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Economic Benefits and Costs of Green Roofs


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Reflections Green roofs are well-known as a sustainable construction practice. Economical benefits of green roofs have been widely discussed by many researchers. This chapter starts with an extensive literature review on the benefits and costs of green roofs. The quantitative estimates of individual and public benefits of green roofs were conducted, and lifecycle costs of green roofs from cradle to grave were analyzed. The net present values per unit area of a green roof were accessed by considering the individual benefits, public benefits, and lifecycle costs. A comparable assessment was performed to evaluate the payback period of green roofs in different markets. The analysis demonstrated that the lifecycle cost of green roofs can be paid back by individual benefits in a mature market. If the public benefits are added into the assessment, the lifecycle cost of green roofs can be retrieved in most of the markets.
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Chapter 4.5
Economic Benefits
and Costs of Green Roofs
Haibo Feng and Kasun N. Hewage
Chapter Outline
Introduction 307
Individual Benefits of Green Roofs 308
Energy Reduction in Heating and
Cooling 308
Membrane Longevity 308
Acoustic Insulation 308
Aesthetic Benefits 309
LEED Certification Bonus 309
Public Benefits of Green Roofs 310
Reduction of Stormwater Runoff 310
Improvement of Air Quality 310
Mitigation of Urban Heat Island
Effect 311
Increment of Urban Biodiversity 311
Life Cycle Cost of Green Roofs 311
Initial Cost 311
Operation and Maintenance (O&M)
Cost 312
Disposal Cost 312
Green Roof Cost Benefit Assessment 313
Net Present Value and Payback
Period 313
Scale of Implementation 314
Green Roof Policy Initiatives 315
Conclusion 315
References 316
Green roofs are well-suited for urban areas, as they provide excellent value
for money at both individual and public levels in comparison with other cur-
rently available green or gray infrastructure. However, the high initial invest-
ment required for green roofs acts as a barrier to their market penetration. In
general, individual benefits of green roof include reduction in energy use for
heating and cooling, membrane longevity, acoustic insulation, aesthetic bene-
fits, and LEED certification bonus (Berardi, 2016; Clark et al., 2008; Nurmi
et al., 2013; USGBC, 2015; Bianchini and Hewage, 2012). Public benefits
include reduction of stormwater runoff, improvement of air quality, mitiga-
tion of urban heat island effect, and increment of urban biodiversity, etc.
(Driscoll et al., 2015; Connelly and Hodgson, 2008; Rosenzweig et al., 2006;
Brenneisen, 2006). The costs in green roofs involve their initial construction,
operations, maintenance, demolition, and disposal (Bianchini and Hewage,
Nature Based Strategies for Urban and Building Sustainability.
©2018 Elsevier Inc. All rights reserved.
2012). The objective of this chapter is to present the economic benefits of a
green roof in terms of its public and individual benefits, summarize the total
costs of a green roof throughout its lifecycle, and estimate the payback
period based on the benefits and costs.
Energy Reduction in Heating and Cooling
Green roofs reduce energy consumption in space heating through shading,
evapotranspiration, insulation, increase in thermal mass, and reduction of
heat loss through radiation. Green roofs can also be more efficient in pre-
venting heat loss in the winter compared with conventional roofs (Liu and
Baskaran, 2003; Berardi, 2016). The reduction in energy bills is usually the
most convincing factor for building owners to install green roofs. For exam-
ple, an experiment conducted in Ottawa found that a 6-inch extensive green
roof reduced heat gains by 95%, and heat losses by 26% compared to a con-
ventional roof (Liu, 2002). Another study on a two-story building was con-
ducted by Florida Solar Energy Center. Its findings revealed that 18% of
energy used for space cooling was saved by a green roof compared with the
conventional roof, and 44% was saved when the plants were more estab-
lished (Sonne and Parker, 2006). The economic benefit of reduction in space
conditioning demand has been quantified by a previous study, which demon-
strated that a green roof can save $0.180.68 m
in cooling, and 0.22 m
in heating annually (Bianchini and Hewage, 2012).
Membrane Longevity
Green roof technology increases the lifespan of a building’s roof by protect-
ing against diurnal fluctuations, UV radiation, and thermal stress. Studies
have revealed that the lifetime of roofing membrane can be easily lengthened
up to 4050 years by green roofs (Clark et al., 2008), while a conventional
roof’s lifespan ranges from 10 to 30 years (Oberndorfer et al., 2007). The
cost of replacing a conventional roof at the end of its lifespan is estimated at
around $160 m
(Bianchini and Hewage, 2012). The benefit of installing a
green roof is the cost of installing a conventional roof 20 years in the future,
which is at $160 m
Acoustic Insulation
Green roofs improve the soundproofing of a building, and reduce the sound
reflection by increasing absorption (Azkorra et al., 2015). For buildings
located near very strong sources of noise such as night clubs, highways, or
flight paths, the sound insulation created by green roofs can be especially
308 SECTION | IV Nature Based Strategies: Social, Economic and Environmental
useful. There are no reliable estimates in the literature about the economic
value of the sound insulation benefit of green roofs. A commonly used tech-
nique to improve noise insulation is to apply an extra layer of plasterboard
into the ceiling. The noise insulation benefits acquired due to green roofs are
similar or higher than that gained by such an additional ceiling element,
since green roofs have more than one layer (Connelly and Hodgson, 2008).
Material and installation costs are approximately $29 m
(h20 m
) for
plasterboard. Therefore, the noise insulation benefit of green roofs is also
estimated to be around $29 m
in air noise zones (Nurmi et al., 2013).
Aesthetic Benefits
Aesthetics are the most intangible benefit, generally left out in cost-benefit
analyses due to the difficulty in valuing aesthetics in monetary terms. An
individual’s willingness to pay a higher price can be used as a method to
attribute a monetary value to qualitative characteristics such as aesthetics.
Commission for Architecture and the Built Environment in London states
that the price of buildings or houses will increase by 6% if there is a park
nearby, and by 8% if the building has a direct view of the park. Green roofs,
especially if spread over a larger area, has a similar function as a local park.
