Sustainable Cities and Society 1 (2011) 67 71

Contents lists available at ScienceDirect

Sustainable Cities and Society

j our nal ho me page: www.elsev ier .c

Embod eensystem

Bruno Lea Materials innb Department o hoven

a r t i c l

Keywords:Industrial hallGreen buildingEmbodied eneLife-cycle enerSensitivity ana

are de perfch oe in we forpaperhe buame f unct alsbodie

1. Introduction

Modern buildings have to achieve certain performance require-ments, at lsafe, healthditioned enwhich are this contexings that coresources; iable strategdesign proc

Green btems) facilindependensustainabilisets of rulesresource.

Becauseand the wamight not data. For ex

CorresponThe Netherlan

E-mail add

in Energy and Environmental Design) certied buildings consumemore energy than conventional buildings (Newsham, Mancini, &Birt, 2009). This nding is understandable in certain cases in spite

2210-6707/$ doi:10.1016/j.east to satisfy those of building codes, to provide ay, and comfortable environment. However, these con-vironments demand resources in energy and materials,both limited in supply, to build and operate. Withint of limited resources, the goal is to construct build-uld provide better performance and yet demand fewern other words, to do it in a sustainable fashion. Sustain-ies are best incorporated into the early stages of theess.uilding rating (GBR) systems (a.k.a. certication sys-itate the sustainable design processes by providingt assessment tools, in which strategies used to improvety of buildings can be evaluated according to common

that cover categories from energy efciency to water

of the diverse scopes and objectives of GBR systems,ys GBR scores are calculated, a highly rated buildingperform well when compared to actual performanceample, it was found that at least 28% of LEED (Leadership

ding author at: Materials innovation institute (M2i), Delft,ds.ress: b.lee@m2i.nl (B. Lee).

of its high signicance; that is because energy efciency of build-ing operation just represents a single aspect of sustainability. Bythe same token, an energy efcient building with poor buildingmaterial choices may not be considered sustainable.

A possible alternative to gauge sustainability is to represent anyof these categories in a common unit; for example, in the unit ofenergy, or more specically, the total life-cycle energy demand. Itincludes:

the embodied energy involved in the acquisition, processing,manufacturing, and transportation of building materials duringthe construction phase;

the operation energy of the building; and the demolition energy in the destruction, removal, and recyclingof building materials.

With the advent of Building Information Modeling (BIM), build-ing materials data from the construction phase till the demolitionphase could be made available, and energy involved in each of thesephases could be estimated (Azhar, Brown, & Farooqui, 2009). Thetotal demand for the whole life-cycle can serve well as a yardstickfor assessing sustainability.

This paper presents some preliminary results of an on-goingproject Sustainable Energy Producing Steel Frame Industrial

see front matter 2011 Elsevier B.V. All rights reserved.scs.2011.02.002ied energy of building materials and grsA case study for industrial halls

ea,b,, Marija Trckab, Jan L.M. Hensenb

ovation institute (M2i), Delft, The Netherlandsf Architecture, Building and Planning, Eindhoven University of Technology (TU/e), Eind

e i n f o

ratingrgygy analysislysis

a b s t r a c t

Green building rating (GBR) systems evaluate in a few categories about thegory might weight differently in eastrategies over others due to differenccurrent GBR systems are catered morsignicantly different geometry. This vs steel) on the embodied energy of tunder the material category for the sembodied energy, the major source oThis paper forms part of a project thabuilding, which together with the emom/ locate /scs

building rating

, The Netherlands

eveloped to provide independent assessment standards thatormance and sustainability of buildings. However, same cat-f the GBR systems. A particular system might favor certaineighting. This is particularly the case for industrial halls since

commercial buildings than for industrial halls, which pose a explores the impact of different building materials (concreteilding structure, and compares that to the GBR score earnedstructure. Through a sensitivity analysis in the calculation ofertainty is identied and its effect on GBR score is discussed.o studies the operation energy and the demolition energy ofd energy constitute the total life-cycle-energy demand.

