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Energy and Buildings 64 (2013) 73–89

Contents lists available at SciVerse ScienceDirect

Energy and Buildings

j ourna l ho me page: www.elsev ier .com/ locate /enbui ld

ife cycle analysis in the construction sector: Guiding theptimization of conventional Italian buildings

rancesco Asdrubali a,∗, Catia Baldassarri a, Vasilis Fthenakisb

University of Perugia, Industrial Engineering Department, Via G. Duranti 67, 06125 Perugia, ItalyBrookhaven National Laboratory and Columbia University, New York, USA

r t i c l e i n f o

rticle history:eceived 7 January 2013eceived in revised form 9 April 2013ccepted 25 April 2013

eywords:ife Cycle Assessmentuildingsnergy optimization

a b s t r a c t

Life Cycle Assessment (LCA) is a widely known methodology for “cradle to grave” investigation of theenvironmental impacts of products and technological lifecycles; however, this methodology has not beenyet broadly used as an eco-design tool among the practitioners of the building sector. We applied LCA onthree conventional Italian buildings – a detached residential house, a multi-family and a multi-story officebuilding. Our analysis includes all the life stages, from the production of the construction materials, totheir transportation, assembling, lighting, appliances, cooling- and heating-usages during the operatingphase, to the end of life of all the materials and components. We found that the operation phase has thegreatest contribution to the total impact (from 77% of that of the detached house, up to 85% of the office

CAnvironment

building), whereas the impact of the construction phase ranges from about 14% (office building) to 21%(detached house). We carried further analyses to evaluate the influence of various optimizations of thebuildings, e.g., more efficient envelopes and facilities, on the entire life cycle of the three buildings. Inaddition, we propose a methodological approach, which can contribute to the acceptance of LCA as a toolin the eco-friendly design of buildings, especially those buildings whose impact during the constructionphase needs to be carefully checked, such as Nearly Zero Energy Buildings.

© 2013 Elsevier B.V. All rights reserved.

. Introduction

Energy consumption in the building sector can reach up to 40%f the total energy demand of an industrialized country [1]. Accord-ngly, the usage of green building strategies can be effective inaving fossil fuels, and reducing greenhouse gasses. Sustainableaterials (e.g., natural or recycled materials) play an important

ole because less energy generally is required for their productionhan that needed for conventional materials [2]. Also, integratingenewable energy systems (e.g., solar thermal collectors, photo-oltaic modules) in the buildings’ envelopes can be a key step inowering the environmental impact of the construction sector.

In European countries, national laws and EU Directives [3,4]ave recently introduced limits and restrictions on energy con-umption in buildings, and requirements for energy certificationn retrofitted and new buildings. Such new legislation aims ineducing the energy demand of new buildings, and we witness an

ncrease in the importance of the energy used in the constructionhase which was not previously included in energy-certificationrocedures. Hence, more attention is given to the embodied energy

∗ Corresponding author. Tel.: +39 075 5853716; fax: +39 075 5853697.E-mail address: fasdruba@unipg.it (F. Asdrubali).

378-7788/$ – see front matter © 2013 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.enbuild.2013.04.018

of a building, and to the possibility of recycling construction mate-rials at its end of life. The application of a Life Cycle Assessment(LCA) is necessary to certify the global environmental-impact andenergy demand during the entire life span of a building. Buildingshave complex product life cycles as they are made of many dif-ferent materials and material combinations, have a long life, needlife-long maintenance, and, some are unique [5]. Therefore, apply-ing LCA procedures to buildings may not be straightforward, andcan present difficulties and uncertainties.

This paper presents our assessment and comparison of thelife-cycle impact of three typical Italian buildings: two residen-tial ones (a detached house and a multi-dwelling building), andan office building. We assessed the relative importance of thebuildings’ various life phases, along with evaluating the energy-and environmental-benefits due to improvements of the buildingsthemselves. We also explored methodological aspects that can beexpanded to developing specific guidelines for the implementationof LCA in the construction sector.

2. LCA in buildings

Among the many different procedures and tools used to per-form an Environmental Performance Evaluation (EPE) of a materialor product are the Environmental Indicator Systems (EPIs), the

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This study aims to evaluate the environmental impact of threebuildings throughout their entire life and also to assess the impact

4 F. Asdrubali et al. / Energy

nvironmental Management Accounting (EMA), the Environmen-al Management Systems (EMSs), the Eco-labeling [7], and the Lifeycle Assessment (LCA) [8,9] which is the most complete one. Theoncept of LCA is based on the following key points:

the entire life cycle that includes the extraction and processingof raw materials, production, and use up to recycling or disposal;

all environmental impacts connected with the life cycle, such asair-, water-, and soil-emissions, wastes, raw material consump-tion, or land use;

the aggregation of the possible impacts of the environmentaleffects and their evaluation so to give environmentally orientedsupport to decisions makers.

There is a significant amount of literature on LCA applica-ions to buildings. Sartori and Hestnes [10] surveyed 60 LCA casesrom 9 countries, and showed a linear relationship between theperating- and total energy-demand of the buildings. Furthermore,hey showed that the design of low-energy buildings is beneficialn terms of total life-cycle energy demand, but can increase thembodied energy. A similar analysis, by Ramesh et al. [6], demon-trated a correlation between the reduction in operational energyue to energy-savings measures and the life-cycle energy sav-

ng. Thormark [11,12] investigated the effect of material choicen embodied energy and the recycling potential of a building,hile Nassen et al. [13] and Verbeeck [14] detailed the lifetime

nergy use (GJ/m2) and CO2 emissions (kg/m2) of various buildings,nderlining the lower efficiency of detached buildings comparedo multi-dwelling ones. Optis and Wild [15] focused on the relativemportance of life-cycle energy components of a building and foundhat the embodied energy can vary from 2% to 51%, the operationalnergy from 46% to 97%, and disposal energy from 1% to 3%. Moreecently, Sharma et al. compared the environmental impact asso-iated with various buildings [16]. Finally, several papers discusshe results of LCA procedures applied to different single buildingssed as case-studies [17–21]; nevertheless, there are only a fewtudies pertaining to Italy [22–24]. Our paper, in addition of pro-iding a detailed analysis of conventional Italian buildings, offers

methodological approach for using LCA in optimizing the eco-riendly design of buildings.

. Methodology

According to EN ISO 14040 [8] and EN ISO 14044 [9], a Life Cyclessessment includes four main steps:

goal and scope definition; life-cycle inventory; life-cycle impact analysis; and; interpretation of the results.