Accordingly, 2%5% and 5%8% of property value increments for exten-
sive and intensive green roof respectively have been assumed (Bianchini and
Hewage, 2012). The extensive green roof may raise property value from
$2.6 to $8.3 m
, while intensive green roofs may increase property value
from $8.3 to $43.2 m
. Besides the aesthetic benefits, green roofs can also
provide recreational spaces in urban areas if they are designed for public use
similar to parks.
LEED Certification Bonus
LEED certified buildings are gaining in popularity because of their lower
operating costs, better employee performance (in commercial and industrial
buildings), improved public relations, better health standards, as well as other
community benefits (CaGBC, 2014). The most attractive aspect for owners
is that it increases access to capital. It is estimated that the return-on-interest
of LEED certified buildings improved by 19.2% on average for green retrofit
projects in existing buildings, and 9.9% on average for new green construc-
tion projects (USGBC, 2015). Under the Canada Green Building Council
LEED program, buildings with green roof installations gain one point for
stormwater management, and one point for reducing heat island effect if the
roof covers at least 50% of the building. Another benefit of green roof tech-
nology is that the vegetation and soil media of green roof can be used as a
filter for the storm runoff, so that the water from the green roof system can
be used to irrigate other landscaping features without pretreatment (LEED
Economic Benefits and Costs of Green Roofs Chapter | 4.5 309
Canada, 2009). Under the LEED scheme, this may warrant an additional
point for water efficient landscaping. The ability to reduce energy demand
for cooling and heating, and increased energy efficiency may also garner
additional points for optimized energy performance. Furthermore, potential
points can be gained for reduced site disturbance, protection or restoration of
open space, and innovation in design.
Reduction of Stormwater Runoff
Green roofs can impact the stormwater retention capacity of buildings. Most
importantly, with the presence of green roofs, the rainwater that falls onto
the roof surfaces flows into the sewers at a slower rate, as green roofs are
able to retain water. Depending on regional climate, green roofs can lower
the sewer system capacity requirement, by holding as much as 50%95%
of annual rainfall precipitation (Driscoll et al., 2015; Beecham and
Razzaghmanesh, 2015). An investigation by the city of Portland revealed
that $30 m
is needed to manage the stormwater falling on impervi-
ous areas that do not absorb rainwater (City of Portland, 2008). Based on the
retention performance of green roofs listed above, green roofs will be able to
create $1528 m
savings per year by reducing the public infrastructure
management fees.
Improvement of Air Quality
Green roofs are recognized as an air quality control technology. The vegeta-
tion reduces air pollution by actively absorbing many pollutants, and by pas-
sively filtering and directing airflows. It was estimated that eight metric tons
of unclarified air pollutants can be removed per year by 109 ha of green
roofs in Toronto, Canada (Currie and Bass, 2010). Another study conducted
in Chicago estimated that the annual mass of air pollutants which can be
removed by 19.8 ha of green roofs amounts to 1675 kg (Yang et al., 2008).
The cost estimate for the air quality benefit of a green roof is calculated
by considering the negative effects of pollutant on health, environment,
infrastructure, and climate change. The cost would be significantly higher in
urban environments, due to the effect on a larger number of people. In North
America, the NO
emissions tax is $3375 ton
(Clark et al., 2008). In
Europe, the SO
cost in a populated area is $2500 ton
, and $500 ton
cost (Nurmi et al., 2013). Based on the results from Yang et al. (2008)
and Clark et al. (2008), the benefits from the improvement of air quality
would be around $0.03 m
annually assuming all the air pollutants removed
by green roof are NO
310 SECTION | IV Nature Based Strategies: Social, Economic and Environmental
Mitigation of Urban Heat Island Effect
In urban environments, vegetation has often been replaced by impervious
and dark surfaces. Dark surfaces reflect less solar radiation and absorb more
energy. Due to the lack of vegetation and the presence of dark surfaces, the
urban heat island effect is created. A simulation study in New York showed
that the average roof temperature can be reduced by as much as 0.8Cif
50% of the roof area is covered with vegetation (Rosenzweig et al., 2006).
In Venice, the field observation and simulations results showed that the tem-
perature of a green permeable surface could be 4C lower than the existing
paved roof (Peron et al., 2015). It was also estimated that the urban heat
island effect can be reduced by 12 degrees Celsius if 6% of Toronto was
covered with green vegetation (Peak, 2004). Another report on the
Mediterranean region shows that 10%14% of the electrical energy con-
sumed in cooling residential buildings can be saved by green roofs (Zinzi
and Agnoli, 2012). Green roof performance in reducing the urban heat island
effect varies in different locations, due to the conditions in the surrounding
environment, and changes in building density.
Increment of Urban Biodiversity
Green roofs can help to increase local biodiversity by providing habitats for
different animal species such as birds and insects within a city. A study
conducted in Switzerland found that 79 beetles and 40 spider species were
supported by a single green roof, of which 20 species were endangered
(Brenneisen, 2006). Another study conducted in England on green roofs
which mimic conditions found in derelict sites discovered that these sites are
favored by black redstart, a rare species of bird in the United Kingdom
(Grant and Lane, 2006).
However, creation of a habitat for animals is treated only as a bonus
compared with other quantifiable benefits. It is not easy to quantify the
increase in biodiversity and estimate the corresponding costs and benefits
using a common methodology. While it is difficult to directly quantify the
economic benefits of habitat increase due to green roofs, the resulting envi-
ronmental benefits may be translatable to economic terms based on environ-
mental priorities.
Initial Cost
There is a significant price variation among green roofs due to factors such
as type and size, locations of green roofs, and country. The current cost in
British Columbia, Canada for a standard extensive green roof varies from
$130 to $165 m
, and the cost of a standard intensive green roof starts from
Economic Benefits and Costs of Green Roofs Chapter | 4.5 311
$540 m
(Bianchini and Hewage, 2011). Many factors such as labor and
equipment costs affect the installation price. In Singapore, a green roof price
ranges from $40 to $65 m
depending on the type of green roof and struc-
ture of the foundation (Wong et al., 2003). In China, the average price of a
green roof investigated from three provinces is between $48 and $76 m
(Jia and Wang, 2011; Liu and Hong, 2012). In a mature market like
Germany, the average green roof costs range from $15 to $45 m
. The
lower green roof prices in Germany are a result of ongoing research and
development as well as market penetration spanning two decades. In newer
markets, no economies of scale exist and competition is scarce. Labor is also
more expensive because of the lack of experience and the tendency to use
custom design systems. One way to reduce the initial cost of green roofs is
to adopt the low-cost techniques developed by mature markets. The cost of
green roof generally decreases by 33%50% once the industry has estab-
lished itself (Toronto and Region Conservation, 2007).
