Embodied Carbon in New Zealand Commercial Construction

Abstract

Decarbonization is gaining priority from the macro to the micro level. However, achieving this is a critical challenge, as industries are still immature. This study explores the practices used to calculate and reduce embodied carbon (EC) in New Zealand (NZ) commercial construction projects. In the Paris Agreement, NZ pledged to reduce its net GHG emissions to 50 percent below the gross 2005 levels by 2030. The built environment generates approximately 40% of global greenhouse gas (GHG) emissions, with 11% being generated by manufacturing materials. EC represents carbon dioxide (CO₂) emitted into the atmosphere throughout the extraction, fabrication, transportation, and assembly of building materials. A survey questionnaire was distributed to stakeholders in commercial construction via the New Zealand Institute of Quantity Surveyors (NZIQS) open forum. Twenty-seven valid responses were analyzed. The survey tested and expanded on the interview findings. Calculating and reducing EC are not mandatory in NZ. Most industry professionals had yet to experience EC calculation in projects. Clients most commonly drive EC reduction in public projects with calculations that are often conducted during the concept or detailed design stages. The challenges in measuring and lowering EC include a lack of client willingness to fund EC calculation, lack of knowledge and experience, lack of previous cost data, lack of EC materials, and lack of fit-for-purpose EC calculation tools. These findings may inform NZ government policy initiatives supporting EC reduction to meet their 2050 target.

1. Background

In the Paris Agreement, New Zealand pledged to reduce its net greenhouse gas (GHG) emissions to 50% below the gross 2005 levels by 2030 [1]. The built environment generates approximately 40% of global GHG emissions, with 11% being generated by manufacturing materials. The New Zealand construction sector is a major contributor to GHG emissions and accounts for 20% of the country’s total carbon emissions [2]. Embodied carbon (EC) represents carbon dioxide emitted into the atmosphere throughout the extraction, fabrication, transportation, and assembly of building materials [3]. Commercial construction contributes 43% toward the total number of all non-residential building projects and 44% of their total value, totaling NZD 11.1 billion in New Zealand according to the National Construction Pipeline Report 2023 [4]. This makes decarbonizing commercial construction a priority. Yet, there has been little gain in reducing carbon used in constructing commercial buildings to date [5].

In addition to the structural stability of commercial buildings, there is a requirement that people can escape the building safely but not withstand catastrophic events and continue use, as per Building Act in New Zealand [6]. However, in a material perspective, structural timber offers better sustainability through lower emissions than steel or concrete. Timber also offers improved seismic resilience [7]. In 2011, Christchurch, New Zealand was struck by a 6.3 magnitude earthquake that killed 185 people and injured several thousand [8]. While other buildings were demolished and rebuilt, timber structures proved far more resilient to earthquakes during the major earthquake in Christchurch, New Zealand in 2011, particularly when combined with seismic bracing systems [9] and base isolation [10]. However, purpose Statement 3.(a).(iv) of the Building Act [6] requires that ‘buildings are designed, constructed, and able to be used in ways that promote sustainable development’. The use of cross-laminated timber (CLT) and laminated veneer lumber (LVL) appears to address this. Their use has become more widespread recently. Otago Polytechnic’s Student Village and Trades Training Center are among the largest CLT buildings by volume in New Zealand, also adopted sustainability measures. However, many commercial buildings are still designed and built using steel and concrete. Finnie et al. [11] interviewed two construction companies, a project manager, and an interior fit-out subcontractor about their practices to reduce EC in New Zealand. It is noteworthy the supply chain does not have the capacity to deliver CLT and LVL, as there is only one supplier dominant in New Zealand, sometimes causing project delays. However, most of the suppliers of prefabricated products in New Zealand are facing critical performance challenges [12,13]. It is noted that a second supplier of CLT and LVL has recently come online. Timber is considerably more sustainable than steel and concrete by emitting less embodied carbon, and it is substantially more earthquake resilient [10]. However, risks in supply chain disruptions are increasing as demand for timber structures for higher-rise buildings grows [14], though these structures’ use was previously confined to low-rise buildings only. Furthermore, most logging in New Zealand forestry is shipped offshore, which has caused the closure of most New Zealand sawmills [15]. Re-importing timber would certainly add to EC. Nevertheless, New Zealand’s moving from steel and concrete to lower-EC structural timber, with its improved seismic resilience, does not appear to be without hurdles.

