10th Anniversary Booklet - The Professional Green Building Council

More documents

Recommendations

Info

Sparkling Green156Quantitative Approach in Greening our BuildingsGreening provides benefits in enhancing the visual and aesthetic qualityof our built environment, improving air quality by absorbing air pollutantsand carbon dioxide, providing psychological comfort, reducing peak stormwaterdischarge, increasing bio-diversity and mitigating the Urban HeatIsland (UHI) effect. This article briefly describes the quantified findings ofthermal benefits in greening and the quantitative approach in the provisionof greening in building developments in Singapore and Hong Kong.Thermal Benefits of GreeningThe UHI effect is a phenomenon in which the urban area is warmer than itssurrounding rural area. The UHI is mainly caused by urban area dominatedwith hard surfaces with materials which absorb and retain heat. A higherenergy consumption which generates larger amount of waste heat to theurban environment is also an important contributory factor. Greeningby means of planting vegetation in urban area is one of the effectivemitigation measures in ameliorating the UHI effect. The exterior buildingspaces provide ample opportunities for greening and these include plantingat-grade, on roofs, podia and walls of buildings.With reference to the findings in Hortpark Vertical Greenery Research andDemonstration Project in Singapore published in 2009, the results indicatedthat the temperaturedifference between the wallsurface covered with greeneryand that of the control wallwith bare surface could beas high as 12 o C (see Figure1). The findings supportedthat vegetation cover caneffectively reduce the thermalgain into buildings by shadingthe solar radiation andevapotranspiration coolingeffect of the plants.Figure 1: Temperature readings on bare control wall surface(black) as well as the wall (red) and substrate (green) surfacesof a vertical greenery wall in HortPark. (Source: Chiang K. andTan A. (2009))Energy simulations of the different scenarios of greening extent on buildingenvelope were also conducted in the research. The Envelope ThermalTransfer Value (ETTV) as adopted in Singapore is a measure of the averageheat gain into a building through its envelope. This composes of three keyheat transfer components: (1) heat conduction through opaque walls, (2)heat conduction through glass windows and (3) solar radiation throughglass windows. In the scenario of a building with full glass façade, 40%ETTV reduction could be achieved with 50% vertical greenery over theglass facade. In the scenario of a building with glass and concrete façadeat a ratio of 2:1, 13% ETTV reduction could be achieved with verticalgreenery covering the concrete façade. The findings illustrated that energyconsumption required for cooling the internal space of buildings can beeffectively lowered with greening provision on building surfaces.In the research, the daily fluctuation of the wall surface temperature ofthe control wall was recorded as approximately 10 o C while the wall withgreenery was recorded as low as 1 o C. The results showed that greeningprovision can stabilize the daily fluctuation of temperatures in the buildingsurfaces as an additional benefit. The significant reduction in dailytemperature differences of a building surface by greening can avoid theextreme daily expansion and contraction of surface building materials. Thiscan prolong the lifespan of the building materials and minimize the needfor replacement and maintenance costs of building surface.The ambient temperatures away from the surface of the control wall andthe wall with greenery were also recoded in the research. The resultsindicated that a reduction of ambient temperature could reach as high as3.3 o C at a distance 0.15m away from the surface of the wall with greenery.With the cooler ambient temperature, the air conditioning system installedin area with greening provision can take in air at a lower temperature andthus saving the energy required for cooling the internal building space.Development of Green Plot Ratio in SingaporeWith a better understanding of the benefits of greening, a sophisticatedapproach in greening provision in developments by the application ofGreen Plot Ratio (GnPR) is evolving in Singapore. The GnPR is the ratioof