What Are Blue Roofs & How Can They Help Tackle The Water Crisis?

With warnings now being issued with increasing regularity regarding the global water crisis, here in the UK it’s predicted that England will see a shortfall of five billion litres of water each day by 2050… and with summers expected to get hotter and drier as time goes on, it is essential that action is taken now to mitigate the impacts and ensure full preparedness.

While climate change is having an impact on water availability, other factors need to be considered when assessing how best to address the UK’s water-related challenges, including population growth, urbanisation, industrialisation, ageing infrastructure and pollution.

The fact that there are many different problems associated with the water crisis, coupled with the fact that different parts of the UK will face their own unique water issues, means that there’s no one-size-fits-all approach that can be adopted.

There are various strategies that can be implemented to help build resilience into the network, including asset upgrades and investment, a reduction in the use of combined sewer overflows and prevention of illegal sewage discharges into waterways, awareness campaigns to reduce demand, greywater recycling and so on.

Water capture and storage, however, is one of the best ways to ensure that we have ready access to water supplies – and, to this end, you could consider investing in a blue roof for your business premises to help you harvest rainwater as part of a solid sustainable urban drainage system.

What is sustainable urban drainage?

Developing sustainable urban drainage systems at your place of business will help you account for water quantity (flooding), water quality (pollution), amenity and biodiversity.

These systems replicate natural environmental processes, with rainfall managed close to where it falls. You can design the systems to suit whatever it is you need, whether you’re keen to transport surface water somewhere or slow runoff down before it enters waterways to help address flooding by allowing water to soak into the ground or evaporate.

Water retention forms a key part of these systems – and blue roofs can be installed to help facilitate this, no matter how big or small your site.

What are blue roofs?

Quite simply, blue roofs are flat roofs that support water storage during periods of heavy rainfall and storm events, treating and releasing the water at a properly controlled rate into sewer networks, rivers, lakes and streams.

You can use your blue roof in one of two ways:

– For slow water release back into sewage systems to prevent flooding and overflow

– To store water that can then be used elsewhere on your site for purposes like irrigation, cooling and recreation

How do blue roofs work?

Typically, blue roofs are installed on either flat or sloped surfaces so that they can work effectively to manage water runoff and store/release rainwater slowly over time.

This is unlike more traditional roofs, which allow water to run off the surface of the roof immediately via a system of guttering and drainpipes.

Blue roof construction is unique to the site in question and its geographical location, as well as specific planning approval and permissions.

Typically, these facilities feature a void at either roof or podium level located above a waterproofing element in which water can be stored. Void capacity will be calculated in line with the specific load-bearing capabilities of your particular roof.

What are the benefits of blue roofs for businesses?

There are various benefits associated with blue roof installation for businesses and local communities, including:

– Helping you to become more sustainable by alleviating urban flooding caused by stormwater runoff

– Reducing the need for rainwater attenuation at ground level in urban centres

– Reducing reliance on mains water supplies by harvesting rainwater for use elsewhere, such as toilet flushing and irrigation

– Helping you to make use of redundant spaces on your site

– Reducing cooling costs for buildings

– Reducing water usage and consumption costs

Blue roofs in action: 3 case studies

Telford property development

An award-winning housing development in Telford in East London made use of a combination of both blue and green roofs to provide wildlife habitats, support rainwater attenuation, and deliver amenity areas and thermal standards.

The issue here was that the site was restricted somewhat in terms of limited below-ground space to locate SuDS and water attenuation systems, so it was necessary to look skyward for a solution.

Strict planning restrictions were imposed by Newham Council to prevent residents from being overlooked or shaded. To address the various issues, blue roof storage reservoirs were set up beneath a standard green roof buildup to store excess rainwater and allow for controlled release into sewers during heavy rainfall.

The project won the AJ Specification Awards in 2020, showcasing what can be achieved when green roof specialists, architects, developers and planners work together.

Northwestern University cancer research centre

This case study focuses on the combination of stormwater retention and detention (where space is provided to temporarily hold back specific volumes of stormwater for controlled release over a specified amount of time).

The Chicago-based Northwestern University Simpson Queery Biomedical Research Centre project required management of at least 10,000 cubic feet of stormwater because of its close proximity to Lake Michigan.

Blue roof decks were made out of concrete with a zero slope to support optimum water detention volume across the roof, featuring a plastic voiding component to detain stormwater. These were installed in a single layer on top of thermal insulation, connecting to create a firm surface upon which garden roof components and pavers could be installed.

Flow control drains were installed at drain points to create detention in the blue roof and deliver required water release rates. When stormwater influx exceeds outflow rates of these drains, water backs up into the voiding space where it remains until it can be drained back through the flow control system.

Bloc, Manchester

In 2021, work was completed on blue-green roof construction on the Block city centre tower in Manchester, with the installation retrofitted to the flat roof to store rainwater beneath a planted surface.

This research project aimed to deepen understanding of how storing and reusing rainwater at roof level could reduce surface water runoff volumes from entering sewer networks.

This type of technology helps to protect plants during drought periods, reduce potable water demand in hot weather and support local biodiversity, with plants on the Bloc roof specifically chosen from local varieties to attract pollinators and support the rare Manchester Argus butterfly.

How else can businesses save money on water?

As well as helping businesses operate more sustainably, blue roofs can help them save money by reducing water usage and consumption… but this isn’t the only way in which this can be achieved.

Interestingly, one of the most effective water conservation strategies you can consider is switching water supplier, a process that involves a thorough water audit of your entire site.

Here, the water usage of your business (including volumes) is compared with what you’re being charged for. This allows you to identify any weak or vulnerable areas where you could improve, revealing the best opportunities to save water – and money.

If you’d like to find out more, get in touch with the SwitchWaterSupplier.com team today.