In the context of the Urban Heat Island effect, landscape professionals need practical guidance to design for managing surface urban heat. The apparent surface temperatures of samples of 19 hard and soft landscape elements (LEs) found in Perth (Australia) were measured. Thermal images of LE samples on an oval were taken at a 1 m height. The study was conducted in two phases. Phase 1 LE surface temperatures relative to ambient (ΔT) were measured over one day in all four seasons. LEs were ranked by average ΔT, and maintained a similar order across seasons, with summer LEs the hottest. Some LEs were 30–44 °C above ambient in spring and autumn, so these seasons are also significant. Phase 2 repeated the summer test, but used only 14 larger LEs, which were well-coupled to the ground, i.e. more representative of in situ LEs. ΔT values were averaged over daytime and evening periods. Larger LEs were generally hotter than corresponding smaller LEs, with the effect more evident for heavier, denser LEs in the evenings. Future tests should be performed as per phase 2. Averaged measured values of grey pavers were the hottest, whilst ground-cover plants were the coolest. In the evening, grey pavers were also the hottest, whilst decking, soil and turf grass were the coolest. This data will help landscape professionals to assess and compare the thermal performance of different landscape designs, particularly when considering the time of use.

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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.

Abstract. The microclimate of a residential landscape can affect both the energy use in your home and the human thermal comfort in your garden, ultimately affecting the heat in the neighbourhood or precinct. A thermal imaging camera provides information about the temperature of surfaces. By using Stefan-Boltzmann's law and the surface properties, these temperatures can be used to calculate the emission of longwave radiation (radiant exitance) in W m À2 . A thermal camera was used to determine the amount of radiant exitance from a range of residential landscape elements. A standard procedure for capturing these images was developed, taking into account factors which affect the quality of the radiometric data. A quantitative database comparing this radiation has been compiled for different times of day and different seasons. The sky view factor of these elements was chosen such that it was as close to 1 as possible. For a particular landscape design, areas of each landscape element can be measured and the amount of radiation reduced or emitted at different times can be calculated. This data can be used to improve landscape designs to reduce home energy use and human thermal comfort through shading and reduction of surfaces which emit longwave radiation close to the house.

Loss of green space in our suburban environment is contributing to increased urban heat. The material properties of surface treatments or landscape elements (LEs) are a determining factor in the amount, timing, and type of radiation present in the local environment. Landscape designers can use this information to better design for urban heat management, as emitted and reflected radiation (radiosity) from LEs can affect pedestrians via heat stress and glare and affect energy usage in buildings and houses if the landscape sky view factor is low. Low-cost black painted iButton temperature sensors were successfully used as radiometers to concurrently measure the daytime radiosity from 19 LEs samples located on an oval in the warm temperate climate of Perth, (Australia). Normalisation against gloss white paint on polystyrene removed the effect of varying weather conditions. Each LE had the same normalised average radiosity (DRav) between seasons (within ±5%), meaning the relative radiosity of new LEs can be measured on any day. White and lighter coloured LEs had the highest DRav and would have the most detrimental effect on nearby objects. Plants and moist LEs had the least DRav and would be most beneficial for managing local daytime urban heat. Measuring relative radiosity with iButtons presents a new way to examine the effect of LEs on the urban environment.