Investigating the use of green design parameters in UAE construction projects

Abstract

Construction practices tend to have an adverse impact on the environment through their contribution to CO₂ emission, increased waste and energy consumption. The United Arab Emirates (UAE) has launched many initiatives to encourage green design over the past years and to work towards a sustainable community. Nonetheless, such initiatives require a considerable amount of time to penetrate the professional psyche and showcase real results that are easily utilised by the construction community. The aim of this research was to study the current degree of use of Green Design Parameters (GDPs) in the UAE construction projects and to identify the main constraints that hinder their application. To achieve the study's objective, a survey was designed and distributed to engineering design professionals in different consulting and contracting companies in the seven emirates of the UAE. Feedback from 112 projects was examined and statistically analysed. The analysis showed a degree of awareness and use of some key GDPs. Moreover, the data showed no correlation between the degree of using GDPs in a project and its cost and schedule. Not surprisingly, the lack of knowledge about green parameters and the lack of trust in recycled materials are the main constraints that featured in the responses.

Keywords::

• engineering design
• green design parameters
• sustainable construction
• UAE

1. Introduction

The construction industry involves various types of projects, and all are likely to have an impact on the environment by higher emission of CO₂ gases, increased landfill waste and higher energy consumption. The sustainable construction concept aims to reduce damage to the environment while maintaining social justice and economic prudence. It promotes efficient construction methods that reduce gas emission and decrease energy consumption. To get the best impact out of green design concepts that breed sustainable construction practices, it is important that the green concepts are considered at the early stages of any construction project.

Migration from conventional to sustainable construction is not an easy practice, and it cannot be accomplished within days or weeks but may take years before it becomes common practice. Yet prompt action in the right direction needs to be taken.

The United Arab Emirates (UAE) came a long way in the past decade. Elsheshtawy and AboulNaga in a 2001 study found that contemporary buildings in the UAE use almost six times more energy than traditional buildings. They performed their study by comparing the total energy use, artificial lighting and cooling energy use per square metre in a year for contemporary and traditional buildings. The energy consumption of these building was high in comparison with buildings in Europe due to the lack of energy saving features in the UAE. They attested that the actual performance of buildings must be improved to meet the CO₂ emission targets. Moreover, later studies showed resistance and barriers to incorporating sustainable practices in the UAE construction industry (Jabbour and Beheiry 2011). Among others, the high cost of incorporating sustainable practices, the tendency to be schedule driven during boom time and the lack of expressed interest from the owners featured as the highest obstacles delaying the adoption of sustainable construction techniques in the UAE.

In later years, the UAE started promoting sustainability practices in all its domains, and especially in the construction field which is responsible for the majority of CO₂ emissions. ‘The UAE is leading the region in the sustainability trend, having the highest share of green buildings in the Middle East and North Africa Region (MENA)’ (Gulf News, June 20, 2013). They go on to point out that approximately 800 buildings in the UAE obtained the leadership in energy and environmental design (LEED) accreditation, from a total of 1200 in the MENA region. Thus, the UAE houses 65% of green aspiring buildings located in the area.

The article further explains that while the MENA region lags behind other markets when assessing sustainable practices, green construction is still being encouraged for the benefit of real estate developers, as well as owners and tenants. The reason quoted being the effect of green practices on the reduction of lifecycle costs.

2. Research problem

The UAE, like other countries, has the responsibility for saving the environment by reducing the adverse impact of the construction industry. A sustainability practice in construction starts from site selection and continues through the lifecycle of a project. The design has to incorporate sustainability practices, as design factors for later construction. Therefore, several parameters have to be considered during the design phase, such as the type of materials to be used in construction, the techniques to save water and energy, benefit from daylight and natural ventilation, decrease noise and pollution during and after construction, and facilitate lifetime maintenance with a minimum environmental impact.

To influence construction sustainability positively in the UAE, one has to first design with green concepts in mind, then apply these designs meticulously. It was therefore necessary to first study the degree to which design engineers in the UAE approach the design process with green concepts in mind before proceeding to examine the actual process application of the green design concepts.