The calculation of EC is performed to compare designs using steel and concrete, with lower-carbon-emission alternatives, such as comparing steel and concrete designs with CLT and LVL. However, this means that changing would require redesign. Problems with calculations have also been found. Finnie et al. [11] found that a key issue was the lack of a fit-for-purpose calculation tool. Concrete admixtures can reduce carbon in concrete applications, replace unsustainable waterproofing solutions, extend the service life of concrete structures, provide self-healing concrete capabilities, make concrete impermeable, minimize future waterproofing-related maintenance, help to maintain or shorten construction schedules, increase protection against rebar corrosion and carbonation, increase chemical resistance, and provide a non-toxic solution for potable water [16]. However, pricing premiums may represent a barrier to its uptake.

Practices used to calculate and reduce EC are central to reducing emissions used to construct commercial buildings. Maximum gain can be achieved at minimal gain early in project lifecycles. As design develops, the opportunity for changes decreases, and redesign costs more.

2. Research Rationale

This study evaluates the efficacy of practices used to calculate and reduce EC in New Zealand commercial construction projects. The key objectives include evaluating the level of stakeholder experience calculating and lowering EC in projects, the timing of EC calculation, the key drivers for EC reduction, the types of projects in which EC is considered, general challenges and opportunities, EC data availability, and the use of the Greenstar sustainability tool in terms of EC calculation. Previous research reported the perceptions about zero carbon buildings in New Zealand and focused on government and building professionals [17]. To achieve New Zealand’s Paris Agreement target, practices for reducing EC emissions within the construction industry must be put into place [18].

Previous studies have suffered from an inconsistent scope. For example, they have included both EC and operational carbon and both commercial and residential buildings. Nevertheless, they have raised serious concerns about New Zealand’s ability to achieve its Paris Agreement pledge.

Research is needed to study practices used in New Zealand’s commercial construction to calculate and reduce EC, to gauge how well the sector is doing in reducing its emissions, such as moving from steel and concrete to timber structures.

New Zealand ranked lowest in global carbon emissions proportionate to its population [19]. However, none of the mitigation strategies for reducing carbon emissions have been fully adopted in New Zealand’s built environment, including more intensive developments; extending the life of buildings; more lightweight designs; material substitutions; low energy transitioning; and improving production efficiencies [20]. Again, considering EC early in project lifecycles optimizes the opportunity to therefore reduce emissions.

The following sections analyze previous studies on calculating and reducing carbon emissions. The research methodology is then presented. Results from the study are analyzed and discussed in terms of previous studies. Finally, conclusions are drawn and opportunities for further study are presented.

3. Literature Review

3.1. Embodied Carbon (EC)

Previous studies about lowering carbon emissions in New Zealand construction have been inconsistent in their research design. Nevertheless, they have raised serious concerns about New Zealand achieving its Paris Agreement pledge. Symons and Critchley [21] focused on the relationship between seismic resilience and improving material efficiency toward achieving zero-carbon buildings in New Zealand. They found that further research was required to establish design solutions that are both seismically robust and lean in design and recommended a greater focus on methods for lowering carbon building in New Zealand. Bui et al. [22] used semi-structured interviews with government representatives and construction professionals to explore how the construction industry plans to tackle zero-carbon buildings in the future. They found New Zealand’s construction industry to be in the early stages of transitioning to a net-zero-carbon built environment. Leading construction firms plan to reduce carbon by rethinking how buildings are designed and built, with central and local governments playing a leading role in carbon reduction. However, the study included both EC and operational carbon (not solely EC). It also studied the construction sector without distinguishing between residential and commercial construction. More emphasis was on residential buildings to investigate the performance of construction materials for energy efficiency [13]. Moreover, building contractors were not included in the interviews. Figure 1 below [23] demonstrates the distinction between EC and operational carbon. Carbon emissions comprise both operational and EC. EC factors contributing to carbon emissions are shown in Figure 2 as reported by the International Standard Organization [24], production and construction stages from A1 to A5 in grey color.

