Understanding Blue Roof Assembly and Options

Blue roof assemblies are designed to store and release rainwater, reducing stormwater runoff and alleviating pressure on drainage systems. These systems can be a cost-effective solution for managing stormwater.

There are different types of blue roof assemblies, including green roofs, which integrate vegetation into the system. Green roofs not only provide insulation but also help to mitigate the urban heat island effect.

The benefits of blue roof assemblies are numerous, including reduced stormwater runoff and alleviated pressure on drainage systems.

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A blue roof is a great way to go, and one of the main benefits is that it's made to be water-resistant, making leaks far less likely to occur.

This is because a blue roof has to be heavily reinforced to handle the extra weight of rainwater, which is a big plus. Not to mention, it's also a great way to turn your rooftop into a self-watering garden, which is perfect for growing your own food.

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All you need to do is install a pump that sends rainwater directly from the roof to the beds, and you're good to go. Some plants can even be grown on floating beds, allowing your blue roof to become a magnificent water garden.

If you're not into gardening, you could also turn your blue roof into a shallow rooftop pool, which is perfect for hot environments. Just remember to install a filtration system to keep the water clean.

Here are some key advantages of blue roofs:

Blue roofs are nearly always flat roofs, which can be a bit vulnerable to leakage, but a blue roof gives you a way to deal with this problem. They're also a great alternative to traditional flat roofs, which can leave little room for error.

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A Blue Roof can be created on a typical Hydrotech PMR (Protected Membrane Roof Assembly) using standard loose stone for ballast. This is the simplest blue roof that can be created.

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A heavier than typical application of stone ballast is designed to keep the loose-laid Styrofoam insulation from floating during rain events. This is crucial for the blue roof's operation.

Using standard ballast stone, the water in the blue roof is stored within the void spaces of the stone and to the required level above the ballast.

For a Hydrotech PMR Blue Roof, you can use standard loose stone for ballast, which is the simplest blue roof to create. This design keeps the loose-laid Styrofoam insulation from floating during rain events.

A Blue Roof created with standard ballast stone is ideal for utilitarian roofs that aren't designed for tenant use. This type of roof is perfect for spaces that don't require a lot of amenities.

On the other hand, the Ultimate Assembly Blue Roof uses void spaces beneath concrete pavers to store stormwater. This design is ideal for rooftop terraces or roof decks with some roof slope.

Heavier, thicker pavers are typically required for the Ultimate Assembly Blue Roof to keep the loose-laid Styrofoam insulation from floating during rain events. The pedestals supporting the pavers are also adjustable, making it a great option for roof decks with varying slopes.

The key to successful stormwater management is flexibility in design. The design of blue roofs is not limited to the examples shown within this text.

Combining materials and designs specific to each site is crucial for effective stormwater management. Successful stormwater management plans will combine appropriate materials and designs specific to each site.

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Blue roofs can be a great solution in areas where infiltration isn't feasible.

They're particularly useful in combined sewer areas where they can help meet Water Quality release rate and pollutant-reducing requirements.

Blue roofs can be installed on a wide range of roof types, including terraces, high-rise building roofs, and low podium or at-grade on-structure installations.

They're also a viable option for fully built-out or highly-constrained sites.

In some cases, blue roofs can even be installed as a Stormwater Retrofit on existing buildings, but this requires confirmation of adequate structural loading capacity, waterproofing, and protection of rooftop utilities.

Blue roofs come in different types, each designed to manage rainwater in unique ways. One type is the roof drain restrictor system, which detains water on the roof with eventual discharge to the existing roof drain.

Roof check dam systems are another type, used on rooftops or sections of rooftops without a parapet to increase storage volumes over roof areas with greater than 2% slope.

These dams create temporary ponding areas during rain events before slowly discharging to the roof drain. The ponding areas are created behind the dam, which is secured to the roof structure and has perforations for slow release.

The outlet control component is a crucial part of a blue roof system, providing functions such as meeting drain down time requirements and controlling the rate of discharge from the SMP.

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Blue roofs can seamlessly integrate with other rooftop systems, such as solar panels and HVAC mechanical equipment. This makes them a versatile option for building owners.

Some blue roofs even incorporate waterplay areas that double as irrigation systems for green roofs, reducing the need for external water sources. This can help minimize the strain on local water supplies.

Blue roofs can also store water for cooling solar panels and irrigating green roofs, reducing the load on mechanical refrigeration equipment. This is a great example of how blue roofs can provide ancillary services.

