substrate layer to reduce the loading 

and cost. However, this is a mistake that 

would be more difficult – and expensive 

– to rectify once the structure is built 

and the green roof installed. 

The benefits of deeper substrates 

include: 

• Increased ability to retain water and 

help mitigate the risk of flooding. 

• More room for plant roots to develop, 

therefore vegetative layer is more 

robust. 

• Allows a wider choice in the planting 

pallet enabling facilities managers to 

adapt the vegetative layer should local 

conditions alter due to climate change. 

• Happier plants lead to a self-sustaining 

community which needs lower amounts 

of irrigation and fertiliser applications, 

saving on some maintenance costs. 

• More effective at protecting the 

waterproofing from daily variations in 

temperature. 

• Deeper substrate also helps moderate 

temperatures within the building. 

Deciding on substrate depth 

The GRO Code recommends that 

green roof substrate depth should be 

a minimum of 80mm for a relatively 

simple extensive sedum roof. However, 

don’t limit your planning to the plant 

palette you intend to use at the point 

of installation. Will the conditions on 

this roof still be the same in a decade’s 

time? Maybe a bigger building will have 

appeared next door making this space 

too shaded for shallow rooted sedums. 

What will the local climate be like? 

Will 80mm depth of substrate still be 

enough to absorb enough water from 

a severe rainfall episode in a changing 

climate? When planting needs to evolve 

along with changes that are beyond 

your control, a deeper substrate will 

keep your options open. 

When deciding substrate depth, try 


to consider all of the benefits 

that the substrate offers. 

Areas of deeper substrate 

interspersed with areas of 

shallower substrate will allow 

you to not only spread costs by 

concentrating the loading on 

stronger areas of the building, 

whilst creating different habitats; 

Imagine a wealth of different 

plant species enjoying different 

conditions. You can create 

berms, humps and hollows and 

even engineer potential nesting 

sites for bee species that like to 

burrow. From an ecological point 

of view, variable topography is a 

wonderful thing. 

Substrate depth and reducing 

the cost of green roof 

ownership 

A good green roof is designed to 

perform long after the installers have 

left the building. And, in order for that 

to happen, the vegetative layer of the 

roof must be maintained – and this 

must be budgeted for. 

Plants with insufficient room for their 

roots, too many or too few nutrients, 

inadequate water or the wrong 

amount of sunlight will not thrive 

and environmental and aesthetic 

performance will suffer. This is also 

important on bio-solar green roofs 

where the activity of healthy plants 

helps to optimise the performance of 

PV panels. 

A deeper substrate layer has been 

shown to help plants become more 

resilient to frost and to drought. It also 

allows a greater degree of biodiversity 

so that if any species struggle with a 

particular season, there are always 

others that will thrive. In any wildflower 

meadow at ground level, the plant 

species mix will change every year 

depending on weather conditions, and 

the same effect can be seen on living 

roofs, which are subject to even harsher 

extremes. 

Above: substrate depth recommendations. 

Deeper substrate will retain more 

water for longer which eases 

pressure on drainage systems from 

stormwater runoff and supports the 

vegetative layer reducing plant losses. 

Better plant health means stronger 

evapotranspiration and cooling effects, 

maintains a great aesthetic, and all 

of the associated wellbeing benefits 

for people overlooking the roof. It 

also means that unwanted plants will 

be hard pressed to find the space to 

establish on the roof, thus lowering the 

maintenance requirement. 

Another aspect of green roof 

maintenance that is costly for the 

owners of shallow substrate sedum 

roofs but free for owners of deep 

substrate roofs is fertiliser. Because 

green roof substrate is necessarily 

low in organic matter, you need 

enough substrate to get enough soil 

microbes to fix nitrogen (plant food) 

from the air. With a deep substrate, 

plant nutrient levels are usually quite 

self-sustaining and will prevent plants 

from getting too large and sappy. On a 

shallow substrate additional fertiliser 

may be needed (this should only be 

applied when downpipes are isolated 

from the main sewage system - 

(please refer to section 5.1.2 of 

the GRO Code). 

The cost of getting it wrong 

Ultimately, the price you pay for 

a green roof has to be in line 

with your long-term objectives 

for that project. If you are 

designing a structure that is 

to be sustainable, valuable to 

the local environment, resilient 

to climate change, offer great 

PR and wellbeing benefits and 

boost biodiversity, then a green 

roof is a must. It is more costeffective 

to build it properly 

in the first place than to cut 

initial installation costs and then 

make changes ten years down 

the line. 

The singer Meatloaf sang that the two 

saddest words in the English language 

are “If Only”. If you are designing or 

installing green roofs, don’t let that be 

your legacy! 

In summary 

The deeper the substrate layer on your 

green roof design, the stronger the 

structure beneath it will need to be and 

of course there are associated costs 

with that. 

However, with careful design and 

installation, those costs will be offset 

by more manageable maintenance, 

enhanced benefits and a beautiful roof 

that will go down in history as being an 

asset to the environment. 

Contact 

GRO 

www.greenrooforganisation.org 

Tweet: @RoofGro 


GREEN ROOF SUBSTRATES 

WHAT LIES BENEATH? 

