Improving efficiency in zero energy building design: a conversation with TODA Corporation

Toda Corporation has developed Toda Zebu-kun – a design support tool that significantly improves the efficiency of zero energy building (ZEB) design work and enables the creation of optimal, client-specific proposals. Given that buildings account for roughly 30% of Japan’s CO2 emissions, addressing these issues is critical to achieving carbon neutrality. During our conversation with Mr. Hashidate – researcher at TODA Corporation – he highlighted how the adoption of modeFRONTIER allowed them to include multi-objective design optimization in the Toda Zebu-kun tool with the aim of enabling data-driven, scientific decision-making instead of relying only on intuition and past experience.

ESTECO: What motivated the development of the new ZEB design tool, “TODA Zebu-kun”?

Mr. Hashidate: The creation of "Toda Zebu-kun" was driven by the need to overcome four major challenges in zero energy building (ZEB) design. First, coordinating architectural design and energy simulations is complex. If the initial design fails to achieve the required energy efficiency target (such as a building energy index of 0.5), time-consuming rework efforts are needed, stretching project timelines. This added task places a significant burden on design teams, often leading to project delays. Second, there is a shortage of specialized ZEB knowledge in the industry – particularly in complex facilities like hospitals where ventilation requirements are high and there is little knowledge on energy saving strategies. Third, proposing solutions tailored to each client’s priorities, such as environmental impact or cost, involves assessing numerous design combinations, a process that is too slow and not feasible in real-time using traditional methods. Finally, as a certified ZEB planner, we set an ambitious goal for ZEB projects to account for over 50% of our design and consulting work by 2025. Our rate in 2024 was 37%, and Toda Zebu-kun design tool development was urgently needed to meet the 2025 target.

ESTECO: What was the reason for integrating the Toda Zebu-kun design tool with modeFRONTIER?

Mr. Hashidate: We integrated Toda Zebu-kun with modeFRONTIER to address the main challenge of optimizing multiple, sometimes competing, objectives in ZEB design. Traditional approaches rely on designer intuition and typically limit the exploration to just a few design patterns. Even after identifying a ZEB-compliant solution, there is no guarantee that it is the most optimal. By leveraging modeFRONTIER, we can quickly and systematically optimize conflicting objectives, such as cost and building energy index (BEI), within a single process. This integration enables scientific, data-driven decision-making and empowers us to provide clients with tailored and reliable proposals.

This is the overview of the design steps our TODA Zebu-kun tool supports:

1. Extract essential building data from the design drawings, such as exterior dimensions and room areas.
2. Automatic selection of exterior specifications and heat load calculations based on building information, and automatic selection of optimal air conditioning equipment.
3. Envelope and air conditioning equipment information is automatically transferred to the WEBPRO input sheet, and then WEBPRO automatically calculates the BEI.
4. modeFRONTIER automatically calculates costs and evaluate the relationship between BEI and costs.
5. Based on the results, the exterior and air conditioning equipment are automatically adjusted, and a large amount of recalculation is carried out using WEBPRO.
6. Looking at the modeFRONTIER design charts together with the customer, we select the optimal ZEB proposal.

The key advantages of this methodology for our customers include maximizing cost-effectiveness by achieving ZEBs while maintaining low initial costs. It also offers customized solutions, allowing multiple optimal options to be selected based on budget or preference. Additionally, results are clearly explained through visual graphs, making selection factors easy to understand and supporting confident decision-making.

ESTECO: What software tools are integrated into your modeFRONTIER workflow?

Mr. Hashidate: Our modeFRONTIER workflow currently integrates:

• WEBPRO: a web-based application used for calculating building energy consumption performance and deriving the building energy index (BEI).
• Excel: used for various functions, including heat load calculations vital for equipment selection and managing our comprehensive cost database (Cost DB).

Looking ahead, we are planning to integrate building information modeling (BIM) software. This will allow for the automatic extraction of building envelope data and enable real-time recalculations whenever design modifications are made.

ESTECO: Could you explain an application scenario for ZEB design by using modeFRONTIER?

Mr. Hashidate: We applied modeFRONTIER to an existing building primarily used as office space. The original heating, ventilation, and air conditioning (HVAC) system was relatively simple, consisting of multi-split air conditioning units and an outdoor air handling unit with a direct expansion coil. Using modeFRONTIER, we developed and evaluated multiple design scenarios against the original plan.

The Balanced Plan shows almost no change in BEI, maintaining the original level (0% change), while reducing HVAC costs by 24%. This plan achieves significant cost savings without compromising energy performance. The Low-cost Plan results in a 7% increase in BEI, indicating a slight decline in energy performance, but offers a 35% reduction in HVAC costs. It is best suited for clients who prioritize cost savings. The Super Energy-Efficient Plan reduces BEI by 5%, improving energy performance, while keeping HVAC costs unchanged (0% change). This plan is ideal for environmentally conscious clients.

Rather than delivering a single ZEB-compliant design solution, modeFRONTIER enabled us to provide clients with multiple scientifically validated options tailored to their individual priorities and constraints.

ESTECO: What are the key advantages of using modeFRONTIER?

Mr. Hashidate: Our design team highly values three main aspects of modeFRONTIER. First, its world-class multi-objective design optimization capabilities. We can handle conflicting goals such as minimizing costs while improving building energy index (BEI) to identify the most balanced and rational design solutions. Second, modeFRONTIER offers significant time savings through automation. The software automates hundreds or even thousands of simulations, allowing our engineers to rapidly find optimal design. Finally, modeFRONTIER facilitates data-driven decision-making. It provides advanced data analysis and visualization tools that empower us to deliver scientific, confident, and well-justified proposals instead of relying on intuition.

ESTECO: Do you have any further plan for modeFRONTIER at TODA Corporation?

Mr. Hashidate: We have two major expansion projects underway to further enhance the capabilities of Toda Zebu-kun design tool combined with modeFRONTIER.

1. BIM integration: we are working to integrate BIM software into our workflow. This will enable automatic extraction of building envelope data directly from BIM models and allow real-time recalculations whenever design changes occur. Such automation will streamline the design process, improve accuracy, and accelerate optimization cycles.
2. Expansion of optimization targets: beyond optimizing cost and building energy index (BEI). We plan to incorporate whole-life carbon emissions and life cycle cost (LCC) for comprehensive environmental optimization.

Through these developments, Toda Zebu-kun will evolve from a calculation tool into an advanced platform for sustainable architecture. Our goal is to make ZEB design more accessible and intuitive for architects, ultimately accelerating widespread adoption of ZEBs and contributing to a more sustainable society.