Bui et al. [25] used interviews to examine the viability of NZ achieving zero-carbon buildings. They raised serious concerns about the NZ construction sector’s ability to deliver zero-carbon buildings. The most significant challenges included financial problems, lack of knowledge, capacity and capability issues, insufficient legislation, and cultural barriers. The most significant challenge is a lack of knowledge in the construction industry regarding carbon. Again, this paper focused on all greenhouse gas emissions without separating EC and operational carbon. Bui et al. [25] reviewed international literature about zero-carbon refurbishments to find suggestions for future research. Three main topics for future research included stakeholder participation in decisions, reliability of quantities for counting carbon, and establishing processes to support carbon reduction decision-making. This research project also did not distinguish between operational and EC, nor commercial and residential buildings.

Cielo et al. [26] found that NZ has been slow in adopting transitioning to net-zero-carbon buildings. The primary reason was an absence of specific legislation dealing with carbon reduction. This study also included both EC and operational carbon and both residential and commercial buildings. However, the role of architecture, engineering, and construction professionals in EC reduction remains crucial [27].

The built environment contributes 40% of GHG emissions, with material manufacturing responsible for 11% [28]. However, energy and materials contribute approximately 20% of New Zealand buildings [2]. This indicates the opportunity to reduce NZ’s emissions by focusing on EC reduction.

Concrete is used extensively in commercial construction and infrastructure, including precast and cast in-situ concrete [29]. There is relatively more carbon used than timber [30,31], which is a renewable resource. Although much of NZ’s forestry logging is exported, processed is timber imported back, adding to the EC used in its transportation.

It has been reported that EC for commercial buildings is relatively higher [32]. However, environmental assessment of the buildings is still not widely in practice for commercial construction [33]. Rydlewski et al. [34] reported the EC in Kg CO₂ of material assumptions for a typical high-rise commercial building steel (2.9), rebar (2.6), concrete (0.25), timber (1.09), masonry (0.24), and composite concrete (0.18). It shows alternatives to construction materials must be highly efficient with the least EC.

3.2. Embodied Carbon Calculation Methods

Methods for measuring EC are topical in previous studies. De Wolf et al. [35], using document analysis, semi-structured interviews, pilot study, and focus groups based in Europe, North America, and Australia, found a lack of dependable targets and inconsistent measuring of EC. However, the study included both residential and commercial buildings but did not distinguish between the two. Jackson and Brander [36] discussed switching from measuring EC to whole-of-life calculation. They found that in one of the four cases considered, EC emissions were reduced initially, only for the end-of-use emissions to be increased. This study focused on the broad infrastructure sector and not commercial construction. Mustafa et al. [37] highlighted the lack of industry maturity in measuring and reducing EC, and the need for effective tools for monitoring EC in construction projects. They found through surveys and interviews that emissions management and monitoring remain underdeveloped in Malaysian construction despite growing awareness and commitment toward lowering carbon emissions. The study recommended greater government support, building capacity, and the ‘development of emissions monitoring techniques and technologies’ which were found to be ‘vital to minimizing emissions’. Again, this study did not distinguish EC from whole-of-life carbon.

Past studies have also found limitations in EC calculation tools. Moncaster and Symons [38] described a tool for calculating EC and the energy impact of buildings for use in early design stage decisions. The study found that further construction, demolition, and energy data were required to improve its accuracy. The study did not distinguish commercial buildings nor provide for use beyond the UK. Victoria and Perera [39] detailed a model for predicting EC that combines multiple estimation techniques. The model provides an allowable accuracy of ±89.35% which is adequate for early stage estimating. Improving accuracy beyond this proved difficult without detailed design documentation. They called for more standardization toward measuring EC. A tool for measuring the EC of cementitious materials in commercial construction has been proposed, based on KgCO₂/Kg [40]. However, cementitious materials is only one contributing factor to EC emissions. Zhang and Wang [41] found that a hybrid method for the assessment of EC would be most beneficial in terms of accuracy and detail. Manufacturing of materials accounted for 80–90% of total emissions and the main structure/foundation work equated to over 60%, respectively. The scope of this study was limited to China. Sato [42] critically analyzed estimations of the world trade’s carbon emissions in 2004. It was found that the range of these estimations was between 4.4 and 6.2 Gt CO₂. The difference between the ranges equated to approximately fifty percent of Europe’s annual carbon emissions. This study struggled due to the uncertainty of individual countries’ EC emissions. The wide distribution margin of the calculations makes consistency during measuring EC essential.

