Applying the Life Cycle Analysis in the Construction of Social Housing in Cameroon: The Case of Single-Store Houses at the Sic Residential Area in Olembe (Yaounde)

This study proposes an analysis approach of the life-cycle of two types of social housing of “T4 single-storey houses”. This is to determine which phase of the life-cycle calls for special attention in the process of reducing the impact of this sector on the environment. In order to successfully carry out this task, we first carried out a general review of the LCA as a decision-making guiding tool. Then, we alluded to social housing projects in Cameroon as the implementation framework of our guiding tool. Finally, after updating the database of some components of the building sector, we proceeded to the implementation on our two samples. Results obtained high light the importance of the exploitation phase. More interestingly, considering all twelve environmental impact indicators taken into account, the utilization phase that involves exploitation and maintenance is more predominant, causing 82 to 86% of the total impact, followed by the construction phase with 13 to 18%, and then by the demolition phase with 0.01 to 1%. As concerns the economic aspect, the utilization phase remains the most preoccupying. It represents at least 65% of the overall cost of the life cycle, followed by the construction phase and demolition phase.


Introduction
The housing crisis that has been plaguing Cameroon for close to twenty years has prompted the State to launch social housing projects in various cities of the country. That is why a pilot program for the construction of 10.000 low-cost houses was initiated in the two major cities of Cameroon, that is Yaoundé, the political capital at the Olembéneighborhood (at the northern entrance of the city) and in Douala, the economic capital, in the Mbanga-Bakoko area. However, it is well-known that the civil engineering works in general, and construction of houses in particular, transform and severely damage the environment. As matter off act, the construction activity requires the massive use of natural renewable or non-renewable raw materials. This also implies the production of important quantities of inert wastes and the emission of pollutants such as carbon dioxide, fine particles, and volatile organic compounds. That is why it is imperative to integrate the environmental preservation aspect in the management of projects of such magnitude, because for too many years, the emphasis was mainly laid on the cost of activities, leaving aside the analys is of impacts made on the environment. Thus, in order to render buildings more ecological, it is important to know the various phases of their life cycle. We should also be able to determine the most important phase interms of environment a impacts and avoid shifting pollution from one phase to the other. In order to fill this need and have an integral view of the issue, the Life Cycle Analys is appears to be the appropriate tool. It is in this light that this paper was drafted with the objective of applying the life cycle analys is to a "T4 one-storey" low-cost house in the urban area of the center Region. We shall present the LCA tool, the various phases of the life cycle of a building and determine the most toxic phase in terms of environmental impacts. A better knowledge of the impacts as sociated to products helps to seta order of priorities for improving and informing organizational and technical options.

Life Cycle Analysis
The Life Cycle Analysis (LCA), that was developed in the sixties, is used to quantify the impacts of a "product" (good, service or process), from the collection of its constitutive raw materials up to their destruction, through their distribution and use ("from the cradle to the grave" analysis). The flow of raw materials and energies involved and produced teach step of the life cycle relisted, and an exhaustive account is made of the consumption of energy, natural resources and polluting emissions in the environment (air, water and soils). The ISO14040 standard describes the essential characteristics of an LCA and good practices in conducing such a study (methodological framework, transparency requirements, measures applicable in case of transmission to third persons, etc.).
The four main steps of a life cycle analysis areas follows: • The definition of the objective and scope of the study: ISO14041.
• The inventory of resource consumption and of emissions: ISO14041.
• The impact assessment of the life cycle: ISO14042.

•
The interpretation of the life cycle's results: ISO14043. The aim of our study is to apply the LCA to the low-cost house in urban areas in order to measure the environmental impacts during the life cycle of our building. This will bed neon the basis of the LCA methodology that thoroughly assesses the impacts of a building using twelve environmental indicators: i. Indicators on the consumption of: • Energy; • Water; • Resources.

Defining the Scope
The scope with in which we shall carry out our study features the following items:

i. Function and related functional units
Functional units adopted to determine the value of the various indicators during the three phases of the building's life span: • Internal usable surface: 93.7m 2 ; • Internal usable volume of the building: 225m 3 ; • Occupation: 6 persons; • In-house services provided by house hold appliances and usual entertainment products such as the gas cooker, the refrigerator, the air-conditioner, the computer, the TV set and the radio; • Water supply by CDE; • Electricity: voltage provided 220 volts.

ii. Life span
It is supposed that construction works of our buildings train July 2016 and end in December 2016.
Thus, our house is readyon 1 st January 2017; the life span of our house is estimated at 50 years.

iii. Limits of the system
The limits define the scope with in which the system is studied. Al what fall without this framework is not taken into consideration. The system studied covers the construction, utilization maintenance and demolition of the building period and designed following a good number of well-established hypotheses. Figure 2 presents asketchyvie was well as the scope within which all the flows of materials and energy are listed for the life cycle of the building. This sketchy model of the life cycle is designed to include the astuteness of giving more importance to the nearest material supply points.

Presentation and Justifications of the Building
This is a single-storey low-cost house located in the Olembén eighbor hoodatal attitude of 3.9500° and alongitude of 11.533° in Yaoundé, whose characteristics are given in the Tables below, as well as the Distributionplan. Anestimate of the building is also attached.

Equipment Description
Carpentry Carpentry works must be done with good quality materials according to the rule book; measures for perfect adjustments and setting up must be respected to the letter.
In any case, the choice of the type of materials must be justified technically (resistance, behavior, durableness, water-proofness, the rmalandacoustic performances) and financially. Entry doors of the houses must also obey to safety and anti-intrusion requirements by the type of materials used, the sealing method and the shutting system. Inshort, carpentry works must be carried out according to international rules and norms relatingto the type of the proposed carpentry works.