The phase of defining the goal and scope details the overall aimf the study, the system’s boundaries, the sources of data, and theunctional unit. All input- and output-data refer to the functionalnit. The Life Cycle Inventory (LCI) phase encompasses a detailedescription of all the environmental inputs, in terms of both mate-ials and energy, and outputs, in terms of air, water, and solidmissions, at each stage of the life cycle.

The Life Cycle Impact Assessment (LCIA) phase quantifies theelative importance of all the environmental impacts obtained inhe LCI phase by using several environmental indicators at the var-

ous stages of the life cycle. Finally, the results from the LCI- andCIA-phases must be interpreted to show critical aspects, to eval-ate alternative scenarios, and to introduce optimizations. Therere many evaluation methods used within LCA studies and various

uildings 64 (2013) 73–89

different commercial codes for implementing them. We employedEco-indicator 99(H) v2.03, IPCC 2007 GWP 100a v1.02 and Cumu-lative Energy Demand v1.07 methodologies [25], implemented inthe SimaPro 7.2 [26], to estimate the environmental impact of thethree case studies throughout their entire life.

The IPCC (International Panel on Climate Change) method clas-sifies the different emissions according to their contribution to thegreenhouse effect; the indicator used is global warming poten-tial (GWP), which is measured in kg CO2-eq. The energy requiredduring the entire life cycle of the building is calculated by cumu-lative energy demand (CED), the unit is MJ-eq. The categories arethe following: non-renewable, fossil; non-renewable nuclear; non-renewable, biomass; renewable, biomass; renewable, wind, solar,geothermal; and renewable, water. The Eco-indicator 99 com-bines the accounting of eleven impact categories (carcinogenicsubstances, respiratory diseases, climate changes, ozone depletion,radiation that causes ionization, acidification/eutrophication, eco-toxicity, land use, mineral resource depletion, and fossil fuels),grouped into three damage categories:

1. Those to human health, expressed as the number of years ofhuman life lost or in suffering from disease;

2. Those to the quality of ecosystems, expressed as the loss of livingspecies in a certain area over a certain time;

3. Those to resources, expressed as the surplus of energy necessaryfor further extracting minerals and fossil fuels.

Results of this method are available in ecopoints (Pt). It is notedthat the eco-indicator calculations, being more complex than thoseof CED and GWP, introduce higher uncertainty than the former.

4. LCA application to Italian buildings

4.1. Case studies

We chose three different, existing buildings, typical of currentItalian construction techniques and building typologies (Fig. 1), forour from-cradle-to-grave LCA analysis:

a) a detached house;b) a multi-dwelling building (block of flats); and

(c) an office building.

Table 1 lists the main features of the three buildings. The build-ings were built in the last decade and are located in Perugia, Italy(Table 2). They all have a concrete structure, an envelope made ofbricks and thermal insulating materials, aluminum windows, andgas-fired heating systems.

As Table 1 shows, moving from the single family detached houseto the office building the shape coefficient (the ratio between theexternal skin surfaces (S) and the inner heated volume (V) of thebuilding) decreases, whereas the Window to Wall Ratio (WWR, therelationship between opaque- and transparent-surfaces) increases;this affects the LCA results as discussed in Section 4.4.2.

4.2. Goal and definitions

4.2.1. Goal

of some energy optimization scenarios. The lifetime of the buildingsis assumed to be 50 years, which is consistent with most of the pub-lished case studies [10]. The maintenance is evaluated according tothe lifetime of the various components and materials.

F. Asdrubali et al. / Energy and Buildings 64 (2013) 73–89 75

analy

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Fig. 1. Views of the three buildings chosen as case study for LCA

.2.2. Functional unitThe functional unit is a reference to which we linked the

nput–output materials and energy flows. In most published LCAtudies of buildings [6,10,21,27,28] the functional unit is one squareeter of usable/living floor area, over one year (m2/year). We

dopted this unit in our study, as it supports comparisons of differ-nt sized buildings. In addition we also presented results per m3 ofross volume, and per m3 of temperature controlled volume, sincehe three buildings have different elevations per floor.

.2.3. System boundariesThe system boundaries determine which unit processes are

ncluded in LCA study. The system-building is broken down intorocess units, encompassing all the elements, materials, and com-onents that constitute the building and are affected by flows ofatter and energy during their life phases. For classifying the build-

ngs’ elements, we used the “classification of the technological

ystem” provided in UNI 8290-1:1981+A122: 1983 [29] (Fig. 2a).ccording to this procedure, the “envelope system” and the “equip-ent system” are classified into six levels of increasing detail:

echnological unit classes, technological units, classes of technical

able 1ain features of the three buildings.

Type (a) Single family detached house (b)bui

Year of construction 2002 200No. of floors 3 4

Elevation per floor (m) 3.00 2.7Structure Reinforced concrete ReiNet area 443 m2 182Gross volume 1875 m3 678Gross heated volume 1102 m3 326Shape factor (S/V) coefficient (1/m) 0.957 0.5Window to wall ratio 0.11 0.2External walls Bricks with thermal insulating

materials in the space, internal plasterand external plaster and bricks

Brimaand

Windows Aluminum windows AluRoof Insulated roof FlaOrientation Longitudinal axis of the building

north–south orientedLoneas

Heating and cooling Gas-fired heating system Eachea

able 2ain geographic-related characteristics.

Climate and geographic data

Altitude 493 m

Latitude and longitude 43◦6′18′′

12◦23′11′′

Global irradiation on optimal tilt (kWh/m2/year) 1646

a According to Italian law (DPR 26/08/1993 n.412), the national territory is divided inthe law fixes a conventional heating period.

sis (a) detached house, (b) block of flats, and (c) office building.

elements, sub-systems, components, and sub-components. In thelast level, the building materials used to make the building compo-nents are listed. They are the smallest parts of the building-system.To facilitate the widespread employment of the LCA-based eco-design, it is desirable that the instruments used in the designprocess, such as architectural drawings, are adapted to the needsof LCA methodologies. In Fig. 2a, the various components andsub-components of the technological system were also classifiedaccording to the standard UNI 8290.

