Life Cycle Cost of water efficiency measures in commercial

buildings

Case study of SONAE SIERRA

Pedro da Fonseca Teixeira

Extended abstract

Superviser: Professor Maria Cristina de Oliveira Matos Silva

Superviser: Professor Vitor Faria e Sousa

October 2015

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Abstract

Nowadays it is accepted that the consumption of resources surpasses the existing natural reserves,

which has urged the demand for sustainable constructions at many levels. In particular, there has

been a development on water efficiency certification systems. In that matter, it is of interest to know

which solutions are more competitive in both technical and financial ways. The water efficiency

measures implemented in Colombo Shopping Center are presented as following. In 2008 took place

the replacement of the WC’s disposable equipments with more efficient models and, in 2011, there

were constructed the rainwater harvesting system, for the supply of the Cogeneration Facility, and the

Cooling Towers’ purge water harvesting system, for the supply of the toilets of 4 WCs. For the

components of each measure it was conducted a life cycle cost (LCC) analysis that covers the

investment, utilization and maintenance stages, taking into account the water and energy

consumptions and labor costs. Along the review it is evaluated the impact of management decisions

on the LCC and the image of Colombo. The conclusions state that the WC’s intervention has a

significant higher LCC comparing to the other considered measures, which costs of utilization and

maintenance are negligible. Among the disposable equipments, the higher investment and utilization

costs correspond to the toilets whereas the higher maintenance costs are assigned to the urinals.

These costs allowed to estimate the image costs associated with the WCs, which is about 3% of its

total monthly maintenance costs.

Key-words: water, Shopping Center, water efficiency, life cycle cost, RHS.

1. Introduction

One of the United Nations millennium goals includes the implementation of sustainable development

politics and the reversal of the loss of natural resources. In particular, renewable water resources are

becoming progressively scarcer, which has pushed the search for sustainable solutions that, on one

hand, reduce the water consumption and, on the other, avoid its waste on non-potable purposes.

Regardless of the environmental benefits associated with the application of these measures,

investment decisions are based on the highest benefit-cost ratio.

In these terms, Colombo Shopping Center (CSC), owned by SONAE Sierra, was selected to conduct

a study on the costs involved in every stage of the water efficiency measures life cycle that have been

implemented in the last 6 years, assessing its competitiveness. This work aims to give answers to this

interest on behalf of SONAE Sierra, having as main objectives: (i) to identify the most relevant water

efficiency measures nowadays; (ii) to identify, in time and space, the water efficiency measures that

have been installed in CSC, describing its components and the way they are related; (iii) to evaluate

the LCC of the identified measures, through the gathering of the records on water and energy

consumptions and investment, operation and maintenance costs; (iv) to identify and evaluate the

impact of the management decisions on the LCC and the external image of the Center; (v) to give a

contribution to the management of the Center, by the analysis of the data, building a methodology that

can be replied to similar cases.

2. Water management

The growing concern regarding the sustainability of water resources arises, partly, by the alarming

perspective that the conjugation of the uneven geographical distribution of fresh water reserves, the

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growing of the world population and the climate changes constitute to the current and upcoming

generations (United Nations 2003).

Table 1 shows that the uneven geographical distribution of fresh water reserves associated with each

continent’s population density puts enormous pressure on the withdrawal of water and its quality,

putting at steak the sustainability of its use and the surrounding ecossistems.

Table 1 – Proportion of fresh water and the population in each continent (United Nations 2003)

Continent % Population % Potable Water

North America 8% 15%

South America 6% 26%

Europe 13% 8%

Asia 60% 36%

Africa 13% 11%

Australia and Oceania <1% 5%

This inequality tends to worsen in the next decades with the growing of urban population. According to

United Nations (2014b), in 2050 the urban population will represent two thirds of the global population.

This growth has a direct impact on the pollution of local ecossistems and contributes to the imbalance

of the global climate. Although the effect of climate change on the water resources may be uncertain,

United Nations (2003) points it as responsible for the increase of worldwide water scarcity by 20%.

The goal to promote water sustainability in urban areas has led to the development of water efficiency

labelling systems all over the world, as the one developed by Associação Nacional para a Qualidade

nas Instalações Prediais (ANQIP) in Portugal, the european WELL (Water Efficiency Labelling), the

australian WELS (Water Efficiency Labelling and Standards) or the Watersense, created by the U.S.

Environmental Protection Agency (EPA).