3.3. Embodied Carbon Impact

Past studies have compared EC in terms of construction methods and materials. Monahan and Powell [43] used a lifecycle assessment to calculate the EC of a modern off-site modular timber-framed system compared to two traditional methods of construction. They found that the timber-framed modular system reduced EC by 34%. They also found that concrete was the worst contributor to EC (36%). The study was limited to the UK and focused on residential housing only, not commercial. Purnell and Black [44] found that EC in concrete can be reduced significantly by altering its basic mix. A Hong Kong study compared EC in high-rise buildings. Gan et al. [45] found that in high-rise buildings in Hong Kong, steel had the largest amount of EC despite weighing the least. Steel building EC was 25–30% more than composite and reinforced concrete buildings. However, if 80% of the steel is recycled, the EC is reduced by 60%, making it the most efficient design parameter. This study was restricted to Hong Kong and concentrated entirely on the structural elements of high-rise buildings. However, other steel buildings based on portal framing showed relatively better results [46].

4. Research Methods

A questionnaire survey is suitable to determine the stakeholders’ perceptions related to EC practice [47]. The questionnaire for this study was designed based on the findings of previous interviews [48]. This harnessed the benefit of exploratory interview questions followed by a wider survey sample size to test and expand on the interview findings. As such, the exploratory interview findings became the hypothesis findings to test through the survey. All the findings were consistent, adding overall validity.

The online survey questionnaire was distributed [49], considering participant convenience and time constraints [50], via the New Zealand Institute of Quantity Surveying (NZIQS) open forum. The authors also utilized the snowballing technique [51] to involve respondents from leading NZ construction companies. A total of 41 responses were received from NZIQS, out of which only 22 were selected. However, in addition, five more responses were added through snowballing. Hence, the final number of responses was 27. Data were analyzed using SPSSv29 [52] formulated into tables to present the findings. Mean values were determined challenges and opportunities of EC determined through a five-point Likert scale [53]. All the participants were either directly or indirectly involved in EC estimation, calculation, assessment, or decision-making in the construction companies. This study was approved by the research ethics committee under Category ‘B’. A subsequent case study on mass structural timber is also currently underway as a logical next step in the greater research design (see Section 6).

5. Results and Discussion

This section covers the key findings of this study.

5.1. Demographics

The survey sample included professional quantity surveyors (PQS), 52%, engineers, 11%, main contractors, 15%, and others comprising academics, 7%, estimators, 4%, and sustainability advisers or managers, 11%. A high number of participants from the PQS category indicated that their practices involve EC more compared to other professions. The participants were from major NZ cities or towns. These included Auckland 41%, Christchurch, 22%, Tauranga, 7%, Wellington, 7%, Dunedin, 11%, Hawkes Bay, 4%, Queenstown, 4% and Invercargill 4% for commercial construction activity. All the participants had more than six years of industry experience.

Of the 27 survey responses, only 8 (30%) had any experience calculating EC; see

Table 1. EC (Direct) Experience.

	Response	%
Yes	8	30%
No	19	70%

. These findings support Bui et al. [25], who found that a significant challenge to achieving NZ’s net-zero-carbon target by 2050 was a lack of knowledge in NZ construction. It also highlights that EC calculation is not mandated on many commercial construction projects. A lack of clear definition of EC calculation has been reported among the practitioners [54]. This all suggests an opportunity to improve training in EC reduction.

5.2. Embodied Carbon Consideration during Design Phases

Participants were asked about their understanding of EC across different stages of design. More than one-third of the sample agree that EC assessment should be implemented at concept design, followed by detailed design, and lastly preliminary design; see

Table 2. When EC Is Considered in the Design Phases.

