An environmental, economical and feasibility study of green roofs and rainwater harvesting systems in Ireland.

Abstract

This minor thesis is a comparative study of the environmental and economical impact of normal roofs versus green roofs, as well as an examination of the feasibility of integrating a rainwater harvesting system with a green roof. Water is becoming more and more valuable as a resource in today’s environment and society. Domestic water charges are also being re-introduced in Ireland in order to fund the high cost of treating water to drinking quality, as well as the cost of maintaining and upgrading sewerage and stormwater drainage systems around the country. Green roofs have been installed in a number of international cities in order to harness the environmental and cost benefits they bring to urbanised areas. However, they are a relatively new sustainable build technique in Ireland. Rainwater harvesting systems are also quite uncommon in commercial and domestic buildings in Ireland. There are no government incentives for either technology in this country. This study aims to outline the description, benefits, limitations and potential applications of green roofs, as well as rainwater harvesting systems, in Ireland. An extensive literature review was carried out in order to acquire as objective a point of view on the topic as possible. The study begins with describing the problem of climate change; action that is being taken at various levels to combat climate change; sustainable building techniques - namely, green roofs and rainwater harvesting systems; different methodologies that are used to calculate the environmental and financial impacts of green roofs and rainwater harvesting systems — Life Cycle Assessment and Whole Life Costing. A comparative LCA/LCCA analysis was then carried out in order to determine the environmental and financial impact of each system in the study. This study was carried out for the benefit of an Irish company, Bauder Ltd., who expressed an interest in the results of the LCA/LCCA. The author worked closely with the staff at Bauder, who provided all the normal roof and green roof technical information and images in this thesis without hesitation. In order to carry out an accurate study, a hypothetical building on which each roof and rainwater harvesting system would be installed, was developed. The author used the Eco Indicator method to calculate, in millipoints (mPt), the environmental impact of each system. An NPV (Net Present Value) formula was used to calculate the cost of each system over the course of 70 years. The results showed that the green roof had a lower environmental impact than the normal roof. However, the cost of the green roof was higher than the cost of manufacturing and maintaining a normal roof over the course of 70 years — the average lifespan of a building. Recommendations were then made as to which system would be most suitable for both a domestic and commercial building in Ireland.