2011 Elsevier B.V. All rights reserved.

68 B. Lee et al. / Sustainable Cities and Society 1 (2011) 67 71

Halls. The project takes on the whole life-cycle approach towardstotal life-cycle energy demand of the building, in particular, a steelframe industrial hall. The goal of that project is to develop compu-tational design and assessment support tools that could facilitatethe design are tted wto exceed tinvestigatiostep. The inembodied eThis paper penergy in ttrate the idconstructedsteel, is preto the GBR

2. Assessm

The sustmeasured bretired builbuilding ma

Buildingstructural ishift; and efunctions. Texible it iConcrete stcost that m(Bodman &many casesReadaptinging buildingonly saves nciated envirmaterials.

When thcled (or reurecycled w97.5% of stris being mamost commcoarse aggr2007). The demand of proximity twithin econ

The propan indicatois greater thcertain perccrete, the bThe bindingcentage witslag, and sitives. The rbut also elimthe otherw

2.1. Green bmaterials

Many GBgreatly in t

Table 1Sub-categories and the possible points awarded under the materials and resourcescategory (USGBC, 2009).

Credit

reusand th

thesed.

ED

er thograials d wuse athis cnts ahan 5dit 1.teriaal to rom singavoi. For d asokenals unoth

this he caycledaran, blasin thdit 5

800 , drilocatble f

nera

systems, under most categories, are prescriptive-based (forle, the material category of LEED), in which credits are givenin prescribed values are achieved in the design; and under ategories, are performance-based, in which the performanceuilding for such categories have to be proved to offer certainement over a benchmark. Due to this mix of prescriptive andance based scoring methods, together with the difference

hting assigned to different categories and the rule-of-thumb used in the rating of each category; the resulting GBR scoresbe highly distorted.of energy producing industrial halls, in which the hallsith sustainable energy technologies that satisfy if nothe energy demand of the halls. Therefore, a thoroughn of total life-cycle energy demand is the natural rstvestigation will be performed in parts, in terms of thenergy, the operation energy, and the demolition energy.resents the results of the rst part the total embodiedhe building structure due to material choice. To illus-ea, a case study of a typical industrial hall, which is

with two different building materials concrete andsented. The embodied energy results will be comparedscores earned under the material category.

ent of sustainability of building materials

ainability of a building material could be commonlyy, the reclamation rate and the recyclability of theding material, and the recycling content of the newterial.s come to their end-of-life usually not because of anyssue, but rather the original purposes of the buildingsxisting buildings no longer support their new roles andhe possibility of remodeling depends largely on hows for the original building to adapt to its new roles.ructures can only be modied to a certain extent at aight be more expensive than building new structures

Shelton, 1986). By contrast, steel structures, which in are bolted together, facilitate deconstruction and reuse.

existing building for other purposes, or reusing exist- materials for the construction of a new building notew materials from being used, but also cuts the asso-onmental impacts of producing and transporting those

e building is demolished, steel is commonly being recy-se) in practice. In the UK, 86% of structural steel wasith another 13% reused (Corus, 2007), and in the U.S.,uctural steel was recycled (SRI, 2008). The recycled steelde into other steel products. In the case of concrete, theon recycling option in urban areas is to crush it intoegate mainly to serve as road base or ll (Van Geem,recycle potential of concrete is therefore limited by thethe recycled end-product (coarse aggregate) and theo possible sites of application (where road works areomical travelling distance of the demolition site).ortion of recycled content of the new materials is alsor to sustainability. Since the demand for steel productsan the supply of scrap steel, it is inevitable to have aentage of virgin steel in any steel products. As for con-ulk is just natural materials like sand or crushed rock.

agent, cement, can be replaced by up to a certain per-h industrial waste products like y ash, blast-furnacelica fume (Van Geem, 2007), which are added as addi-eplacement not only improves the quality of concreteinates the environmental impacts of having to dispose

ise dumped wasted products.

uilding rating (GBR) systems applied to building

R systems are available today and these systems differheir purposes and scopes. In general, they all concern

1 23 4 5 6 7

about able aDue todiscus

2.2. LE

Undtion prMatergory anis on reunder

Poimore tfor Creing madisposAside fand reuers by scrapsrecyclesame tmaterifrom amakes