	N	%
At the preliminary design stage	8	30%
At the concept design stage	10	37%
At the detailed design stage	9	33%

. This supports previous arguments that EC should be estimated in the early stage of the project [39]. However, EC consideration has a different influence on design stages [55]. At the preliminary design stages, the available information is based on the design brief and building performance requirements, so a target value of EC could be set based on the reference value. In concept design, EC depends on the existing expertise, and reference knowledge such as databases, and broad quantities per unit depending on the type of building. Here, the standard value for EC is focused on the standard structure and generic material data. Lastly, at detailed design, EC is based on product-specific data from manufacturers. This is more robust without presumptions based on comparable data. More specific information may become available for systems such as the HVAC system, but less so for the main building structure. EC calculation informs design decision making including material choice [56]. Under traditional procurement, contractor involvement is limited, thus, reducing the ability to make informed design decisions until after detailed design. Yet, most responses indicate that EC was considered at concept design when data were therefore less accurate. Procurement pathways that involve main contractors after concept design such as two-stage early contractor involvement (2S-ECI) may help support EC reduction.

The responses also indicate varying approaches for calculating EC perhaps depending on the procurement pathway adopted per project. The scope of EC in concept design normally covers building elements such as flooring, roofing, walls, doors, and windows. There are relatively low responses for EC consideration in the preliminary design phase, using the target value for the carbon footprint. One option might be to focus on the building structure, substructure, frame structure, floors, and walls, and compare with the published work [57]. Building information modeling (BIM) can also help by creating a digital twin of the project.

5.3. Main Drivers for Embodied Carbon

Participants were asked for main drivers for EC reduction on commercial projects; see

Table 3. Main Drivers for Embodied Carbon Reduction.

	N	%
Client sustainability objectives	14	52%
NZ’s commitment to the Paris Accord to lower carbon emissions	7	26%
Consultants driving reduced carbon solutions	3	11%
Other, please specify	3	11%

. More than half mentioned that ‘client sustainability objectives’ represent the main driver of most commercial projects. This contrasts the findings by Bui et al. [22], who found that the NZ government would play the leading role in carbon reduction initiatives. Interestingly, the consultant-driven driver is mentioned by only 11% but the option ‘others’ also has a similar score. There are proactive construction consultants who are considering EC for commercial projects to maintain their reputation and engagement in sustainability and environmental aspects. Participants mentioned that ‘other’ drivers were present 100% of the time. The findings suggest opportunity for clients to take a greater lead in driving EC reduction. Indeed, construction practitioners have been found apathetic in EC reduction [58].

Private clients were more likely to drive sustainability objectives compared with public clients who may face greater budget constraints. However, the New Zealand government has taken initiatives such as the ‘Carbon Neutral Government Programme’ to accelerate emissions reductions within public sector [59]. The ‘Building for climate change’ by MBIE [2] also provides guidance to the greater construction industry. There have also been calls for ‘tax incentive for carbon emission reduction’ schemes to motivate stakeholders [60]. This could help motivate companies toward more sustainable services or products environmentally friendly. There is still a long way to go to achieve a holistic impact.

5.4. Embodied Carbon for Project Type by Funding Source

Participants were asked about what type of projects are most likely to apply EC assessment; see

Table 4. Project Types Considering Embodied Carbon.

	N	%
Government funded projects	14	52%
Privately funded projects	5	19%
Both types of projects	8	29%

. More than half thought that EC is most associated with government-funded projects. Less than one-quarter associated EC with privately funded projects. Almost one-third considered EC applied to both types. The findings are consistent with Bui et al. [22], who found that the government was planning to lead the way in net-zero-carbon building practices in NZ.

The ‘Carbon Neutral Government Programme’ requires EC reduction on all public-funded projects [59], while guidelines and tools are available for building for climate change [2]. However, despite legal requirements, budgets may restrict reduction. The extent that which projects invest in sustainability measures, irrespective of the project funding could be topical in further studies. There is an opportunity to explore innovative procurement strategies such as public-private partnerships [61] to achieve the sustainability goals on commercial construction projects.