the total leaf area of all greenery in a site to the site area. It is threedimensional in nature taking account into the measurement of greenvolume instead of greening provision by number of plants or planting area.The calculation of GnPR relies on the Leaf Area Index (LAI) and canopyarea. The LAI of a plant is its one-sided leaf area per unit ground area. Thecanopy area of a plant is the vertical projected area of the plant’s canopyon the ground. The total leaf area of a plant species in a site is calculated bymultiplying the LAI of that species by the total canopy area covered by thatspecies. The total leaf area of all greenery in a site is the sum of total leafarea of all species planted in a site.GnPR = (total leaf area) / (site area)= (LAI1 x Canopy Area1+ LAI2 x Canopy Area2+… LAIn x Canopy Arean)(site area)The GnPR is considered as a better quantified greening measure as itis directly related to the leaves of plants which are the key componentresponsible for environmental function of greenery such as carbonassimilation, cooling by transpiration and shading. The approach in usingGnPR is to stipulate the minimum amount of “green density” in a site asappropriate to suit its land-use type.To facilitate the practical application of GnPR, the Centre for UrbanGreenery and Ecology (CUGE) in Singapore developed a database of valuesfor the LAI and canopy area of 300 commonly used local landscape plants.The measurement of LAI involved (1) direct method by harvesting andmeasuring the area of all leaves in a plant within a sampled area and (2)indirect method by measuring the transmission of light through the canopyof vegetation using the plant canopy analyzer LAI-2000.The measurementof canopy area was simply by measuring the projected canopy area onground of the sampled plants. The collected data were then arranged intodifferent categories and statistical tests were conducted to derive generic
categorical values taken account into the natural growth habit, form ofplants, variations in plant age and landscape uses. The summarized LAI andcanopy area values are shown in the following table.Plant GroupLAISub-CategoriesLAIValue to Use Canopy Area to Use (m 2 )Trees Dense Canopy 4.0 Girth 1.5m : 150(Girth refers to trunkcircumference at height of1m from ground)Palms Solitary 2.5 20Cluster 4.0 17Shrubs Monocot 3.5 Planted areaDicot 4.5 Planted areaTurfs Nil 2.0 Planted areaThe calculation of GnPR in a site can be carried out by (1) collecting theinformation on site area, number of trees (and their girth sizes), palms andplanted areas for shrubs and turfs, (2) determine the LAI sub-categories ofthe plants with reference to the database in the website of National Parks(NParks), (3) computing the total leaf area by summing up the leaf area foreach plants species and (4) dividing the total leaf area by site area to obtainGnPR in a site.Adoption of Greenery Coverage Requirements in Hong KongIn Hong Kong, the Council for Sustainable Development (SDC) publishedthe “Report on the Public Engagement Process on Building Design to Fostera Quality and Sustainable Built Environment” in June 2010 upon extensivepublic consultations and discussions with professional organizations, greengroups, councilors and relevant key stakeholders. The SDC recommendedthe minimum requirement to provide greenery for sites no less than1,000m 2 in new building developments or redevelopments with fixedplanting areas of 20% to 30% of the site areas.Following SDC’s recommendation for greening provision, the Governmentof Hong Kong SAR issued “Development Bureau Technical Circular (Works)No. 3/2012 – Site Coverage of Greenery for Government Building Projects”in 2012 which sets out the standards and requirements on greenerycoverage for new government buildings. This requires the minimum sitecoverage of greenery of 30% for site area equal or above 20,000m 2 and 20%for site area between 1,000m 2 and 20,000m 2 . As planting at grade withindevelopment provides a more natural condition for plant establishmentand improves the setting at street level, the Technical Circular also requiresat-grade greenery area should not be less than 50% of the minimumsite coverage of greenery requirements. The greenery coverage ofminimum 30% site area is also recommended for both public and privatedevelopments in the Kai Tak