The built environment contributes around half of total greenhouse gas emissions and with 87% of residential buildings that we will have by 2050 already built, it is vital to adopt sustainable retrofitting practices. The question is: what are the viable solutions? One answer may be green roof retrofitting. The environmental benefits include reduced operational carbon emissions, reduced urban heat island effect, increased bio-diversity, housing temperature attenuation and reduced stormwater run-off. The economic benefits are the reduced maintenance costs and lower running costs. The social gain is the creation of spaces where people have access to green areas. However, the barriers to retrofitting include the perceptions of structural adequacy, the risk of water damage, high installation and maintenance costs, as well as access and security issues. Many Australian and Brazilian residential buildings have metal sheet roofs, a lightweight material with poor thermal performance. During the summer, temperatures in Sydney and Rio de Janeiro reach 45 degrees Celsius, and in both cities, rainfall patterns are changing, with more intense downpours. Furthermore, many residential buildings are leased, and currently, tenants are restricted by the modifications that they can perform to reduce running costs and carbon emissions. This research reports on an experiment on two small-scale metal roofs in Sydney and Rio de Janeiro to assess the thermal performance of portable small-scale modules. The findings are that considerable variation in temperature was found in both countries, indicating that green roof retrofitting could lower the cooling energy demand considerably.

The evaluation of wastewater concentrations in coastal environments has to be accurate for water quality control. The description of the physical process in a comprehensive model is a complex task. Due to the different spatial and temporal scales involved, the use of different numerical models is required: far-field hydrodynamic models; near-field and pollutant transport models. In this paper, a coupled application of these models is described. Capabilities and limitations of modelling techniques applied to wastewater mixing and dispersion from submerged multiport discharges are discussed for environmental impact analysis. The recommended procedure combines a near-field mixing zone model, such as NRFIELD, with the Lagrangian far-field flow and water quality models within SisBaHia® (http://www.sisbahia.coppe.ufrj.br/). The results showed that the model coupling improves the description and analysis of treated wastewater discharges over large scales. This allows a more realistic evaluation of the environmental impact due to domestic sewage discharges in coastal waters.