5.5. Challenges for Embodied Carbon Calculation and Reduction

Participants were asked to rate the relevance of challenges for EC calculation and reduction faced by practitioners. According to

Table 5. Challenges to Calculating Embodied Carbon.

Challenges	Mean
#1 Clients not willing to spend more for the time and cost involved	4.2
#2 Difficult to accurately compare costs between design options due to an absence of cost data for low EC design alternatives	3.6
#3 Difficult to accurately compare costs between design options due to effectively having to re-measure and price different design options	2.6
#4 No single fit-for-purpose embodied carbon calculator tool	2.6
#5 Consultants reluctant to spend the time calculating embodied carbon	2.1

, the main challenge in EC calculation is client reluctance to spend time or money (M = 4.2). Clients in New Zealand are still transitioning to EC consideration in commercial projects and may not yet be willing to invest extra resources [22]. However, in the commercial construction context, the client plays a vital role in EC initiatives. The lack of comparable cost data is also evidence of this transition (M = 3.6). The application of a probabilistic EC estimation may help address this [62]. One participant indicated that the “Lack of data for EC materials, embodied carbon calculations have a long list of materials excluded due to no data input”. This seems a prime reason for EC calculation inconsistencies [63]. The government providing an EC database of construction materials could help toward decarbonization initiatives in construction. There also appears a lack of expertise in conducting comprehensive EC calculations.

The least concerning challenge was the consultants’ lack of engagement in EC calculations (M = 2.1). Consultants are paid by clients to conduct EC assessments but there are not many consultants capable of performing EC calculations for commercial projects [64]. The remaining two challenges with relatively lower mean scores were re-measuring and pricing of design alternatives for comparison (M = 2.6) and no single fit-for-purpose EC calculator (M = 2.6). There are several tools for EC calculation but their effectiveness is always questionable [37] due to complexity, lack of user-friendliness, and reporting. In New Zealand, many tools are available, e.g., CO₂NSTRUCT by the Building Research Association of NZ (BRANZ) [65] and the Homestar EC calculator by the New Zealand Green Building Council (NZGBC) [66]. This tool is useful for residential construction but is the only available tool for commercial construction. Some private construction companies such as Naylor Love have developed their own “building carbon calculator” [67] reflecting a lack of fit-for-purpose tools. This raises consistency issues across the various tools and bespoke approaches [57].

‘Other’ responses included a ‘lack of awareness of the threat that brings to humanity’, ’lack of experience and information available generally’, ‘lack of Green Professionals’, ‘sometimes it’s just too difficult to justify’, and ‘the main factor is that few manufacturers have the data related to the EC for their materials (especially composite or multiple material component or services) and no one has shipping carbon info, that is to be estimated based on generic calculations derived by estimating where the product has been.’ Interestingly, like other industries, construction relies on data provided by manufacturers about construction materials for environment product declarations (EPD) [68], essential for lifecycle assessment. There is an obvious cross-over reinforcing the lack of clear data for calculating EC. This could be achieved by comparing to published case studies [57].

According to

Table 6. Challenges to Reducing Embodied Carbon.

Challenges	Mean
#1 Lack of buy-in from clients	3.6
#2 Low embodied carbon materials are more expensive	3.5
#3 Difficulties calculating embodied carbon	3.5
#4 Lack of availability of low carbon materials and systems such as timber structure, such as cross-laminated timber (CLT) and laminated veneer lumber (LVL) or low embodied carbon cement	2.4
#5 Lack of buy-in from consultants	2.0
#6 Lack of buy-in from contractors	2.0

, the top challenge for EC reduction is ‘lack of buy-in from clients’ (M = 3.6). Clients may support EC reduction, especially by specifying materials that contribute to a low carbon footprint of buildings [55]. This highlights the need to introduce EC reduction as part of construction contracts, both traditional [69] and relational [70], and drawings or plans and specifications [71].