Hence, this study was geared towards examining the degree of use of Green Design Parameters (GDPs) in the UAE construction projects and identifying the main constraints to the deployment of the green design concepts into sustainable construction practices. The purpose of this study was to facilitate the movement towards sustainability through green engineering design and encouraging further deployment of GDPs until sustainable alternatives become more conventional in construction.

3. Scope of work and what to follow

The research explored the considerations of green concepts during preliminary and detailed engineering design and their later applications in construction. It was very rapidly clear from this study sample that all cases where some GDPs were considered were ultimately applied on site. Hence, the study focused on overall use as opposed to consideration and later application separately.

This project studied the usage level of GDPs in the UAE construction projects by collecting and analysing data from a questionnaire circulated among 112 UAE construction industry professionals. The three main objectives were as follows:

• To examine the industry professionals' perception on the current level of use of GDPs in the UAE.

• To study the actual level of use in the respondents' projects that were included in the data sample.

• To identify the constraints to the use of GDPs in the UAE construction projects.

4. Engineering design

Design is defined as the process of developing solutions to certain problems using experts and necessary tools. Engineering design precedes the execution of any construction project where ideas are translated into drawings and blueprints ready for work execution. In other words, engineering design dictates the built habitat and infrastructure we utilise. Furthermore, the debated changes in the planet's climate have led to the ‘go green’ concept and to sustainable construction with initiatives such as the Earth day starting almost 40 years ago (Moskow 2008).

The design process can be summarised by three phases: conceptual design phase, preliminary design phase and detail design phase. Conceptual design phase includes the highest level of uncertainty, where the customer's need is selected, scope of work is defined and design feasibility is ensured (Dieter 2009). The structural development of the design concept takes place in the preliminary design (Dieter 2009) where decisions are made and materials are selected, and the owner can review the plan before the detailed design commences (Halphin 2006).

The design step is the last step in the design process in which details are finalised to guarantee that the design reflects the project's concept. The main aim of the design phase is to provide the completed and detailed engineering drawings necessary for the project's construction in the plan views, side and front views. Section views, isometric views and enlarged views that clarify the details should be included in the drawings where the materials to be used to perform the execution can take place in the drawing (Dieter 2009).

Consequently, a project has to be well defined in the pre design stage, project managers and engineers should have a clear procedure and a well-defined goal in order to reach sustainability. Good communication is required between architects, engineers and builders, as that can enhance the planning work and decrease the project's cost (Robichaud and Anantatmula 2011). Most importantly, green parameters and sustainable construction are met only when the environmental, social and economic considerations are equally addressed and followed up in the design process.

In sustainable design, social and environmental considerations, as well as economic factors, need to take place prior to designing any construction project. Studies are to be made on the ability to supply raw materials, and whether the benefit of the user is met by using minimum resources with less damage to the environment (Hyde et al. 2007). Moreover, a well-defined design policy between stakeholders could be of high importance prior to starting a ‘green aspiring’ project (Hyde et al. 2007).

During detailed engineering design, the design team should take into consideration negative social, economic and environmental impacts and explore ways to reduce them. Design parameters become costlier to change as the project time line proceeds and should be clearly defined in this stage to avoid high costs due to changes in design (Dator 2010). Green design considerations should also be reflected in the architectural design of a building, and improvement in environmental performance should be addressed (Hyde et al. 2007).

Several researchers believe that the designers can make changes on design mentality and process to engage the green issues. Construction requirements for any sustainable project should be decided prior to the construction phase and enough time should be spent to come up with a proper plan in order to avoid changes during construction and save time and cost (Hyde et al. 2007). Therefore, designers should be involved in the project processes from the very early stages, the ‘planning stage’, in order to be able to incorporate effective changes with their responsibilities exceeding the structure, since they are not limited to the exterior shape of a building but rather to the impact of a building on its surrounding environment (Mackenzie 1997). Engineers are skilful and knowledgeable and should be involved early in the design process and have the authority to improve the building's design as noted in the Engineering & Technology magazine on 4 December 2009.

