Moving away from simple replacement: How to approach ZEB Renovation (Part 1)

In recent years, words such as "carbon neutral" and "ESG investment" have become commonplace. It is necessary to have a detailed understanding of what efforts each company is making regarding these various environmentally related social topics, and what is expected of us as designers.

運用時に多くのエネルギーを消費するオフィスビルには、世の中から多様な環境配慮への取り組みが要請されています。しかし、ビルの所有者にとって、その取り組みは事業として投資に見合うあり方で行われる必要があるので、まずはエネルギーの使用量を低減し、「CO2の排出量を削減する」ことが大切です。
それぞれの企業に対して、① 現状の把握、② 削減目標の設定、③ 削減目標に対する計画と実行、というサイクルを回し、サステナビリティレポートやTCFDなどに代表される情報の開示が求められています。

Starting in November 2021, we established the Carbon Neutral Planning Office (formerly known as the Carbon Neutral Promotion Office) within Renovation Design Department, which is mainly engaged in "considering CO2 emission reduction" by making technical proposals related to ① to ③, and "considering and promoting the conversion of existing buildings to ZEBs," which tackles energy conservation and energy creation from a more fundamental level as an extension of energy conservation.
In the past, we received many consultations about planning, such as "By when and how much CO2 can we reduce in the buildings we own?", but recently there have been more cases where companies are asking, "Which buildings can be Renovation to become ZEBs?", aiming for ZEB status itself. While this is thought to be due to the lack of a certification system for reducing CO2 emissions, we feel that it also indicates an increasing need to attract environmentally conscious tenants and investment.

Energy conservation standards for new buildings were raised from April 2024. Due to the growing need for high environmental performance as mentioned above, it is expected that the spread of newly constructed buildings with ZEB certification will increase. On the other hand, progress has been slow due to the lack of specific regulations and policies, so unless efforts are made to make the large number of existing buildings energy-efficient and ZEB-compliant, it will be difficult to achieve the national goals of "reaching ZEB standards on average for existing stock" and "realizing a carbon-neutral society."

The Carbon Neutral Planning Office's clients come from a wide variety of business sectors, and we consult with them daily on a variety of energy conservation and ZEB-related matters. This includes investment corporations, financial institutions, and companies that own multiple office buildings. Our "renovation to turn buildings into ZEBs" can also be proposed to these businesses' entire portfolios (a series of real estate assets). As we can approach multiple buildings simultaneously and work to make them more energy-efficient and ZEB-compatible, this can be said to be an effort to promote carbon neutrality throughout society.

The reason why existing buildings, especially tenant office buildings, are not being converted to ZEBs is that in many cases, operators are concerned about complaints from tenants that come with changes to specifications, such as "Will the lighting become too dim?" or "Will they complain that it's too hot or too cold?" and so avoid making major changes to the air conditioning and lighting environment, and instead simply renovate by "replacing" existing facilities with highly efficient equipment.

The first step towards ZEB is to "avoid simple replacement." It is important to reset design conditions based on on-site surveys to match actual usage, carefully explain to clients and building managers how "it will change from the current situation," and proceed with the design while ensuring their understanding. In doing so, we may propose changes to the air conditioning system, air conditioning capacity, and design illuminance, but there are many cases where there is concern that such changes to the environment will lead to complaints, and there is a certain amount of risk involved in making such proposals.
However, ZEB is not just about replacing existing facilities with highly efficient equipment, so I think it is important for designers to make in-depth proposals. Risks can be reduced by utilizing past renovation results, accumulated know-how, and verification at the time of use.