3.1. Case Study: Comparison of Window Frame Solutions
Table 1,
Table 2 and
Table 3 show data sourced from the EPD of the window frame solutions considered here. The three selected EPDs could be directly compared because they follow the same standard and possess the same functional unit and system boundaries (
Table 1). In addition, the publication and expiry dates were consistent with the period of analysis (2023/2024).
Table 4 shows the normalized environmental impacts of different window frame solutions. The normalized environmental impacts were computed by the eco-design tool, and the resulting radar chart can be seen in
Figure 2.
The results show that the different window frame solutions present very distinct impact profiles. Aluminium window frames display the highest global warming potential (GWP), eutrophication (EP), and photochemical ozone formation (POCP), whereas PVC and wood window frames presented the lowest impact in different impact categories. Aluminium window frames presented a total impact area of 2.05 m
2, while PVC and wood window frames display similar impact areas of 1.51 m
2 and 1.56 m
2, respectively. These results demonstrate that selecting aluminum window frames entails higher environmental impacts while, by choosing between PVC and wood window frames, one can obtain lower impacts.
Table 5 shows the resource consumption normalized results as explained above in
Section 2.1.2, as well as the consumption values of non-renewable and renewable materials, both shown in
Figure 3. Aluminium window frames have shown the highest consumption of non-renewable resources (
Figure 3a), in line with the environmental impact analysis. The normalized area was found to be 1.03 m
2, whereas significantly smaller areas were found for PVC and wood frames: 0.33 m
2 and 0.27 m
2, respectively. However, the consumption of renewable resources was naturally superior in wood frames (0.49 m
2), surpassing the resource consumption of both PVC (0.06 m
2) and aluminum frames (0.15 m
2). Despite the rather similar global environmental impacts of PVC and wood window frames, wooden frames are deemed preferable due to the primarily renewable nature of the resources consumed.
The eco-design tool was also embedded with a complementary board featuring the best-performing solution by parameter to provide users with a quick and easy method of evaluating specific parameters during the decision-making process.
Table 6 summarizes the performance of the different window frame solutions assessed by impact category. As can be observed, wood and PVC windows are the best performing solutions in a similar number of impact categories (seven and six, respectively), whereas aluminum window frames only presented the best performance in three impact categories, namely acidification (AP), abiotic depletion potential—non-fossil resources (APDE), and use of secondary material (MS).
The eco-design tool also provides information regarding possible output flows for the different window frame solutions at the end of life.
Table 7 shows that all the solutions examined can be landfilled or recycled at the end of life, but only wooden frames can be used in energy recovery processes. This information is particularly relevant when analyzed in the regional context of a specific construction project for considering the availability of waste management facilities and recycling centers in their vicinity, thus minimizing transport-related environmental impacts and costs at the end of life.
In addition to the environmental assessment, the eco-design tool also provides an economic assessment. The economic profile of different window frame solutions was examined in this case study by sourcing financial information from the CYPE Cost Estimator. The total acquisition cost of each solution was determined by multiplying the number of units by the unit cost (
Table 8). Maintenance frequency and cost per maintenance action were also collected from the CYPE Cost Estimator and, along with the estimated service life retrieved from the EPD, used to estimate the life cycle maintenance cost (EUR) of each frame solution (
Table 9).
A graphic representation of the cost structure is generated by the tool for easy interpretation, as shown in
Figure 4. The results of the case study under analysis show that PVC window frames present the lowest acquisition cost (EUR 51,016.74) and maintenance cost (EUR 13,775.94), representing an average total cost per year of EUR 2159.76 over the 30-year service life. Wooden window frames were found the least economically attractive option, with the highest acquisition (EUR 79,554.87) and maintenance costs (EUR 59,664.18), representing an average annual investment of EUR 4640.64. The economic results contrast with the environmental analysis, where wooden window frames were found to be the best-performing solution in the majority of the environmental indicators analyzed.
Therefore, it is clear that decision-making in this and other analyses can heavily rely on the relative importance that designers will attribute to environmental and economic performance. The new version of the tool includes a final overall assessment covering the environmental and economic dimensions, allowing the user to introduce weighting factors that reflect their relative importance. In this analysis, equal factors were assigned to environmental impacts (25%) and non-renewable resource consumption (25%), with their total equaling the factor attributed to the sum of acquisition and maintenance cost (50%).
The results shown in
Table 10 suggest PVC window frames as the best solution among those considered for the CTA building renovation project due to their low associated costs and environmental performance that is comparable to wood frame windows. It should be noted that such an outcome could be modified if the user assigns considerably different weighting factors to the examined economic or environments aspects.
3.2. Communication with BIM
The communication or articulation of the eco-design tool output with BIM was engineered through a visual programming software application (Dynamo) of the BIM family. A routine was created to import information consisting of interconnections between pre-defined nodes existing in the software, represented by black boxes in
Figure 5. Each node has connections, represented by lines, that allow data to be transferred. The nodes are divided either as “inputs” and “outputs”, and the connection can only be established if the data are comparable. In
Figure 5, five groups of nodes are represented by color, and each group is responsible for different tasks: (i) blue group: communication with the Excel tool; (ii) orange group: material category in BIM; (iii) pink group: communication of the code entered into the BIM; (iv) grey group: the values to be searched in Excel and BIM; and (v) green group: parameters to be filled in the BIM.
To enhance communication, a summary spreadsheet was introduced in the tool to filter the most relevant parameters from the EPDs (
Table 11). After selecting the preferred building solution, the user simply enters the associated code, and the information is automatically imported to BIM. Only two additional items must be indicated by the user prior to data import: the material category in the BIM (orange box) and the spreadsheet location (blue box). The material category must be modified according to the material being evaluated. The same parameters are then created in BIM as “Shared parameters”, generating a “*.txt” file that can be easily related to any type of project or material in BIM (
Figure 6a).
To validate the communication between the eco-design tool and the BIM, PVC window frames were selected, as they demonstrated the best overall performance. In the present case-study, the “Windows” category and the “A11” code were selected, as pre-defined earlier. The routine created in Dynamo was executed and the data imported automatically (
Figure 6b). The routine developed in Dynamo allowed effective communication between the eco-design tool and BIM, enabling environmental data storage in BIM models associated with the case study under analysis. It should be mentioned that the data entered are not intended for calculations but rather for future memory, facilitating access to the information throughout the building’s life cycle. This data storage method can also be useful in design maintenance, rehabilitation, and demolition actions and serve as a reference point given the continuous evolution of standards, materials, and EPDs.