Changes

*'Cool' membrane, concrete tile, and metal roofs all produced water of similar good quality for non-potable use,

*'Cool' membrane, concrete tile, and metal roofs all produced water of similar good quality for non-potable use,

*The runoff water from asphalt shingle and green roofs contained significantly more dissolved organic carbon (DOC). The DOC can add a  yellow colour to the water. If the water is treated with chlorine, for drinking purposes, DOC can produce toxic compounds<ref>Mendez CB, Klenzendorf JB, Afshar BR, et al. The effect of roofing material on the quality of harvested rainwater. Water Res. 2011;45(5):2049-2059. doi:10.1016/j.watres.2010.12.015.</ref>.

*The runoff water from asphalt shingle and green roofs contained significantly more dissolved organic carbon (DOC). The DOC can add a  yellow colour to the water. If the water is treated with chlorine, for drinking purposes, DOC can produce toxic compounds<ref>Mendez CB, Klenzendorf JB, Afshar BR, et al. The effect of roofing material on the quality of harvested rainwater. Water Res. 2011;45(5):2049-2059. doi:10.1016/j.watres.2010.12.015.</ref>.

Research in Hamilton, ON assessed the water quality of rain collected from three highly reflective 'cool roof' membranes<ref>Breda, N.J.J. 2003. Ground-based measurements of leaf area index: a review of methods, instruments and current controversies. J. Exp. Bot. 54(392): 2403–2417. doi: 10.1093/jxb/erg263.</ref>. Key findings:

Research in Hamilton, ON assessed the water quality of rain collected from three highly reflective 'cool roof' membranes<ref>Cupido, A., B. Baetz, Y. Guo, and A. Robertson. 2012. An evaluation of rainwater runoff quality from selected white roof membranes. doi: 10.2166/wqrjc.2012.011.</ref>. Key findings:

*The water was free from significant contamination with by-products of plastic manufacture and did not show elevated levels of the five metals tested.  

*The water was free from significant contamination with by-products of plastic manufacture and did not show elevated levels of the five metals tested.  

*Increased microbiological contamination was found in runoff from roof areas where ponding occurred.

*Increased microbiological contamination was found in runoff from roof areas where ponding occurred.

Note: Increased microbiological contamination in roof runoff is also associated with warmer weather <ref>Vialle C, Sablayrolles C, Lovera M, Jacob S, Huau MC, Montrejaud-Vignoles M. Monitoring of water quality from roof runoff: Interpretation using multivariate analysis. Water Res. 2011;45(12):3765-3775. doi:10.1016/j.watres.2011.04.029.</ref>.

Note: Increased microbiological contamination in roof runoff is also associated with warmer weather <ref>Vialle C, Sablayrolles C, Lovera M, Jacob S, Huau MC, Montrejaud-Vignoles M. Monitoring of water quality from roof runoff: Interpretation using multivariate analysis. Water Res. 2011;45(12):3765-3775. doi:10.1016/j.watres.2011.04.029.</ref>.