Fully establishing the system boundaries requires not onlydefining process units, but also determining the life-cycle phases toinclude in the assessment (Fig. 3). This model encompasses threedistinct phases of evaluation:

(1) Construction phase:Materials production phase: extraction of raw materials,

recovery of recycled materials, transportation to the factory,

manufacturing processes;

Building construction phase: transportation of materialsfrom the factory to building site, components assembly andtheir possible replacement during the building’s lifespan, the

Multi-dwelling (18 flats) residentiallding

(c) Office building

8 20095

0 3.30nforced concrete Reinforced concrete7 m2 3353 m2

3 m3 13,602 m3

8 m3 6226 m3

05 0.3297 0.41cks with thermal insulatingterials in the space, internal plaster

external plaster and bricks

Bricks with thermal insulatingmaterials in the space, internal plasterand external claddings (copper,aluminum, ceramic)

minum windows Large-sized aluminum frame windowst insulated roof Flat insulated roofgitudinal axis of the buildingt–west oriented

Longitudinal axis of the buildingnorth–south oriented

h flat has a gas-fired autonomousting system

Air-conditioning system with primaryair and fan-coils

Perugia, Italy

Heating degree daysa 2289Climate zonea E

Conventional heating perioda 183 days

o six climate zones, from A (warmer climate) to F (colder climate). For each zone,

76 F. Asdrubali et al. / Energy and Buildings 64 (2013) 73–89

detac

Fig. 2. (a) Summary classification of the technological system of the

energy consumption associated with the hydraulic diggerused for excavation and transforming rural to urban-land,building discontinuous- (detached house) or continuous-(multi-dwelling residential building) structure;

hed house. (b) Example of classification of the technological system.

(2) Use phase: all activities related to the use of the buildings,including all operating energy for heating, cooling, gener-ating hot water (DHW), cooking, lighting, and poweringappliances;

F. Asdrubali et al. / Energy and Buildings 64 (2013) 73–89 77

ystem

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3) End-of-life phase: dismantling and the demolishing the build-ing’s components, their transport to the landfill site and/or torecycling sorting plants.

.2.4. Data-quality requirementsFor the goal of producing sufficiently detailed information to

eet the requirements of the adopted standard [29], we estimatedhe quantities of materials from the building’s bill of materials, andhe architectural-, structural-, and equipment-drawings.

The inventory data gathered with this method were coupledith their corresponding “unit processes” in the widely used Ecoin-

ent database [30], to enable a transparent, comparable analysis.

.3. Inventory analysis

The inventory is a list of all substances involved in the process.ach of the three buildings’ life-cycle phases (construction phase,perating phase, and end-of-life phase) was evaluated separately.

boundaries.

Regional aspects are not considered during the construction phase(with the exception of the actual architectural choices and con-struction techniques of the three buildings), since most data is fromthe Ecoinvent database, whereas during the operational phase, theenergy consumptions uses come from energy simulations that takeinto account local climatic data (Table 2). We use the Italian elec-tricity mix given in Ecoinvent. The origin of the energy source usedin each country, in fact, plays an important role in defining envi-ronmental impacts, as shown by Ortiz et al. [21].

4.3.1. Construction phaseDuring the inventory of the construction phase, we define the

flows of materials and energy related to each building component.Unit processes chosen by the Ecoinvent database are matched with

their quantities and then grouped in technological units accord-ing to Ref. [30]. In addition to accounting for the production of allconstruction materials, we also included their phases of transporta-tion, excavation (fuel consumption, impacts due to the occupation

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8 F. Asdrubali et al. / Energy

f soil and its transformation) and assembly. In particular, we esti-ated the impact of the assembly phase: this value was evaluated

n terms of electrical consumption and, for each building, it wasssumed to be equal to 2% of the embodied energy of its construc-ion materials as reported in the literature [31]. To obtain the impactf transportation, we estimated the total weight for all the buildingaterials and assumed a 50 km average distance from the factories

o the building site [32,33]. It is noted that the choice of the meansf transport and number of needed trips is affected by weight andolume of materials and components [34].

.3.2. Use phaseThe energy sources considered are natural gas and electricity.

atural gas is used for heating in the winter, producing hot water,nd cooking (just for the residential buildings). Electricity is con-umed by appliances, artificial lighting, and cooling systems; theatter was considered only for the office building as A/C is not com-

on in Perugian houses.The primary energy consumption for heating and producing hot

ater and thermal energy for cooling are estimated through theode MC4 Suite 2010 [35] based on UNI/TS 11300 [36,37]. Thistandard includes a quasi-steady-state monthly method, definedy EN ISO 13790:2008 [38]. This kind of method tends to over-stimate buildings energy needs, especially as far as the coolingemand assessment. Recent studies, which compared simplifiedethods and more complex, dynamic tools, showed that the dif-

erence between MC4 Suite (quasi-steady-state monthly method)nd Trnsys or Design Builder (dynamic tools) is in the range of0–30% [39,40]. Anyway, within the present study, the assessmentf the impacts due to the use phase is referred to a “conventional”se of the three examined buildings and is aimed at comparinghe impacts of the entire life of the buildings themselves and cor-espondingly at proposing optimization measures. The use of theame input data and of the same calculation methodology for eval-ating the energy performance of the three buildings guaranteeshat the results obtained for the use phase, though not extremelyccurate, are comparable among the buildings themselves.

Loads were assessed by establishing a seasonal-comfort tem-erature set point (20 ◦C for wintertime and 24 ◦C for summertime,ith 50% humidity and infiltration rates typical for local construc-

ion), and quantifying the thermal energy required to maintainhese indoor conditions. The natural gas consumption for cookings based on data gathered from ENEA’s Energy and Environ-

ent Report [41]. The source we used to evaluate the global

able 3onstruction phase – environmental impacts for the three buildings according to the thre

Construction phase Equivalent CO2 emissions Equivalent CO2

emissions/net arIPCC GWP100 kg CO2-eq kg CO2-eq/m2

Detached house 427,821 966

Multi-dwelling building 1,138,907 623

Office building 1,715,248 512

Construction phase Energy demand Energy demand/net area

CED MJ-eq MJ-eq/m2

Detached house 5,242,653 11,834

Multi-dwelling building 14,439,455 7903

Office building 22,513,476 6714

Construction phase Damage Damage/net area

Eco-indicator 99 Pt Pt/m2

Detached house 31,087 70

Multi-dwelling building 84,217 46

Office building 179,094 53

uildings 64 (2013) 73–89

annual-electric-requirement of residential buildings was ISTAT(Italian Statistical Institute) [42], whereas for office buildings it wasUE Energy Star [43] for appliances and fan coils, the DIALux software(developed by DIAL GmbH) for lighting, and the standard UNI/TS11300 for cooling.

4.3.3. End of life phaseThe Ecoinvent database v2.2 provides three options for dis-

posing of construction material: direct recycling; partial recyclingafter sorting; and disposal without recycling [44]. The Directive2008/98/EC of 19/11/2008 [45] requires by 2020 the recoveryof 70 wt.% of all waste products. To meet the Directive require-ments, we assumed the following: glass, aluminum, steel andcopper are 100% recycled. For concrete, partial recycling after sor-ting; for demolition materials, their transportation to the sortingplant, where the inert materials are separated from the steel.Then, the steel is recycled and a certain quantity of inert materials(0.582 kg/kg of reinforced concrete) is also recycled.