Green buildings also known as high-performance buildings or sustainable buildings emerged through late nineteenth and early twentieth centuries (Peng and Sui Pheng 2010). Green building design has many advantages over conventional design; besides minimising the cost of energy and water, green buildings bring comfort to residents by incorporating natural daylight and outdoor living while improving indoor ventilation and using non-toxic furnishing to enhance the health of building occupants (Rajendran, Gambatese, and Behm 2009). Since most of the large companies are self-insured, employees' health would be of considerable financial concern (Yudelson 2009). In conventional buildings, residents suffering exposure to high humidity and temperature, artificial ventilation and poor indoor air quality are shifting to green buildings with improved indoor environmental quality reflected positively on the occupants' health and decreased levels of stress and depression (Singh et al. 2010).

5. Green design parameters

Each country is facing a challenge to improve the energy and the sustainability performance of new buildings through improving their design. The planning, design and performance of sustainable projects as well as their site and location are important parameters in green concepts. The GDPs considered in this analysis are discussed below:

• Early involvement of designers in the design process: This reduces the chances of design changes. Construction requirements for any sustainable project should be decided prior to construction and enough time should be spent to propose a proper plan in order to avoid later changes during construction and to save time and cost (Hyde et al. 2007). Designers should be involved in the project processes from the early planning stage to affect the design and reduce further changes (Mackenzie 1997)

• Fly ash concrete: In order to decrease carbon usage, the use of fly ash concrete ‘HFAC’ instead of regular concrete increases strength and durability and reduces the impact on construction ‘less carbon emissions’ during the production process (King 2005).

• Natural and controlled ventilation: Controlled vents opening for the internal flow of natural air is required in summers as well as in winters. It decreases reliance on air conditioning, saves energy and improves health disorders (Holliday 2008).

• Mechanical design and electrical consumption: Lighting control design, efficient electrical fixtures and mechanical systems that reduce energy consumption are required to achieve a sustainable environment (Gambatese, Rajendran, and Behm 2007).

• Use of insulation materials: The use of good insulation materials and climate wall panels decrease the reliance on Heating Ventilation and Air Conditioning systems and reduce energy consumption (Carpenter 2009; Gambatese, Rajendran, and Behm 2007).

• Solar panels: The use of economic solar panels for lighting and heating water will also reduce energy consumption (Carpenter 2009).

• Water usage reduction: Designing with the reduction of water usage in mind encourages efficient water consumption, innovation in plumbing fixtures and efficient landscape irrigation by using captured rain water and reusing grey water (LEED 2009).

• Environmental impact limitation: Implementing a plan that limits environmental impacts during construction encompasses all the elements discussed above in a comprehensive, traceable approach to construction and considers the reduction of noise and pollution (Landers 2010).

• Non-smoking buildings: Non-smoking and designating smoking areas in buildings improve health and reduce environmental pollution for users (LEED 2009).

• Insulated walls: Double-glazed, well-insulated walls or cavity walls that are filled with heat-absorbent insulation materials to decrease the effect of the weather elements in summer and winter, hence decreasing energy consumption (Mackenzie 1997).

• Light distribution control: Design to control the amount, size and method of distribution of glass windows, light shelves and skylights used for daylight reduces energy consumption and improves users' well-being (Carroon 2010).

• Recycled and durable materials: Using high durable, recycled, non-toxic and environment friendly material reduces landfill wastes and decreases energy consumption (Carroon 2010; Halliday 2008).

• Materials use reduction: Building designs that reduce material use such as exposed ceilings and floors with no finishes save resources and finances (ADUPC 2010).

• Green materials: Using green and natural materials or products such as natural stones and wood reduces toxic components (Mackenzie 1997).

• Safety and firefighting: Safety and firefighting considerations such as removable skylights, large and open-ended light courts and exterior light shelves positioning help to avoid ladder interfere in fire cases and save lives (Spadafora 2010).

6. GDPs use (consideration/application)

The study explored the consideration of GDPs during preliminary and detailed engineering design and the later manifestation of these design parameters on the construction process. It was clear from the response data sample that all projects that considered GDPs in the design stage, later applied these considered parameters in the construction stage. Therefore, the study adopted the term ‘used’ to signify ‘considered and later applied’ GDPs.