Operation and Maintenance (O&M) Cost
Economic and environmental benefits of green roofs rely on their perfor-
mance. Therefore, O&M of vegetative roofs are critical in securing their pos-
itive impacts. The maintenance cost also depends on the size of green roofs,
the characteristics of the building, the complexity of the green roof system,
the type of vegetation, as well as the market O&M price. It is estimated that
annual O&M cost of green roofs in the United States is between $0.7 and
$13.5 m
(Bianchini and Hewage, 2012).
Disposal Cost
There are different disposal options for green roofs at the end of life.
Materials can be landfilled, reused, or recycled. Water retention layer, drain-
age layer, and root barrier layers of green roof can be recycled again at the
end of the lifespan. However, many cities do not have the necessary facilities
for the recycling process. Landfill costs depend on many factors such as
technology, location, size of the facility, and available landfill capacity in a
A study indicated that the operations and maintenance cost in landfilling
is on average $56 per ton waste disposed without considering the energy
recovery option (Chang and Wang, 1995). Another report compiled in
Europe did a complete analysis on the green roof disposal cost, including
inert material landfill, sanitary landfill, and incineration with energy recov-
ery. The disposal cost for an entire green roof is estimated at $1120 ton
(h784 ton
)(Peri et al., 2012). Bianchini and Hewage (2012) illustrated
that the cost to dispose green roof materials is in the range between $0.03
and $0.2 m
312 SECTION | IV Nature Based Strategies: Social, Economic and Environmental
Net Present Value and Payback Period
In order to assess the total benefits and costs of green roof, the values
need to be converted into a net present value (NPV) by the means of dis-
counting. The lifespan of a green roof has been estimated as about 40
years minimum and 55 years maximum (Mahdiyar et al., 2016). In this
analysis, 40 years is used to conduct the assessment. Based on the study
from Gollier and Weitzman (2010), 3% of the discount factor was applied
to this analysis. Based on the benefits and costs of green roofs introduced
above, Table 1 summarized all the economic inputs for the analysis and
NPVs as output.
There is a wide range in terms of the values in Table 1, especially the
aesthetic benefits and stormwater runoff reduction benefits, and the life-
cycle costs. One of the reasons is due to the different systems of green
roofs. For example, extensive green roofs have shallow soil roofs with
simple growing plants, and are usually not accessible. Therefore they have
a lower lifecycle cost.
On the other hand, intensive green roofs are similar to a ground level
garden with a deep growing medium and artificial irrigation (Kosareo and
Ries, 2007). Therefore, the initial cost and O&M cost are higher. At the
same time, intensive green roofs have higher benefits in stormwater run-
off deduction due to its deep growing medium, and better aesthetic values
because it acts like a garden. Another reason is the cost and technique
variances between different markets. In the mature market like Germany,
the costs are much lower than the new markets in Asia and North
America, and the benefits generated from green roofs are more than the
new markets because of its mature techniques and great popularity. Some
other reasons are sizes of green roofs, weather conditions, and building
features etc.
As shown in Table 1, the total NPV of individual benefits in 40 years is
between $135.9 and $195.8 m
, and the total NPV of public benefits in 40
years is between $478.7 and $751.7 m
. Based on the result, it is obvious
that the public benefits are over three times greater than the individual bene-
fits, even though two of the public benefits are not counted in the calculation
due to the unavailable data.
If the total NPV of lifecycle costs for green roofs in 40 years is close to
, which is at the lower side of the range ($42.3978.8 m
), it will
only take 13 years of the individual benefits to balance the cost of green
roofs. If the public benefits are considered, the payback period will be
reduced to 3 years. If the total NPV of lifecycle cost for green roofs in
40 years is close to $978.8 m
, this cost could still be paid back in its life-
time by the individual benefits and public benefits together.
Economic Benefits and Costs of Green Roofs Chapter | 4.5 313
Scale of Implementation
As shown in Table 1, the values created by the mitigation of urban heat
island effect and increment of urban diversity are not available in this analy-
sis, because the value would be very small if only one or a few green roofs
were installed. However, the benefits of green roof will increase
TABLE 1 Economic Data Input and NPV Output ($ m
) for the Cost
Benefit Assessment
Value Time
($ m
Lifespan (year) \ 40 \
Discount rate (%) 3 \ \
($ m
Reduction of energy 0.40.9 Annual 15.735
Use in heating and
Membrane longevity 160 At year 20 88.6
Acoustic insulation 29 One time 29
Aesthetic benefits 2.643.2 One time 2.643.2
LEED certification
n/a n/a n/a
Total NPV 135.9195.8
Public Benefits
($ m
Reduction in
stormwater runoff
15 - 28 Annual 477.5750.6
Improvement of air
0.03 Annual 1.18
Mitigation of urban
heat island effect
n/a n/a n/a
Increment of urban
n/a n/a n/a
Total NPV 478.7751.7
Lifecycle Costs
($ m
Initial cost 15540 One time 15540
Operation and
maintenance cost
0.713.5 Annual 27.3438.7
Disposal cost 0.030.2 At year 40 0.010.06
Total NPV 42.3978.8
314 SECTION | IV Nature Based Strategies: Social, Economic and Environmental
tremendously if implemented at a larger scale. Intangible benefits such as
aesthetic appeal of green roofs and increased urban biodiversity can be
gained with large scale of implementation (Niu et al., 2010; Nurmi et al.,
2013) . The costs of green roofs will also be reduced with a higher imple-
mentation rate. Large scale of implementation would also reduce the volume
of stormwater entering local waterways, which will lead to lower water tem-
peratures, less in-stream scouring, and better water quality (Spengen, 2010).
Green Roof Policy Initiatives
Based on the analysis above, the public benefits of green roofs are over three
time larger than the private benefits. Therefore, municipal authorities should
play a key role in promoting green roofs in urban areas and residential neigh-
borhoods through policy and regulatory measures.
