Modified iButtons: A low-cost instrument to measure the albedo of landscape elements

Abstract

Urban infill can lead to increased urban air and surface temperatures. Landscape elements (LEs) which can maintain cooler surface temperatures also reduce night-time re-emission of heat; however, reflected solar radiation (albedo) from these LEs during the day potentially increases heat loads on nearby objects, pedestrians or buildings. Albedo is traditionally measured using two pyranometers, however their expense can be prohibitive for researchers and landscape professionals. A low cost albedometer was developed consisting of a pair of black-and white-painted temperature sensors (Thermochron® iButtons). The albedos of 14 LEs typically found in suburban landscapes in Perth, Western Australia, were measured. Three approaches were tested: The first two used white-painted polystyrene (WPP) as a reference (one taking view factors into account, and one ignoring the albedo of the background material), whilst the third approach used upwards-facing iButtons as a reference, similar to conventional pyranometer methods. The WPP approaches controlled for weather effects, providing a consistent albedo over a longer daytime period than recommended by the standard ASTM-E1918-16. Measured albedos were similar to literature values. This instrument could be used as an alternative to more expensive pyranometers and could assist landscape professionals to design for, and manage, urban heat.