IIJ Announces Plans for Phase 3 Server Building Construction, Expanding the Shiroi Data Center Campus to Meet Growing Demand for IIJ Services

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TOKYO - May 8, 2025 - Internet Initiative Japan Inc. (TSE Prime: 3774), one of Japan's leading Internet access and comprehensive network solutions providers, today announced plans for expansion of its Shiroi Data Center Campus ("Shiroi DCC"), a data center located in Shiroi City, Chiba Prefecture, with the construction of the phase 3 server building. Construction of the phase 3 building is scheduled to begin June 1, 2025, toward the planned start of operation during fiscal year 2026. With the phase 3 building, service facilities will be expanded further to meet growing demand for such IIJ service solutions as cloud, security, IoT, and MVNO, as client companies move ahead with digital transformation (DX) and make greater use of AI.
The phase 3 building will have a site area of approximately 5,400 square meters, maximum incoming power capacity of 10MW (expandable to 25MW), and scale of 1,000 racks. The building will adopt the same outside-air conditioning as the phase 1 and 2 buildings, realizing high electric power usage efficiency. In addition, a "liquid-cooling ready design" is being adopted, securing in advance the dedicated heat source space and cooling pipe routes needed for liquid cooling equipment, with a view to future accommodation of IT equipment having exceptionally high heat value such as GPU-equipped servers for AI use.

Phase 3 building (illustration)

Background

The Shiroi Data Center Campus began with the construction of the phase 1 server building in May 2019. Actively incorporating the latest energy-saving technology, AI, and automation technologies, it was built to meet large-scale data processing needs arising from progress in digital transformation (DX) and the spread of AI and IoT. In July 2023, operation of the phase 2 building began in response especially to strong demand for collocation service by cloud data center service providers, content providers and others. During 2026, the phase 2 building is expected to reach maximum capacity. Construction of the phase 3 server building announced here is mainly for the purpose of boosting facilities to accommodate IIJ's own service solutions as they continue to grow.

Main Features of the Shiroi DCC Phase 3 Building

A liquid-cooling ready design and flexible building design adaptable to various equipment uses

A "liquid-cooling ready design" is being adopted, securing in advance the space for installation of a dedicated heat source for liquid-cooling equipment such as DLC (Direct Liquid Cooling), and cooling pipe routes from the heat source to server rooms, anticipating the future use of IT equipment having exceptionally high heat value such as GPU-equipped servers for AI use. Flexible ceilings(*1) are also being adopted, enabling the rack position and ceiling opening locations in the server rooms to be changed readily as needed. This is to accommodate server racks with liquid-cooling equipment, which are larger than conventional racks and need more space for their power supply, as well as to meet needs for increased cooling capability. Moreover, the phase 3 building will have a hybrid structure, with the total area divided into zones and structural plans applied as suitable for each zone. The reason for this design is that the server rooms and electrical rooms in the building will have different structural load demands and different floor heights. In addition, technology gained from the joint research project on ultra-high-efficiency AI computing infrastructure(*2) will be utilized to the extent possible.

• (*1)Flexible ceiling: A ceiling that achieves both low cost and high usability by adopting an efficient structural plan and lightweight, easy-to-use ceiling material.
• (*2)Press release dated December 5, 2023 https://www.iij.ad.jp/en/news/pressrelease/2023/1205.html

Use of energy-saving technology toward realizing carbon neutrality

Aiming to be a carbon neutral data center, the Shiroi DCC adopts various air conditioning and cooling technologies and adopts other measures for raising the efficiency of electric power usage. The phase 3 building adopts an outdoor air cooling system making use of external air, and a wall-mounted blower scheme by which blowers mounted on walls that separate server rooms from the air conditioning machine room provide direct cooling of the server rooms. As electrical equipment, a three-phase, four-wire UPS(*3) enables efficient supply of electricity to 200V power supply equipment.

• (*3)Three-phase, four-wire UPS: A system in which an N phase (neutral phase) is added, grounded to the three wires of a three-phase AC circuit, with the N wire running from the neutral point of the transformer, enabling power to be supplied on four wires, the three voltage wires and the neutral wire.

Shirai DCC equipment overview

	Phase 1 building	Phase 2 building	Phase 3 building
Location	Shiroi City, Chiba Prefecture
Overall site area	Approx. 40,000m2
Starting operation	May 2019	July 2023	Planned for FY2026
Maximum power received	10MW	10MW	10MW (Expandable to 25MW in anticipation of liquid cooling and other increases in equipment density)
Electrical equipment	Three-phase, four-wire UPS
Air conditioning system	Direct outdoor-air cooling system
Rack capacity	Approx. 700 racks	Approx. 1,100 racks	Approx. 1,000 racks

• Please see the following site for details of the Shiroi DCC.
  https://www.iij.ad.jp/en/datacenter/tech/iijdc/shiroidcc.html

IIJ will continue to offer stable infrastructure platforms by providing high-quality data center facilities and various added-value networking services.

The statements within this release contain forward-looking statements about our future plans that involve risk and uncertainty. These statements may differ materially from actual future events or results.

For inquiries, contact

IIJ Corporate Communications

• +81-3-5205-6310
• +81-3-5205-6377
• press@iij.ad.jp

• (*)All company, product, and service names used in this press release are the trademarks or registered trademarks of their respective owners.