Assessment of a fiber-optic distributed-temperature-sensing system to monitor the thermal dynamics of vegetated roof

Abstract:

Vegetated (green) roofs include a growing media and vegetation layer, and offer a range of benefits such as the reduction of: the heat island effect, rooftop runoff peak flows, roof surface temperatures, energy used for cooling or heating buildings, and noise levels inside infrastructures. Vegetated roofs also offer aesthetic benefits and increase the biodiversity of the urban environment, and are increasingly used in sustainable urban development.

Understanding the thermal dynamics of vegetated roofs will make it possible to improve their design and to better assess their impacts on energy efficiency. Here, we evaluate the first vertical high-resolution distributed-temperature-sensing (DTS) system installed in a vegetated roof. This system allows a continuous measurement of the thermal profile within a vegetated roof – going from the interior, upward through the drainage layers and soil substrate of the vegetated roof and ending in the air above the vegetation. Temperatures can be observed as frequently as every 30 s at a spatial resolution on the order of centimeters. This DTS system was installed in the “Laboratory of Vegetal Infrastructure of Buildings” (LIVE – its acronym in Spanish), located in the San Joaquín Campus of the Pontifical Catholic University, Santiago, Chile. The laboratory features 18 experimental modules to investigate different configurations of the vegetated roof layers.

The LIVE was designed with the installation of the optical fibers in mind, and the DTS system allows simultaneous monitoring of three or four modules of the LIVE. In this work, we describe the design of this DTS deployment, the calibration metrics obtained using the software provided by the manufacturers, and other calibration algorithms previously developed. We compare the results obtained using single- and double-ended measurements, highlighting strengths and weaknesses of DTS methods. Finally, we present the observations obtained from this biophysical environment highlighting the features that are harder to observe using more traditional methods to measure temperature.