4.4. Analyses of life cycle impact, and interpretation of the results

4.4.1. Construction phaseTable 3 shows the results of the three methodologies imple-

mented using SimaPro (GWP100, CED and Eco-indicator 99), forthe construction phase of the three buildings. As expected, allmethodologies indicate that the absolute impacts in this phaseincrease with the size of the building. In unitary values, the low-est impact is from the office building (0.512 t CO2-eq/m2), followedby the multi-dwelling building (0.623 t CO2-eq/m2), and then thedetached house (almost 1 t CO2-eq/m2).

This holds not only for the indicator “equivalentCO2emissions/net area” but also for the indicators related tothe gross and heated volumes. In all three buildings, the verticalenvelope (vertical external walls and glazing, see also Fig. 2a) hasthe greatest environmental impact, representing more than 20%of the total (Fig. 4). The choice of envelope materials can greatlyaffect the impact during the construction phase, particularly foroffice buildings.

4.4.2. Operating phase

For the operating phase of the detached house, we observed that

heating during winter had the most Eco-indicator-based impact(69%), mainly due to the use of fossil fuels. For the two other build-ings, electricity consumption had the greatest impact (respectively

e methods.

eaEquivalent CO2

emissions/gross volumeEquivalent CO2

emissions/heated volumekg CO2-eq/m3 kg CO2-eq/m3

228 388168 349126 275

Energy demand/gross volume Energy demand/heated volumeMJ-eq/m3 MJ-eq/m3

2796 47572129 44181655 3616

Damage/gross volume Damage/heated volumePt/m3 Pt/m3

17 2812 2613 29

F. Asdrubali et al. / Energy and Buildings 64 (2013) 73–89 79

r 99H

4Abmg

mvialameitav

teh

tda

Fig. 4. Construction phase – damage/impact categories (Eco-indicato

3% and 74% for the block of flats and the office building) (Fig. 5).s mentioned earlier, cooling loads were considered for the officeuilding only. Our results show that damages to human health areostly due to the coal-based power contribution in the electricity

rid.Table 4 summarizes the results obtained by applying the three

ethods of evaluation to the three buildings. In agreement with thealues obtained for the construction phase, in absolute terms, thempact, emissions, and fuel-consumption increase with the net areand the volume. After normalizing the impact, in most cases, theowest emissions are associated with the multi-dwelling building,nd the highest with the office building. Using the three metricsentioned, the impact divided by the heated volume is almost

qual for the detached house and the multi-family dwelling, ands higher for the office building. Finally, the IPCC-GWP results showhat the detached house and the office building’s impacts havelmost the same impacts when normalized on net area and grossolume.

The results also show that the two residential buildings seemo follow the relationship of their ratios of the area of the buildingnvelope (S) to its heated volume (V). The environmental impact isigher for the detached house that has the higher S/V value.

The office building’s main feature is the large amount ofransparent surfaces; therefore, it exhibits high thermal losses. Evi-ently, the WWR (window to wall ratio) is the main parameterffecting energy consumption.

/H) evaluated for each construction sub-phase of the three buildings.

4.4.3. End-of-life phaseTable 5 summarizes the results obtained by applying the two

primary environmental impact metrics (i.e., GWP, CED), and theEco-indicator 99 to the three buildings. The detached house hasa greater impact than the multi-dwelling building, according toall indicators. For the office building, the CED and Eco-indicatormethods yielded impacts lower than those of the residential build-ings, whereas, using the IPCC-GWP metric, the office building had alarger impact than the block of flats. Nevertheless, the office build-ing has a higher content than the others of aluminum, steel, andglass available for recycling, thus benefits would come from thereturn of recycled materials into the building materials industry. Inthe present study, for the impacts related to the end-of-life phase,both burdens from the industrial processes to recycle materialsand benefits from avoided impacts are kept outside the systemboundaries, as they are assigned to secondary goods (new materialsproduced from recycling processes).

4.4.4. Results for the complete life cycleFig. 6 compares the contributions of the three life-cycle phases

to the buildings’ overall impacts.The relative impact of the construction phase is significant, vary-

ing from 20% of the total impact for the office building to 23%for the independent house (using the Eco-indicator metric). Theoperation of the buildings (assuming a 50-year life span) had thegreatest contribution to the total impact (up to 78%). As shown

80 F. Asdrubali et al. / Energy and Buildings 64 (2013) 73–89

indica

boidam

p

TO

Fig. 5. Operating phase – comparison between the

y the impact categories in Fig. 6, the relationship between theperating- and construction-phase changes varies. Moreover, thempact of the operating phase is expected to decrease in futureue to new regulations on energy efficiency in buildings [46]

nd increased penetration of renewable energies in the electricityix.Our finding that energy consumption during the operating

hase greatly surpasses that of all the other life cycle phases is

able 4perating phase – yearly environmental impacts for the three buildings according to the

Operating phase Equivalent CO2 emissions Equivalent CO2

emissions/net arGWP100 kg CO2-eq kg CO2-eq/m2

Detached house 22,840 52

Multi-dwelling building 72,903 40

Office building 180,509 54

Operating phase Energy demand Energy demand/net area

CED MJ-eq MJ-eq/m2

Detached house 387,849 876

Multi-dwelling building 1,169,167 640

Office building 2,801,835 836

Operating phase Damage Damage/net area

Eco-indicator 99 Pt Pt/m2

Detached house 1978 4.5

Multi-dwelling building 5948 3.3

Office building 14,208 4.2

tors (Eco-indicator 99H/H) for the three buildings.

in agreement with other studies [21,27,31,47–49]. It is noted thatthis result is specific to the selection of the case-studies. We alsoassess the sensitivity of the operation related impacts to variousoperational optimization measures.

Table 6 summarizes the results for the complete life cycle anal-ysis. The multi-dwelling building has the lowest and the detachedhouse has the highest CO2 emissions per net area. When we nor-malized the results of the operating phase per heated volume, the

three methods.

eaEquivalent CO2

emissions/gross volumeEquivalent CO2

emissions/heated volumekg CO2-eq/m3 kg CO2-eq/m3

12 2111 2213 29

Energy demand/gross volume Energy demand/heated volumeMJ-eq/m3 MJ-eq/m3

207 352172 358206 450

Damage/gross volume Damage/heated volumePt/m3 Pt/m3

1.1 1.790.9 1.821.0 2.28

F. Asdrubali et al. / Energy and Buildings 64 (2013) 73–89 81

Table 5End-of-life phase – environmental impacts for the three buildings according to the three methods.

