Use of rooftop gardens is becoming more widespread in many areas, however, they are relatively rare in southwest Florida. Rooftop gardens provide many environmental benefits including the regulation of temperatures in buildings, reducing urban heat islands, reducing ecological footprints, increasing the lifespan of roofs, providing faunal habitat in urban environments and lowering energy costs. This study was conducted in Naples, Florida and utilized two types of semi-intensive rooftop gardens, a wetland system which is relatively uncommon and a more commonly used xeric system. We compared the efficacy of a modular wetland rooftop garden system and a xeric rooftop garden system to reduce heat flux into a residential building compared to a traditional (bare) roof with no rooftop garden. Air temperature, rooftop surface temperature, and heat flux were measured for each of the three rooftop systems for a year and data were compared to determine differences due to rooftop garden type and seasonality.
Results/Conclusions
In this study, both the wetland system and the xeric system significantly reduced heat flux into the home by about 81% compared to the bare rooftop. Variability in daily heat flux was also greatly reduced in both systems (p<0.05). This pattern of reduced heat flux and reduced heat flux variability was not significantly different between the warmest and coldest months of the year. Our data indicate both the wetland system and the xeric system reduced the mean surface temperature and minimized exposure to solar radiation compared to the bare roof system. This study provides evidence that rooftop gardens in southwest Florida greatly decrease heat fluxes and heat flux variability, and have the potential to significantly lower energy usage and costs. Based on this study, there are potentially large economic and ecological benefits of expanding the application of rooftop gardens in subtropical climates like southwest Florida.