LIFE CYCLE ENVIRONMENTAL IMPACTS ASSESSMENT FOR RESIDENTIAL BUILDINGS IN CHINA

Transcription

1 Proceedngs: Indoor Ar 2005 LIFE CYCLE ENVIRONMENTAL IMPACTS ASSESSMENT FOR RESIDENTIAL BUILDINGS IN CHINA DJ Gu 1,*, JJ Lu 1, LJ Gu 1 1 Department of Buldng Scence, School of Archtecture, Tsnghua Unversty, Bejng, Chna, , ABSTRACT Buldng ndustry has made sgnfcant contrbuton to economc development of Chna, but meanwhle t has harmed the envronment to a severe extent, whch aroused broad recognton. Snce buldng s an nteractve ntegraton of buldng materals and products nstead of a smple collecton and envronmental mpacts of buldngs are varous and long-term, how to assess and quantfy n whch way the buldngs affect the envronment becomes a worth concernng topc. In ths study, through a perspectve of a lfe-long span, we wll analyze the envronmental mpacts of a buldng wthn ts every stage, propose some hypothess and smplfcaton accordng to Chnese partcular condtons, and advance the framework of Lfe Cycle Assessment (LCA) amed at buldngs, especally for resdental buldngs. By usng ths framework and relatve toolkts developed for research, not only can the envronmental mpacts of exsted buldngs be observed, but gudance for archtectural desgns s provded. Consequently, t contrbutes to green or ecologcal desgn and assessment of buldngs. Further more, an LCA case study on resdental buldng fabrcs desgn and constructon effectng on the envronment energy and resource consumpton s ntroduced. INDEX TERMS LCA, green buldng, envronmental mpacts, buldng materals, energy savng INTRODUCTION The resdental area n Chna s developng rapdly, whch has reached 600 mllon m 2. Therefore research on the envronmental mpacts related to buldngs should be performed, whch s also essental to form a regular market and standardzed assess system for green buldngs n Chna. Ths work pay regards to the quantfcaton of the lfe cycle envronmental mpacts systematcally and comprehensvely. THE METHOD FOR LCA OF RESIDENTIAL BUILDINGS Dffer from some other LCA research, the work emphaszes gudance on desgn and constructon of new buldngs rather than analyss for exstng or certan buldngs, amng at provdng gudelnes to the buldng desgners. Hence many smulaton methods wll be taken n the work. System Analyss Take the lfe-span of a resdental buldng for 50 years, and that of the buldng materals, components and equpments dffers. The lfe of a buldng can be dvded nto fve man stages: raw materals producton, materal manufacturng, transportaton and buldng constructon, operaton and recycle/dscardng. Most of the consumptons and pollutons n a buldng s whole lfe are dstrbuted n the producton and operaton phase, whch wll be stressed here. Specfcaton of envronmental mpacts The envronmental mpact of resdental buldngs concerned can be concluded as consumptons of resources and energy as well as emssons of pollutants. By stuatons of Chna, 8 envronmental mpact factors are consdered: fossl fuel consumpton, mneral consumpton, forest consumpton, water consumpton, global warmng, acdfcaton, dust, and sold waste generaton). * Correspondng author emal:goldng@tsnghua.org.cn 3166

2 Proceedngs: Indoor Ar 2005 Methods for assessment To establsh a well operable assessng framework whch can gve nstructons for amendng archtecture desgns s the prncple of ths study. Thus, the assessng calculatons for sub-processes of every phase are modularzed, as llustrated n Fgure 1 and the software named EI-Chna has been developed based on the database and modules. The calculaton methods for every module wll be analyzed as follows. Fgure 1. The Framework and methods for LCA of buldngs 1)Emboded Energy & Input/Output Database In order to get data of emboded energy of buldng materals and components, a great deal of nvestgaton and demonstraton work s requred whch happen to be lack n naton. So the database employed here s partly based on natonal condton (Laoson 2000, Yang and Wang 2002), whle adopted some data of developed countres(toshharu Ikaga 2003). An ndcator of resource qualty s proposed to emphasze the value dfferences between varous fossl fuel resources. Here, resource qualty represents the level of the resource shortage and s defned as an nverse rato to the explotable lfespan (e.g. Coal 240 years, Ol 20 years, Natural gas 60 years n Chna) on the bass of that the resource qualty of coal s defned as 1.0. Fnally the resource qualty s used to calculate the fossl fuel resources consumpton by the consumed quanttes of fuels weghted by resource qualtes. 2)Materal Consumpton Forecast Module As the research ams at gudng archtectural desgn, pre-calculatons of materal consumpton and equpment selecton are needed. The calculaton method employed here focused on the followng chef components: structure and foundaton, exteror and nteror walls, floors, doors and wndows, and decoratons. The quanttes of lghtng facltes should follow calculatons accordng to the desgn, whle the HVAC equpments are accordng to the energy smulaton results. 3)Transportaton Calculaton Module Transportaton s ncluded n all phases n a buldng s lfe cycle. The consumpton E s s determned by the relatonshp E t = k E D k T where E k s the energy provded by the fuel k n MJ/t km; T s the weght of materal or equpment n t; D s the average dstance of goods transportaton n Chna n km. 4)Heat/Cool Load Smulaton Module Accordng to the archtectural desgn, the dealzed heatng and coolng load s calculated wth DeST, the buldng load smulaton software of developed by Tsnghua Unv (Yan 2004). (1) 3167