End-of-life phase Equivalent CO2 emissions EquivalentCO2emissions/net area

EquivalentCO2emissions/gross volume

EquivalentCO2emissions/heated volume

GWP100 kg CO2-eq kg CO2-eq/m2 kg CO2-eq/m3 kg CO2-eq/m3

Detached house 37,283 84 20 34Multi-dwelling building 92,931 51 14 28Office building 212,072 63 16 34

End-of-life phase Energy demand Energy demand/net area Energy demand/gross volume Energy demand/heated volumeCED MJ-eq MJ-eq/m2 MJ-eq/m3 MJ-eq/m3

Detached house 496,445 1121 265 450Multi-dwelling building 1,396,936 765 206 427Office building 2,129,373 635 157 342

End-of-life phase Damage Damage/net area Damage/gross volume Damage/heated volumeEco-indicator 99 Pt Pt/m2 Pt/m3 Pt/m3

vWuooo

Detached house 5435 12.27

Multi-dwelling building 16,002 8.76

Office building 26,532 7.91

alues between these two residential houses were almost the same.hen the GWP estimates are normalized per net area and gross vol-

me, the life-cycle impact of the detached house exceeds that of theffice building. Although the two have the same impacts during theperating phase, the detached house has a higher impact than theffice building during construction.

Fig. 6. Eco-indicator methodology – relative contributions of the l

2.90 4.932.36 4.901.95 4.26

The histograms in Fig. 7 show that the relationship betweenthe impacts associated with the entire life cycle of the two resi-

dential buildings are also related to the S/V ratio, while the officebuilding’s performance indicators appear to be influenced primar-ily by its envelope characteristics, and, particularly, by the ratioof transparent- to opaque-surfaces (Table 1 shows that WWR

ife-cycle phases to the overall impact of the three buildings.

82 F. Asdrubali et al. / Energy and Buildings 64 (2013) 73–89

Table 6Complete life cycle – yearly environmental impacts for the three buildings.

Complete life Equivalent CO2 emissions EquivalentCO2emissions/net area

EquivalentCO2emissions/gross volume

EquivalentCO2emissions/heated volume

GWP100 kg CO2-eq kg CO2-eq/m2 kg CO2-eq/m3 kg CO2-eq/m3

Detached house 32,142 73 17 29Multi-dwelling building 97,540 53 14 30Office building 219,055 65 16 35

Complete life Energy demand Energy demand/net area Energy demand/gross volume Energy demand/heated volumeCED MJ-eq MJ-eq/m2 MJ-eq/m3 MJ-eq/m3

Detached house 502,631 1135 268 456Multi-dwelling building 1,485,895 813 219 455Office building 3,294,692 983 242 529

Complete life Damage Damage/net area Damage/gross volume Damage/heated volumeEco-indicator 99H/H Pt Pt/m2 Pt/m3 Pt/m3

Detached house 2708 6.11 1.44 2.46Multi-dwelling building 7952 4.35 1.17 2.43Office building 18,321 5.46 1.35 2.94

0

1000

2000

3000

4000

Detach ed houseMu lti - dwell ing

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0

250

500

750

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ase

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500

1000

1500

2000

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kg

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End -of- life pha se

the impact indicators obtained for the three buildings.

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0

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0 500 1000 1500 2000 2500 300 0 3500

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Oper ating phase en ergy de mand /ne t area

(MJ- eq/m2 year)

Residential buildings from literature review Office buildings from literature review

Detached house Multi-dwelling building

Office building Linear regression (Residential buildings)

End -of- life pha se End -of- life ph

Fig. 7. Complete life cycle – comparison between

ncreases from the detached house to the office building, whereashe S/V ratio has an opposite trend).

.4.5. DiscussionFig. 8 shows the relationship between the life-cycle energy and

he energy used during operation for the three case studies, andompares those with results from previous studies. We confirmedhe observation by Ramesh et al. [6], that the relationship between3 case studies from 13 developed countries is almost linear despiteifferences in architectural choices, heating- and cooling-systems,aterials, components, building techniques and building types

office and residential), and sizes.Fig. 8 displays two regression lines, one for residential buildings,

nd one for offices. The lines divide the figure into two parts: abovehe line, there are the buildings whose embodied and demolitionnergy is higher than the average value; the latter is 17.5% of thentire life-energy demand for residential buildings, and 16.8% forffice buildings; below the line are the buildings whose embodiednd demolition energy is lower than the average values.

The three case studies of the present paper lie in the part of theraph were most of the case studies are concentrated. The detachedouse and the multi-dwelling building show impact values duringhe construction and end-of-life phases higher than the averagerespectively 20.8% and 19.4%), while the office building is belowhe average value (13.7%). Furthermore, the office building has a

ow complete life energy demand compared to the values of con-entional offices (250–550 kWh/m2, excluding tropical countries6]), while the two residential buildings have a medium-highomplete life energy demand, compared to that of conventional

Linear regression (Office buildings)

Fig. 8. Comparison between the operating phase energy demand and the completelife energy demand for the three buildings (filled symbols), in comparison with 73published LCA case studies [6].

and Buildings 64 (2013) 73–89 83

rc

o

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Vertical envelope

9

10

Window

6

7

8

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4

5

6

Pt

x 1

,000

Masonry

2

3

4

Exterior finish: exposed brick,

plaster, skirting

0

1Interior finish: plaster and

coverings

Scenario IIScenario IDesign scenario

TS

F. Asdrubali et al. / Energy

esidential buildings (150–400 kWh/m2 for temperate- and cold-ountries [6]).

These results guided us toward the energy- and environmentalptimizations proposed in Section 5.

Fig. 8 shows that the three buildings, that are obviously a limitedample of typical Italian construction practice, have operational andomplete life-cycle energy demand comparable to the ones of mostf the case studies found in literature. For this reason, the analysisarried out in the present study is significant to put in evidencehe advantages of using LCA as a tool in the eco-friendly design ofuildings.

. Energy optimizations and LCA implications

Following the LCA of the three reference cases in their originalesign configuration, we assessed scenarios aiming at reducing theuildings’ environmental loads. The analysis focused on the build-

ngs’ technological units with the greatest environmental burdens.e examined various approaches starting with envelope solutions

such as insulating materials and type and width of masonry), facil-ties (heating boiler replacement), and the integration of smartystems (such as active- and passive-solar systems). The envi-onmental effects of the proposed optimizations were evaluatedithin the life-cycle context, using the Eco-indicator 99 method.

here is no complete agreement among the scientific communityn the use of aggregated indexes, since both resource-orientedndicators (such as CED) and “impact-related” indicators (such asco-indicator) have their own strengths and weaknesses. CED haseen used since the early seventies because it is the methodol-gy with the lowest data requirements and it is quite easy toudge whether or not major errors have been made. Neverthe-ess LCA studies cannot avoid to include a comprehensive andomplex environmental impact assessment method such as Eco-ndicator 99 [25]. Despite the fundamental differences among thesewo approaches, studies from literature show that for many com-

odities groups (construction materials included) there is a strongorrelation among environmental assessment methodologies andumulative energy demand results, particularly when the impacts mainly related to the use of fossil energy in electricity and fuel

ixtures [50]. Therefore, in this study, as the main objective is to

chieve a greater understanding on the relative importance thatmprovements can bring to the environmental impact, rather thano produce absolute estimates, a single score indicator such as Eco-ndicator allows for practical applications.

able 7ingle-family detached house, energy and environmental optimizations.

