Value revitalization and BCP (Business Continuity Planning) enhancement of existing buildings in the era of whole-life carbon emissions.

In recent years, the concepts of "whole life carbon" and "life cycle carbon" have been attracting global attention in the environmental field of architecture.
This approach focuses on CO₂ emissions "over the entire lifecycle" of a building, including not only the operational phase but also the construction and demolition phases. New construction and rebuilding involve enormous amounts of energy for material production and CO₂ emissions associated with construction, raising questions such as, "Should we really rebuild?" and "Can't we utilize the existing building?"

In Japan, the national goal is to achieve ZEB (Net Zero Energy Building) standards for the average stock (total volume) of existing buildings by 2050, and making existing buildings ZEB is key to decarbonization.

This project involves a 25-year-old building in Tokyo with a total floor area exceeding 10,000 square meters. The goal was to "clearly improve the value of the building," requiring two initiatives: energy conservation and strengthening the BCP (Business Continuity Plan) to ensure safe use even during disasters. Here, we proposed achieving a proactive environmental performance target of "ZEB (Zero Energy Building) status" with the aim of creating a "building that can be used for a long time." A new challenge to address modern issues has begun.

Our first step was to conduct a current situation survey with a view to achieving ZEB (Zero Energy Building) status. From here,

• Simply replacing equipment will not improve energy efficiency. Understanding the current situation is essential for optimizing the capacity of heat source air conditioning and lighting.
• Achieving ZEB (Zero Energy Building) status is difficult with the current central heat source system; therefore, an individual distributed heat source system (air-cooled HP package system) is required. At the same time, adopting this system is expected to reduce the equipment installation space.

These two points have become clear.

"Optimizing and streamlining the capacity of air conditioning equipment" is a key element of energy-saving proposals. Existing equipment is often excessively large, making downsizing to match actual needs possible. Here, it was found that the installation area of air conditioning equipment could be reduced to approximately 40% of the existing size.
In response to the significant reduction, some operators expressed concerns that it might not be possible to accommodate future facility expansions. However, by presenting a roadmap for achieving ZEB (Zero Energy Building) and supporting various consensus-building and decision-making processes, we promoted its achievement.

Furthermore, as part of strengthening the business continuity plan (BCP), a request was made to install a new 400kVA, 72-hour-operating private power generation system on the rooftop. However, due to the reduction in the aforementioned air conditioning equipment, it became possible to secure approximately three times the existing space for the generator. After conducting load-bearing capacity surveys, a safe installation location was selected, and a layout plan was formulated that also considered equipment separation distances and maintainability.

The underground warehouse is equipped with five 1,500L oil tanks (totaling 7,500L), enabling it to handle emergency and security loads. Space has also been secured for future tenant-dedicated generators, and a new refueling port has been installed on the south side of the first floor to improve the convenience of inspection and refueling.

The primary focus of this project was to share a common vision with stakeholders and build consensus towards optimizing and downsizing air conditioning capacity.
When making significant changes to existing facilities, we addressed each of the "conservative" opinions, such as "Do we really need to change equipment that has been working without problems until now?" and "Will we be able to respond if tenants make any inquiries or requests?", by demonstrating, with technical justification, that optimizing capacity is not simply about reducing the amount of equipment, and that there is room and flexibility to expand facilities to properly accommodate future building use and tenant growth. In doing so, we gained their understanding.

As part of strengthening the Business Continuity Plan (BCP), expanding the generator capacity in the limited rooftop space while simultaneously constructing a new oil tank room in the basement significantly impacted the streamlining of the air conditioning capacity and the consolidation of equipment layout. Therefore, the electrical and mechanical equipment departments collaborated on the design, maintaining daily contact with the business operator, management company, and construction company, working together as a team to advance the project. This allowed us to provide new value by ensuring that a sufficient power and fuel supply system can be maintained even in the event of a disaster.

In this way, by overcoming the complex challenges of optimizing air conditioning, power supply, fuel, and space, the renovated Building Energy Index (BEI) achieved 0.56, and ZEB Oriented certification was obtained. A major achievement was that the involvement of MEP Engineering allowed for the optimization of the building's overall energy-saving performance while making it "visible."
Furthermore, it is clear that facility renovations aimed at achieving ZEB (Zero Energy Building) are meaningful from a "decarbonization" perspective, as they not only lead to energy conservation during building operation but also to a reduction in CO₂ emissions during construction.

This project can be considered a practical model case toward the goal of "achieving ZEB (Zero Energy Building) standards on average for existing building stock." It embodies a new architectural culture of "nurturing" rather than "consuming" buildings, and has succeeded in breathing new life into them through gradual value enhancement.
Making existing buildings, especially large-scale tenant office buildings like this one, into ZEB (Zero Energy Buildings) presents various challenges, such as the diverse demands of tenants and the need for larger equipment. However, this is an area where the technical skills, conceptual abilities, and communication skills of MEP Engineering can be fully utilized. Furthermore, collaboration between MEP Engineering and architectural/ Structural Engineering leads to optimization of the entire building, further expanding the possibilities for reducing the environmental impact of existing buildings. In parallel with new construction projects aimed at reducing CO₂ emissions, we believe that our work as MEP Engineering, which responds to social demands and environmental challenges by adapting existing buildings to next-generation environmental standards, will become increasingly important in the future.