# Improving Sustainability of Steel Roofs: Life Cycle Assessment of a Case Study Roof
## 4 Discussion and Recommendations  
### Importance of Source of Steel Coil for Roofing in LCA  
Simple software tools such as LCAQuick and OneClick LCA are becoming commonplace in the industry and use generic environmental impact data for simplicity. However, LCAQuick only allowed data from typical NZ products to be used for steel roofing, while OneClick LCA typically used generic data with some additional options for the input of recycled steel content, such as EPD, but was not widely available for New Zealand products. Therefore, the GaBi Ts were used in the study using the process LCA method to quantify the environmental impacts of the long run roofing profile with five ribs from the local producer attached to the house roof. The study found significant variations in the environmental effects of similar products due to the source of the materials, location, transportation, and manufacturing processes. These factors were discovered to have a significant impact on the assessment's outcomes. When completing an LCA, there is a potential for the result to be misleading if the generic data does not match the product used. It could become even more important as state-of-the-art sustainable steel technologies, such as hydrogen-based iron reduction, are adopted globally and the difference in environmental effects from different producers is exacerbated. Steel roofing has a significant effect on the overall environmental impact. Developers with resources and know-how would likely engage in detailed LCA to benefit from the improved performance of imported steel roofing. However, it could be fairer to provide all developers with the opportunity to achieve their sustainability targets by considering steel coil manufacturers, even in a simplified LCA. Given the small number of dominant market  
Figure 8: Outputs from GaBi showing the environmental impacts of steel roofing including ancillary items for 1 m\({}^{2}\) of the case study house: (**a**) GWP; (**b**) AP; (**c**) EP; (**d**) ODP; (**e**) ADP elements; (**f**) ADP fossil; (**g**) POCP. players in the steel coil industry that is used for roofing, this could be easily achieved by providing guidance on how steel coil from each manufacturer is assessed. According to the findings, steel coil production was the most significant process that produced environmental impacts in the majority of indicators. In terms of the GWP values, this production process emitted 14.9 kg CO\({}_{2}\)eq/m\({}^{2}\). In order to check the validity of the result, the results from previous studies were considered. The range of GWP values of the production processes of the steel roofing products in New Zealand by Thinkstep ANZ ranged between 14.6 and 18.1 kg CO\({}_{2}\)eq/m\({}^{2}\) for the 0.55 mm base metal thickness (BMT) [74]. A study by [PERSON] et al. [75] found that the production process of the steel roofing sheets (including raw material acquisition and manufacturing process) was responsible for 98% of the total carbon emissions during the product's life cycle. In addition, in investigating each process during the production of the steel roofing products, the effects of roll forming were negligible due to its low environmental impacts compared to the other processes studied. Therefore, the outcome of the assessment of steel roofing in the study can be used for other roof profiles created by local producers using the 0.55 mm coil. However, the data would need to be adjusted for the weight of the coil used per square metre of roof. Future research should be completed on the 0.44 mm BMT steel coil, which is also used by the same local producer. It would also be prudent to investigate the life cycle impacts of regular imported steel coils suppliers instead of global average data. In addition, in an ideal system, users would purchase steel with different environmental gradings at different price points to achieve their targets and project needs. Ultimately, it could result in an improved business case for steel mills by improving the environmental performance of their processes.