Development located at the former Hong KongKai Tak International Airport.The calculation of site coverage of greenery under the Technical Circularis a two dimensional approach which is relatively simple and direct. It isbased on the horizontal soil areasfor planting and this includessoil areas at-grade, on podiumand roof levels. The TechnicalCircular defines the calculationbasis of site area and countableareas for greenery. For specialgreenery provision such as verticalgreening, greening on slopes andcovered greenery areas, the totalcountable areas for inclusion inthe calculation of greenery iscapped at 30%. Priority is given forat grade-tree planting for optimalgreening effect.The same greenery coveragerequirements with similarcalculation basis are also appliedfor non-government buildingdevelopments under “PracticeNote for Authorized Persons,Registered Structural Engineersand Registered GeotechnicalEngineers – APP 152”. Through thevetting of landscape design by planning and lease controls, a balance mix oftrees and other plant types can be provided in a development to achieve aquality green setting. With the join effort from the public and private sectors,a greener built environment in Hong Kong is anticipated in the coming decade.Concluding RemarksThe greening requirements should be adequately addressed at planningand design stages so that the greenery can be smoothly integrated withthe buildings to facilitate management to achieve the goals in landscapedesign. The quantitative approach stipulates clear requirements in greeningprovision for building developments. Continual improvements on thequantitative approach are required to yield a more thorough, practicaland sustainable methodology to cater for different land uses. Yet, qualitylandscape design and management are equally important to address thesafety, aesthetic, functional and maintenance concerns in the green setting.It is hoped that both quantitative and qualitative development in greeningcan lead to a safer, greener and more sustainable built environment.Simon NGHKILA RepresentativeFigure 2: The Central Government Offices inHong Kong has greenery coverage of over35% site area. This provides a pleasant andgreen outdoor setting to ameliorate builtenvironment. (Photo: Architectural ServicesDepartment, HKSAR)ReferencesChiang K. and Tan A. (2009). Vertical Greenery for the Tropics, National Parks Board,Singapore.Tan P.Y. and Sia A. (2010). Leaf Area Index of Tropical Plants – A Guidebook on its Usein the Calculation of Green Plot Ratio, 2 nd Ed., Centre for Urban Greenery and Ecology,Singapore.“Report on the Public Engagement Process on Building Design to Foster a Quality andSustainable Built Environment (June 2010)”. The Council for Sustainable Development,Hong Kong SAR.“Development Bureau Technical Circular (Works) No. 3/2012 - Site Coverage of Greeneryfor Government Building Projects”, Development Bureau, Hong Kong SAR.“Practice Note for Authorized Persons, Registered Structural Engineers and RegisteredGeotechnical Engineers – APP 152”, Buildings Department, Hong Kong SAR.157
Page 1:
Professional Green Building Council
Page 4 and 5:
Table of Contents03 | About PGBC04
Page 6 and 7:
Congratulatory Message from the Gue
Page 10: Messages from PGBC Founding Members
Page 14 and 15: Congratulatory MessagesMr. Thomas C
Page 16 and 17: Congratulatory MessagesMr. Frank CH
Page 18 and 19: Congratulatory Messages from Suppor
Page 26: 24PGBC Past Chairmen
Page 29 and 30: PGBC almost immediately. In the beg
Page 31 and 32: Ir Prof. Reuben CHUPGBC Chairman [2
Page 33 and 34: 131
Page 36 and 37: 12003 2004 20052006PGBC Key Events2
Page 38 and 39: 2009PGBC Key Events20098-Jan Semina
Page 40: 38Green Building Award
Page 43 and 44: 1234516789101112131415411617181920
Page 45 and 46: 12341567891011124313141516
Page 47 and 48: 12345167891011121314151617181920452
Page 49 and 50: 12341567891011124713141516
Page 51 and 52: SUSTAINABLE BUILDING: DEFINITIONSus
Page 54 and 55: 152Sparkling GreenHong Kong and Bey
Page 56 and 57: Sparkling GreenBiofuel in Operation
Page 60: 58Acknowledgement
Page 72 and 73: Gold SponsorsArupHong Kong Housing
Page 74: Professional Green Building Council
show all

10th Anniversary Booklet - The Professional Green Building Council

Create successful ePaper yourself

Delete template?

Save as template?