The following challenges with the same score (M = 3.5) were ‘low EC materials are more expensive’ and ‘difficulties calculating EC’. Unfortunately, low EC construction materials are relatively more expensive in the market as less common traditional construction materials [72]. Despite having EC tools available, practitioners still face problems in actual implementation as these tools require intense training, otherwise results are not representative. Sato [42] also found a wide margin between EC estimations depending on the calculating method. There is a need to establish the job profiles designated to lifecycle assessment services with relevant formal qualifications or certifications. Moreover, when a practitioner from another industry conducts EC calculation, then several technical aspects are possibly unaddressed such as the method of construction.

Bottom-scoring challenges (M = 2.0) are ‘lack of buy-in from consultants’ and ‘lack of buy-in from contractors’. A relatively low score challenge with M = 2.4 is the ‘lack of low EC materials and systems’. NZ supplier companies providing innovative materials and systems face critical performance [53] and capacity [11] challenges that impact the supply to cope with demand. ‘Other’ responses received include ‘more legislation and development of standards’, ‘lack of training, industry-wide standards, and regulations’, ‘there are lots of low-carbon products, but they are expensive and mostly European’. Even Abodo is NZ timber, but shipped all over the world and then brought back here. And, ‘very new perspective on construction, with older folk in the industry it’s tough to get them on board.’ Again, there is obvious cross-over with ‘lack of low EC materials’, and ‘low EC materials being too expensive.’ The ‘other’ challenges perhaps also shed some light on reasons for the lack of buy-in’ from contractors and consultants.

5.6. Embodied Carbon Data Availability

Participants were asked about their awareness of EC data availability and sourcing, crucial for design decision making; see

Table 7. EC Data Availability.

Status	N	%
Not available	4	14%
Somewhat unavailable	11	41%
Somewhat available	11	41%
Readily available	1	4%

. Most answered that EC data were ‘somewhat available’, 41%, equally by ‘somewhat unavailable’, 41%, ‘not available’, 14%, and ‘readily available’, only 4%. Data availability to conduct EC calculation is still a crucial aspect for practitioners in NZ [73]. It has been reported that better data are the answer for EC in buildings [74]. Further studies could explore improving existing EC calculation tools such as BRANZ tools [65]. Acquiring relevant data from reliable EPD databases for construction materials could also be explored. However, there is a plethora of information published in peer-reviewed journal articles, which could potentially be used, accounting for individual country contexts.

5.7. Opportunities to Reduce Embodied Carbon

Participants were asked to rate the listed opportunities for reducing EC in commercial construction; see

Table 8. Opportunities for Reducing Embodied Carbon.

Opportunities	Mean
#1 Improved buy-in from clients	3.8
#2 More supply chain capacity for low embodied carbon materials and systems	3.6
#3 Fit-for-purpose embodied carbon calculator	3.5
#4 More use of timber structure, such as cross-laminated timber (CLT) and laminated veneer lumber (LVL) in place of steel and concrete	2.7
#5 Improved buy-in from contractors	2.3
#6 Improved buy-in from consultants	1.7

. The top three opportunities reported are ‘improved buy-in from clients’ (M = 3.8), ‘more supply chain capacity for low EC material and systems’ (M = 3.6), and ‘fit-for-purpose EC calculator’ (M = 3.5). Greater client engagement in the procurement process could help make EC reduction a step in design decision making. Suppliers also play a vital role in initiatives for sustainability in the construction [75]. Interestingly, the lowest-scoring opportunity is ‘improved buy-in from consultants’ (M = 1.7). It has been reported that consultants’ involvement in the early stage of design development consequently results in more requirements than needed [76]. The use of timber has also been given some consideration by participants. Monahan and Powell [43] also found that opportunity exists for reducing EC by utilizing off-site modular timber framed systems compared to traditional methods. In the ‘other’ category, participants shared ‘improved EC cost information being known to manufacturers and having them be willing to make it available. Most know that it’s not good. E.g., polystyrene cladding products. The focus should be on waste reduction and prefabricated items, there is much more carbon there to be saved’, and ‘more government support.’ Overall, decarbonization is the responsibility of all the stakeholders and all opportunities should be explored to reduce EC in design decision making.

5.8. Green Star Framework Effect on Embodied Carbon Reduction

Participants were asked to rate the Green Star accreditation process for its effectiveness in helping to lower EC on construction projects; see

Table 9. Green Star Process Affects Low Embodied Carbon in Buildings.

