How cold climates challenge data centre structures

Structural engineering is so important in design that the term "structure" can be used as a synonym for "building." However, data centres are not merely buildings - they are complex systems requiring careful design and engineering to meet the increasing demand for data processing and storage.

Given the rise in the number of data centres, companies often use a reference design to speed up facility delivery globally. However, each must be built with different climatic conditions in mind while optimising space and efficiency. A reference design in Spain will differ greatly from one in Sweden, as the weather and temperature are very different.

To account for this, structural engineers need to find ways to make allowance for the different conditions of the facility. Each variable affects the build differently, and to ensure efficient delivery, clients need a team of experienced engineers who can account for these differences.

Where does the structural design begin?

For a structural engineer, designing a data centre first begins with the column grid. This is the most important part of the build as it forms the layout for the rack and equipment – the beating heart for colocation providers. Efficiency in this part of the design is key, and decisions need to be made around the building’s elevations and the depth of ceilings to incorporate space for service distribution. There are two main choices:

• More storeys which give the client more floor area for data racks, which is often their top priority.
• Taller ceilings which provide more space for flexibility in MEP design, installation, and maintenance, facilitating future maintenance and potential changes.

The decision on structural size is also governed by material selection. Considerations need to be taken at the beginning of the project to make sure that the material chosen will be suitable for the environment – as well as availability, cost, and construction trends in the region. The right decision will mitigate design risk further down the line.

Once each choice has been made, structural loads can be established. These are the forces applied to structural elements that can cause stress, displacement, or damage, so the structure is designed to resist these forces. There are usually consistent loading requirements across a client’s data centre portfolio, for example, finishes, floor-mounted equipment, and rack weights. However, there are loads such as wind, snow, rain, and temperature, which can vary significantly across seasons and locations in Europe.

The challenges and solutions of working in cold climates

In cold climates, like Scandinavia, the natural environment of snow and low thermal temperatures require changes to be made to a client’s reference design. These include:

Foundations

The challenges to the foundation in these climates come from the effects of frost on the terrain. Typically, foundation depths should be extended to below the depth of frost penetration in frost-susceptible soil in these builds. However, in a cold environment, deep excavation is required to reach this level, thus making it a less sustainable design solution.

We have recently worked on a project in the Nordics that faced this challenge. Operating around 150km from the Arctic Circle, there was frost penetration at a depth of over 2m. To solve this, we avoided deep excavations by implementing an insulated shallow foundation design. This is an alternative to deeper foundations that use insulation to raise the frost depth around a building, enabling more shallow foundations.

Concreting

When concreting in cold temperatures, the cold environment can affect the concrete curing process and the construction programme.

Low temperatures slowdown the development of the concrete strength, which impacts the formwork striking time. Low temperatures can also cause damage to the concrete, such as micro-cracking, which disrupts the material, making it weak.

As such, the aim during the cold weather is to maintain the temperatures of the concrete so at least it achieves the required strength. To do so, concrete protection techniques such as frost blankets, insulation or hot air blowers are common in cold temperature regions. The experience and good understating of the concrete behaviour is essential whilst implementing these protection techniques, ensuring that concrete being dried out is avoided.

Thermal actions

Extreme temperatures can influence the structural behaviour of buildings, including frame movement, which is how much the building moves from its original position. This can be caused by the expansion and contraction of the building materials due to temperature, which leads to challenges in maintaining integrity and performance. This is a particular issue for the movement joints, which are susceptible to these changes.

To manage the challenges posed by thermal actions, structural engineers must carefully consider the design and placement of movement joints. By optimising the number and location of these joints, engineers can reduce unnecessary complexity and minimise the amount of steelwork required. This optimisation of the movement joints with the strategic positioning of the stiff elements within the building mitigates the amount of thermal expansion and contraction and reduces the project's embodied carbon.

Roof structure

Snowfall is common in these environments. When it lands on the roof, snow loading occurs. This is the measure of the force that the weight of snow has on the roof and is a variable that the structural engineering teams need to consider.

A lighter roof compared to conventional steel or concrete roof systems can be constructed to combat snowfall by adopting structural insulated timber roof panels. These panels are formed using locally sourced material manufactured in the Nordic region, which are a more sustainable option. They can also be designed to span a greater distance than a typical metal deck or concrete plank. This reduces the building's roof's self-weight and the facility's embodied carbon.

Natural air cooling

Given the nature of data centres and the high temperatures they operate in, many developers seek to utilise natural air cooling when building in these climates. This involves using the natural cold temperatures of the external atmosphere to remove heat rather than relying on mechanical chillers. However, bringing in air of variable temperature results in changes to the thermal actions on the internal parts of the building.

From our professional expertise, louvres (passive devices that enable air to flow into the building) are selected to work in tandem with the building's structural design to predict the effects on the internal thermal actions on the facility.

Experience can help to prevent a slowdown in delivery

Many data centre clients use reference design developments to accelerate the delivery of their data centres. This brings them to market quicker and can reduce the costs of developing new data centre designs every time. However, when bringing a reference design from a hot climate to a cold climate, it can result in a slowdown. Taking these conditions into account in the design for these conditions is necessary to ensure a swift delivery.

To mitigate these risks, data centre clients should look to an experienced engineering team that understands the need for localisation. Our experience in cold climates have helped us to re-engineer reference designs to ensure prompt delivery of projects which account for the local regulations that each region requires. Through this knowledge, we can incorporate reference design developments across the globe and employ techniques to reduce embodied carbon.