3 Proceedngs: Indoor Ar )Lghtng Load Smulaton Module The lghtng energy consumpton calculaton s based on the lghtng capacty of the rooms and the assumed workng schedule of the lamps. 6)Water Consumpton Module The water consumpton G wt calculaton s expressed as G wt G, d d where rate. = ( 1- α ) G, s the water consumpton of the household and day number d n m3; and α s the water savng d 7)Waste Predcton Module Buldng waste conssts of the non-recyclable materals and equpments. In addton, the recyclable parts and recyclng energy consumpton n ths process should be taken nto account. (2) G = ( 1 λ ) waste G (3) where λ s the recycle rate of materal I (Chna Buldng Materals Scence Research Center 2003). 8)Envronmental Impacts Characterzaton Module In order to assess the envronmental mpacts of varous pollutants unformly, the characterzed classfcaton method s llustrated n Fgure 2. Fgure 2. Envronmental mpacts characterzaton flow 9)Envronmental Impacts Normalzaton Module For general comparsons the normalzed envronmental ndcators EI s obtaned by dvded by ts basc value, whch s defned as the per capta statstc( Chna Statstc Insttute 2003, Envronmental Protecton Admnstraton of Chna 2000). EI = REI / NEI (4) where REI s the absolute classfed envronmental mpact value of the materal ; NEI s the per capta basc value of the envronmental mpact. CASE STUDY Bass Analyss The case s a typcal resdence n Bejng, wth a renforced concrete framework. The exteror envelope conssts of 200mm thckness concrete wall and 20mm thckness nsulaton, and the shape coeffcent s Untary ar condtoners are used for coolng n summer, whle local heatng are utlzed n wnter. The result of the energy consumpton durng manufacture stage s shown n Fgure 3. The foundaton and framework producton and the wall, floor and roof producton domnate the energy consumpton, and they both share about 40%. The dstrbuton of energy consumpton over 50-year lfetme s llustrated n Fgure

4 Proceedngs: Indoor Ar % 40% 3% Foundaton & Framework wall & floor & 40% roof wndow & door equpment Materals 12.2% 1.9% 15.8% Manufacturng Components 0.4% Manufacturng Operatonal 11.0% Coolng Operatonal Heatng Operatonal Lghtng 58.7% Equpments Mantenance Fgure 3. Energy consumpton n manufacture stage Fgure 4. Energy consumpton n Lfetme Improved Desgn From above analyss, t s concluded that the heatng energy consumpton accounts for nearly 60% of the total energy consumpton n lfe cycle. Then the relatonshp between resdence energy consumpton and the thckness of nsulaton s analyzed, and the result s showed n Fgure 5. It shows that the energy savng effect decreases wth thckness of wall nsulaton f the thckness of wall nsulaton exceeds 90mm (supposed 10 years lfe cycle for nsulaton). The mproved desgn enlarges the thckness of heat-solatng materal to 40mm, and changes the heatng energy source type from coal to natural gas, consequently the comparson result s showed n Fgure 6, where the values of basc desgn are assumed as 1. However ths case study ddn t consder the nfluence of feld demolshment, snce t was rebult on the former ste. Results show that fossl fuel consumpton wll become lager for the resource qualty of gas s better than that of coal, but the energy and pollutant emssons wll be cut down sgnfcantly, so natural gas s proved to be a better choce for energy source for resdental heatng n Bejng. energy savng(mj/m2) energy savng n operatonal stage energy savng n lfetme nsulaton thckness(mm) Fgure 5. Energy savng analyss between operaton stage based and LCA Sold Waste Dust Basc Plan AP Fossl Fuel Consumpton GWP Advanced Plan Mneral Consumpton Forest Consumpton Water Consumpton Fgure 6. LCA results comparson CONCLUSION In ths study, an ntegratve assessment framework s proposed, whch can systemcally and quantfcatonally assess the envronmental mpacts of a resdental buldng durng ts lfetme. Several sub-modules are proposed to calculate the specfc processes of a lfe cycle and many smulaton methods and tools are ntroduced to the calculaton. The calculaton of a typcal resdence n Bejng ndcates that the heatng energy consumpton n operaton phase accounts for 60% of the total energy consumpton over 50-year lfe span. The rato of materal and equpment producton energy consumpton to the operaton energy consumpton s 1:5. And of the producton energy consumpton, that of the foundaton and framework producton and the wall, floor and roof producton account for 40% respectvely, wndow and door producton accounts for 15%, equpment producton accounts for less than 2%. Accordngly, the advanced plan leads to mprovng the envronmental performance and reduce 30% of the pollutant emssons by the heat source substtuton. References Laoson B. Sustanable Buldng Materal, Energy and Envronment Yang JX. and Wang RS. Product Lfe Cycle Analyss and Applcaton. 2002: Weather Publshng House. TOSHIHARU IKAGA, LCA Gudelne of Buldngs

5 Proceedngs: Indoor Ar 2005 Yan D., Xe XN., Song FT. and Jang Y., Buldng envronment desgn smulaton software DeST(1) : an overvew of developments and nformaton of buldng smulaton and DeST, HV&AC Chna Buldng Materals Scence Research Center, Green Buldng Materals. 2003: Chna Chemstry Publsher. Chna Statstc Insttute, Annual Chna Statstc. 2003: Chna Statstc Publshng House. Envronmental Protecton Admnstraton of Chna, Past Years Communque of Chna Envronment