7. Constraints

Scientists have encouraged prompt action to save the environment before we reach a point of no return. Green construction is important in decreasing the CO₂ gases and helping the environment. Yet, many constraints hinder the green movement in construction. Some of these constraints include the lack of trust in recycled materials, which was considered a main constraint to achieving a sustainable society by Bonda and Sosnowchik (2007). Many people do not trust the quality of recycled material because it may contain toxic components (Calkin 2009). Perceived high costs ofgreen materials is also one of the major and most common constraints mentioned among construction projects professionals for achieving green standards (Landers 2010). Furthermore, lack of knowledge about GDPs, lack of interest from private owners/ government entities and lack of availability of green products were also quoted as constraints in previous research (Landers 2010). For the purposes of this research, the constraints identified by prior studies were amalgamated and used to solicit feedback on the most perceived obstacles in the UAE industry.

8. Cost

The high price of energy and building materials and the government facilities offered for encouraging green construction in some countries such as the USA increase the growth and expansion of the green building market, while the most common constraint among construction projects is still considered to be the cost (Robichaud and Anantatmula 2011), although the cost of designing and constructing a mid-rise building to achieve a LEED Silver could be the same as a conventional building (Spittler, Leon, and Zann 2009). The higher cost of green buildings is still perceived as a constraint for achieving green standards (Mackenzie 1997). However, failure to achieve the certificate after spending the time and energy on the building design would lead to an economic loss to the building's owner.

The main reasons for decreasing the construction costs in the long term are reducing the amount of water and energy consumed, reducing maintenance costs, using advantages of the incentive programmes that some governments offer to encourage to go green, productivity gains, increased value of the green building (Yudelson 2009) and the effective use of resources and materials (Carpenter 2009). Furthermore, to make green design a good business, the use of local materials in constructing green projects could minimise the transportation cost (Gambatese, Rajendran, and Behm 2007). Yet, training the crews in the new processes could increase the cost of green projects. The extra cost will be recovered and reduced through the operational and lifecycle project cost, which is less in green projects (Carpenter 2009).

The building sector is considered to be the largest source of emissions after the transportation sector (Peng and Sui Pheng 2010); hence, urgent action is needed to minimise its effect, and hence, conventional construction needs to move towards green design. Global warming attracts universal attention, so the UAE has launched many initiatives to work towards a sustainable community. The aim of this research was to study the current degree of use of GDPs in the UAE construction projects and to identify the main constraints that hinder their application.

9. The questionnaire

To achieve the project's objectives, a questionnaire consisting of 21 questions was designed. The survey was validated by a panel of experts. The survey examined the percentage of projects that use GDPs in the UAE. The survey also highlighted the degree of use of these parameters and the main constraints hindering green design.

The questionnaire was distributed among different firms involved in the consulting and construction process inside the UAE. The respondents were predominantly engineers and were requested to answer the 21 questions. The first 6 questions were based on personal experience and the remaining 15 questions were directly related to the specific project design parameters.

The first part of the design-related questions looked at the degree to which GDPs are used in the UAE construction projects during the preliminary and detailed design phase. The second part was used to rank the respondents' view on the main constraints that hinder the use of green parameters in construction projects. A Lickert's scale from 1 to 5 was used to rank the five identified constraints: lack of knowledge about green parameters, lack of trust in recycled materials, perceived high cost, lack of interest from private owners/government entities and lack of availability of green products.

The last part of the survey explored issues that may constraint the deployment of green construction practices, such as involvement of designers in the early phase of the project; considering environmentally friendly, economic, natural, socially acceptable, high durable and recycled materials; providing natural ventilation and controlling lighting design, using insulation materials, climate wall panels, solar panels, cavity and double-glazed walls; designating non-smoking buildings; and considering fire and safety issues in the design.

10. Data analysis

10.1 Descriptive analysis

The data collected was cleaned and validated by personal interviews and reviews. On examining the sample, more than 38% of the data collected were mixed use residential and commercial projects, 24% were purely residential projects, 19% were purely commercial projects, 9% were industrial projects, 8% were roadway and highway projects, and 1% were service projects. To preserve the integrity of the data, the service project was not considered in the analysis. Moreover, 67% of the respondents were contractors performing detailed design on projects and 32% were design consultants, while only 1% were government regulators as seen in Figure 1).