In Toronto, Green roofs are required on all new institutional, commercial,
and multiunit residential developments. The incentive offered for green roof
is $75 m
up to an upper limit of $100,000 (City of Toronto, 2016). In New
York, green roof tax abatement is implemented, so that each square foot of
green roof can get a rebate of $5.23, up to $200,000 per project (NYC,
2014). In Singapore, the National Parks Board aims to increase greenery pro-
vision by funding up to 50% of the installation cost of rooftop greenery
(National Parks, 2011). In Tokyo, it is mandatory for a new building to cover
25% of roof with greenery (Growing Green Guide, 2013).
In Munich, all building roofs with a surface area larger than 100 m
should be landscaped. This policy was implemented around 20 years ago,
and it makes the green roof a recognized construction standard in Munich
(IGRA, 2011). As a world leader in green roof development, Germany’s
experience shows that it is necessary to introduce a green roof policy rather
than rely solely on the goodwill of building owners (Ngan, 2004).
Green roofs have personal and social benefits. The cost benefit assessment
showed that the lifecycle costs of green roofs can be retrieved in most of the
markets around the world. The payback periods in the mature markets and
markets with average initial costs are shorter than the lifespan of green roofs.
With a larger implementation scale, the social benefits of green roofs will be
increased tremendously. Governments should play a key role in promoting
the green roof construction by providing incentives to transfer the social ben-
efits into private investors, such as tax abatement, direct cash rebate, low
interest loans, etc. These incentives will also expand the public benefits, and
lower the lifecycle cost of green roofs.
Economic Benefits and Costs of Green Roofs Chapter | 4.5 315
Azkorra, Z., Pe
´rez, G., Coma, J., Cabeza, L.F., Bures, S., A
´lvaro, J.E., et al., 2015. Evaluation
of green walls as a passive acoustic insulation system for buildings, Appl. Acoust., 89.
pp. 4656.
Beecham, S., Razzaghmanesh, M., 2015. Water quality and quantity investigation of green roofs
in a dry climate., Water Res., 70. pp. 370384.
Berardi, U., 2016. The outdoor microclimate benefits and energy saving resulting from green
roofs retrofits, Energy Build., 121. pp. 217229.
Bianchini, F., Hewage, K., 2011. How ‘green’ are the green roofs? Lifecycle analysis of green
roof materials., Build. Environ., 48. pp. 5765.
Bianchini, F., Hewage, K., 2012. Probabilistic social cost-benefit analysis for green roofs: a life-
cycle approach., Build. Environ., 58. pp. 152162.
Brenneisen, S., 2006. Space for urban wildlife: designing green roofs as habitats in Switzerland.
Urban Habitats 4 (1), 2736.
CaGBC, 2014. Canada Green Building Trends: Benefits driving the new and retrofit market.
Available at
20Cdn%20Market%20Study.pdf (accessed at 15.11.16).
Chang, N.B., Wang, S.F., 1995. The development of material recovery facilities in the United
States: status and cost structure analysis. Resour. Conserv. Recycling 13 (2), 115128.
City of Portland, 2008. Oregon Cost benefit evaluation of Ecoroofs. Available at https://www. (accessed at 14.11.16).
City of Toronto, 2016. Eco-roof incentive program review. Available at
Eco-Roof/Eco-Roof%20Incentive%20Program%20Review%202016.pdf (accessed at 14.11.16).
Clark, C., Adriaens, P., Talbot, F.B., 2008. Green roof valuation: a probabilistic economic analy-
sis of environmental benefits. Environmental Science and Technology, American Chemical
Society, Department of Civil and Environmental Engineering, College of Engineering,
University of Michigan, Ann Arbor, MI 48109-2125, United States, 42(6), 21552161.
Connelly, M., Hodgson, M., 2008. Thermal and acoustical performance of green roofs: sound
transmission loss of green roofs. Green. Rooftops Sustain. Communities 111.
Currie, B.A., Bass, B., 2010. Using green roofs to enhance biodiversity in the city of toronto.
Driscoll, C.T., Driscoll, C.T., Eger, C.G., Chandler, D.G., Roodsari, B.K., Davidson, C.I., et al.,
2015. Green Infrastructure: Lessons from Science and Practice. (June).
Gollier, C., Weitzman, M.L., 2010. How should the distant future be discounted when discount
rates are uncertain? Econ. Letters 107 (3), 350353.
Grant, G., Lane, C., 2006. Extensive green roofs in London. Urban Habitats 4 (1), 5165.
Growing Green Guide, 2013. Green roofs, walls & facades policy options background
paper. Available at
20Options%20Paper%20-%20Green%20Roofs,%20Walls%20and%20Facades.pdf (accessed
at 14.11.16).
International Green Roof Association (IGRA), 2011. Green Roof News. Available at http://www.
(accessed at 14.11.16).
Jia, R., Wang, Y., 2011. Analysis of cost-benefit of green roof in Xi’an. 2011 2nd International
Conference on Mechanic Automation and Control Engineering, MACE 2011 - Proceedings
316 SECTION | IV Nature Based Strategies: Social, Economic and Environmental
Kosareo, L., Ries, R., 2007. Comparative environmental life cycle assessment of green roofs.
Building and Environment, Elsevier Ltd, Department of Civil and Environmental
Engineering, University of Pittsburgh, 949 Benedum Hall, 3700 O’Hara Street, Pittsburgh,
PA 15260, United States, 42(7), 26062613.
LEED Canada, 2009. LEED Canada for new construction and major renovation 2009 rating system.
Available at
En-Jun2010.pdf (accessed at 15.11.16).
Liu, K., Baskaran, B., 2003. Thermal performance of green roofs through field evaluation. In:
Proceedings for the First North American Green Roof Infrastructure Conference, Awards,
and Trade Show, pp. 110.
Liu, K.K.Y., 2002. Energy efficiency and environmental benefits of rooftop gardens NRCC-
45345 energy efficiency and environmental benefits of rooftop gardens. Construct. Canada
44 (17), 2023.
