IBEC 建築省エネ機構(一般財団法人 建築環境・省エネルギー機構)


BEST (Building Energy Simulation Tool) Program

Due to issues regarding natural resources and environments as well as increasing demand for reducing CO2 emissions, a comprehensive energy modeling tool that is capable to analyze not only the performance of building envelope and HVAC system, but also lighting, water use and additional equipment loads such as elevators, has become more necessary.

The Japanese Government aims to reduce the annual CO2 emission 15% by 2020; 80% by 2050. In order to meet the large reduction in CO2 emission, an effective design tool for calculating CO2 emissions by building and for analyzing overall building energy consumption, especially for commercial buildings that emit one-third of total CO2 emission, is required. BEST (Building Energy Simulation Tool) is an effective computer simulation program for building energy research and evaluation.


BEST's Features and Effective Uses

BEST is a simulation tool that calculates and visualizes annual energy consumption of a building. The simulation includes HVAC and plumbing equipments, telecommunications and all other building loads.

It generates overall building energy consumption (annual CO2 emission) at every phase (design, construction, operation and retrofitting phase), and identifies the optimal solution (minimum) for the integrated building envelope and HVAC system.

BEST consists of three methods; Simplified, Basic and Professional method. The choice of method is determined by the modeling purpose at each phase such as design (schematic, detailed, construction), operation or retrofitting phase. The numbers of accessible and changeable parameters in each method are varied. Simplified method has the least parameters while Professional method has the most.

Simplified Method: The cooling and heating peak loads and annual building energy consumption are generated by simply providing building size, type and major HVAC system types. Since the majority options are defaulted or determined by the minimum energy codes, the input parameters are minimized. Consequently, the modeling result indicates a base-case model for proposed design comparisons.

Basic Method: In addition to the information provided in Simplified Method, the more detailed inputs are possible. This method is suitable to study and to optimize the building envelope (including openings and insulations) and HVAC system.
Since April 2010, Ministry of Land, Infrastructure and Transportation (MLIT), Housing Bureau has been requited to submit building energy conservation measures of all newly constructing buildings with the total building area of 300 m2 or more during the construction. With supports from Housing Bureau, both Simplified and Basic methods have been developed to generate the compliance form for the building energy conservation measures. This not only reduces time and efforts on creating the compliance form, but also minimizes administrative efforts by the Bureau.

Professional Method: This method allows accessing to change all available parameters. It is capable of evaluating overall building energy use and identifying the fairly detailed optimal design solutions which include the detailed envelope selections (dimensions and constructions of glazing; singe and double glass, dimensions of Mullion eaves, insulation thickness, etc.) and the building system optimizations (HVAC system and the control, zoning, air flow, daylighting system and the lighting control, etc.)

For operational and retrofitting phases, BEST identifies the most appropriate solution to improve building performance based on detailed HVAC system data, actual building operational schedule and measured energy consumptions. The optimal solution is selected amongst various energy conservation possibilities by evaluating performances that can be seen in hard and soft.


BEST Application and Effectiveness

BEST is an effective tool to evaluate CO2 emission of building and to identify plans to reduce the CO2 emission. It enables us to assess Life Cycle Management (LCM) for any kind of building. The LCM confirms effects of utilizing energy efficient equipments, developing new equipments, changing operational schedules (change operation hours, daylight saving operation and Cool Biz etc.), increasing supply-side energy efficiency and altering the type of energy source. Beyond a design tool for architects and building system designers, BEST is used as a tool to deliver building information as well as to assess building operation and life cycle.