3. Water efficiency measures

Almeida et al. (2006) divides the water efficiency measures in two categories, according to the locals

where they are implemented, i.e, in the buildings water supplying system or concerning the uses in

domestic toilets. On the other hand, Silva et al. (2015) proposes a classification according to the

purpose of each measure, differentiating between those which allow the reduction of potable water

consumption and the ones which substitute its use for alternative sources.

On Table 2 it is proposed a classification that adoptes the division of Silva et al. (2015), introducing a

previous level of distinction as to the level of intrusion that these measures imply on the buildings

structure, in other words, in structural and non structural measures. In that matter, awareness

campaigns are considered as non structural measures, although its purpose is to reduce the water

consumption on the disposable equipments. The presented measures are based in two documents,

Almeida et al. (2006) and APA (2012).

Table 2 – Water efficiency measures applicable to buildings (adapted from Almeida et al. (2006) and APA (2012))

Type Water efficiency measure

Non structural Awareness campaigns

Revision of the landscape designs

Structural

Reduction of consumption

Reduction of the pressure on the supplying system

Isolation of the hot water distribuition network

Adjustment/substituion of the disposable equipments

Utilization of alternative water sources Construction of rainwater, groundwater, grey and black

water harvesting systems

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Depending on the dimension of the building and the life cycle stage in which these measures are put

to terms, its implementation may be more or less viable from both financial and technical points of

view. In the majority of the cases, the control of the pressure on the water supplying system and the

isolation of hot water tubing are guaranteed in the design stage, including the definition of the

technical requests that should be required to the materials used in the building phase. Besides there

should exist an active control of the water losses along the buildings services, by the programming of

periodic inspections.

Concerning the goal of reducing the consumption of potable water, the traditional disposable

equipments can be converted or replaced by water efficient models. Nowadays the market offers a

wide range of devices and accessories that not only reduce the water flow in each usage but enhance

the comfort of its use, its hygiene and the security against vandalism.

On the other hand, it is not of current practice to construct poor quality harvesting systems on

buildings, so its implementation in the operation stage of the life cycle might be conditioned by the

availability of space and money. In fact, the complexity of these systems varies according to the

quality of the water and its destined used. In Portugal, the DL 23/95 allows the use of non-potable

water esclusively to the washing of pavements, watering, fire fighting and non-alimentary industries

4. Life Cycle Cost

The philosophy behind the LCC analysis of an infrastructure or any of its components arrises by the

perception that the early investment for its acquisition or construction might be much less than the

costs due to the stage of operation and maintenance. Woodward (1997) sintetizes the main objectives

of a LCC analysis: (i) allows the effective evaluation of different investment options; (ii) takes into

account the impact of every costs and not only the initial sum; (iii) gives guidance to the management

of buildings and (iv) facilitates the choice between competitive alternatives.

In this sense, the ISO 15686 - Part 5 presents the distinction between the approach of LCC and the

whole-life cicle costs (WLC), according to the kind of costs that are considered (Figure 1). In this case

study only CCV are considered.

Figure 1 – Life cycle stages considered on WLC and LCC (Adapted from International Organization for

Standardization (2007))

The main advantage to a firm that implements an LCC analysis before the decision of buying certain

kind of product, is to contribute in the search of the best benefit-cost relation to the allocation of

WLC Whole Life Cicle

LCC

Life Cycle Cost Externalities Revenews Non-construction

costs

Construction

Operation

Maintenance

End of Life

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resources, time and money at its disposal (Langdon 2007). In spite of its benefits, the main obstacles

to a wider application of this methodology, related by Clift (2003), are the lack of an universal

methodology, which would allow a clearer LCC calculation, the difficulty in considering and estimating

proceeding costs and maintenance strategies in the early project stage, and the achievement of

meaningless output.

Although these studies are far from being massivily used in the construction industry, the fact that the

new Directive 2014/24/EU requires that they must be included as an evaluation criteria in public

contrats, encouraging a sustainable development and an intelligent and efficient usage of money

during the life cycle of goods or products. According to this document, unless the evaluation is

performed only in a price basis, the contracting authorities may determine the proposal that is the

most economically advantageous using a calculation approach based on the costs of the life cycle.

5. Case study

Colombo Shopping Center, in late 2011, inaugurated a rainwater harvesting system (RHS) and a

cooling towers’ purge water harvesting system. Besides, it is used the water from two artesian wells, in

a system that dates the construction of the Shopping Center.

This study contemplates three interventions, chosen for their relevant set of records on water

consumption, energy and costs of manpower (Table 3). Then, the methodology used to derive costs at

every life cycle stage is reported.

