The European Code of Conduct for Datacentres

For nearly fifteen years, the European Code of Conduct for Datacentres (EU CoC) has shaped how energy efficiency is understood and implemented in European digital infrastructure. Long before the Energy Efficiency Directive (EED) introduced mandatory reporting obligations for metrics such as PUE, WUE, renewable energy share, and heat reuse, the EU CoC articulated a comprehensive, vendor-neutral set of best practices for responsible datacentre design and operation.

This article is intended for operators, designers, and technology buyers who use — or are considering using — the EU CoC as a reference framework for datacentre design and technology selection. The Code remains one of the few European instruments that translates policy objectives into practical, engineering-level guidance without prescribing specific vendors or solutions. For organisations seeking broad, balanced guidance based on best practices rather than single-metric optimisation, the EU CoC continues to provide a strong foundation.

As the EED moves from policy into implementation, the relationship between the two frameworks becomes clearer. The EED requires datacentres to assess performance across multiple dimensions, explicitly moving beyond PUE alone. The EU CoC anticipated this shift by promoting a holistic view of efficiency in which energy use, water consumption, thermal management, heat reuse, monitoring, and system integration are treated as interdependent design considerations rather than isolated targets.

This balanced perspective is the reason the EU CoC has remained relevant over time. Rather than encouraging optimisation around a single outlier metric, it supports architectures and operational practices that perform consistently across a broad set of criteria — an approach that aligns closely with the intent of the EED and emerging European sustainability frameworks.

Within this context, certain technologies align more naturally with the Code’s principles than others. In particular, many of the operational outcomes promoted by the EU CoC correspond closely with the technical characteristics of immersion cooling.

This article examines the role of the EU CoC in Europe’s policy landscape, explains why it remains a useful guide for design and procurement decisions, and analyses how immersion cooling maps to its core recommendations.

A Voluntary Framework with Lasting Policy Influence

The EU CoC is neither a regulation nor a certification scheme. It is a voluntary initiative supported by datacentre operators, equipment vendors, research institutions, and public bodies, with the objective of reducing the environmental impact of digital infrastructure.

Its influence derives from three factors:

·      It provides engineering-level guidance, rather than abstract principles.

·      It has been regularly updated to reflect changes in technology, density, and workload characteristics.

·      It has informed regulatory thinking, with several concepts later reflected in the EED and related policy instruments.

For many operators, the Code has functioned as a practical reference that bridges the gap between high-level sustainability objectives and concrete technical decisions.

What the EU CoC Emphasises: Efficiency as a System Property

At its core, the EU CoC treats the datacentre as an integrated system. Efficiency is not defined by a single parameter, but by how IT equipment, cooling, power distribution, monitoring, and control interact.

Across its guidance, several recurring principles emerge:

·      Reducing reliance on mechanical cooling

·      Improving the effectiveness of heat transfer

·      Eliminating airflow-related inefficiencies

·      Avoiding thermal bottlenecks and throttling

·      Strengthening monitoring and control

·      Minimising water consumption

·      Designing for heat reuse where feasible

·      Maintaining efficiency at increasing rack densities

These principles anticipated many of the concerns now embedded in the EED’s reporting framework. In this sense, the EU CoC can be seen as an operational precursor to Europe’s current regulatory approach.

Cooling Architecture as a Determinant of CoC Alignment

The EU CoC is explicitly technology-neutral. However, its best practices tend to favour architectures that reduce structural inefficiencies rather than compensate for them through operational tuning.

As rack densities increase and thermal loads become more concentrated — particularly in AI and high-performance computing environments — the practical limits of air-based cooling become more visible. In this context, immersion cooling aligns closely with many of the outcomes the Code promotes.

The following sections examine this alignment in more detail.

Reducing Dependence on Mechanical Cooling

The EU CoC highlights the energy overhead associated with chillers, CRAC units, and compressor-based systems, particularly under variable ambient conditions.

Immersion cooling transfers heat directly from components into a dielectric liquid, significantly reducing the need for mechanical refrigeration. In many deployments, chillers can be eliminated entirely, lowering auxiliary energy demand and seasonal sensitivity.

From a CoC perspective, this directly supports the objective of minimising mechanical complexity and energy overhead.

Eliminating Airflow-Related Inefficiencies

Air movement is a substantial source of energy consumption in datacentres. The EU CoC identifies inefficiencies associated with server fans, pressure differentials, recirculation, and containment failures.

Immersion cooling removes air from the thermal equation. Server fans are eliminated, and there is no need for airflow management at room or rack level. An entire class of inefficiencies targeted by the Code is therefore avoided by design.

Operating at Higher Temperatures Without Reliability Trade-offs

The EU CoC encourages operation at higher temperature setpoints where reliability can be maintained. In air-cooled environments, this often leads to thermal throttling or increased failure risk.

Immersion cooling maintains components within narrow and stable temperature ranges, reducing thermal stress and enabling higher coolant temperatures. This aligns with the Code’s guidance on both efficiency and equipment longevity.

Supporting High and Scalable Rack Densities

The EU CoC recognises that future datacentres must support higher power densities without disproportionate increases in overhead.

Immersion cooling can accommodate very high rack densities while maintaining stable efficiency metrics, aligning with the Code’s emphasis on scalability and future-proof design.

Minimising Water Consumption

Water efficiency is a recurring concern in the EU CoC. Evaporative cooling is explicitly discouraged where alternatives are available.

Immersion cooling systems, particularly when combined with dry heat rejection, can operate with negligible or zero operational water use, directly supporting the Code’s environmental objectives.

Enabling Practical Heat Reuse

Heat reuse is promoted by the EU CoC where local conditions permit. The feasibility of reuse depends on temperature stability and heat quality.

Immersion cooling produces heat at relatively high and consistent temperatures, improving compatibility with district heating and industrial reuse schemes and reducing technical barriers to implementation.

Simplifying Monitoring and Environmental Control

The EU CoC places strong emphasis on continuous monitoring and optimisation.

Immersion cooling creates a stable thermal environment, simplifying the measurement of temperatures, energy flows, and recovered heat. This supports data quality and transparency — attributes that are increasingly important under EED reporting obligations.

The EU CoC in the Context of Emerging Regulation

With the EED now in force and discussion underway on European sustainability labelling for datacentres, many principles first articulated in the EU CoC are being reflected in mandatory policy instruments.

In this context, the Code functions as a practical bridge between regulatory intent and technical implementation. Architectures that align naturally with its guidance reduce reliance on compensatory measures or complex optimisation strategies.

Conclusion: Long-Standing Best Practices, Structurally Enabled

The European Code of Conduct for Datacentres does not prescribe technologies. However, its best practices — reducing mechanical cooling, eliminating airflow inefficiency, supporting high density, minimising water use, enabling heat reuse, and strengthening monitoring — describe outcomes that immersion cooling delivers by design.

As Europe moves from voluntary guidance toward mandatory reporting and comparative assessment, alignment between operational frameworks such as the EU CoC and regulatory instruments like the EED becomes increasingly important.

In that context, immersion cooling should be understood not as a policy-driven choice, but as a cooling architecture whose technical characteristics are structurally consistent with Europe’s holistic, multi-metric approach to datacentre sustainability.