Urban Energy + Thermal Comfort Design Software Development

Urban Weather Generator Workflow

In a recent survey of energy modelers and architects by Samuelson et al. (2012) ^[1], 23 out of 62 participants [37%] answered that the results of energy simulations “rarely” or “occasionally” had impact on design decisions even in AEC [Architecture, Engineering, and Construction] firms which employ in-house energy modelers. This is a direct result of this delayed use of tools within the design process, and therefore it is crucial that we create a tool within the designers’ current design platform to encourage early integrations of energy and thermal comfort concepts with massing design.

Using UWG, the urban designer can iteratively improve their design for thermal comfort and energy consumption within Rhino.

Making The Research Software Usable for Designers

UWG's engine was developed by the predecessor of this project Bueno [2012] ^[2] and is a building energy model based on Town Energy Balance scheme and energy balances applied to control volumes in the urban canopy and boundary layers. It estimates the hourly urban canopy air temperature and humidity using weather data from a rural weather station.

As this research model requires over 50 inputs, sensitivity analyses were conducted for Boston, MA and Singapore, Singapore to reduce the number of required input parameters. The commonality of results allowed us to decrease the number of inputs by over 46% [below left] and thus increase the speed at which the users can evaluate their designs for thermal comfort and energy usage. The key parameters [below right] are site coverage ratio, façade-to-site ratio, and sensible anthropogenic heat, which are designed during the master planning phase of the urban design process. All of the parameters that have small influence on the UHI are moved to the advanced setting.

In the Rhino version, urban geometry parameters [above right] is automatically calculated from the 3D model, leaving building construction materials, land usage, and non-building sensible heat [i.e. traffic] as required inputs.

GUI User Experience

As this is the first design tool for UHI modeling, the initial interface design is based on the existing and widely used interfaces [i.e. DesignBuilder and umi] so that users can easily familiarize themselves with the environment. The program was tested with seven urban design practitioners and novice users who have not used design simulation tools before as well as five energy consultants who have previously used other environmental performance simulation tools.

The user interface is organized by the users’ goals. The output from each functions or already existing files can be used to run another successive feature of the GUI.

Tool Validation: Kendall Square Development

The workflow is demonstrated through a case study of the new 130 thousand square meter development on the MIT East Campus in Cambridge, MA, USA.

We propose the below alternative [Alt 6] to MIT's plan for a more thermally comfortable and energy-efficient development.

An IPCC-based climate change prediction is considered along with UHI to evaluate the outdoor comfort. The average contribution of UHI is about a tenth of the climate change. The urban cooling in 2020 is most likely from the increase in open space [i.e. the urban canyon is wider and less heat is trapped]. In other words, the climate change is mitigated via a local change in the site morphology.