We talk substrate composition with Wallbarn and partner 

company Sedum Growers, and hear about the growing media 

they’ve developed for the M-Tray system which encourages plant 

growth and complies with all relevant standards... 

A 

farm tucked away 

in the Hampshire 

countryside has been 

leading a quiet revolution 

in the development of high 

quality, low organic and peatfree 

substrate that meets fire 

ratings and follows GRO Code 

guidance. 

It could, perhaps, be 

considered the holy grail of 

green roof growing media, 

delivering an optimum blend 

and supply of slow release 

nutrients coupled with great 

moisture control qualities, 

enabling plants to flourish 

throughout the life of the 

roof. The mix represents a 

fine balancing act between 

the basic elements of 

the substrate – compost, 

lightweight aggregate and coir 

– and the need to achieve compliance 

with BS 8616:2019, Approved Document 

B, the GRO Code and the B ROOF t(4) 

fire rating. 

And it’s only available with the awardwinning 

M-Tray modular green roof 

system from Wallbarn. The substrate 

has been developed for the British 

producer by partner company Sedum 

Growers in conjunction with renowned 

soil scientist Susie Holmes, a specialist 

in horticultural growing media and soil 

management. 

Composting 

Producing this BS-compliant substrate 

relies heavily on the quality of the green 

compost and it’s here that the greatest 

of care has been taken to ensure that 

sedum and wildflower plants in M-Tray 

are grown in the highest quality media, 

as Sedum Growers’ joint Managing 

Directors David Holloway and Keith 

Pegren know. David explained: “For us, 

a lot of the commercially available Pas 

100 compost is of unknown quality. 

It might contain weeds or hormonal 

herbicides which don’t breakdown in 

the composting process. We therefore 

manufacture our own on site using 

local, known sources of raw materials. 

We control the whole process from start 

to finish, which can take in excess of a 

year and produces a very high quality 

product.” 

So if you think your delivery of 

M-Tray modular trays smells sweetly 

fragrant and herby, then you may 

well be right, for one ingredient used 

Green roof substrate 

components 

in the compost is discarded 

matter from a local business 

producing chamomile and 

other essential oils. This high 

nutrient waste stream meets 

David and Keith’s exacting 

standards because they know 

its provenance and quality, 

and it has already been heated 

to high temperatures, killing 

weeds etc. 

Sourcing these raw materials 

ultra-locally – usually within 20 

miles – also means Wallbarn 

minimises road miles. 

Other carefully selected 

agricultural waste is combined 

into the mix, which is then 

left to compost. “It’s quite a 

complex process,” explained 

Keith. “It has to be warm 

enough to kill weeds etc. 

so we continually check 

the temperature, and the chemical 

composition of the final compost is 

key. Chemicals released during the 

composting process create salts, which 

can be harmful to plants so they have 

to be allowed to leach out. We carry out 

electro conductivity tests to measure 

salts content and only release the 

compost for use when it has physically 

cooled down sufficiently, and salts are 

at a safe level.” 

To complete the Wallbarn substrate, coir 

and Lytag or Leca are combined with 

the compost: 

Coir: a lightweight, natural by-product 

of the coconut industry used in 



GREEN ROOF 

Above: Wallbarn’s M-Trays filled with substrate (left of image) and waiting to be filled. Inset: Sedum trays. Below: The composting process. 


M-Trays to lighten the substrate 

mix and introduce fibres that lock 

in moisture and nutrients. In use, 

interaction between the green 

compost and the coir gives a 

slow release of nutrients over an 

extended period of time. 

Lytag: a lightweight ballast which is 

a waste product from power station 

waste. 

Leca: an expanded clay which 

is also a waste product and super 

lightweight/bulk forming. The roots 

of sedum and wildflowers grip the 

particles to bind into the substrate and 

support the whole green roof. 

The GRO Code advises 50% non-organic 

content within the substrate and Wallbarn 

achieves this by including Lytag/Leca 

pellets, which it sources in the UK. That 

both the coir and Lytag/Leca are waste 

materials from other industries is no 

coincidence; Wallbarn says it strives to 

make its M-Tray system as environmentally 

friendly as possible within the bounds of 

performance and regulatory compliance. 

The green red line 

David and Keith are also very clear 

that peat has no place in any compost 

Sedum Growers produces: “It is a red 

line for us and has been for the last 10 

years. We were determined to phase 

out peat rather than wait for the 

legislation to change,” Keith said. 

The legislation he refers to is aimed 

at protecting peatland habitats and 

meeting net zero targets, with the 

government set to ban the use of peat 

in horticulture retail by 2024 and by 

2028 for commercial growers. 

Rigid adherence to high quality and 

environmental responsibility is 

an ethos driven by Wallbarn, as 

Director Julian Thurbin explained: 

“Wallbarn goes above and beyond 

legislation and guidance relating 

to green roofs. We’ve been at the 

forefront of many industry changes 

and always strive to physically test 

ingredients to ensure they perform 

as we wish, using Warringtonfire for 

fire tests and STRI for growth tests. 