In tthe recthat guy ashto atta

Crewithincuttingbe the attaina

2.3. Ge

GBRexampif certafew caof the bimprovperformin weigvaluesmight Description Points

Building reuse 4Construction waste management 2Materials reuse 2Recycled content 2Regional materials 2Rapidly renewable materials 1Certied wood 1

bility and recyclability, but the amount of credits avail-e criteria to achieve the credits are vastly different.

limited length of this paper, only the LEED system is

e LEED 2009 Rating System (part of version 3 certica-m) (USGBC, 2009), 14 points can be awarded under theand Resources (hereafter referred as material) cate-orth close to 13% of all available points. LEEDs emphasisnd recycling. Table 1 lists the sub-categories and pointsategory.re awarded if more than 55% of the exterior structure or0% of the interior non-structural elements are retained

With Credit 2, points are awarded for demolished build-ls (from the retired building) being diverted from thebeing reused for the assessed building or being recycled.the environmental benets, the possibility of recycling

also provides economic incentives to the building own-ding dumping costs, and proting from the sale of theexample, if concrete from the retired building can be

ll or road base, this credit can be achieved. By the, LEED also awards points to buildings using reclaimednder Credit 3, in which the materials can be transferreder site, or acquired from suppliers; bolted steel structurecredit easily attainable.se where building materials must be purchased new,

content of structural steel can reach a high percentagetees the award of Credit 4. Recycled materials, such ast-furnace slag, silica fume, in precast concrete also helpis credit.

is awarded for use of local/regional materials that iskm of the project site. The fabrication shop, which doeslling, and welding, for structural steel is considered toion of manufacturing; and as a result, this credit is likelyor any site location, particularly for those in Europe.

l issues with GBR systems

B. Lee et al. / Sustainable Cities and Society 1 (2011) 67 71 69

Table 2A breakdown of mass of the building structure.

Tonne Steel Concrete Hybrid

Steel-wall 276 43 43Steel-roofConcrete-waConcrete-ro

2.4. Embodmaterials

In fact, twell as an materials. Tand the manin earlier seeven at a vdatabases.

3. The case

In this seence of uncbuilding thawidth 170built with t

steel clad reinforced

3.1. Invento

The steesteel stud wjoist roof ofof 1 mm. A and roof is p

The conwalls of 200by open wethe steel joiis commonthickness th

Becauseported spanfewer columsupport theroof structuthe roof of steel exampfor industriit serves noally of eithea third examconcrete exmass accordin Table 2.

3.2. Sensitiv

In the cathere will a

the amou the embo the sourc

Table 3Embodied energy according to Alcorn and Wood (1998) and Hammod and Jones(2008).

Embodied energy [MJ/kg] A&W H&J

te steeled ste

thusaramrgy tial i

cert

ed onll is

3888tructartic

diffon tere mpoth

as u

cert

embis baient

The kg, a

MJ/riginre arbuildacturanu

bodia Insr of UembtionaThis tudied tof 90%

valu).

certals

re ay theEAF),resphan delle231 432 231ll 1440 1440of 2448

ied energy another view of sustainability of building

he embodied energy of the building materials can servealternative metric to reect the sustainability of thehe energy involved in the reclamation, the recycling,ufacturing processes of building materials as describedction can all be estimated and accountable for with BIM,ery early stage during the design phase with available

study

ction, the calculation of embodied energy and the inu-ertainty in the calculation will be explored. A case studyt represents a rectangular shape industrial hall of 80 m

m depth 6 m height, is being studied. The building iswo exemplary construction methods:

ding on steel frame with steel deck on steel joist, and concrete wall with concrete deck on steel joist.

ry of the building materials for the case study

l frame example consists of exterior walls of IPE 400ith steel proled cladding of 0.7 mm, and an open web

IPE 200 and IPE 100 beams with steel structural decksummary of the total amount of steel used in the wallresented in Table 2.crete example consists of tilt-up reinforced concrete

mm thickness, with a concrete slab of 75 mm supportedb steel joist. Because of the weight of the concrete slab,st has to be spaced at tighter distance. The concrete slably placed on steel deck (in place of rebar) of nominalat weighs roughly the same as the replaced rebar.