Design scenario Scenario I

Insulating material of sloped roof: Glass wool Neopor 100K6 cm (EPS) 12 cm

Insulating material within verticalwalls:

Glass wool Neopor 100K4 cm (EPS) 4 cm

Insulating material within flat roof: Extruded polystyrene Neopor 100K6 cm (EPS) 8 cm

Vertical wall plug: Masonry in hollow bricks Light cellular25 cm × 25 cm × 20 cm 25 cm × 25 cm25 cm × 25 cm × 10 cm –

Building development: - Change in quantity of building materials t- Change in energy expenditure for assemb

Changes in natural gas consumptions for heating −17%

Eco-indicator results U.M. Pt/year Pt/year

Construction phase 622 605

Operating phase 1978 1747

End-of-life phase 109 108

Complete life cycle 2708 2459

Fig. 9. Single-family detached house – reduction of the impact during the construc-tion phase due to the proposed optimizations (Eco-indicators method).

5.1. Single-family detached house

As mentioned, the detached house has a high cumulative energydemand and also a significant amount of embodied energy. There-fore, it is important to reduce its environmental impact duringthe operating phase without increasing it during the constructionphase. Since the highest impacts during the construction phase aredue to the “vertical envelope” and “upper horizontal boundary”(Fig. 4), the first changes were related to the materials of thesestructures (Scenario I and II, Table 7). In particular, LCA resultsreveal that the impact of ceramic materials represents almost 25%of the total involved in constructing the detached house. Accord-ingly, the hollow bricks of masonry walls were replaced withaerated concrete blocks (Gasbeton). Moreover, the upper hori-zontal boundary (flat and sloped roof) was improved by addinginsulation.

As shown in Table 7, in both Scenarios I and II the impact declinesduring each phase of the building’s life cycle; in particular, duringthe construction phase, the increase in the thickness of the insula-tion is more than compensated by the lightweight cellular-concretesubstitution for the bricks (Fig. 9). The concrete blocks, chosen from

the Ecoinvent database, have a lower embodied energy for the samethermal-resistance than bricks; this lower density results in a lesseramount of material. The results show that changes in type andthickness of the vertical envelope and roofing materials, Scenario I

Scenario II Scenario III

® Neopor 100K®

Starting with Scenario II, a passivesolar- greenhouse addition is evaluated

(EPS) 15 cm® Neopor 100K®

(EPS) 4 cm® Neopor 100K®

(EPS) 12 cm concrete Light cellular concrete

× 20 cm 25 cm × 25 cm × 20 cm25 cm × 25 cm × 12 cm

ransported from the factories to the building site;ly.

−18% −19%

% Pt/year % Pt/year %

−2.8 608 −2.3 636 +2.2−13.2 1735 −14.0 1701 −16.2−1.1 107 −1.4 107 −1.5−10.1 2450 −10.5 2444 −10.8

84 F. Asdrubali et al. / Energy and Buildings 64 (2013) 73–89

Fig. 10. Architectural simulation of the sunspace.

aid

ssStcsdsdoawipr

Fig. 11. Energy- and environmental-optimizations of the multi-dwelling residentialbuilding – Scenario VI. PV panels installed on the flat roof cover a surface of 74 m2,they produce up to 5901 kWh/year, with a total installed power of 7.59 kWp. Oneach slope of the pitched roof (the total useful surface is 138 m2) 96 PV panels areinstalled, the capacity is 215 kWp and the estimated production is 22,290 kWh/year.

fuel demand and electricity consumption. New materials withreduced thermal-transmittance values [52] were introduced, as

Fl

nd II (Table 7), significantly reduced the building’s impact duringts lifetime (more than 10%), with respect to the building’s initialesign configuration.

A third proposed optimization is a sunspace placed on theouth fac ade of the building (Fig. 10; Scenario III): the energyavings introduced by this architectural change were evaluated.imulations (“Method 5000” [51]) were carried out to estimatehe thermal contribution only during winter time, since it can beompletely opened during summertime. We estimated that theunspace contributes approximately 3% of the building’s energyemand. The increased impact during construction of the sunpace (+4.6% compared to the Scenario II) is balanced by theecrease during the operating phase (−2%), and also at the endf life phase the impact slightly decreases. Compensating for thedditional impact associated with the constructing the sunspaceould take almost 35 years because it was introduced in a build-

ng configuration whose masonry (Scenario II) had high insulating2

roperties (U = 0.23 W/m K). This analysis shows that optimizing

etrofit strategies is site-specific.

ig. 12. Changes in environmental effects (Eco-indicator 99H/H) resulted by the energy

ife.

PV modules are also integrated into sunshade blades, their energy production is2435 kWh/year. The thermal solar panels (47 m2) produce 120,092 MJ, they cover81.8% of the heating demand for DHW.

5.2. Multi-dwelling residential building

Fig. 8 shows that the complete life energy demand of thisbuilding (226 MJ/m2 year) is close to the average value of 73case studies (234 MJ/m2 year); also, the embodied and demoli-tion energy (19.4% of its complete life energy demand) is closeto the average value (17.5%). For this reason, the energy opti-mizations of this building aim at transforming this conventionalbuilding into a low-energy building, as defined by Sartori and Hes-tnes [10]. The LCA results indicated the need to lessen both heating

well placing as solar thermal- and photovoltaic-panels placed onthe roof. The initial design of the building included conventional

optimizations on technological units and on the different phases of the building’s

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85

Table 8Multi-dwelling residential building, energy and environmental optimizations.

