BDA: Integrated Decision Support for the Building Life Cycle
Building Design Advisor (BDA) is a decision-making tool that addresses multiple performance considerations through an entire building life cycle. Over time, BDA has evolved to provide the theoretical basis for developing integrated decision-making tools. Such tools permit architects, engineers, facility managers, and other decision-makers to consider multiple building-performance aspects and their interdependencies. With BDA they can also consider multiple points of view, collaborate toward setting priorities and making decisions, and maintain a dynamic virtual model of a building with all the historical data needed for optimizing the design, operation, and maintenance.
A conceptual model that addresses both data management and process-control requirements for integrated decision-making has been developed for BDA. A single, object-based representation of building components and systems supports the data requirements of multiple simulation and analysis tools. The activation of multiple simulation tools and data exchange is automatically handled by integrating the mechanism for process control within the data schema for the building representation.
Data management and process control
The foundation of the BDA model is an integrated, object-based representation of both data and processes, in the form of a Meta Data Schema. Processes are modeled as objects that are related to parameter objects through input/output relations. Data and processes can be added to this environment without any restructuring of the code, because the code operates on a model with an abstraction of processes as relations among data, rather than on the specific contents of data and processes. Including the "Process Object" as a part of the Meta Data Schema, with input and output links to data objects allows keeping track of interdependencies between the processes and data, and streamlining and automating the activation of processes.
The conceptual model for data management and process control has been implemented and tested as the BDA software, which is now successfully linked to daylighting, lighting, and energy-simulation tools. Most important, the BDA allows use of the output of one simulation program (e.g., daylighting or lighting) as input to another (e.g., energy). Although the underlying concepts involve great complexity, the BDA software is easy to use. Users can analyze and compare the energy and lighting performance for multiple, alternative designs with a few button-clicks.
The BDA has a simple graphical user interface that is based on three main elements: the Schematic Graphic Editor, the Building Browser, and the Decision Desktop.
The Schematic Graphic Editor (Figure 1) allows designers to specify basic building geometric parameters. Through a default value selector, the BDA automatically assigns "smart" default values to all non-geometric parameters required by the simulation and analysis tools. These values are selected from databases of alternative building components and systems, based on building location and building/space type. These default values can be easily reviewed and changed through the Building Browser.
The Building Browser (Figure 2) allows building designers to navigate the multitude of descriptive and performance parameters addressed by the simulation tools linked to the BDA. Through the Browser the user can edit the values of input parameters and select input and output parameters to display in the Decision Desktop.
The Decision Desktop (Figure 3) allows designers to compare multiple designs with respect to multiple parameters, as addressed by the simulation tools linked to the BDA. The Decision Desktop offers a graphic display of data, supporting a large variety of data types, including 2-D and 3-D distributions, images, sound, and video. It is structured as a matrix of cells, where the matrix rows correspond to the parameters selected by the user in the Building Browser and the columns correspond to alternative design solutions that have been defined by the user.
Performance prediction and analyses
The latest version of the BDA software (BDA 3.0) supports performance prediction with respect to various performance considerations, through links to a simplified Daylighting Computation Module, a simplified Electric Lighting Computation Module, and the DOE-2.1E Building Energy Simulation software.
For lighting and daylighting analyses, BDA users can define spaces and place luminaires, windows, overhangs, and vertical fins in the Schematic Graphic Editor. Sensor points may be added to observe lighting levels at particular points. Users can select various performance parameters to be computed, e.g., spatial illuminance from daylight, temporal illuminance from daylight, spatial illuminance from electric lighting, and spatial or temporal glare values from daylighting. BDA also supports analysis of control strategies and sensor placement for maximizing energy savings from lighting control while providing visual comfort.
For energy analyses, BDA supplies DOE2.1E with hourly weather information along with a description of the building and its HVAC equipment and occupancy patterns. The energy-related performance parameters that can be computed include annual and monthly energy-use values broken down by end use and by fuel type. BDA 3.0 also supports DOE2.1E parametric evaluations of energy requirements by end use as a function of window-to-wall ratio, allowing quick and easy optimization of window size.
Current status and future directions
Currently, the BDA software is in its 3.0 release and is available free of charge.
The BDA software is continuously evolving. Current development plans focus on developing links to the Window 5 databases and the Radiance lighting/daylighting simulation and rendering software. Radiance is one of the most accurate lighting simulation tools available today and allows modeling of spaces of arbitrary complexity. The current tools linked to the BDA (Daylight Computational Model and Electric Lighting Computation Module) can only model simple rectilinear spaces.
The most prominent areas for future research and development are:
- streamlining the process control mechanism and allowing user-defined rules for the automation of value assignment, including default values.
- linking the BDA to commercial CAD systems that are already in use by the building industry and will allow greater freedom in specifying geometrically complex spaces.
- addressing collaborative decision-making by allowing
- concurrent use by multiple users, as well as management of argumentative processes to address multiple positions and arguments for and against them.
- developing a distributed computing environment that would allow use of the BDA software over the Internet, which will be especially useful for collaboration among geographically dispersed participants.
For more information, contact:
- Vineeta Pal
- (510) 486-4781; fax (510) 486-4089
- Konstantinos Papamichael
- (510) 486-6854; fax (510) 486-4089
This work was supported by Public Works and Government Services Canada and the Panel on Energy R&D of the Federal Government of Canada, through Enermodal Engineering Ltd. of Kitchener, Ontario, Canada and by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Building Technology, State and Community Programs, Office of Building Research and Standards of the U.S. Department of Energy. Past BDA work has also been supported by Pacific Gas and Electric (PG&E), Southern California Edison (SCE) and California Energy Commission (CEC) through the California for Institute for Energy Efficiency (CIEE).