Who said that blue roofs could never work for data centres?

The move is all part of a major initiative now sweeping across the urban planning landscape as cities tackle the escalating pressures of climate change, population density and an overwhelmed Victorian-era infrastructure. Local authorities are actively rewriting their building regulations and development practices as a result. 

Comprehensive frameworks like The London Plan, the Greater Manchester Spatial Framework, Birmingham's Green Infrastructure Strategy and Leeds' Core Strategy are no longer suggesting, but increasingly mandating, the integration of sustainable drainage systems (SuDS) and green infrastructure into new developments. This means that for any new build with a flat roof, a blue roof system, designed to attenuate and control stormwater runoff, is now becoming a non-negotiable requirement. This presents a problem for data centre developers, who now have to reconcile the absolute imperative for water security above critical IT equipment with the new, equally pressing, demands for urban environmental responsibility.

Blue roofs are ingeniously engineered flat roofing systems designed to temporarily store rainwater and then release it at a controlled, attenuated rate, significantly reducing peak flows into the drainage system. They achieve this through a series of carefully constructed layers, including a robust waterproof membrane, a drainage layer and most critically, an attenuation void or chamber system that can hold a specific volume of water. 

While the environmental benefits are clear - mitigating flood risk, reducing the urban heat island effect and potentially even contributing to biodiversity – the core design principle of most blue roof systems has historically relied on the primary waterproof membrane as the sole containment barrier for this stored water. 

Blue roofs and the risk factor
For a data centre owner, the thought of water intentionally sitting on the roof, with only a single membrane preventing it from reaching millions of pounds worth of critical servers below, has understandably evoked deep apprehension and often outright rejection. This perception, based on logical risk aversion, has historically meant that blue roofs are totally unsuitable for such sensitive installations – until now.

A revolutionary advancement in blue roof technology has fundamentally redefined this risk, offering a solution that perfectly reconciles the demands for urban compliance with the uncompromising security requirements of data centres. 

This solution is known as Attenu8®, a total roof system, in which the critical difference lies in its unique dual-containment design. Unlike conventional blue roofs where the main waterproof membrane forms the primary and often sole, barrier for stored water, the Attenu8® system introduces an entirely separate, engineered reservoir system above the primary waterproof membrane. In simple terms, the roof waterproofing does not get wet/used as in a conventional roof exposure - the blue roof stores any collected water above it.

Within this innovative Attenu8® system, sophisticated, purpose-designed drainage components, using those from a specialist provider, are integrated to create a dedicated, independent attenuation zone. This zone acts as a robust, self-contained reservoir, engineered to manage and control rainwater flow with precision. 

Any water that enters this reservoir is carefully held and then released at a pre-determined, controlled rate through a calibrated outflow restrictor. The integrity of this primary containment is handled by the design of the reservoir itself and its integrated drainage components, ensuring that water is purposefully managed within this dedicated upper layer.

This means that the main waterproofing membrane of the building's roof, which forms the core of the building envelope, is not under constant hydrostatic pressure from the blue roof's stored water. Instead, it serves as an extraordinary, fail-safe secondary barrier. Only in extremely rare and unforeseen conditions, such as a once in every 100 years’ extreme rainfall event exceeding the system's design capacity or an unlikely blockage within the primary reservoir, would water ever rise sufficiently to come into contact with the main waterproof membrane. 
Even then, that membrane, independently installed and protected, would act as a final, impermeable safeguard, providing an unparalleled layer of security. This unique, two-tiered containment strategy is what truly sets the Attenu8® system apart in the market, offering data centre owners a level of peace of mind previously unattainable with traditional blue roof technology. However, drainage should be checked periodically as part of a maintenance plan put in lace for every blue roof.

Multitude of benefits
This innovative approach unlocks a multitude of benefits specifically tailored to the unique operational and strategic needs of data centres. Foremost is the absolute peace of mind it delivers. The primary concern of water damaging sensitive server equipment is directly addressed by the containment layers. This means that data centre owners and operators can now confidently embrace blue roof technology, knowing that the integrity of their critical infrastructure remains uncompromised, while at the same time complying with new urban regulations. This security also enables guaranteed compliance with the stringent SuDS requirements now commonplace in major UK cities.
As an added bonus, the Attenu8®system also delivers enhanced operational resilience and energy efficiency. By attenuating stormwater and creating a controlled, cooler environment on the roof, the system contributes to the building's thermal regulation. This can lead to a demonstrable reduction in the internal heat load within the data centre, consequently lessening the demand on energy-intensive HVAC and cooling systems. 
For facilities where cooling accounts for a significant portion of operational expenditure, these energy savings are not just environmentally beneficial, but represent substantial, long-term financial advantages. Furthermore, the capacity for water management and reuse is significantly enhanced. The carefully attenuated rainwater can be harvested and treated for non-potable uses within the data centre, such as supplementing cooling towers, thereby reducing reliance on mains water supply and contributing to water conservation efforts, a valuable aspect of corporate sustainability.
The adoption of such a system also contributes to optimised land use. The roof, traditionally a purely protective layer, transforms into a productive, compliant asset that enhances the building's overall environmental performance, rather than remaining a security liability. This contributes directly to a data centre's ESG (Environmental, Social, and Governance) credentials and public reputation. 
Understandably, introducing a blue roof system of this sophistication demands meticulous planning and design. At Proteus Waterproofing, our Attenu8® system delivers that process as part of a one stop package that provides everything from design to the supply of all materials – all installed by fully trained contractors.

Design, Develop, Deliver
All this means that it is now possible for data centres to install a blue roof together with all the environmental and energy benefits they offer – more than just a roof – a real game changer.