Table 3 – Description of the type of LCC considered for each water efficiency measure

Measure Year LCC

Investment Operation Maintenance

Replacement of the 2008 Equipment acquisition

Water consumption

Maintenance, inspection and replacement

Rainwater utilization for supplying the Cogeneration Faciliy

2011 Construction Energy

consumption Maintenance, inspection

and cleaning

Cooling towers’ purge water utilization for the disposal of 4 WCs’ toilets

2011 Construction Energy

consumption Maintenance, inspection

and cleaning

Investment costs: theses costs were provided by the maintenance team of the Center or

through the research for current market prices. For the cases in which the costs refer to 2014, they

were updated to the date of the intervention, taking into account the annual discount rate.

Operation costs: operation costs with water taps and toilets are only traduced by the bill of

water consumption, taking into account the EPAL tariff. Through the reading of water meters it was

possible to obtain the average parcelling of consumptions, where 90% correspond to the toilets and

only 10% to faucets. For the RHS and purge water harvesting system operation costs, it is used an

equation which takes into account the power and water flow of the pumps, the volumes of water

pumped in each year and the unit cost of electric energy.

Maintenance costs: these costs are dependent on the labor costs practiced by the Center for

the maintenance requests and the time spent in each intervention. Nowadays the Center practices

four types of maintenance to the WCs: (i) planned (PL); (ii) routines (R), (iii) preventive (PR) and (iv)

unplanned (NP). The goal is to obtain each type of maintenance costs per disposable equipment

(urinals, toilets and water taps). In that matter, there were taken the following steps:

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1. obtaining the number of NP maintenance requests and the respective duration, individualizing

this information for each type of disposable equipment and WC;

2. taking into account the hours spent on NP maintenance, it was calculated the labor costs for

each type of disposable equipment, by afecting the hourly rate;

3. based on the division of the NP maintenance costs for each disposable equipment, each

percentage was applied to the remaining types of maintenance that were obtained through the

management software of the Center (PL, PR and R).

In this view, it is assumed that the division of the unplanned maintenance costs between urinals,

toilets and faucets is similiar among the other types of maintenance. It means that the number of

requests and the time spent repairing each equipment doesn’t vary with the type of considered

maintenance. In fact, this hypothesis translates the reality of the Center, as the planned, routine and

preventive maintenances occur, in a great majority, as a consequence of the unplanned interventions.

In the majority of times, the frequency of cloggings in the urinals drainage system makes it difficult to

guarantee its fixing in only one NP repairing intervention, which leads to the creation of a more

profound, planned repairing, scheduled with anticipation.

Once the maintenance software keeps a record on the RHS and purge water harvesting system

maintenance requests, the calculation of its costs results from the direct application of the labor costs.

6. Results

6.1 Replacement of the WCs diposable equipments

The comparison between Figure 2 and Figure 3 allows concluding that this intervention had an impact

on the reduction of the water consumption, as between 2009 and 2010 although the number of visitors

was kept roughly constant, it is noted that there was a reduction by 3.000 m3

on the consumed water.

Additionally, comparing the values of 2009 and 2014, it is shown that despite of having the same

number of visitors, the WC consumption is approximately 10.000 m3 inferior in 2014. The volume of

water consumed per visitor in the WCs has reduced considerably in the years after the replacement of

the disposable equipments, having stabilized in the past three years in 1,46 l/visitor, which represents

a reduction of about 20% from the average value of 1,82 l/visitor before the intervention.

Figure 2 –Evolution of the water consumption in all

WCs between 2006 and 2014

Figure 3 – Evolution of visitors to the Center

Concerning the maintenance requests, it is proven that the urinals have the most significant number of

unplanned maintenance request, of approximately 697 in the average of this three years analysis

(2012, 2013 and 2014), which represents 75% of the total requests, comparing to the toilets (164

requests, 18%) and the water taps (61 requests, 7%), as shown on Figure 4 (A). It is also shown that

30

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Wat

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2122232425262728

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the number of request has decreased steadily in the last three years for the urinals, in a leaner way for

the toilets and has increased slightly in 2013 for the faucets. In Figure 4 (B) it is shown that the time

spent in each type of equipment in this kind of maintenance doesn’t vary significantly.

A B

Figure 4 – Number of requests (A) and hours per request (B) in NP maintenance for each equipment in every WC

Then it was applied the hourly cost of labor in order to determine the costs of unplanned maintenance

for each type of equipment. That calculation shows that 73% of the total unplanned requests between

2012 and 2014 were due to urinals, 20% to toilets and only 7% to faucets.