“M-Tray exceeds all regulations by 

a significant degree. Our ethos is 

to provide customers with industryleading, 

healthy green roofs that 

thrive throughout their lifetime, meet 

regulatory and industry standards and 

are as eco-friendly as possible.” 

Contact 

Wallbarn 

www.wallbarn.com 

Tweet: @wallbarn 


SIKA NOW OFFERS A COMPLETE 

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Building on our reputation in roofing, Sika’s complete 

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SOLAR PV RESIDENTIAL PROJECTS 

THE YEAR WHEN PART L 

BECAME REAL! 

By Stuart Nicholson, Roof Systems Director at Marley. 

This year has been a pivotal 

point in the nation’s journey to 

decarbonise and move towards 

the net zero target set for the middle of 

the century. 

The summer months finally saw the 

introduction of amendments to Part 

L of the Building Regulations. The 

changes have been implemented to 

ensure newly built homes produce 31% 

lower carbon emissions. With houses 

creating 40% of the UK’s greenhouse 

gases according to the Climate Change 

Committee, by tackling home-related 

emissions in this way considerable 

progress can be made. 

Various sectors within the construction 

industry are now grappling with the 

implications of Part L and how they 

will ensure compliance with the 

requirements going forward. Many 

are already looking at the benefits 

that opting for renewable energy 

solutions can deliver in the fight to 

reduce household emissions and 

tackle tangible consumer challenges 

associated with energy consumption 

and cost. 

Experts have stated that improvements 

to energy efficiency and lower 

emissions levels simply can’t be 

achieved just by enhancing the building 

fabric on its own. That is why an 

innovative combination of renewable 

technology is being favoured. 

Over the short term, bringing 

together solutions such as solar PV 

on roofscapes is one of the easiest 

and most cost-effective ways to 

satisfy the Part L carbon reduction 

targets. Not only does it make use 

of currently available and proven 

green technologies, but it also opens 

a pathway for homeowners to access 

dependable, sustainable, and costefficient 

sources of energy. 

Looking ahead to the future 

The specification of solar PV on 

roofscapes is now increasingly gaining 

traction as an immediate and effective 

answer. Aside from the obvious 


Marley SolarTile is an 

integrated PV roof solution 


Technical support 

Roofing experts on-hand to offer help and advice 

Assured standards 

Meets all British Standards and regulations 

High-quality components 

Tested for maximum performance, meaning no call backs 

Estimates & fixing specs on demand 

We’ll help you create them on site and on the go 

Comprehensive roof solution 

Easy installation with tried and tested compatible components 

Need a complete 

roof system? 

We’ve got you covered. 

With all elements brought together from a single 

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will work together perfectly – and that high 

performance is all backed up with a 15-year 

system guarantee. Find your peace of mind. 

marley.co.uk/roofsystem

SOLAR PV RESIDENTIAL PROJECTS 


attraction as a renewable energy 

source, it can also add overall value to 

properties. According to Solar Energy 

UK, adding solar PV can increase the 

market value of a house by around 

£1,800. 

In addition, awareness of solar is also 

growing across the construction sector, 

with 40% percent of housebuilders, 

specifiers and architects recently polled 

by Marley saying they are already aware 

of the positive impact solar PV can have 

as a sustainable technology within the 

overall building fabric. 

Whilst specifiers, housebuilders and 

consumers may have concerns about 

the appearance of bulky, on-roof solar 

panels, the latest integrated PV roof 

systems now offer a more visually 

appealing, cost effective and easier to 

install option. 

Replacing a section of roof tiles, an 

integrated PV solution such as Marley’s 

SolarTile provides a sleek aesthetic and 

acts as a seamless part of the overall 

roof. This type of solar panel can also 

be installed at the same time as the 

rest of the roof tiles, without a specialist 

contractor. 

Marley SolarTile can also come as a key 

component of a fully integrated roof 

system from a single source supply 

with the substantial offer of a 15-year 

guarantee providing peace of 

mind to specifiers and home 

purchasers. 

With electric charging points on new 

builds, and homeowners looking to 

embrace green technologies such as 

heat pumps and solar on the roofscape, 

specifiers are responding and seeking 

new solutions. 

Doing so also helps safeguard people 

against energy price concerns as 

they use cleaner, greener, and 

cheaper power. 

For more information 

about Marley SolarTile visit: 

www.marley.co.uk/solar 

Tweet: @MarleyLtd 


THE GRO GREEN ROOF CODE 1 

Green Roof Code of Best Practice 

incorporating Blue Roofs and 

BioSolar Applications 

Anniversary Edition 2021 

Photo: ABG Limited 

THE GREEN ROOF ORGANISATION 

THE G 

ROO 

Green Roof 

incorporatin 

BioSolar Ap 

Anniversary 

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: 

E: membership@greenrooforganisation.org 

COMING 

SOON 

THE GRO GREEN 

ROOF CODE 

W: www.greenrooforganisation.org : 

GRO CODE 

@ROOFGRO 

@WGRD2021

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• Utilises surface water to introduce and sustain urban green assets 

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Unlock the future at polypipe.com/watershed 

Civils & Green Urbanisation

Winter 2022

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