Liu, L.-P., Hong, G.-X., 2012. Popularizing path research on green roof project in China rural
region: cost-effectiveness assessment. 2012 World Automation Congress, WAC 2012.
Mahdiyar, A., Tabatabaee, S., Sadeghifam, A.N., Mohandes, S.R., Abdullah, A., Meynagh, M.
M., 2016. Probabilistic private cost-benefit analysis for green roof installation: a monte carlo
simulation approach. Urban For. Urban Gree. 20, 317327.
National Parks, 2011. New incentives to promote skyrise greenery in Singapore. Available
in-singapore (accessed at 14.11.16).
New York City, 2014. Green roofs for stormwater management. Available at http://columbia- (accessed at 14.11.16).
Ngan, G., 2004. Green roof policies: tools for encouraging sustainable design. (December),
Niu, H., Clark, C., Zhou, J., Adriaens, P., 2010. Scaling of economic benefits from green roof
implementation in Washington, DC. Environ. Sci. Technol. 44 (11), 43024308.
Nurmi, V., Votsis, A., Perrels, A., Lehva
¨virta, S., 2013. Cost-benefit analysis of green roofs in
urban areas: case study in Helsinki.
Oberndorfer, E., Lundholm, J., Bass, B., Coffman, R.R., Doshi, H., Dunnett, N., et al., 2007.
Green roofs as urban ecosystems: ecological structures, functions, and services. BioScience
57 (10), 823.
Peak, S., 2004. The green roof infrastructure monitor. North 5 (May), 124.
Peri, G., Traverso, M., Finkbeiner, M., Rizzo, G., 2012. The cost of green roofs disposal in a life
cycle perspective: covering the gap. Energy, 48(1), 406414.
Peron, F., De Maria, M.M., Spinazz, F., Mazzali, U., 2015. An analysis of the urban heat island
of Venice mainland. Sustain. Cities Soc. 19, 300309.
Rosenzweig, C., Gaffin, S., Parshall, L., 2006. Green roofs in the New York metropolitan region
research report. Columbia University Center for Climate Systems Research and NASA
Goddard Institute for Space Studies. p. 59.
Sonne, J.K., Parker, D., 2006. Energy performance aspects of a florida green roof. Fifteenth
Symposium on Improving Building Systems in Hot and Humid Climates.
Spengen, J. Van., 2010. The effects of large-scale green roof implementation on the rainfall-
runoff in a tropical urbanized subcatchment, pp. 1222.
Toronto and Region Conservation, 2007. An economic analysis of green roofs : evaluating the
costs and savings to building owners in Toronto and surrounding regions. (July), 15.
USGBC, 2015. The business case for green building. Available at
business-case-green-building (accessed at 15.11.16).
Economic Benefits and Costs of Green Roofs Chapter | 4.5 317
Wong, N.H., Tay, S.F., Wong, R., Ong, C.L., Sia, A., 2003. Life cycle cost analysis of rooftop
gardens in Singapore. Build. Environ. 38 (3), 499509.
Yang, J., Yu, Q., Gong, P., 2008. Quantifying air pollution removal by green roofs in Chicago.
Atmospheric Environment, Elsevier Ltd, Department of Landscape Architecture and
Horticulture, Temple University, 580 Meetinghouse Road, Ambler, PA 19002, United
States, 42(31), 72667273.
Zinzi, M., Agnoli, S., 2012. Cool and green roofs. An energy and comfort comparison between
passive cooling and mitigation urban heat island techniques for residential buildings in the
Mediterranean region. Energy Build. 6676. Available from:
318 SECTION | IV Nature Based Strategies: Social, Economic and Environmental
... The significant emissions from hospitals increase the risk of climate change related health issues and contributes to the general degradation of the environment caused by climate change (Costanza et al., 2014;Eckelman and Sherman, 2016;Toli and Murtagh, 2020). Urban hospitals provide ideal space for supporting green roofs because of: the ability for hospitals to mitigate environmental concerns affecting public health through ecosystem services provided by the green roofs; the hospitals' goals to improve the health and well being of the community; and the relatively high proportion that have large, flat, unoccupied roof space that is commonly unutilized (Ulrich, 2002;Coutts and Hahn, 2015;Feng and Hewage, 2018). ...
... Green roofs in urban areas, on the other hand, have been documented to reduce a roof 's surface temperature as well as the rate of solar radiation transferred, in addition to cooling the air through evapotranspiration. Collectively, these actions reduce the UHI effect (Rakhshandehroo et al., 2015;Bevilacqua et al., 2017;Feng and Hewage, 2018;Cai et al., 2019). The naturally occurring insulating properties of plants and vegetation create a barrier between the sun and the building, limiting the amount of solar radiation that is absorbed and released as wasted energy (Shafique et al., 2018). ...
... The naturally occurring insulating properties of plants and vegetation create a barrier between the sun and the building, limiting the amount of solar radiation that is absorbed and released as wasted energy (Shafique et al., 2018). The rate of solar radiation transferred onto building roofs with green roofs ranges from 6-30% in the summer and 10-80% in the winter based on the density and type of plants and the amount of evapotranspiration occurring (Rakhshandehroo et al., 2015;Feng and Hewage, 2018). The reduced solar radiation transferred, in addition to the cooling effects from evapotranspiration, result in green roofs having surface temperatures less than half that of a traditional roof (Bevilacqua et al., 2017). ...
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If worldwide healthcare was a country, it would be the fifth largest emitter of greenhouse gases on the planet. The increase in global temperatures, combined with the negative impacts of urbanization, has made it more important than ever to introduce green spaces where possible. With climate change worsening, human health, both physically and mentally is on decline, making the effects of climate change especially pressing to the stability of healthcare systems. In order to mitigate the lasting impacts of climate change on healthcare facilities, a holistic solution is needed. Access to green space in hospitals has been shown to reduce emotional distress, improve mental health, increase socialization and community connection, increase physical activity, decrease cardiovascular and respiratory diseases, decrease pain management needs and hospital stay lengths and increase both patients' and staffs' overall satisfaction at the facility. Beyond benefiting those interacting with the hospital, green roofs have the ability to reduce the urban heat island effect, improve stormwater mitigation, increase biodiversity, and absorb toxins and pollutants through air filtration. Additionally, green roofs can offer lower maintenance costs and higher energy savings than traditional roofs, and improve patient satisfaction, which can result in future funding opportunities. However, the upfront and upkeep costs of installing a green roof can vary and must be considered before implementation. In this review, we explore the symbiotic relationship between urban green roofs and hospital/patient wellness through the lens of sustainability, which includes environmental, societal, and economic impacts. We review scientific journal articles investigating benefits of green space and green roofs and highlight examples of green roofs on hospitals in the United States; together, these approaches display the environmental, societal, and economic benefits of green roofs installed on healthcare facilities. This review offers insight to hospitals, decision makers, and government systems on the importance of green roofs in urban areas and how these infrastructures can support the economic growth of the institute. Using our framework, decision makers and planners for urban hospitals can evaluate how the addition of green roofs to their healthcare facilities can contribute to increased environmental resiliency, community health, and patient satisfaction.