of the weight of the concrete slab and the long unsup- (manufacturing processes usually demand spaces withns), the open web structure that has to be placed to

concrete slab is more massive than that of the steelre. Table 2 indicates that the amount of steel placed inthe concrete example is in fact more than that of thele. In practice, concrete roof is not a common optional hall not just because of its weight, but also because

additional purpose. The roof for industrial hall is usu-r steel or built-up construction. To illustrate the idea,ple is studied, it is a hybrid structure with wall of the

ample and roof of the steel example. A breakdown ofing to material and structural component is presented

ity analysis in the calculation of embodied energy

lculation of embodied energy of the building structure,

ConcreVirginRecycl

It isinput pied eneinuen

3.3. Un

Bastrial haand ofcrete sfor a pimposestructistructuthis hytreated

3.4. Un

Thesteel) coefc2008).1.5 MJ/and 9.8their o

Theery of manufof the mthe em(Athennumbeing assthe nacities. in the sassumlevel oenergytypical

3.5. Unmateri

Thenamelnace (93.3%, more tbe molways be uncertainty in:

nt of materials used,died energy of the materials, ande and content of the materials.

being reduction facilitithan that of

It is estimash, the em1.6 1.432.0 35.3

el 10.1 9.5

important to estimate the range of uncertainty of theeters such that the resulting uncertainty in the embod-

of the building structure can be predicted and the mostnput parameters can be identied.

ainty in the amount of materials

the case study building, it is estimated that the indus-composed of 507 tonne of steel for the steel structure,

tonne of concrete with 475 tonne of steel for the con-ure. The estimate might not represent any industrial hallular industry. Due to the diversity of industries (thaterent structural requirements) and variations in con-chniques, the amount of materials used in the buildingay deviated from what it is estimated here. Because ofetical nature, the uncertainty range should therefore beniformly distributed, and is assumed to be 20%.

ainty in the embodied energy of the materials

odied energy of the building materials (concrete andsed on the two widely referenced embodied energydatabases (Alcorn & Wood, 1998; Hammod & Jones,average embodied energy of high strength concrete isnd those of virgin steel and recycled steel are 33.7 MJ/kgkg, respectively. The average values are deviated fromal values (Table 3) by 37%.e multiple steps involved in the production and deliv-ing material to the building site; the proximity of theing facility to the building site, and the whole logisticfacturing process play a signicant role in determininged energy of a building material. The Athenas databasetitute, 2010) for building assemblies provides data for a.S. and Canadian cities. The embodied energy of build-

lies varies among cities, and falls within a range froml average of 5% for U.S. cities, and 10% for Canadian10% range represents the largest variation presenteded literature; therefore, the embodied energy values are

have a condence interval of 10% with a condence, normally distributed (since the assumed embodiedes are drawn from databases, and are assumed to be

ainty regarding the source and content of the

re basically two types of steel production facilities, basic oxygen furnace (BOF) and the electric arc fur-

with an average recycled content rate of 32.7% andectively (SRI, 2009). Since the production of EAF is 50%that of BOF, the embodied energy of recycled steel cand as the embodied energy of virgin steel (33.7 MJ/kg)

ed by either 23.3% or 66.4%, depending on the produc-es, in which the reduction of 66.4% is 50% more likely

23.3%.ated that for every 1% replacement of cement with y

bodied energy of concrete is reduced by 0.7% (Van Geem,

70 B. Lee et al. / Sustainable Cities and Society 1 (2011) 67 71

Table 4Embodied energy of building materials and the range of uncertainty (due toreduction).

