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CPD - Green roof design principles

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Organic Roofs

on 14 November 2017

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Transcript of CPD - Green roof design principles

Green roof best practice
Understand, commit, publicise
Market it appropriately
....then join wider conversations
Integrated design
Enhanced products & services
Why choose Organic Roofs
Improve yield
-7% to 20% in optimum
Why choose Organic Roofs
Living wage employer
Simple. Efficient. Transparent. Ethical.
Trained, experienced staff
Designing-in nature: habitat roofs
Design considerations for long-lasting roofs
Loadings: not signficiantly higher
Integration with building envelope: type of membrane
Aspect: wind, sun and rain
Access & safety for maintenance
Client liaison
New build
Design service
Further training
Cost-sensitive design
for the right performance metrics

Integration with renewables
Pitched green roofs
Minimise legacy risk
-H&S compliance

Price-sensitive innovation
Ecology AND buildings expertise
We understand finish
Full compliance - NFRC & Constructionline
Green roof design service
One stop shop, inc waterproofing

Understand, commit, publicise
Market it appropriately
....then join wider conversations
Why choose Organic Roofs
Lifecycle support
Excellence in supply chain
What to do next
- @organicroofs
- linkedin.com/in/leemevans/en
- pinterest.com/oroofs
- flickr.com/organicroofs
Helping new & old buildings work better

80% - UK carbon reduction target, by 2050
40% - architects directly or indirectly responsible for nearly half UK emissions

Better design is the answer, but also extensive retrofit

85% - currently available building stock that will still exist in 2050
26 million - number of buildings that will need to be retrofitted


Unpredictable climate: heat, drought, rainfall
Energy costs
Habitat & species loss

How can green roofs contribute? Resilient design WITH nature:
- internal climactic control
- membrane lifespan
- improved solar yield
- wellbeing and performance
- recreation of habitat

- the building 'envelope' can do SO MUCH MORE

Benefits: ecological

Urban green isn't an 'add-on', it should be spatial design that takes social interaction
and physical/mental improvement as important metrics

Make landscapes work harder; make buildings work harder within them (as stepping stones)

Contribution to landscape scale initiatives eg Gt London Natl Park & B&H Biosphere
Even small roofs provides stepping stones incl food source & shelter
Can be targeted to specfic species

London 'species of concern' include:
- Yellow Rattle
- Chalk Eyebright
- Autumn's Lady-Tresses (Orchid, 'Spiral Flower')
- Bastard Toadflax (traditional foodsource, narcotic)

2002 Natural England report said 'sedum roofs do not provide refuge for rarer invertebrates associated with brownfield sites'. On meadow roofs emulating brownfield in London, 59 species of spider were found: Top of the foodchain!

1 apple orchard needs:
20,000 honey bees to pollinate
250 solitary bees
Climate resilience
Adapting our built environment to cope with the unpredictable:
Rainfall expected to increase in SE England by 22% by 2030
'Urban Creep' means sewer system will be outgrown by 2040 - attenuation will be priority in years to come, as evidenced by Sust Drainage Action Plan public consultation

First element of wider storm water management strategy
Retention: Stuttgart roofs hold 70% of rainfall
Brighton: roof area COULD hold back 100 Oympic pools worth of water in rain event
Detroit study: £1.37 per m2 saved from authority budget p.a

Reduction of UHE - NYC estimates 50% green roof cover would reduce urban temp by up to 0.8C, saving 495M KWh in aircon costs

Carbon capture

Wellbeing and performance
Performance improves with increased connection with & access to nature
Mental and physical health improvements [HN evidence base]

Noise insulation - 8db
Promoting social cohesion & community engagement
Environmental education opportunities
Economic resilience
M&E costs - 95% less heat enters building at 150mm, 26% less escapes
- Barclays Tower 450m2 saving £10/m2 p/a
Treble lifespan of membrane e.g. Moos filtration plant = 100 year life
Increase PV yield up to 20%
Up to 50% increase in tenancy rates in office space with usable roof space

Why does it predominate: weight, cost, maintenance?
Why failure rate so high? weight, cost, maintenance!

Meadow (from seed or pregrown)
Lightweight Meadow (HayBase)
- Shear
- Planting
- Substrate depth
- Irrigation
- Maintenance

Specification: overview
What elements do you need for a roof that will last?

Insulation & Waterproofing
Technical layers
Substrates & Planting

Detailing & Biodiversity Hotspots
Typical build-up

Single ply membrane
9mm OSB sheathing
120mm PIR insulation
Alutrix VPB
18mm structural deck
Where possible, one-piece membrane
Partially adhered, ballasted
External corners on skylight upstands
Run up 150mm min above top of substrate eg 250mm

Pre-bonded insulation/sheathing if possible
Tissue-backed (eg TR27) where no sheathing
Always insist on a flood test
Root barrier
Essential on seamed roofs

Non-woven fabric, allow min 150mm overlap

Drainage or no drainage?
Different schools of thought (25mm standard)
Not needed for HayBase

Filter fleece
Water permeable, holds granular fines

Wind stablising
Jute or manmade alternative in extreme conditions

Broadly, 3 types of substrate
(4 if you count 'none' as a type)

Encourages grass/invasives
Naturalistic growth
Ensure rootproof membrane used

Brick based
85% inorganic matter (low nutrients)
150kg/m2 at 100mm
Good for meadow plants, chalkland

105kg/m2 at 100mm
Low nutrients
Good general mix

6 months

Two types of planting
Seeded and pregrown (sedum or wildflower)

24 months
0 months

0 months

18 months

3 months

Parapet capping

Powder coated
Slimline profile
Warrantied colour-
matched fixings
Perimeter retainer

Variety of sizes
Additional separator
Significant cost
Prototype U section
Ecological enhancement

Creating refugia for
Emulates natural
Ensure good drainage
Remove invasives
Augment substrate
Monitor plant development
Cut/no-cut biomass management
Repair bird damage

Nesting for
solitary bees
Log piles
Shingle basking areas
18 months (summer)
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