To the other types of maintenance it was collected the number of monthly hours spent in each

intervention since 2007. The annual total maintenance costs increased substantially and regularly until

2012, in spite of the less utilization (see Figure 3). The reduction of the unplanned interventions is the

main goal of the maintenance management team of the Center, as it means that there is a decrease in

the occurrence of uncomfortable situations associated with the clogging or malfunctioning of the

disposable equipments. In the course of 2009 it was registered a marked increased in the unplanned

maintenance costs, of about 7.000 €, which was fought with the increase of routined maintenance, in

2010, and preventive maintenance, in 2011. The combination of these corrective actions led to the

steady reduction of unplanned repairings since 2011.

On the other hand, in the second semester of 2014 the total annual costs of maintenance to the WCs

has slightly increased (Figure 5) due to the increase of routined repairings, reaching approximately

more 100 € per month comparing to the total minimum cost. This value for image is insignificant

considering the whole monthly maintenance costs to the WCs, representing only 3% of the average of

these costs between 2012 and 2014. The annual evolution of the investment, operation and

maintenance costs for urinals, toilets and faucets shows that the urinals don’t have operational costs,

as it doesn’t consume water, but have much higher maintenance costs when compared to toilets and

faucets. In their turn, toilets present the highest costs associated with investment and operation, due

to the water consumption, but relatively low maintenance costs. The faucets present little operational

and maintenance costs. It is also shown that the evolution of the costs along the period of analysis is

uniform.

0

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Urinóis Sanitas Torneiras

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Urinóis Sanitas Torneiras

Nº

of

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Equipment

2012 2013 2014

Urinals Toilets Faucets Urinals Toilets Faucets

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Figure 5 – Annual (A) and monthly (B) costs of each type of maintenance to the 3 equipments in all WCs

6.2 Rainwater harvesting system

The study of the operation stage of the RHS showed that the level of non potable water savings is only

9,4% of the Cogeneration consumption, but in absolute terms it is not despicable (approximately 18,07

m3/day average). These operation data indicate that only for the Cogeneration Facility there is still a

large margin for the utilization of rainwater. In fact, the average daily consumption of the Cogeneration

in the lowest consumption month is about 80 m3/day, for there is a significant demand for non potable

water which could be secured with the increase of the RHS capacity.

The construction of the RHS included the adaptation of the existing networks and some constructed

elements in the technical area of Floor Level -4, but also the construction of new infrastructures for

storage and treatment of the rainwater. One of the three HVAC tanks was refurbished to collect the

rainwaters (tank P1) and another was contructed from bottom (tank P2), from which the water is

pumped and filtered to the preexisting HVAC tanks. The existing water pumping group that supplied

the Cogeneration Facility before the intervention was adjusted, once it is no longer supplied by tank

P1 and the trajectory of the pipings was intercepted by the construction of the new rainwater tank P2.

The costs associated with these changes constitute the investment part of the LCC. In Table 4 it is

shown the annual evolution of the RHS costs in each life cycle stage.

Table 4 – Annual cost evolution of the RHS

Stage 2011 2012 2013 2014

Investment (€) Appendix

Operation (€)

102,92 120,28 113,91

Maintenance (€) 3.000 3.000 3.000

Total (€) Appendix 3.102,92 3.120,28 3.113,91

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500

1.000

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nov-11 mai-12 dez-12 jun-13 jan-14 jul-14 fev-15

WC

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Total R NP PR PL

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6.3 Purge water harvesting system

Through the analysis of the operating scheme of this water efficiency measure it was concluded that in

the months of August and September there is an excess of harvested water from the cooling towers to

the level of consumption registered in the toilets of the 4 WCs supplied by this water source, which

allows concluding that its potential is fully seized. In average terms, since the begining of its

functioning, the purge waters satisfy 71% of its final consumption per year.

The total investment costs associated with the purge water harvesting system is composed by the

acquisition of two water storage tanks (5 m3 each), fabricated in high density polyethylene; the UV

treatment and pre-filtering equipments; the installation of the water pumping set, including pumps,

accessories and the command and control electric panel and, at last, the construction of the

distribution network between the cooling towers and the storage tanks and from the latter to the WCs.

In this purge water harvesting system there isn’t any predicted routine maintenance concerning

inspections, cleaning or maintenance of its components. Taking into account the dimension of CSC, it

is understandable that this is not taken as a priority to the cost control system, as they constitute

derisory sums. For that reason these costs are neglected. Table 5 shows the annual evolution of all

these costs, in each stage of the life cycle.