Figure 1 Type of projects.

The survey respondents were Civil Engineers, Architects, Project Managers, Construction Managers, Commercial Managers, QA/QC Managers, MEP Managers, Planning Manager, MEP Engineers and Design Managers. The highest percentage of the respondents, more than 47%, was Civil Engineers. The collected data were also analysed based on the level of experience of the respondents; 51% had more than 10 years of experience, 39% had between 5 and 10 years of experience and 10% had less than 5 years of experience.

10.2 Quantitative analysis

Upon analysis, the collected surveys showed that only 4% of the respondents believe that the use of GDPs in the UAE is 0%, 46% believe that it is between 0% and 10%, while 23 % believe that it ranges from 20% to 30%, 22% believe that it is between 10% and 20%, and only 5% believe that it is more than 30%. It was also clear from the data that 45% of the respondents were contractors, 50% were consultants, 59% of respondents working in residential projects, 52% working in commercial projects and 39% working in mixed projects believe that the level of use of GDPs in the UAE ranges from 0% to 10% (Table 1).

Table 1 The level of use of GDPs in UAE projects based on respondents' views.

	Questionnaire responses of projects using GDPs (%)
		By work sector		By project type
Level of use of GDPs (%)	Total	Consultant	Contractor	Residential	Commercial	Mixed (residential and commercial)
0	4	3	4	7	5	0
0–10	46	50	45	59	52	39
10–20	22	16	24	15	24	27
20–30	23	28	21	19	19	27
>30	5	3	5	0	0	7

Table 2 on the other hand reflects a very different reality, it illustrates the range of use of GDPs in projects. It is clear that although the industry professionals believe that green concepts are still stagnant and rarely applied, our data sample is reflecting the rising use of the various GDPs. The highest visible parameter was the use of double-glazed walls and cavity walls in 69% of the projects, and the lowest visible parameter was fly ash concrete in 40% of the projects.

Table 2 Percent use of GDPs in UAE construction projects based on the data sample.

Items	Percentage
Early involving designers and reduce design changes	58.2
Fly ash concrete	40.2
Natural and controlled ventilation	56.6
Light control, efficient fixtures and mechanical system	63.6
Insulation materials and wall panels	67.9
Solar panels	47.5
Decrease water usage and use grey water for irrigation	55.2
Limits environmental impact during construction	54.3
Non-smoking building	60.7
Double-glazed, well-insulated and cavity walls	69.3
Uniform glass distribution	62.5
High-durable, recycled and non-toxic materials	55.2
Reduce materials used on finishes	51.4
Natural materials on finishes	55.0
Fire fighting considerations	58.6

Table 3 shows that there is a little correlation in our data sample between projects' characteristics and the level of use of GDPs in engineering design. There is also a little correlation with company type and/or respondents years of experience.

Table 3 The level of use of GDPs versus respondents' and projects' characteristics.

	Correlation coefficient R
Initial cost	0.05
Actual cost	0.25
Initial duration	0.07
Actual duration	0.15
Years of experience	0.27
Company type	0.08

10.2.1 GDPs use versus projects' initial and actual costs

A linear regression analysis was conducted between the degree of applying GDPs in various projects and the project total initial costs. The independent value X stands for the degree of applying GDPs and the dependent variable Y stands for projects' total initial costs. The linear correlation coefficient R has a very weak value of 0.047 as shown in Table 3. This indicates a very weak relationship between the tested parameters, where the P-value of 0.638≫α value of 0.05. The R² of 0.002 means that only 0.2% of the variance can be predicted by the test. In other words, there is no clear correlation between the level of green GDPs use and projects' initial cost.

The same was observed with actual cost. A linear regression analysis was conducted between the degree of using GDPs in various projects and the project total actual costs. The independent value X stands for the degree of applying GDPs and the dependent variable Y stands for project actual costs. The linear correlation coefficient R has a weak value of 0.25 as shown in Table 3. This indicates a weak relationship between the tested parameters. Since R ² is 0.063, then only 6.3% of the variance can be predicted by the test. There is no clear correlation between the level of GDPs use and projects' actual costs. Hence, it can be inferred from our data that expensive projects do not necessarily consider green parameters more nor apply them more; and green parameters do not necessarily raise project cost or lower it.