Buildingmaterials

Embodiedenergy[MJ/kg]

Possible reduction inembodied energy

Concrete 1.6 10% 735% ( distributed)Steel 33.7 10% 23.366.4% ( distributed)

Fig. 1. Probabbuilding struc

2007). Basecement witproperty ofreplacemenvery likely embodied e

The embpaper and marized in

4. Results

The resustructures a

4.1. Monte structure

The com(Palisade, 2(with 10,00of the threerated valuprobability results are p

Table 5 sied energy than that of

Some iners on the The correla

Table 5Summary of to

(000 GJ)

Mean St. dev. 90% condenMinimum Maximum

orrelae exem

tial

auseres, st im

largaram

R scry

systy cass pren grore Ct of 1n Creeast

of 2 jobsonal ts foegor

m Tat of sility distribution of total embodied energy of the three exemplarytures.

d on the ndings in the literature, a 10% replacement ofh y ash is a common practice to improve the overall

concrete, and a 50% replacement is seldom applied. Thet can be translated into a triangular distribution of acase of 7% to an unlikely case of 35% reduction in thenergy of concrete.odied energy of steel and concrete assumed in thisthe corresponding possibilities in reduction are sum-Table 4.

lts of the case study with three exemplary new builtre presented here.

Carlo simulation of embodied energy in the building

mercial quantitative risk analysis package @RISK

Fig. 2. Cthe thre

inferenFig. 2.

Becstructuthe moativelyinput pone.

4.2. GBcatego

GBRin manLEED ibuilt oLEED acontenpoint ibe at laward

Anyto regi2 poinrial catbuilt.

Froconten009) is deployed to perform a Monte Carlo simulation0 iterations) that predicts the possible embodied energye exemplary building structures with randomly gen-es for the input parameters according to the selecteddistribution as described in the previous sections. Theresented in Fig. 1.ummarizes the statistics of the simulation. The embod-of the whole concrete structure is signicantly more

the steel or the hybrid structure.put parameters have a greater impact than the oth-resulting embodied energy of the building structure.tion coefcients (Spearman Rank) of the top three

tal embodied energy of the three exemplary structures.

Steel Concrete Hybrid

9.0 13.6 6.82.0 2.4 1.1

ce interval 5.812.2 10.117.2 4.98.74.9 8.0 4.9

15.1 20.6 10.4

under the m

5. Discussi

Even thoshow little tions. The eof the hybrof the calcuare two reacability of Gway points

Table 6LEED points aexemplary str

LEED points

Credit 4 (assCredit 4 (assCredit 5tion coefcient of the top three most inuential input parameters forplary building structures.

input parameters are presented as tornado chart in

of the vast amount of steel presented in any of the threethe uncertainty in the recycled content of steel causespact on the resulting embodied energy. The compar-

er roof surface (than the wall surface) also makes theeter mass of roof in steel, the second most inuential

ores of the building structure under the material

ems award credits or points in a discrete manner, whiches lead to a all or none situation. To illustrate the point,sented here as an example. If the construction is a newund with no existing structure, the credits available forredit 4 (2) and Credit 5 (2). LEED requires a recycled0% by total cost to achieve 1 point and 20% for an extradit 4. Since the recycled content of steel is assumed to32.7%. A high recycled content of steel guarantees thepoints for both the steel and the hybrid structures.ites in the urban or suburb areas that have ready accessmaterials (within a distance of 800 km) could easily earnr Credit 5. Out of the 13 LEED points under the mate-y, Table 6 lists the possible points achievable for a new

ble 6, it could be observed that regardless of the recycleteel or the construction method, the points achievableaterial category are similar under the LEED system.

on

ugh the LEED points earned under the material categoryor no variation among structures of different construc-mbodied energy of the concrete structure is double thatid structure. There is a discrepancy between the results

lation of LEED points and that of embodied energy. Theresons for the discrepancy; one being the issue of appli-BR systems to industrial halls, and the other being the

are awarded.

chievable for new built under the material category for the threeuctures.

Steel Concrete Hybrid

umed 32.7% recycled steel) 2 1 2umed 93.3% recycled steel) 2 2 2

2 2 2

B. Lee et al. / Sustainable Cities and Society 1 (2011) 67 71 71

First of all, Credit 4 of the material category of LEED requiresa mere 10% recycled content by cost to earn 1 point, and 20%to earn 2 points. The prescriptive values are suitable for com-mercial buildings, in which the construction is complex and istted with high value assemblies. 10% or 20% recycled contentby cost already reects the effort made in choosing the moresustainable materials. By contrast, the prescribed percentagesare readily achievable for industrial halls, which are constructedwith simple steel or concrete assemblies that are high in recy-cled content. The prescribed percentage simply falls outside therecycle content ranges of the building materials for the indus-trial halls. In other words, improvement in material choice forthe industrial halls simply cannot be reected under the LEEDsystem.