... Its presence can enhance the natural aesthetic of an area (Lee et al., 2018;Williams et al., 2019). and provide value for money at both public and private levels (Feng and Hewage, 2018) by augmenting property values, rental income, and tax revenue. GRGW can improve citizens' physical and mental health and reduce hospital admissions (Sutton, 2014). ...
... The NBS cost values found in literature broadly differ (i.e. Bianchini and Hewage, 2012;Locatelli et al., 2020;Zhou and Arnbjerg-Nielsen, 2018;Feng and Hewage, 2018). This research considers cost values derived from four NBS European projects: UNaLab, SOS4LIFE, Urban GreenUP and ThinkNature. ...
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Globally, flood events are considered the costliest natural hazard. Changes in precipitation patterns and large areas of impervious surfaces in urban environments are increasing the sensitivity of these systems to runoff production. At the same time, projected global sea-level rise may further increase the frequency of compound flooding due to simultaneous storm surge, sea-level rise and pluvial runoff that cause vast socio-economic and ecological impacts to coastal cities. In this context, over the last decade, the role of Nature-Based Solutions (NBS) has been recognised to support climate change adaptation by addressing ideas of multi-functionality, non-linearity and heterogeneity in urban design. Thus, increasing awareness about NBS benefits increases the willingness to accept these solutions. However, empirical evidence of NBS effectiveness at the urban catchment scale is still subject to debate. This study develops a spatial biophysical-economic framework that allows for the integrated assessment of NBS flood risk mitigation impacts, costs and benefits in the face of climate change, combining the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, benefit transfer methods and Geographic Information System (GIS) tools. Specifically, the InVEST Urban Flood Risk Mitigation model was used to assess the biophysical impacts of NBS on urban pluvial flood risk, benefit-transfer methods were used to evaluate the economic implications of such solutions, and GIS was used to integrate and map biophysical impacts and economic implications. For the case of the coastal lagoon city of Aveiro (Portugal), NBS scenarios of green roofs and bioswales under current and future climate conditions were assessed. The main findings of this study show that green roofs scenarios would save 32 % of the flood damages to buildings and infrastructures every year, while bioswales help save only 0.1 %. Moreover, green roofs implementation provides larger benefits in the future climate scenario (representative concentration pathway - RCP - 4.5). The findings confirm the extent to which knowledge on NBS benefits and costs is partial and uncertain, thus requiring constant progress through biophysical-economic assessment to support an evolutive decision making process in climate adaptation planning.
... In the last decades, the gradual recognition of the need to make cities more sustainable and adapted to climate change has produced a radical shift in urban stormwater management practices. The conventional approach based on gray infrastructures has widely been replaced by solutions based on Low Impact Development (LID) concept, which has been regarded as a more innovative and sustainable solution for urban stormwater management (Zhou, Lai, and Blohm 2018;Feng and Hewage 2018;Kourtis, Tsihrintzis, and Baltas 2020). ...
This study aims to apply a cost-effectiveness approach to identify optimal Low Impact Development (LID) designs for peak flow management when two specific practices are simultaneously employed: Permeable Pavement (PP) and Green Roofs (GR). Four design parameters were considered, associated with coverage ratios and underlying layer thicknesses of the LIDs. The results showed that optimal costs and parameters were more affected by the level of peak flow reduction than by storms’ intensity and duration. The best settings occurred with permeable pavement treating 100% of the adjacent impervious area. In this case, the optimal designs were dominated by smaller coverage ratios (20 to 60%) and deeper (190 to 330 mm) storage layer of PP, combined with a very small or non-existent area of GR. The findings of the present study demonstrate how the optimization of design parameters may lead to more economic LID designs and provide additional guidance for LID practice implementation and to assist in the decision-making process for the most cost-effective and sustainable solutions.
... Green roofs are now common in many countries, from Germany (where 35% of cities have integrated them into their regulations) to Denmark, from the United States (New York, Chicago, and Seattle) to Australia (Sydney, with also green wall policies) [14]. Since 2009, Toronto, the largest city in Canada, has adopted a law that obliges industrial, commercial, institutional, and residential buildings with a square footage gross exceeding 2,000 square meters to install green roofs [15,16]. Since 2018, the European Commission has encouraged the spread of green roofs and walls, roof gardens, hedges, and trees in the city with EU Directive 2018/844 [17]. ...
The Millennium Ecosystem Assessment in 2005 defined and categorized the concept of Ecosystem Services and the strategic role of natural capital. The need to rethink our cities and public spaces is even more pressing in the COVID-19 era. In this context, green strategies could be the answer to the new demands raised by citizens about the built and natural environment. Green roofs, along with the other green spaces, form the city’s green network, contribute to improving the quality of life and wellbeing of citizens. The present contribution aims to evaluate green roofs from an ecosystem perspective, by considering the evidence of their benefits on inhabitants’ wellbeing, their ability to mitigate climate change and preserve biodiversity. A proposal for an integrated evaluation model is presented to take into account the different dimensions of value in the study of Ecosystem Services (ESs) and to support decision makers (DMs) in the definition of actions able to increase the quality of life in cities.KeywordsIntegrated evaluation modelGreen strategiesMulticriteria Decision Analysis (MCDA)
... Incentives for the wider application of green roofs are required for cities in India that face high temperatures during summers. Nature-based solution can also help build resource efficiency by reducing the urban heat island effect and problems related to urban flooding (Feng & Hewage, 2018). The market for naturebased solutions such as green roofs is low even though there is evidence to show that green roofs reduce the energy used for cooling (Bianchini & Hewage, 2012). ...
