## 3 Materials and Methods
### Sector-Specific Example  
A comparison of a particular approach as C2C Certified with the generic ISO requirements on Type I and Type III labels must unavoidably remain on a generic level. To make the analysis more explicit and concrete, a second step involved the assessment of C2C Certified against concrete examples of Type I and Type III labels within a specific sector. The C2C Certified categories of certified products were reviewed in order to define a relevant industry sector for the example. The ones that dominated with the most certified products were Building Supply & Materials, and Interior Design & Furniture (183 and 170 certificates respectively, as of September 2017) [22]. Consequently, these products were hereafter assigned to one common sector, \"Construction and construction services\" (as classified by the Central Product Classification v2.1 of the United Nations Statistics Division [23]), which was selected as the subject of the example. The selected exemplary sector is also relevant for the other labeling approaches that were observed. In the last few years, there has been a high interest in the assessment and certification of construction-related materials through EPDs [24; 25; 26]. Moreover, green-building certification schemes (GBCS) such as the ones of the German Sustainable Building Council (DGNB) [27], the British Sustainability Assessment Method for Buildings (BRESAM) [28] or the United States (US) Leadership in Energy and Environmental Design (LEED(r) v4 [29], recognize the use of EPDs for the disclosing of the environmental information of construction products. Type I eco-labels do not necessarily find application in GBCS; nevertheless, many programs certify end-consumer products applicable in the \"Construction and construction services\" sector for both B2C or B2B relations and are used in Green Public Procurement (GPP). Further, two exemplary approaches (in that they are typical representatives for Type I and Type III labels) were selected and compared with each other, and with C2C Certified. They were chosen based on literature research and a predefined criteria set that is described in Table 2.  
As a typical Type I eco-label, BA was selected. Established in 1978, the eco-label is the first and oldest eco-label worldwide [30], and the one that has the highest number of certified products and the largest market share [31]. From over 100 product categories covered by BA, 16 are classified under \"Construction\" products [12]. The eco-label was established in Germany, but BA certified products can be found beyond it, in almost all of the European countries, as well as worldwide. BA is a member of the Global Eco-label Network (GEN), an organization that is leading Type I eco-labels worldwide [32]. Founded in 2004, IBU is one of the most prominent Type III program operators nowadays, and was therefore selected as an example in this work. IBU is the biggest Type III operator in Germany, and only operates within the scope of construction products and components [18]. EPDs issued by IBU can be found on products all over Europe and beyond. The program operator is a founding member of the ECO Platform, a cooperation of program operators and LCA practitioners working on the \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline \hline
**Criterion** & **Description** \\ \hline ISO typology & The selected program shall be a typical representative of the respective ISO typology (i.e., Type I or Type III); \\ \hline Operation within the selected product sector & The selected program shall certify products applicable in the selected industry sector; \\ \hline Market recognition & The selected program shall be well established and recognized on the market with proven traditions along the years. \\ \hline Geographic coverage & The selected program shall operate in the same countries where C2C Certified operates. \\ \hline \hline \end{tabular}
\end{table}