Sub-systems Design scenario Scenario I Scenario II Scenario III Scenario IV Scenario V Scenario VI

Insulating material of thefloor under the sloped roof:

Glass wool Cellulose fibers slab Cellulose fibers slab Cellulose fibers slab Cellulose fibers slab Cellulose fibers slab Cellulose fibers slab10 cm 12 cm 12 cm 12 cm 23 cm 23 cm 23 cm

Insulating material withinvertical walls:

Wood wool Cellulose fibers slab Cellulose fibers slab Cellulose fibers slab Cellulose fibers slab Cellulose fibers slab Cellulose fibers slab7.5 cm 10 cm 10 cm 10 cm 10 cm 10 cm 10 cm

Insulating material of flooron unheated space:

Expanded polystyrene Cellulose fibers slab Cellulose fibers slab Cellulose fibers slab Cellulose fibers slab Cellulose fibers slab Cellulose fibers slab6 cm 8 cm 8 cm 8 cm 10 cm 10 cm 10 cm

Vertical wall plug:Masonry in hollowbricks

– Hollow brick clay andsawing(wedge-shaped)

Hollow brick clay andsawing(wedge-shaped)

Hollow brick clay andsawing(wedge-shaped)

Hollow brick clay andsawing(wedge-shaped)

Hollow brick clay andsawing(wedge-shaped)

25 cm × 25 cm × 20 cm – 25 cm × 25 cm × 30 cm 25 cm × 25 cm × 30 cm 25 cm × 25 cm × 30 cm 25 cm × 25 cm × 30 cm 25 cm × 25 cm × 30 cm25 cm × 25 cm × 10 cm – 25 cm × 25 cm × 12 cm 25 cm × 25 cm × 12 cm 25 cm × 25 cm × 12 cm 25 cm × 25 cm × 12 cm 25 cm × 25 cm × 12 cm

Heating system andrenewable energysources (RES):

Boiler modulating(natural gas)

– – Central heating boilercondensing modulating(natural gas)

Central heating boilercondensing modulating(natural gas)

Central heatingboiler + thermal solarpanels

Central heatingboiler + thermal solarpanels + solarphotovoltaic panel(PV) + external wallsystem integrating RES

Building development:- Change in quantity ofbuilding materialstransported from themanufacturer to thebuilding zone

155,284 tkm 163,909 tkm 166,323 tkm 166,323 tkm 166,416 tkm 166,475 tkm 246,657 tkm

- Changes in energyexpenditure for assembly

78,362 kWh 77,989 kWh 81,795 kWh 81,795 kWh 82,532 kWh 84,227 kWh 118,226 kWh

Changes in natural gasconsumptions for heating

485,920 MJ 453,054 MJ 463,520 MJ 437,601 MJ 404,748 MJ 312,996 MJ 296,279 MJ−7% −5% −10% −17% −36% −39%

Changes in electric energyconsumption

47,344 kWh – – – – – −5572 kWh(grid-connected PVsystem)

Eco-indicator results U.M. Pt/year Pt/year % Pt/year % Pt/year % Pt/year % Pt/year % Pt/year %

Construction phase 1684 1697 +0.74 1720 +2.11 1720 +2.11 1732 +2.86 1790 +6.25 3030 +79.90Operating phase 5948 5730 −3.66 5799 −2.49 5446 −8.43 5242 −11.87 4671 −21.47 1703 −71.37End-of-life phase 320 318 −0.51 315 −1.49 315 −1.49 318 −0.51 318 −0.51 570 +77.97Complete life cycle 7952 7745 −2.6 7835 −1.48 7482 −5.92 7293 −8.29 6779 −14.76 5568 −29.98

86

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Table 9Office building, energy- and environmental-optimizations.

Design scenario Scenario I Scenario II Scenario III Scenario IV Scenario V

Insulating material –cavity wall:

Glass wool (5 cm) – – Glass wool(5 cm) + glass wool(5 cm)

Glass wool(5 cm) + glass wool(5 cm)

Glass wool(5 cm) + glass wool(5 cm)

Insulating material –concrete wall:

Wood wool (2 cm) – – Glass wool (5 cm) Glass wool (5 cm) Glass wool (5 cm)

Masonry – cavity wall: Hollowbricks + thermal block

Hollow bricks + lightcellular concrete

Light cellular concretefor both layer

Hollowbricks + thermal block

Light cellular concretefor both layer

Light cellular concretefor both layer

Masonry – concretewall:

Masonry in reinforcedconcrete blocks

– – – – Zinc cladding insteadof aluminum cladding

Renewable energysources (RES):

– – – – – Photovoltaic panels(20 kW) and reductionin window dimensions

Building development: - Change in quantity of building materials transported from the manufacturer to the building zone;- Changes in energy expenditure for assembly

Changes in natural gasconsumptions forheating

−2 −3 −5 −6 −12

Eco-indicator results U.M. Pt/year Pt/year % Pt/year % Pt/year % Pt/year % Pt/year %

Construction phase 3582 3566 −0.44 3557 −0.69 3603 +0.60 3579 −0.08 3726 +3.86Operating phase 14,208 14,140 −0.48 14,120 −0.62 14,029 −1.28 14,017 −1.37 12,040 −18.01End-of-life phase 531 529 −0.24 529 −0.33 531 +0.03 529 −0.31 527 −0.67Complete life cycle 18,321 18,236 −0.47 18,207 −0.63 18,163 −0.87 18,125 −1.08 16,293 −12.45

and Buildings 64 (2013) 73–89 87

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50

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F. Asdrubali et al. / Energy

nsulating materials, such as glass wool and expanded polystyrene;hese were replaced by thicker panels of recycled cellulose flocksTable 8), a recyclable, natural material with a low value of embod-ed energy. Lightweight bricks with wood and rice-husk flour

ere used instead of conventional hollow-bricks masonry. A moreechnologically advanced solution was proposed: a steel struc-ure leaning against the southern facade that integrates differentioclimatic construction solutions. At the ground floor, deciduouslimber plants produce a solar shield, the two upper floors use

double-skin fac ade system, and finally, on the top floor, photo-oltaic modules are integrated into sunshade blades (Fig. 11).

All the proposed scenarios were evaluated for their contributiono energy savings and reduction in environmental impact duringhe building’s entire life; the findings from LCA simulations areeported in Table 8.

The advantage of using building materials that have a highecycled and natural content is evident from comparing the ini-ial design scenario and Scenario I (−2.6%), the design scenariond Scenario II (−1.48%) and between Scenario III and Scenario IV−2.5%). Thanks to the material choice, despite the increase in thensulating material thickness, a small growth in the impact of theonstruction phase (vertical envelope and upper horizontal bound-ry) has been observed. At the same time a significant reduction innergy consumption for heating during the operating phase haseen obtained.

Figs. 12 and 13 report the effect of the various optimizations onhe different phases of the building’s life cycle and illustrate howo use the LCA approach as an eco-design tool for buildings.

In particular, for each scenario, Fig. 12 shows the environmentalffects of the various optimizations made during the constructionhase on the vertical envelope, roof, transportation- and electri-al energy-consumption as well as energy consumption during theperating phase. The figure, along with Fig. 13, also shows the rel-tive importance of the impact of the various contributions to theotal impact.