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Energy and waste management sectors are considered important for the country’s progress towards adopting sustainable consumption and production (SCP) practices and achieving Sustainable Development Goals. However, the rapid pace of urbanization, energy-intensive growth approaches, and generation of large quantities of waste have led to severe environmental degradation of cities in India. While the government has taken several initiatives for increasing resource efficiency, limited research has been done in an Indian context to explore the policy and institutional factors. The paper focuses on challenges relating to policy enablers within the energy management in buildings and construction and demolition waste sectors; 28 semi-structured interviews were conducted with stakeholders associated with both these sectors. The findings indicate that though India has been integrating climate change measures into its national policies and enhancing the domestic market’s readiness for a circular economy, successful implementation of policy framework(s) urgently requires lifestyle and behavioural changes in the society. The study further identified the role of key stakeholders including government, businesses, and consumers, for transition to a low-carbon economy for both these sectors. This paper presents a bottom-up approach to understand the changes required in the enabling environment for the uptake of SCP practices that can be adapted by other emerging economies in the Asia Pacific region for building resource efficiency. The importance of soft factors relating to institutional capacities and governance structure is raised by the analysis in this paper.
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Photovoltaic (PV) panels and green roofs are considered as the most effective sustainable rooftop technologies at present, which utilizes the effective rooftop area of a building in a sustainable manner. To assess the most suitable rooftop technology out of the two, it is vital to have an idea on the energy savings potential of these sustainable rooftop technologies, alongside a financial feasibility analysis considering their overall life spans and additional ecosystem services. To achieve this objective, ten selected rooftops located in a tropical city were retrofitted with hypothetical PV panels and semi-intensive green roof scenarios to perform the present analysis. The energy-saving potential for PV panels was estimated with the assistance of PVsyst software, and green roof ecosystem services were evaluated through a range of empirical formulas. The financial feasibility of the two technologies was assessed by Payback Period and Net Present Value (NPV), through data obtained by local information sources such as solar panels and green roof manufacturers. The results indicate that PV panels achieve a rooftop PV potential of 244.39 KWh/yr/m² during their 20-year life span. Furthermore, green roofs reach an energy-saving potential of 22.29 KWh/yr/m² during a 50-year life span. Moreover, based on the financial feasibility analysis, PV panels demonstrated an average payback period of 3-4 years. Green roofs exemplified 17-18 years to recover their total investment for the selected case studies in Colombo, Sri Lanka. Although green roofs do not provide comparatively significant energy savings, these sustainable rooftop technologies aid in energy saving under different response intensities. In addition, green roofs offer several other ecosystem services that improve urban areas' quality of life. Collectively, these findings highlight the particular importance of each rooftop technology promoting building energy savings.
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Increased urbanization combined with the intensification of short rainfall events has worsened the urban flood issue. Among the different blue-green solutions to mitigate pluvial floods, green roofs (GR) and rainwater harvesting (RWH) have been investigated as sustainable systems to reduce runoff from rooftops. Their flood mitigation capacity, however, has been estimated mostly at building-scale. Following the need to estimate discharge reduction at large scale over entire cities, we simulated the installation of (extensive, intensive and multilayer blue) GRs on flat roofs and RWH systems for sloped ones. Performances of such systems were investigated in selected cities, representing different climate regimes. Although at building-scale GRs showed higher retention capacity, the cost-efficiency analysis highlights that at large-scale RWH tanks ensure higher retention with lower costs, due to rooftop distribution. The coupled system of multilayer blue-GRs and RWH tanks guarantees a discharge reduction of 5% even during extreme events.
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Bu makalede, günümüz koşularında sahip olduğumuz bilgilerin ışığında, yapı bünyelerinde üretilebilecek olan açık ve yeşil mekânların yapılma gerekliliği ile ilgili bir durum değerlendirmesi yapılmıştır. Değerlendirme, literatür taraması ile ulaşılan aşağıda özetlenmiş olan verilerin karşılaştırılması ve tartışılması ile yapılmıştır. Yapı bünyelerindeki açık ve yeşil mekânların bir yandan kentleşme ile zarar görmüş doğanın yeniden üretilmesi konusunda önemli katkılar oluştururken, diğer yandan da kentlilerin sağlıkları ve refahları ile yapı zarfının performansı üzerinde olumlu etkiler oluşturdukları görülmüştür. Tüm bu olumlu etkilerinin yanında yapı bünyelerindeki açık ve yeşil mekânların yapılarda ilave yükler ve daha karmaşık tasarım ve uygulama süreçleri ortaya çıkardıkları da görülmüştür. Yapı bünyelerinde üretilebilecek olan açık ve yeşil mekânların ortaya çıkardığı olumsuzlukların temelde bilgi eksiklikleri ve maliyet artışlarından kaynaklandığı görülmüştür. Bilgi eksikliklerinin eğitim çalışmaları ile tamamlanabileceği, maliyet artışlarının ise kentlilerin sağlıkları ve refahlarındaki artışlar ile telafi edilebileceği görülmüştür. Değerlendirmenin sonucu olarak özellikle yoğun yapılaşmış kentsel bölgelerdeki yapı bünyelerinde açık ve yeşil mekânların üretilmesi gerekliliği ortaya çıkmıştır.
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Greenery on buildings is being consolidated as an interesting way to improve the quality of life in urban environments. Among the benefits that are associated with greenery systems for buildings, such as energy savings, biodiversity support, and storm-water control, there is also noise attenuation. Despite the fact that green walls are one of the most promising building greenery systems, few studies of their sound insulation potential have been conducted. In addition, there are different types of green walls; therefore, available data for this purpose are not only sparse but also scattered. To gather knowledge about the contribution of vertical greenery systems to noise reduction, especially a modular-based green wall, two different standardised laboratory tests were conducted. The main results were a weighted sound reduction index (Rw) of 15 dB and a weighted sound absorption coefficient (α) of 0.40. It could be concluded that green walls have significant potential as a sound insulation tool for buildings but that some design adjustments should be performed, such as improving the efficiency of sealing the joints between the modular pieces.
