Review and Critical Analysis of International UHI Studies

A study in Japan tested the effect of mist cooling (spraying mist water onto a surface) to reduce
urban heat flux and save energy. Three types of mist cooling technologies were used on a test
building: rooftop spraying, veranda spraying and spraying to the outdoor unit of a room air
conditioner. The tests yielded positive results on reducing roof surface temperatures (reduced by
16.4°C), room temperatures (reduced by 1.9°C for veranda spraying alone) air conditioning usage
time, consumption (reduced by 36% during the test period) and efficiency in the house. However
in the veranda spraying tests humidity within the house was raised by 1.7 g/kg. The paper did
not comment on the issues relating to water usage which ranged from 66 L/day for spraying the
air conditioner unit to 322 L/day for the veranda spraying. This technology although proven to be
effective would not be suitable for counties with water shortages. The paper also did not
comment on the impact of constant water spraying to the building materials [223].
4.5.5.3 Bamboo
Using bamboo as a construction material is an experimental method of mitigating the urban heat
island according to a recent paper by Kandya in India. The paper measures the thermal and
structural characteristics of bamboo as a construction material. Three cubicles were constructed
and temperatures taken from within. One cubicle was made from half split bamboo, one from a
half split bamboo‐concrete composite and one from bricks and cement but with bamboo beams to
test load bearing capacity. Also solar energy was harvested using half split bamboo panels and
water and air as the heat transfer agents. The results showed that the half split bamboo
constructed cubicle had the lowest average temperature, followed by the half split bamboo‐
concrete, and finally the concrete and brick cubicle. The solar energy collector experiment found
that water provided a better heat transfer agent alongside the use of PU foam insulation. Load
bearing capacity was also measured but not compared to any other materials. The use of bamboo
shows potential but further work needs to be undertaken to measure its creep behavior, non‐
homogeneity, bio degradability, durability etc [227].
4.6 Review for Implementation Issues:
4.6.1 Implementation Issues Principles
In summary, the industrialization and urbanization results in a loss of natural green space, an
expansion of built surfaces both above/below ground and mass concentration of population –
these all help to form the urban heat island and its well documented phenomena. In order to
address the undesirable and costly side effects, referred to in chapter 1.2, a coordinated response
from communities, local/national/international governments is required. Therefore, priorities for
implementing urban heat island mitigations strategies must be set early on. Often the priority is
given to measures that are readily available however; there is an increasing need to address these
issues by adopting larger scale mitigation measures and longer term views. In addressing the
UHI phenomena however the following implementation issues can occur:
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