All optimizations contributed to the reduction of the totalmpact due to natural gas for heating, while it is only with Scenario

(introduction of solar thermal collectors) that there is a signifi-ant reduction of the impact due to natural gas for DHW (domesticot water). Scenario VI (introduction of a smart fac ade southbound)

ignificantly increases the impact during construction and end-of-ife phases, but a drastic decrease of the impact during operationalhase (mainly because of the reduction in electric consumption),o that the overall impact is lowered (Fig. 13).

400

450

300

350

250

300

1,0

00

150

200

Pt

x 1

50

100

0

Design

Scenari o

Sce nario I Sce nario II Sce nario II I Sce nario IV Sce nario V Sce nario VI

Construction phase Operating phase End-of-life phase LCA

ig. 13. Changes in environmental effects (Eco-indicator 99H/H) resulted by thenergy optimizations on specific phases of the building’s life cycle.

Fig. 14. Eco-indicator 99H/H (points on net area), contribution of the specific life-stages to the total Life Cycle Impact.

The use of passive and active systems to improve the per-formance of a building needs to be carefully evaluated, since anexcessive use of one or both may even be counterproductive [6,10].As shown in the results depicted in Fig. 13, this may happen whenthe increase of the embodied energy due to improved buildingmaterials and technologies is not balanced by the reduction of theoperating energy, and thus, the impact of the building’s entire lifeis not further reduced.

Finally, Fig. 14 shows how the environmental impacts related tothe construction phase and particularly to building materials andtheir embodied energy [10] grow in importance while consump-tions of the operating phase decrease: the relative importance ofthe impact of the construction phase grows from 21% of currentdesign to 50% of Scenario VI, which compares well with resultsfrom other studies [53].

5.3. Office building

According to the results shown in Fig. 8, embodied energy inthe office building is lower than the average one of other case-studies found in literature. Hence, the optimizations were aimed atreducing the energy demand during the operating phase, keepingalmost constant the impact during the construction phase. Simi-larly to the previous case-studies, the first step in the optimizationprocess was keyed to enhancing the performance of the exter-nal envelope (materials and thicknesses, Table 9). The LCA resultsshow that changes in thermal insulation materials and masonryfor the office building produce less appreciable benefits in compar-ison with the two other case-studies (Scenarios I, II and III). Thisresults from the main contribution to the energy burden of themetallic- and ceramic-claddings, and by the Window to Wall Ratio.It is noteworthy that although the embodied energy of transpar-ent surfaces and metallic cladding is high, these components canbe easily disassembled, so that it is reasonable to assume that theywill be recycled, resulting in a partial recovery of environmentalimpact.

Lastly, the most advanced optimization rested upon examiningthe effects on both thermal- and lighting-performance with respectto changes in the ratio between transparent- and opaque-surfaces(Fig. 15). Particular attention also was paid to analyzing the equip-ment system, both for their performance and embodied energy.The benefits of introducing blades with integrated photovoltaiccells, as well as installing a photovoltaic system on the roof also

were evaluated (Table 9). This last optimization (Scenario V) sig-nificantly reduces impact throughout the entire life cycle (−12%),even though it may slightly increase embodied energy.

88 F. Asdrubali et al. / Energy and B

Fig. 15. Energy- and environmental-optimizations of the office building (ScenarioV), including an improvement in the thickness of thermal insulation, changes inthe window to wall ratio (from 0.41 to 0.29) and PV installation. Three differentareas of the roof are covered by PV panels. On the flat roof a PV panel surface of50.9 m2 is placed, it is the most efficient part of the PV plant because it can pro-duce up to 8745 kWh/year, with a total installed power of 7.6 kWp. On pitchedr 2

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oofs the installed capacity of 12.4 kWp (83.36 m ) produces 12,974 kWh/year. Theystem has a total peak power of 20 kWp and an annual estimated production of1,720 kWh.

. Discussion and conclusions

Life Cycle Assessment can be a powerful tool to evaluate the realustainability of a building over its entire life and is getting morend more widespread, at least in the scientific community. As aatter of fact the importance of embodied energy in buildings is

rowing as a consequence of the new regulations that require toeduce buildings consumption during the operative phase. In par-icular this is true for Nearly Zero Energy Buildings, for which theres a real risk of shifting the impacts from the operating phase tohe construction and end of life phases, because of all the construc-ive solutions adopted to improve the building performance duringperation. For these reasons, integrating LCA in the calculation ofhe global performance of buildings is more than recommended foruildings with high energy performance such as Nearly Zero Energyuildings, and LCA procedures could contribute to the Internationalefinition of these buildings.

Even if the literature is rich of paper presenting case studiesf buildings evaluated under a LCA perspective, few of them pro-ose operative instruments such as tables and graphs available toractitioners in order to use LCA as an eco-design tool.

The paper aims to fill at least partially this gap and presentshe results of simulations carried out on three typical Italian build-ngs, a detached house, an office building, and a block of flats. Theelative importance of the buildings’ various life phases was investi-ated, both using the original design specifications, and alternative,ptimized configurations.

The results showed that the environmental impact of the con-truction phase, as measured by the Cumulative Energy Demandethod, ranged from 13.7% of the total impact for the office build-

ng to 20.9% for the detached house; the operational stage impactanged from 77.2% for the independent house to 85% for the officeuilding, while that of the end-of-life phase was about 1.3–2.0% ofhe total. These values confirm other cases described in the litera-ure showing the impacts of operation to be in the range of 80–90%nd those of embodied-energy to be 10–20% [6,48]. These resultsonfirm the fact that in future scenarios, with more energy efficientuildings and materials [54], the selection of low embodied energy

onstruction materials will become more important.

The second part of the study examined various approaches inrder to optimize the buildings under the LCA perspective, start-ng with envelope solutions (such as insulating materials and type

[

[

uildings 64 (2013) 73–89

and width of masonry), facilities (heating boiler replacement), andthe integration of smart systems (such as active and passive solarsystems). The results of the various optimizations showed that animprovement of the envelope materials (type and thickness) sig-nificantly reduced the buildings’ overall impact (up to 10.5% for thedetached house in Scenario II). Improvements in heating/coolingsystems also lowered the impact. Installation of thermal solarpanels in the block of flats reduced the total impact by approxi-mately 7% while added only 3.3% to the impacts of the constructionphase. The results showed that it is important to carefully evalu-ate costs/benefits of any proposed optimization so to avoid simplyshifting the environmental burden from one life phase to another.

Acknowledgment

The study was carried out within the national research projectFISR “GENIUS LOCI – The role of the building sector on climatechange”, funded by the Italian Ministry for Education and Researchto Perugia University.

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