  • 1. Urban planning (BEST- Simplified Method)
    • Determine total energy use, by entering the size and type of building as well as its level of energy conservation measures.
    • Calculate overall energy use in the extensive development area (for comprehensive area regulations).
    • Evaluate if CO2 emissions do not exceed the regulation.
    • Generate documents for regional plan permit.
  • 2. Schematic design phase (BEST-Simplified Method and/or Basic Method)
    • Identify suitable building orientation, envelope, systems and exterior outline of project to meet the building quality and performance requirements.
    • Determine energy saving plans at schematic design phase (energy consumption / m², Year, CO2 emissions / m² per year).
  • 3. Detailed/construction design phase (BEST-Professional Method).
    • Evaluate optimal design by entering more detailed data for sensitivity analysis of all energy saving techniques.
    • Select equipment capacities along with peak load calculation program
    • Assist optimal equipment selections.
    • Manage input data as part of construction documents
  • 4. Construction Phase (BEST-Professional Method).
    • Review suitability of design changes on site, and modify changed data.
    • Compare total energy consumptions of the building with equipments specified in design documents and with actually installed equipments.
    • Introduce the building system as a part of tool for BMS, BEMS.
    • Update/deliver changes and modified data as a part of the completed construction records.
  • 5. Operational phase (BEST-Professional Method)
    • Improve building operations based on comparison between the estimated energy consumption at design phase and the actual operational data.
    • Manage energy end use, and detect/confirm degradation of equipments.
    • Estimate total building energy consumption after retrofitting and replacing with energy efficient equipments.
    • Use as a commissioning tool after retrofitting.
    • Continuous data management.


Development Background and History of BEST

There are a number of challenges on HASP/ACLD (dynamic heat load calculation program) and HASP / ACSS (HVAC system simulation program) that were developed 30 years ago as annual energy simulation tools. As a result of seeking the solutions for those challenges with HASP/ ACLD/ACSS, as well as environmental issues, a more effective simulation tool, BEST, was started developing in 2005.

Followings are the main themes for the BEST development;

1.Due to issues associated with natural resources and environmental considerations, conservation of energy and reduction of CO2 emissions became more demanded. The effective comprehensive building energy simulation tool shall be able to analyze energy consumption not only for HVAC system, but also for lighting, water use, and other building equipment loads such as elevators.
2.The tool shall be user-friendly. All disciplines such as researchers, mechanical engineers, construction administrators, maintenance administrators, architects, project managers, owners etc, can use throughout the entire life-time of the building.
3.The tool shall be an academically advanced program, and lead the world.
4.The cost associated with expanding the tool shall remain low.
5.Establish the capitals for maintaining and upgrading the program.
6.Establish training programs and an educational environment for young programmers who contribute improving the tool.
7.Clarify the copyright, and enable a third party to develop the software continuously.

In March 2005, after a number of discussions let by Association of Building Services Engineers (JABMEE), the proposal to develop a new-generation of HASP/ACLD/ACSS program that meets the social needs was established. All of people including professors, researchers and developers who were involved in developing HASP related programs, as well as potential talented young developers and related organizations, would join this development process.

In June 2005, Institute of Building Environment and Energy Conservation (IBEC) took over the role of JABMEE. In order to minimize environmental impacts, the development for the tool to simulate comprehensive building energy consumption started in October 2005 with supports from Ministry of Land, Infrastructure and Transportation, Housing Bureau. The final guideline was published in March 2006. Based on the guideline, Planning and Development Board for the comprehensive building energy consumption simulation tool that can be used from design to operational phase was established and "The BEST program: BEST - Professional Method 0803" was published in March 2008.


BEST Consortium and Functionality

In May 2008, "BEST Consortium" which aims to the continuous development, operation and support, was established within IBEC. The organization consists of Planning and Development Board (chaired by Shuzo Murakami) Steering and Dissemination Board (Chairman Kazuaki Bougaki).

Under the control of the Planning and Development Board, the BEST-Professional Method Development Committee (chaired by Hisaya Ishino) who works on the enhancement and advancement of the Professional Method, the BEST-Support Committee who deals with users' questions and errors related to the operation of BEST, and the BEST-Administrative Tool Development Committee (Chair Sakamoto Yuzou) who develops the tools to help creating a plan and compliance form for energy conservation laws, have been established and run.

The Steering and Dissemination Committee WG holds BEST training workshops that include information on the latest developments for the members of the consortium in the nation. Through the website and magazine BEST provides information, recruits members and promotes BEST software around the world.

The activities of these committees helps to establish a training environment for young program developers, to retain funding for upgrading and maintaining the program and continuously to develop new effective program. This helps to sustain the environment to produce more user-friendly software for all disciplines such as researchers, mechanical engineers, construction administrators, maintenance administrators, architects, project managers, owners etc.