# Improving Sustainability of Steel Roofs: Life Cycle Assessment of a Case Study Roof
## 3 Results
### Life Cycle Assessment of the Ancillary Items  
The ancillary items considered for the case roof LCA were steel flashings and gutters, timber purlins and fascia boards, polypropylene underlay, and flashing tape. The LCA results for the seven impact categories are presented for the 1 m\({}^{2}\) floor area of the case house, and Figure 7 shows the outcomes of the assessment.  
Based on Figure 7, steel gutters and flashings had the largest effect of all ancillary items for most impact categories considered in the study, except for EP. Most notably, these items comprised more than 150% of the GWP and about 100% of the ODP and ADP elements. The ODP had a positive effect, likely due to the known improvement of the ozone layer from increased carbon dioxide. For the GWP impact category, the overall result was significantly reduced due to the use of timber for the purlins and fascia boards. Timber had negative GWP values when it was assumed to be sourced from sustainably managed forests.  
The impact of the EOL landfill had to be considered for the overall effect of using timber purlin as it accounted for approximately 95% of the items disposed in the landfill as applied in the study. Although the GWP impact was still negative, the purlins and their disposal had the largest EP among the ancillary items and a significant POCP. The transportation of materials to the site or landfill at EOL caused between 15-21% of the GWP, AP, and EP but had a positive effect on the POCP. The environmental impacts from  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Impact Category**} & \multirow{2}{*}{**Unit**} & \multicolumn{3}{c}{**Life Cycle Modules**} & \multirow{2}{*}{**Total**} \\ \cline{2-2} \cline{4-6}  & & **A1-A3, D** & & **A2 1** & & **C3-C4 2** \\ \hline Global Warming & kg CO\({}_{2}\)-eq & 9.97 & \(5.17\times 10^{-1}\) & \(7.00\times 10^{-2}\) & \(1.06\times 10^{1}\) \\ Potential & kg CFC11-eq & \(-2.50\times 10^{-8}\) & Negligible & \(7.93\times 10^{-15}\) & \(-2.5\times 10^{-8}\) \\ \hline Acidification & kg SO\({}_{2}\)-eq & \(3.32\times 10^{-2}\) & \(1.22\times 10^{-2}\) & \(2.00\times 10^{-4}\) & \(4.60\times 10^{-2}\) \\ \hline Eutrophication & kg PO\({}_{4}\)-eq & \(2.85\times 10^{-3}\) & \(2.40\times 10^{-3}\) & \(2.82\times 10^{-5}\) & \(5.28\times 10^{-3}\) \\ \hline Photochemical & kg C\({}_{2}\)H\({}_{4}\)-eq & \(4.93\times 10^{-3}\) & \(-1.26\times 10^{-3}\) & \(1.73\times 10^{-5}\) & \(3.69\times 10^{-3}\) \\ Ozone Creation & kg SB-eq & \(8.00\times 10^{-5}\) & Negligible & \(2.68\times 10^{-8}\) & \(8.00\times 10^{-5}\) \\ \hline \multicolumn{2}{c}{Abiotic} & \multirow{2}{*}{MJ} & \multirow{2}{*}{1.09 \(\times\) 10\({}^{2}\)} & \multirow{2}{*}{Negligible} & \multirow{2}{*}{9.70 \(\times\) 10\({}^{-1}\)} & \multirow{2}{*}{1.10 \(\times\) 10\({}^{2}\)} \\ Depletion—Fossil & & & & & \\ \hline \hline \end{tabular}  
* Transport from Busan to NZ factory. These A2 transport emissions are in addition to the A2 transport contained within the Worldsteel data in the A1–A4, D emissions. 2 Waste processing (C3) and disposal (C4) processes data adapted from EPD published by Colorsteel for Maxx 0.55 mm steel roofing product.  
\end{table}
Table 3: Overall life cycle impact for the seven impact categories for 1 m\({}^{2}\) of case steel roofing.  
transport were directly proportional to the mass and timber from purlins and fascia boards, which accounted for 70% of these transport-related emissions. For timber, the positive sequestered carbon effects were reduced by 45% when transportation and landfill disposal were also considered.