Table 5 – Annual cost evolution of the purge water harvesting system

Stage 2011 2012 2013 2014

Investment (€) Appendix

Operation (€)

259,20 246,81 278,98

Maintenance (€) N/A N/A N/A

Total Appendix 259,20 247,81 279,98

7. Conclusions

The scope of this work concerned the evaluation of three water efficiency measures implemented in

CSC. In 2009 took place the replacement of the WCs’ disposable equipments for water efficient

models and in 2011 were built the RHS and the Cooling Towers’ purge water harvesting system.

These new systems were integrated in the existing network and are interconnected between each

other. The rainwaters, collected over 40.000 m2 roof area, are used in the Cogeneration Facility, for

the supply of the chillers cooling condensation circuit. These equipments are responsible for the

production of thermal and electric power used by the Center. This cooling process implies the rejection

of certain volumes of water contamined with high salt concentration which are used for the disposal of

the toilets of 4 WCs. The introduction of water efficient equipments allows the closing of this water

saving cycle.

The calculation of the WC’s LCC showed that the highest investment costs are associated with the

replacement of the toilets, followed by the substitution of the faucets and in last by the urinals. The

highest operation costs belong to the toilets and the highest maintenance costs to the urinals. In total,

the highest LCC correspond to the toilets, followed by the urinals and in last by the faucets (Table 6).

Athough the RHS has the second highest investment cost, its operation and maintenance costs are

quite insignificant when compared to the total cost structure of the Center. The purge water harvesting

system presents the most reduced LCC of the whole analysis.

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Table 6 – LCC of the analised water efficiency measures

Equipment Period of analysis

LCC (€)

Urinals

2008-2014

215.986,67

Toilets 603.395,11

Faucets 126.652,96

RHS 2011-2014

142.837,11

Purge Water H.S. 35.785,00

Among the three analised measures, the one which has the most significant impact towards the clients

is the refurbishment of the WCs. The occurrence of tubing and equipment cloggings have an

immediate impact in the clients’ judgement of the Center. Through the analysis of the performance of

the maintenance actions to WCs was proven that there has been a reduction in the number of the NP

maintenance requests to the WCs, due to the increase of PR and R maintenances. There has also

been a sustained reduction on the total maintenance costs per visitor. The image cost of the Center is

approximately 3% of the total monthly maintenance costs to the WCs, which is very satisfactory

considering the global expenses of CSC.

However, it is noted that in the first years of functioning of the new equipments, although there was a

reduction in the affluence of visitors to the Center, the number of NP maintenance requests to the

WCs increased, matching the numbers of 2007, which might be related to the type of disposable

equipments implemented, namely the water-free urinals. The concentration of urine in both the

equipment and drainage tubing promotes the deposition of minerals and the occurrence of cloggings.

On the other hand, by the fact that it doesn’t uses water, these quipements allow significant savings

concerning the stage of operation which compensate the maintenance costs calculated in this study.

The cost collection done in this study can be used as a point of comparison to viability studies or to

test the performance of similar projects. It also constitutes a reference concerning the actions and

interventions that could be implemented to reduce water consumptions in other commercial buildings.

8. References

Almeida, Maria do Céu, Paula Vieira, and Rita Ribeiro. 2006. “Uso Eficiente Da Água No Sector Urbano.”. Série de Guias Técnicos nº8 - Laboratório Nacional de Engenharia Civil

APA - Agência Portuguesa do Ambiente. 2012. “Programa Nacional Para O Uso Eficiente Da Água.”

Clift, Michael. 2003. “Life-Cycle Costing in the Construction Sector.” UNEP Industry And Environment (September): 37–41.

International Organization for Standardization. 2007. “Buildings and Constructed Assets — Service Life Planning — Part 5: Life Cycle Costing.”

Langdon, Davis. 2007. “Life Cycle Costing (LCC) as a Contribution to Sustainable Construction: A Common Methodology.” (May).

Silva, Cristina Matos, Vitor Sousa, and Nuno Vaz Carvalho. 2015. “Resources , Conservation and Recycling Evaluation of Rainwater Harvesting in Portugal : Application to Single-Family Residences.” “Resources, Conservation & Recycling” 94: 21–34. http://dx.doi.org/10.1016/j.resconrec.2014.11.004.

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United Nations. 2003. The United Nations World Water Development Report: Water for People Water for Life.

United Nations. 2014. “World Urbanization Prospects: The 2014 Revision.”

Woodward, David G. 1997. “Life Cycle costing—Theory, Information Acquisition and Application.” International Journal of Project Management 15(6): 335–44. http://linkinghub.elsevier.com/retrieve/pii/S0263786396000890.