The 2004 Coram Sustainable Design Award winner, Steve Mann, demonstrated this concept with his winning entry, which utilized stored water for cooling solar panels and irrigation.

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Active blue roofs use valve configurations and controls to monitor and regulate the discharge of stormwater runoff from roofs. They can release water in several ways, including via a pneumatically or hydraulically actuated pinch valve or an electronically controlled valve connected to a timer.

The key difference between active and passive blue roofs lies in the method they use to control water flow. Active systems are controlled by a computer that monitors the water pressure against a valve.

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Passive systems, on the other hand, do not require direct control and are usually based on physical obstructions or pressure valves. A smaller drainage hole will drain much slower, and this principle can be used to control the level of drainage.

Active blue roofs were first proposed in 2008 for stormwater detention using forecast integration. This technology has come a long way since then, and it's now used in various applications.

Passive blue roofs, with their focus on physical obstructions, can be a more cost-effective option for some projects. However, they may require more design and engineering expertise to get right.

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There are different types of roof systems designed to handle rainwater and debris.

Roof drain restrictor systems are used on roofs with a parapet to detain water before discharging it to the existing roof drain.

Parapets are walls or barriers that run along the edge of a roof, and roof drain restrictor systems work well with them.

Roof check dam systems are used on rooftops or sections of rooftops without a parapet to increase storage volumes over roof areas with greater than 2% slope.

These systems create temporary ponding areas during rain events before slowly discharging to the roof drain.

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Blue roofs can be categorized into two main types: those that receive direct rainfall and those that receive runoff from adjacent roofs. Blue roofs that receive direct rainfall do not require inlet controls.

Inlet control systems are essential for blue roofs that receive runoff from adjacent roofs. These systems convey and control the flow of stormwater from the contributing catchment area to the Stormwater Management Pond (SMP). The designer is referred to Section 4.11, Inlet Controls, for more information.

Outlet controls within a blue roof system can provide various functions, including meeting drain down time requirements and controlling the rate of discharge from the SMP. Outlet controls can include orifices, weirs, roof restrictors, risers, or impervious liners.

Roof drain restrictors are used in roof drain restrictor blue roofs. These devices restrict flow through an orifice within the drain assembly, causing temporary ponding on the roof. The number and sizing of weirs and orifices are based on a predetermined relationship between the water depth approaching the drain and the flow rate entering the drain.

Roof check dam systems use perforated aluminum T-section dams to retain and slow release rainwater. These inverted T-sections are weather sealed and secured to the roof structure, creating ponding areas behind the dam. Perforations in the dam allow for slow release.

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The storage area component of a blue roof system is a crucial aspect to consider when designing or implementing a blue roof. It temporarily holds stormwater until it can evaporate or be released downstream at a controlled rate.

The storage area is dependent on the chosen blue roof system type, such as roof drain restrictor systems or roof check dam systems. In both cases, the bulk volume occupied by building mechanical systems, roof furniture, and appurtenances must be factored into the storage volume calculations.

A waterproofing membrane is essential for a blue roof storage area, and numerous waterproofing membrane systems exist. High-quality modified bitumen roofing (MBR) systems, such as those with multiple sheets tiled to reduce seam susceptibility, are suitable for blue roof usage.

However, lower-quality MBR systems with multiple layers of asphaltic sheets are not recommended due to their seams that allow water to penetrate. A hot fluid-applied, rubberized asphalt, fabric-reinforced roofing system or a cold liquid-applied system can provide a durable and seamless solution.

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Here are some key points to consider when designing a blue roof storage area:

The outlet control component is a crucial part of a blue roof system, and it's designed to regulate the flow of water from the roof. It can meet drain down time requirements, control the rate of discharge, and even bypass flows from large storm events.

You can use orifices, weirs, roof restrictors, risers, or impervious liners as outlet controls. The designer should refer to Section 4.12, Outlet Controls, for more information on these options.

Roof drain restrictors are a type of outlet control that restrict flow through an orifice within the drain assembly, causing temporary ponding on the roof. They can be purchased commercially or customized by a manufacturer.

Roof check dam systems use perforated aluminum T-section dams to retain and slow release rainwater. These dams can be secured to the roof structure and create ponding areas behind them.

Here are some common types of outlet controls:

Roof drain restrictors can be used in conjunction with roof check dam systems to create a more effective outlet control component.