10.2.2 GDPs use versus projects' initial and actual duration

A linear regression analysis was conducted between the degree of using GDPs in various projects and the project total initial duration. The independent value X stands for the degree of applying GDPs and the dependent variable Y stands for project initial duration. The linear correlation coefficient R has a very weak value of 0.074 as shown in Table 3. This indicates a very weak relationship between the tested parameters, where the P-value of 0.457≫α value of 0.05, which assures that there is enough evidence that there is no significant relationship between the variables, hence they are independent. An R ² of 0.005 means that only 0.5% of the variance can be predicted by the test. There is no clear correlation between the level of GDPs use and projects' initial duration.

The same was observed with actual durations. A linear regression analysis was conducted between the degree of use of GDPs in various projects and the project total actual duration. The independent value X stands for the degree of applying GDPs and the dependent variable Y stands for project actual duration. The linear correlation coefficient R has a weak value of 0.154 as shown in Table 3. This indicates a weak relationship between the tested parameters, where the P-value of 0.168≫α value of 0.05, which assures that there is enough evidence that there is no significant relationship between the variables, hence they are independent. Since R ² is 0.024, then only 2.4% of the variance can be predicted by the test. There is no clear correlation between the level of GDPs use and projects' actual duration. Hence, longer duration projects do not necessarily consider green parameters more nor apply them more, and green parameters do not necessarily lengthen projects' actual duration or lower it.

10.2.3 GDPs use by respondents' years of experience

A linear regression analysis was conducted between the degree of use of GDPs in various projects and the respondents' years of experience. The independent value X stands for the degree of applying GDPs and the dependent variable Y stands for the respondents' years of experience. The linear correlation coefficient R has a weak value of 0.271 as shown in Table 3. This indicates a weak relationship between the tested parameters, where the P-value of 0.004≫α value of 0.05. Since R ² is 0.073, then only 7.3% of the variance can be predicted by the test. There is no clear correlation between the level of GDPs use and the respondents' years of experience. Hence, more experienced respondents do not necessarily consider green parameters more nor apply them more.

10.2.4 GDPs use by company type

A linear regression analysis was conducted between the degree of use of GDPs in various projects and company types. The independent value X stands for the degree of applying GDPs and the dependent variable Y stands for company types. The linear correlation coefficient R has a very weak value of 0.08 as shown in Table 3. This indicates a weak relationship between the tested parameters, where the P-value of 0. 405≫α value of 0.05; there is enough evidence that there is no significant relationship between the variables, hence they are independent. Since R ² is 0.006, then only 0.6% of the variance can be predicted by the test. There is no clear correlation between the level of GDPs use and the company types. Hence, the use of green parameters is not related to company types.

10.2.5 GDPs use by project type

The average value for using GDPs by project type was calculated using the statistical package of social science program. As illustrated by Table 4, 56.3% of mixed projects used GDPs, whereas residential projects have slightly higher use of GDPs of 57.1%. Mixed projects (commercial and industrial) use GDPs of 60%, while industrial projects, mixed projects (residential, commercial and industrial) and commercial projects show very close usage of GDPs of 66.3%, 65.5% and 64%, respectively, and roadway and highway projects show high usage of GDPs of 70%.

Table 4 The level of use of GDPs by project type.