Secondly, points under the LEED system are awarded in limitednumber of levels usually two; 10% or 20% of recycle content, forexample. The limited number of levels does not reect the possiblerange of uncertainty for embodied energy an indicator of sustain-ability. As presented in Table 5, the range of predicted embodiedenergy of the concrete structure is from 8.0 to 20.6 thousand GJ;the range of uncertainty as a percentage ratio between the embod-ied energy range of the concrete structure to that of the steelstructure is from 36% to 320%. In order to adequately reect theimpact on sustainability due to the vast possibilities in constructionmethods, points for the LEED system should be awarded in nersteps.

6. Conclusion

Through a simple case study with three exemplary new builtstructures, this paper demonstrates the potential deciency ofGBR systems, particularly for industrial halls, which might lead tomisleading scores that do not accurately represent the actual per-formance oinclude modemolition impact on:

embodied energy (of the assessed structure), and demolition energy (of the existing structure that counts towardscredits of the assessed structure)

and to explore the corresponding GBR points that could be earned.The impact of building materials does not limit to the embod-

ied energy and the demolition energy but also to the operationenergy of the building. This will be studied in the future. The wholelife-cycle energy demand shall provide better representation forsustainability of building structures.

Acknowledgment

This research was carried out under the project numberM81.1.08318 in the framework of the Research Program of theMaterials innovation institute M2i (http://www.m2i.nl).

References

Alcorn, A., & Wood, P. (1998). New Zealand building materials embodied energy coef-cients database volume IIcoefcients. Centre for Building Performance Research,Victoria University of Wellington.

Athena Institute. (2010). EcoCalculator. http://www.athenasmi.org/tools/ecoCalculator/ (accessed May 3, 2010)

Azhar, S., Brown, J., & Farooqui, R. (2009). BIM-based sustainability analysis: An eval-uation of building performance analysis software. In Proceedings of the AssociatedSchools of Construction (ASC) 45th annual international conference.

Bodman, G. R., & Shelton, D. P. (1986). Existing buildings-remodel or aban-don? NebGuide, Cooperative Extension, Institute of Agriculture and NaturalResources, University of Nebrask.

Corus. (2007). End of life options for pre-nished steel buildings. Corus.Hammond, G., & Jones, C. (2008). Inventory of carbon & energy, version 1.6a. Sustain-

able Energy Research Team, University of Bath.Newsham, G. R., Mancini, S., & Birt, B. J. (2009). Do LEED-certied buildings save

energy? Yes, but. Energy and Buildings, 41, 897905.Palisade. (2009). @RISK. http://www. palisade.com/risk/ (accessed July 20, 2009)SRI. (2008). Steel recycling rates at a glance. Steel Recycling Institute.

9). St.2009)ouncm, M.e Instif the structures. The case study could be expanded tore complex scenarios; for example, the incursion of theor retention of an existing structure so as to reveal the

SRI. (2002007

USGBC. (ing C

Van Geecreteel takes LEED with recycled content. Steel Recycling Institute. Spring

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Embodied energy of building materials and green building rating systemsA case study for industrial halls1 Introduction2 Assessment of sustainability of building materials2.1 Green building rating (GBR) systems applied to building materials2.2 LEED2.3 General issues with GBR systems2.4 Embodied energy another view of sustainability of building materials

3 The case study3.1 Inventory of the building materials for the case study3.2 Sensitivity analysis in the calculation of embodied energy3.3 Uncertainty in the amount of materials3.4 Uncertainty in the embodied energy of the materials3.5 Uncertainty regarding the source and content of the materials

4 Results4.1 Monte Carlo simulation of embodied energy in the building structure4.2 GBR scores of the building structure under the material category

5 Discussion6 ConclusionAcknowledgmentReferences