Abstract
Rooftop gardens have been used in many cultures throughout history and while they are currently popular in many areas of the world, they are relatively new in the United States and rare in southwest Florida. This study was conducted in Naples, Florida and utilizes two types of semi-intensive rooftop gardens, a wetland garden system which is relatively rare and a xeric garden system which is more widely used. Rooftop gardens can provide many environmental benefits and some of these benefits include regulating temperatures in buildings, reducing urban heat islands, reducing ecological footprints, increasing lifespans of roofs, and lowering energy costs. This study compares the abilities of a modular wetland rooftop garden system, a xeric rooftop garden system, and a traditional (bare) roof with no rooftop garden to reduce the heat flux into a residential building. Air temperature, rooftop surface temperature, and heat flux were measured for each of the three rooftop systems and then compared. The results indicate the wetland system and the xeric system were able to reduce heat flux into the home by about 81% when compared to the bare roof. The variations in the daily heat flux are also greatly reduced in the wetland system and the xeric system when compared to the bare roof. The data from this study also indicate that both the wetland system and the xeric system were able to greatly reduce the mean surface temperature and minimize the exposure to solar radiation when compared to the bare roof system. The reduction seen in the surface temperature and solar radiation in the wetland and xeric systems are possible explanations for the reduction seen in the heat fluxes of both systems. This study provides evidence that rooftop gardens have the potential to greatly decrease heat fluxes and the heat flux variability which would lead to lower energy usage and costs. In a subtropical climate like southwest Florida, there are potentially large benefits if rooftop garden installations are expanded.
