Green Walls: Building Thermal and

Hydrological Benefits and Costs

Stuart Archer

Introduction

What are green walls?

Why use green walls?

Project aims

Results

Conclusion

Further work

Acknowledgements

http://www.greenpublicart.com/pages/featured/ur

ban-landscaping-green-walls/

What are Green Walls?

Living Walls Biowalls

Either facade or

panel

Interior function

Artificial irrigation

Green Facades

Climbing plants

Anchored to wall

Natural or artificial

irrigation

Plants in panels

containing substrate

Attached to wall

Artificial Irrigation

Why Use Green Walls?

Aesthetics

Biodiversity

Urban Heat Island (UHI)

Reduction

Air Quality

Health and Wellbeing

Thermal benefits

Hydrological benefitshttp://www.d4b.org.uk/caseStudies/paradisePark/index.asp

Project Aims

Identify thermal and hydrological benefits and

costs of living walls

Literature review

Thermal modelling

Hydrological modelling

Results Literature Review

Manufacturers claims

Green walls can provide environmental benefits

on the form of biodiversity, thermal insulation and

cooling benefit to the building, and noise

attenuation as well as water management and

mental health benefits ANS Group (Europe), 2011

No data provided as back up!

Results Literature Review

Thermal effects

Some experimental studies

Focussed on warmer climates

Up to 7oC reduction observed

More theoretical studies

Hot and cold climates

Generally

Benefits for poorly insulated buildings

Little benefit for well insulated buildings in cooler climates

Results Literature Review

Hydrological effects

Few experimental or theoretical studies

Water use not generally addressed

Evapotranspiration key parameter

Results Thermal Modelling

Used ECO Roof function in DesignBuilder

Compared 1-Storey house in Sheffield and

Dubai

Results Thermal Modelling

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

Winter - Average Winter - Max Winter - Min Summer - AverageSummer - Max Summer - Min

T

e

m

p

e

r

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No Green Wall

Green Wall

Uninsulated - No

Green Wall

Uninsulated -

Green Wall

Sheffield

Dubai

0.0

10.0

20.0

30.0

40.0

50.0

60.0

Winter - Average Winter - Max Winter - Min Summer - AverageSummer - Max Summer - Min

T

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p

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No Green Wall

Green Wall

Uninsulated - No

Green Wall

Uninsulated -

Green Wall

Results Thermal Modelling

Potential thermal energy savings

Sheffield: 544 kWh (6.5%)

Dubai: 811 kWh (4.3%)

Results Hydrological Modelling

Attempted to use DesignBuilder/ EnergyPlus

Evapotranspiration calculated using EToCalc

1-Storey house in Sheffield 2008, using

weather data from Sheffield University

Rainfall used to estimate potential capture

Dubai figures estimated

02000

4000

6000

8000

10000

12000

14000

16000

18000

20000

1 2 3 4 5 6 7 8 9 10 11 12

V

o

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w

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Month

Evapotranspiration

Rainwater Captured

Sheffield

Results Hydrological Modelling

Sheffield:

115,000 L required

100,000 L captured (160 kWh required)

15,000 L mains water (12 kWh required)

Energy cost 172 kWh

Results Hydrological Modelling

Dubai (estimated):

216,000 L required

58,600 L captured (87 kWh required)

157,400 L mains water (630 kWh required)

Energy cost 717 kWh

Conclusion

Overall savings (assume 23p/kWh):

Sheffield: 372 kWh 85/year

Dubai: 94kWh 22/year

Typical installation costs ~500/m2

Thermal benefits small for new buildings

Retrofit standard insulation may be cheaper!

Consider carefully all benefits/costs prior to installing a green wall

Acknowledgements

Virginia Stovin

Hasim Altan

Juri Yoshimi

Tom Young

Sean Farrell (Mobilane)

Questions