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How We Did It Volume 6 — Rain, Rain… Don’t Go Away!


When the skies open up over Edmonton, most of the rain that falls on building sites is diverted to the storm sewer system. The priMED Mosaic Centre is designed to collect valuable rainwater that, in traditional construction, would otherwise go down the drain. By collecting rain, the Mosaic Centre design team projects that the building will use 95% less city water to irrigate the expansive gardens and front plaza.

So how is this done? And moreover, why don’t all buildings collect rainwater?

It is quite a simple system, as you might imagine, that requires a little forethought prior to excavation of the building foundation and site services. At the Mosaic Centre, a 7,000-gallon (25,000-litre) fiberglass storage tank is located below the west landscaping. Below the solar panels, a parapet roof captures rain and directs the water to downspouts that run through the interior of the building. On its journey through the downspouts, any debris in the water is filtered out before storage in the fiberglass tank. Tank sizing was determined by calculating the desired hydration for the landscaping grass, garden boxes, plant and shrub selections and deducting the expected natural rainfall. It was the original aspiration to design the Mosaic Centre to Net-Zero water targets. That objective was abandoned early in the stages of design, as it was determined that the amount of water storage required to supply 100% of the building water demand (including toilets and kitchen needs) for the year required an underground swimming pool due to the long periods of “frozen rain.” In addition, municipal regulations do not allow for domestic water storage and treatment, and the inevitable legal hurdles proved to be too great for this project.

Meet the design team members that help us keep our rain at the Mosaic Centre:

Why We Collect Roof Rain at the Mosaic Centre:

  • Provide nearly 100% of the water required for the landscaping on site
  • No disruption to the design of the mechanical systems
  • It was easy…and the right thing to do
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