Level of Effectiveness	N	% Age
Highly effective	5	19%
Somewhat effective	17	63%
Somewhat ineffective	2	7%
Highly ineffective	3	11%

. Responses were mixed. Over half of the participants ranked it as ‘somewhat effective’, 63%, followed by ‘highly effective’, 19%, ‘highly ineffective’, 11%, and ‘somewhat ineffective’, 7%. Green Star is a voluntary energy efficacy tool for making buildings more green and sustainable [77]. While over three-quarters of participants agree that the tool is very effective for calculating and helpful in the reduction in EC. However, most of the green building rating systems still pertain to operational energy, which created doubt about the certification required for environmental impact during over building lifecycle [78]. The effectiveness could be enhanced by improving data gathering and analysis.

6. Conclusions, Limitations, and Future Research

EC reduction in buildings is challenging and commercial construction is not exceptional as consuming a large proportion of construction materials. EC estimation and minimization strategies need to be examined to set the stage for proper adoption in project, industry, and country contexts [79]. This study investigates the practices related to EC assessment and reduction for commercial projects in the New Zealand context. An online survey questionnaire was used to test and expand on previous interview findings to gauge the perception of commercial project stakeholders about calculating and reducing EC. The calculation and reduction in EC on commercial construction projects appears to still be an emerging practice with 3/4 of the participants yet to experience EC calculation, although many had been involved somehow indirectly in the process.

EC reduction was largely driven by clients and mainly in the public sector. Despite there being numerous EC calculation tools, the industry largely felt that none were fit for purpose. This supports previous interview findings that drew the same conclusion. Some main contractors had subsequently developed their own.

Perhaps more surprising is the timing of the EC calculation. Timber structures can be far more earthquake-resilient than steel and concrete. This is important with New Zealand being located on a seismic fault line. Timber also has far less EC than concrete and steel, which are both major contributors to EC. Yet, it appears that, despite New Zealand being located on an earthquake fault line, buildings are still being designed with steel and concrete. Then, clients pay for EC calculation after the concept and even detailed design stages. By this stage, changing from steel and concrete to structural timber such as CLT and LVL would require investing in substantial redesign. If cost data are available to compare timber structures and steel and concrete, and timber is known to contribute substantially less EC, and be more earthquake resilient, then an obvious question for further research, would be—why design with steel and concrete initially—then maybe to calculate EC when a redesign would be required to change to timber? particularly when it is generally public clients driving EC reduction to meet sustainability objectives, and ultimately toward New Zealand, fulfilling its Paris Agreement pledge. A second question for further research, would be—how many designs are subsequently changed from steel and concrete to timber at that point? Further research could also explore the approximate percentage of commercial projects in NZ being designed and built using structural timber versus steel and concrete and whether the percentage is increasing, decreasing, or remaining the same.

Overall, there appears scope for greater leadership in this space. More available EC data, a single fit-for-purpose EC calculation tool based on end-user preferences to improve consistency, and a greater push for greater use of more sustainable and earthquake-resilient structural timber all appear clear opportunities to help reduce EC in New Zealand’s commercial construction sector. The advent of consultant-client project managers over the past couple of decades appears to have limited impact in setting industry direction or providing lean efficiencies in EC practices.

With shifting from steel and concrete to structural timber providing the greatest reduction in EC, further research could more specifically drill into the barriers and challenges in designing and building with structural timber in commercial construction—for example, where the timber is sourced from, given that most of New Zealand logging is shipped offshore, which has seen the closure of most New Zealand sawmills. Importing back timber would certainly add to its EC. Such information could inform industry-wide education and regulation setting to help the industry toward New Zealand achieve its Paris Agreement pledge and become a more earthquake-resilient nation while fulfilling the Building Act (2004) [6] purpose statement for buildings to be ‘designed, constructed, and able to be used in ways that promote sustainable development’ and hopefully before New Zealand is shaken by its next big seismic event!

A case study is currently being undertaken specifically exploring the use of mass structural timber (such as CLT and LVL) on a large-scale commercial building project in terms of perceived benefits, challenges, and opportunities to improve its use.