Leadership in Energy and Environmental Design (LEED) is one of the most well-known environmental rating systems; developed in the United States, it has been widely adopted around the world. The adoption of LEED in foreign countries is due to the flexibility of this certification system. LEED has five main categories—sustainable sites (SS), water efficiency (WE), energy and atmosphere (EA), materials and resources (MR), and indoor environmental quality (EQ)—and two additional categories—innovation in design (ID) and regional priority (RP). Each category has several prerequisites and credits. Each credit can have a certain number of points. By adding up all these points, LEED projects can achieve one out of four certifications: certified (scores 40–49), silver (scores 50–59), gold (scores 60–79), or platinum (scores 80+) (Section 1.2 provides a summary of all prerequisites and credits for LEED-NC v3).

With such a variety of LEED categories and credits, each country can choose the certification strategy that best reflects its climate, demographics, building technologies, and natural resource availability ^[1][2][1,2]. Thus, it becomes clear that different countries may prefer different LEED certification strategies. For example, in the USA, the highest-priority category was EA, while, in China, the priority categories were SS and WE [3]. A comparison between Northern Europe and Southern Europe showed that Northern Europe outperformed Southern Europe in the EAc1 (optimize energy performance) credit [4]. In Vietnam, SS, WE, and EQ scored highly compared to the other categories [5]. In Turkey, SS and WE were higher priorities than the remaining categories [6]. A comparison of eight U.S. states showed different LEED certification strategies: six states used an EA-high emphasized strategy, while two states used a non-EA-moderate emphasized strategy [7].

Studying LEED-certified projects using inference statistics is a new direction in the science of green construction. In 2017 [8], one of the first studies using inferential statistics aggregated LEED data from six countries: the United States, China, Turkey, Brazil, Chile, and Germany and determined four levels of certification: certified, silver, gold, and platinum. With this research design, the strategies for LEED-certified projects in a single country could not be explored. In a 2018 study [9] on the performance of silver-to-gold cross-certification in LEED projects, the design framework included a comparison of two types of design: (i) four U.S. states were analyzed separately, and (ii) four U.S. states were analyzed as one group. The two different study designs led to different results. The first study design showed the unique properties for each U.S. state. In the second study design, the pooled data showed a result acceptable for only one of the four U.S. states. Therefore, the study of LEED-certified projects in a separate country is an urgent problem. In this context, these studies should use the same study design and the same inference statistics, so that different studies can be compared. These different LEED certification strategies that were revealed for different countries/states can lead to different environmental impacts. However, this problem is understandable, because it is a consequence of the previously noted features of each of the countries.

However, the problem is that, as has recently been shown ^[10][11][12][10,11,12], different LEED certification strategies in office buildings have been used at the state (California, USA), city (Shanghai, China), and borough (Manhattan, New York City) levels. Therefore, these different LEED certification strategies applied to the same country/state/city result in different life cycle assessments (LCA) of their environmental damage (Section 1.3 presents a summary of the LCA methodology). Therefore, the LCA of LEED-certified projects is a timely issue.

For example, California cities have used two different LEED certification strategies: low location and transportation (LT) and high EA or high LT and low EA [10]. In Shanghai, LEED certification strategies have used either high EA and low EQ achievements or low EA and high EQ achievements [11]. In Manhattan, two different LEED certification strategies have been used: either high EA and low MR achievements or low EA and high MR achievements [12]. In all three cases, different LEED certification strategies led to a different LCA of their environmental damage ^[10][11][12][10,11,12]. Thus, the use of different LEED certification strategies for office buildings should be explored in other countries.

In this regard, Germany is a country of particular interest, as it has the highest number of LEED New Construction (LEED-NC)-certified office space projects among the other European countries, such as Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Greece, Hungary, Ireland, Italy, the Netherlands, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland, and the United Kingdom [13].

It should be noted that, in Germany, the Deutsche Gesellschaft für Nachhaltiges Bauen (DGNB), developed by the German Sustainable Building Council, is the most representative national green rating system [14]. Similar to LEED, DGNB is based on indicators of different environmental area protections, such as responsible procurement and waste management. Unlike LEED, DGNB focuses more on protecting the economic sphere by introducing life cycle cost indicators and social protection, such as access for all and user security [15].

This country is a signatory to the Paris Agreement on climate change and has set itself the goal of becoming carbon-neutral by 2050 [16]. Germany also signed the Montreal Protocol to decrease its ozone depletion potential (ODP) [17]. The country has a mandatory AgBB scheme that requires the measurement of volatile organic compounds (VOCs) contained in building materials [18]. German citizens have a high level of willingness to invest in renewable energy [19]. Germany’s current fuels for energy production come from about 50% renewable sources, such as wind, photovoltaic (PV), and bioenergy, and about 50% from fossil fuels, such as coal, natural gas, and oil [20]. This country is making substantial efforts toward the development of hydrogen vehicles and is committed to replacing its electricity system with fully renewable energy sources [21].

Therefore, it can be assumed that operational energy (OE) savings for the heating, cooling, and lighting needs of a building; the use of advanced refrigeration equipment to minimize ODP-related emissions such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs); the replacement of fossil fuels with renewable; and the use of low-emission and fuel-efficient vehicles should be a priority for LEED certification in Germany. However, as mentioned earlier, there are countries where LEED certification has been achieved at the same certification level using different certification strategies ^[10][11][12][10,11,12].

2. LEED Prerequisites and Credits

gives a summary of all prerequisites and credits for LEED-NC v3.

3. LCA Methodology

1.3. LCA Methodology

LCA is a “cradle-to-the-grave” method (the whole life cycle from raw material acquisition to final disposal is taken into account) that focuses on the products, as well as services, to evaluate all (theoretical) environmental impacts [22]. The overall structure of the LCA study is prepared by defining the purpose and scope by selecting a functional unit (FU) and a system boundary. Within the system boundary, inputs (raw materials and energy) and outputs (gases and wastes) are then collected for the FU in the life cycle inventory (LCI) phase. The contribution of the LCI to different environmental impact categories, such as climate change and acidification, is evaluated in the life cycle impact assessment (LCIA) phase. Converting LCI into LCIA becomes possible due to the applied scientific models [22]. A “cradle-to-the-grave” LCA of concrete elements includes (i) the design stage, (ii) the production/execution stage, (iii) the usage stage (operational energy and concrete element maintenance), and (iv) the end-of-life (demolition and recycling) stage [23]. However, depending on the application of the LCA, it is possible to conduct a partial LCA. For example, in order to compare LCAs of building material alternatives, only the production stage needs to be evaluated; to compare the LCAs of fuel sources for operational energy generation, only the usage phase must be assessed; and to compare the LCAs of building materials’ recycling options, only the end-of-life stage needs to be considered.