InfruTreeCity: Understanding Infrared radiative performance of urban trees for better future city

Urban green spaces and trees have substantial beneficial effects on people's health, thermal comfort, pollution and noise reduction, sustainable urban drainage and carbon sequestration. The proposed research focuses on the radiative thermal performance of urban trees in the context of summer thermal comfort and cooling energy consumption in towns and cities that are subject to increasing heat stress under projected climate change.

Trees and green spaces offer significant cooling benefits, thereby helping to create comfortable micro-climates in towns and cities. They are also effective, though to a lesser extent, in ameliorating the urban heat island (UHI) effect. Buildings shaded by trees experience 25-50% reduction of cooling load, often removing the need for energy intensive mechanical cooling.

The effective use of trees and green spaces in urban environments by building designers and urban planners has been impeded by the lack of fundamental insights and quantitative information. It has been found that tree species differ by up to 9C in their canopy surface temperatures. Choosing the right tree species for urban planting schemes is critical for maximizing their cooling effects, but systematic information is currently not available. A further obstacle is the lack of an integrated multidisciplinary approach to the investigation of thermal performance of urban trees, where a tree or a group of trees were treated as a 'black box' , i.e., without consideration of the fundamental physical and (plant) physiological processes, nor the influence of the urban environment on these processes. The results thus have limited applicability to other urban settings. Crucially, the consideration of infrared radiation, which accounts for over 50% of the solar radiation reaching the Earth, is largely missing in previous investigations.

The proposed study aims to overcome these obstacles by investigating urban tree - built environment interactions, focusing on infrared radiative energy exchange, and in the context of prevention of summer overheating in cities. Specific objectives include:
- quantify, for the first time, radiative and other cooling mechanisms of selected common urban trees based on a multidisciplinary approach that integrates building and climate physics with plant physiology, addressing radiative energy exchange, tree physiological processes, urban built forms and materials and the influences of tree forms and species;
- provide guidance to building / landscape designers and urban planners for effective integration of trees in towns and cities including tree species selection and appropriate urban form and building materials;
- develop an online presentation tool to allow rapid access to and effective utilisation of the results and guidance generated from the work.

The main categories of beneficiaries and the way they will benefit from the proposed research are outlined below

Building Environment and Architecture design practices
These consultancies and practices are engaged in the building design in new build and retrofit projects. The knowledge and guidance resulting from the research would allow these companies to better utilise passive cooling benefits of urban trees to minimise or prevent the substantial energy consumption associated with mechanical cooling. This ability would enable the companies to be more successful technically and commercially in the rapidly evolving and expanding eco-building sector.

Urban planning authorities
Urban planning policy makers /local authorities would benefit from the knowledge and guidance to produce new and improved policies that encourage the best practice in tree species selection and mix as well as tree-building integration. These policies will in turn result in future cities that are more energy efficient and facilitate the creation of urban environments that promote healthy outdoor life styles and well-being of residents.

Urban design consultancy
Theprofessional practices specialising in urban design would gain greater expertise and knowledge which will allow them to design more comfortable and healthy outdoor living spaces, and to better integrate green infrastructure with the urban built environment. As a result, the companies will become more successful, technically and economically, in sustainable urban design.

Arboriculture and horticulture companies
These companies will gain greater understanding of the building-tree and climate-tree interactions. As a result, they will be better able to develop the mix and range of tree species that would both thrive in the built environment and provide good cooling benefit to users of buildings and urban spaces. These companies will be more skilled in tree management in our cities too.

Construction material company
Results and guidance from the project could allow these companies to develop and manufacture new building materials that interact with trees in optimal ways resulting in buildings and outdoor urban spaces that are both energy efficient and comfortable to users. The new products would enhance the competitiveness of the companies.