Technical ducts
Four technical ducts must be provided for and putin place according to norms inforce; they will host electrical installations for power, telephone and TV supply

Sewage disposal
system Separate plumbing piping must beprovided for wastes ewage, sewage water and rain water. They could end into a single main sewer, especially in the case of a combined system. Rain water will bedrained through appropriate piping; we should avoid direct draining over front walls or other method that could contribute to their rapid degradation. Subtotal12.00

Hypotheses and Elements of the Study
In order to apply the LCA on social lodging, we need to set down some hypotheses and we must have some elements.

H1:
General environmental impacts indicators obtained at the end of the building's life cycle are assessed following the steps described below.
Data presented, taking into consideration the extraction of the raw materials and the production of materials that are manufactured or not; then impacts resulting from the following processes are added: • Transportation of manufactured parts to the building site; • Energy and carbon dioxide produced during the manual phase of the use of the building's components; • Impact indicators through hout the use of the building (lighting, specific electricity); • Environmental impact of maintenance and improvement materials; • Environmental impacts of the destruction of the house; • However, it should be noted that the value of environmental impacts during the production of building materials (trucks, Wheel barrows, scoops, vibrators, etc.) were not taken into account.

H2:
It is considered that environmental impacts of the building's components are constant over the time.
H3: Processes and factor excluded. Inade concentratedeff or to farchitectural systems that directly impact the use of energy and the overall heating potential of the low-cos thouse, some components of alow-cost house and some external factors were not listed. Belowisa list of some questions that were not included in the study: • The location, since it deals with impacts on local ecosystems, personal questions on transportation, and urban issues on planning (including ewage and road infrastructures); • The house surroundings (for instance foot path concrete, developments, draining); • Furniture (kitchen and bathroom boxes, etc.); • TV and telephone connections (external and internal systems, including wiring and firealarm); • Behavioral models of inhabitants; this involves food consumption, leisure equipment, clothing, furniture, the supply of pet; • animals, cleaning products or other articles that require no energy for the operation; • Other environmental impacts happening in the whole life cycle; • Environmental and social impacts related to the origin of building materials; • Upcoming technological developments that significantly reduce energy consumption and the cost of house hold appliances; H4: Materials supply sites remain the same through hout the life cycle.

H5:
For an overall lappraisal of our building, it is supposed that the price of materials would slightly increase in the long run.

Elements of the Study
We have established acorrelation between the HNPS and the EQUER software inorder to fill the indicator deficit of the HNPS. Of course, we carried out a compatibility operation on our various indicators so that our study should not be distorted.

1) Transportation of materials
• Supply of materials manufactured in Douala; • Gravel supply site: Razel quarry situated at Nkometou. The power of the 16t truck remains equal to that of the 20t truck to take the vehicle's energy consumption in Cameroon into account, due to their age.

Result
Given: E: raw materials extraction indicator; F: indicator for the production of materials; T: transportation indicator; and finally, M: indicator for the putting in place of the building site: being the environnemental impact indicator. We have therefore: I = E+F+M+T   The diagram above shows that the exploitation phase is the most important for all indicators, except for two indicators: waste and radio active waste. This situation is due to the fact that liquid and solid wastes produced by users are not taken into account. Thus, the set wo indicators are two outlier points of the study.

Figure 4. Impact Indicators of Urban Low-Cost Housing
Of the twelve indicators under study, two have the most exploited results of the study with in the frame work of LCA applied to the building. These are power and overall heating potential (GWP 100 ). The power indicator mainly deals with: • Any power taken from nature to produce building materials; • The production of power such as electricity. House holdgas (grey power); • Exploitation power (electricity AES-SONEL); • Production power and power used to pump water into houses.

Impact Study
Here is the list of the twelve environmental impact indicators of the two houses according their various life cycle phases. Of the twelve environmental impact indicator sex amined, it appears that: • The destruction phase is the one that has the smallest number of environmental impacts while the exploitati on phase has the higher number (9/12) and the most important ones. This could be explained by the high speed and the precision with which destruction is generally carried out; conversely, exploitation takes more time.
• For the water consumption indicator, the urban house has a high consumption rate. This is due to the fact that water supply.
• intown(CDE) is done with many losses.
• For consumption indicators of: Waste. Radio active waste and odours. the construction phase features the highest numberofindicators.

Balance Sheet and Interpretation of the Life Cycle of LCH
The results of the LCA of the building constructedup till now apply to all environmental aspects: raw materials and power consumption; waste; green house-effect gas; acidification; eutrophization; Ecotoxicity; human ecotoxicity and odours; power consumption; impacton the climatic change called GWP100 are impacts that could be well directly appraised by users of the buildings.
Of the twelve indicators, except the two on waste (because waste produced by users of the building were not taken into account); the contribution of the use phase (exploitation and maintenance) of the building is very pre occupying as illustrated by the following Table.

Conclusion
At the end of our study, the issue was applying life cycle analysis (LCA) to a "T4 single-storey" urban low-cost house. To that end, we had a data base setup by the HNPSP in 2008; using the data base from Switzerland. We completed the data missing in the 2008 HNPS database. On the basis of these data, we applied the LCA to a low-cost house and to that effect. We used the twelve impact indicators for acomplete implementation of the LCA.
The methodology used for the LCA of our building involved quantifying materials and components, and then the substances taken and released from and into the environment, taking into consideration invent or iesmainly provided by the 2008 HNPS database, the ECOINVENT data base from the EQUER software and field analyses. Results provided by our sample low-cost house reveal that the basis of utilization (exploitation and maintenance) is the most preoccupying at the level of environmental impacts, which reach their highest point during this phase and represent 86% of the life cycle's overall limpacts.