Green considerations/project type	Residential	Commercial	Mixed use (residential and commercial)	Roadway and highway	Industrial	Residential, commercial and industrial	Commercial and industrial
Early involving designers and reduce design changes	2.5	2.6	3.3	3.4	3.2	4.0	4.0
Fly ash concrete	2.3	1.8	2.1	3.6	2.8	2.7	4.0
Natural and controlled ventilation	2.7	3.4	2.6	3.5	2.5	4.7	5.0
Light control, efficient fixtures and mechanical system	2.7	3.5	3.2	3.6	4.0	4.0	4.0
Insulation materials and wall panels	3.0	3.9	3.3	3.7	4.2	3.7	4.0
Solar panels	3.0	2.9	2.0	3.2	2.8	4.0	1.0
Decrease water usage and use grey water for irrigation	3.0	2.7	2.6	4.0	3.7	3.0	3.0
Limits environmental impact during construction	2.8	3.0	2.5	3.6	3.0	1.3	3.0
Non-smoking building	3.2	4.2	3.1	3.0	3.0	1.0	2.0
Double-glazed, well-insulated and cavity walls	3.3	4.3	3.6	3.4	3.7	4.0	1.0
Uniform glass distribution	3.0	3.8	3.3	3.4	2.8	3.0	2.0
High-durable, recycled and non-toxic materials	2.6	3.1	2.6	3.3	3.3	3.7	4.0
Reduce materials used on finishes	2.8	2.5	2.6	2.5	3.4	4.0	4.0
Natural materials on finishes	2.8	3.0	2.7	3.6	3.0	2.3	2.0
Fire fighting considerations	3.1	3.3	2.7	4.7	4.3	3.7	2.0
Percentage usage of GDPs per project	57.1	64.0	56.3	70.0	66.3	65.5	60.0

10.3 Constraints in using GDPs

As it was previously mentioned in the literature review, five constraints were examined in this study. Three constraints featured at the top of the respondents' concern list. Approximately 48% of respondents indicated that lack of knowledge about green parameters, lack of trust in recycled materials and cost of green materials as the three main constraints hindering the use of GDPs. They were followed by lack of interest from owner/government and lack of availability of green products at 42% and 30%, respectively.

10.4 Reliability analysis

Cronbach's α is a popular method to measure reliability (Christmann and Van Aelst 2006), it is used to check the validity and reliability of the collected data and it estimates the consistency between different parameters to be tested (Leontitsis and Pagge 2007). Cronbach's α is defined as:

(1)

For the data to be acceptable and reliable, Cronbach's α defined in Equation (1) (Leontitsis and Pagge 2007) should have a minimum value of 0.7 (Christmann and Van Aelst 2006), where is the variance of each column, is the variance of the sum of each row and k is a correction parameter. In order to avoid a zero denominator, k and n should be greater than 1. If is relatively large, i.e. α tends to 1, then there is consistency on the quantified answers (Leontitsis and Pagge 2007). In this analysis, all the collected data show acceptable values, since their values range from 0.822 to 0.865, when reliability analysis has been applied to measure their internal consistency.

11. Conclusions

Sustainability is becoming an important aspect in the construction industry as it works towards protecting and saving the environment. The UAE started promoting sustainability practices in many domains, and especially in the construction industry which is the largest industry in the country and the biggest culprit in terms of emissions and long-term environmental repercussions. Migration from conventional to sustainable construction is not an easy process and requires time and effort to be fully integrated into professional practice and be utilised by the construction industry.

This study used 112 surveys from professional engineering respondents of consulting and contracting firms located in different Emirates and analysed the data from different perspectives. The most fundamental finding from this study was the discrepancy between the respondents' view and the level of use of GDPs in the UAE, and the real level of use as indicated by the projects' sampled. It, therefore, can be inferred that the use of GDPs is rising while the level of awareness of the viewer is not catching up with this rise.

The second important finding from the study is that there is no apparent relationship between the degree of GDPs use and the cost or the schedule of the studied projects.

This study also showed that the degree of GDPs use ranged from a minimum of 40% for using fly ash concrete to a maximum of 70% for use of double-glazed walls and cavity walls. The high double-glazing usage could be a result of the severe weather conditions and the high-energy prices in the area.

The study also highlighted five main obstacles that hinder the use of GDPs in the UAE construction projects from the industry's professional point of view. Most respondents believed that the lack of knowledge about green parameters, the lack of trust in recycled materials and the cost of green materials are the main constraints that hinder the use of GDPs in the UAE construction industry.

12. Recommendation

For future research, the following two recommendations are put forward:

• Collect further data and develop more specialised samples by projects' types.

• Study further the reasons behind the use, or lack thereof, of each specific GDP.

Notes

^1. Email: [email protected]