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Green roofs offer various kinds of ecosystem services that are often scarce especially urban areas. These services accrue benefits to urban dwellers. However, ecosystem services do not generally have a market price, thus we had to use ecosystem valuation methods to estimate the benefits. Based on the valuation, the most significant benefits were: an increased lifespan of the roof, energy savings due to increased isolation and cooling, improved storm-water management, better air-quality and sound insulation especially in the air craft noise zones. In addition, other potentially significant benefits include aesthetic benefits, health benefits and improved biodiversity. Only a share of the green roof benefits accrues to the owner of the property while other benefits are distributed among the population of a larger area. We found that private benefits are in most cases not high enough to justify the expensive investment of a green roof instalment since the costs are incurred solely by the private decision makers (e.g. developers, real estate buyers). The cost-benefit calculations hint that with a higher rate of implementation and realization of public benefits, the green roofs would be a good investment. However, because the private benefits are not high enough to justify a green-roof installation for a private decision-maker at the current cost level, the rate of implementation can be expected to stay low without corrective policy instruments.
In Italy, as in the rest of Europe, serious land degradation processes are occurring, mostly due to rural abandonment, urbanization and infrastructure development. In particular Veneto, the region around Venice, has undergone considerable land use and land cover change in the last decades. This work integrates field observations and numerical simulations to study the urban heat island (UHI) effect in the mainland part of Venice. The numerical study was performed using ENVI-met, an environment and micro-climatic simulation tool. Different mitigation scenarios are evaluated in a case study area. The study aims to explore the factors that contribute to urban heat island development proposing practical, feasible and specific solutions for mitigating their effects. The focus of the analysis is, in particular, on the use of permeable surfaces vegetative soil or grassed parking instead of conventional asphalt or cement pavement as soil compensation mechanisms for soil loss. The replacement of traditional roofs with cool or green ones is also considered.
Low-energy pollutant removal strategies are now being sought for water sensitive urban design. This paper describes investigations into the water quality and quantity of sixteen, low-maintenance and unfertilized intensive and extensive green roof beds. The factors of Slope (1° and 25°), Depth (100 mm and 300 mm), Growing media (type A, type B and type C) and Species (P1, P2 and P3) were randomized according to a split-split plot design. This consisted of twelve vegetated green roof beds and four non-vegetated beds as controls. Stormwater runoff was collected from drainage points that were installed in each area. Samples of run-off were collected for five rainfall events and analysed for water retention capacity and the water quality parameters of NO2, NO3, NH4, PO4, pH, EC, TDS, Turbidity, Na, Ca, Mg and K. The results indicated significant differences in terms of stormwater water quality and quantity between the outflows of vegetated and non-vegetated systems. The water retention was between 51% and 96% and this range was attributed to the green roof configurations in the experiment. Comparing the quality of rainfall as inflow, and the quality of runoff from the systems showed that green roofs generally acted as a source of pollutants in this study. In the vegetated beds, the intensive green roofs performed better than the extensive beds with regard to outflow quality while in the non-vegetated beds, the extensive beds performed better than intensive systems. This highlights the importance of vegetation in improving water retention capacity as well as the role of vegetation in enhancing pollutant removal in green roof systems. In addition growing media with less organic matter had better water quality performance. Comparison of these results with national and international standards for water reuse confirmed that the green roof outflow was suitable for non-potable uses such as landscape irrigation and toilet flushing.
Conference Paper
In this paper cost-effectiveness assessment techniques were used to evaluate the economic impacts of the widespread emerging of new buildings being aim for green roof projects in a life-cycle scale on three typical rural building stocks. Results show contrast to traditional one the building with green roof bring out more economic benefits by providing a outstanding medium for building energy consumption decreasing, vegetable cultivating to its owner and that the economic benefits of green roof in its life-cycle scale are much bigger than the additional construction investment cost on converting traditional one to green roof building in every research region. After quantitative analysis of the cost-benefits of green roof project in rural region the currently hindering factors of popularizing the project are analyzed and countermeasures are proposed to guide green roof popularizing policy path.
Green roofs have been used as an environmentally friendly product for many centuries and considered as a sustainable construction practice. Economic and environmental benefits of green roofs are already proven by many researchers. However, a lifecycle net benefit-cost analysis, with the social dimension, is still missing. Sustainable development requires quantitative estimates of the costs and benefits of current green technologies to encourage their use. This paper is based on an extensive literature review in multiple fields and reasonable assumptions for unavailable data. The Net Present Value (NPV) per unit of area of a green roof was assessed by considering the social-cost benefits that green roofs generate over their lifecycle. Two main types of green roofs – i.e. extensive and intensive – were analyzed. Additionally, an experimental extensive green roof, which replaced roof layers with construction and demolition waste (C&D), was assessed. A probabilistic analysis was performed to estimate the personal and social NPV and payback period of green roofs. Additionally, a sensitivity analysis was also conducted. The analysis demonstrated that green roofs are short-term investments in terms of net returns. In general, installing green roofs is a low risk investment. Furthermore, the probability of profits out of this technology is much higher than the potential financial losses. It is evident that the inclusion of social costs and benefits of green roofs improves their value.
Green roofs can be classified as intensive and extensive roofs based on their purpose and characteristics. Green roofs are built with different layers and variable thicknesses depending on the roof type and/or weather conditions. Basic layers, from bottom to top, of green roof systems usually consists of a root barrier, drainage, filter, growing medium, and vegetation layer. There are many environmental and operational benefits of vegetated roofs. New technology enabled the use of low density polyethylene and polypropylene (polymers) materials with reduced weight on green roofs. This paper evaluates the environmental benefits of green roofs by comparing emissions of NO2, SO2, O3 and PM10 in green roof material manufacturing process, such as polymers, with the green roof’s pollution removal capacity. The analysis demonstrated that green roofs are sustainable products in long-term basis. In general, air pollution due to the polymer production process can be balanced by green roofs in 13–32 years. However, the manufacturing process of low density polyethylene and polypropylene has many other negative impacts to the environment than air pollution. It was evident that the current green roof materials needed to be replaced by more environmentally friendly and sustainable products.