Are net zero water buildings far off?

One of the starkest facts I learnt during World Green Building Week 2015 was that 93% of the heat we have gained as a result of climate change since pre-industrial times is going into the ocean. Only 1% of the same heat is going into the atmosphere. Yet it’s that 1% which all our negotiating efforts to remain within 2 degrees will relate to at the Conference of Parties in Paris in December.

This shows once again how little we focus on water. Yet water is the one basic need of humanity that is likely to be most affected by the impacts of climate change. Precipitation levels and frequency, freshwater availability, seawater rises, snow and ice melt, ocean and marine life – these are all critical concerns in a planet whose temperature is increasing. Although there is a lot of water on the planet, sustainably managed water is becoming scarce and if present trends continue, 1.8 billion people will be living with absolute water scarcity by 2025, and two-thirds of the world could be subject to water stress.

It is perhaps not surprising then that at least 2 of the 17 new post 2015 Sustainable Development Goals put forward only last week by the United Nations explicitly refer to water, and virtually all of the remaining 15 are implicitly affected by our ability to more sustainably manage our water resources.

Let’s adopt a far more holistic approach to sustainable water management, and to water-sensitive design, procurement and construction methods.

Nowhere is this more important than in our cities and built environments, where reducing water consumption, and protecting water quality ought to be key objectives. Yet the water performance of buildings is little understood, and as some have suggested cheap pricing policies have resulted in it becoming the ‘forgotten utility’. We’re all reasonably familiar with the concept of sensor taps and dual flush toilets or waterless urinals. But the inescapable irony is that such water conserving devices often fail to work properly and have been known to result in more rather than less water being wasted due to poor design.

Furthermore, if we’re really serious about constructing buildings that have zero adverse impact on the environment, we need to think far more holistically about all their water-related impacts. It’s not just rainwater harvesting or greywater recycling that will solve the problem, but the systematic consideration of development impacts on local watercourses, water tables, surface water run-off, flood defence management, and green and blue infrastructure. We need to be thinking beyond the operational water impacts of specific fittings and start to consider the embodied water impacts of different building materials and construction products. It is estimated that the construction of a house using a combination of methods requires about 6million litres of water. Likewise our heating, ventilation and cooling technologies are often heavily water-dependent and give rise to more invisible yet no less significant water usage and treatment.

So let’s not over-simplify the water impact of buildings. Rather let’s adopt a far more holistic approach to sustainable water management, and to water-sensitive design, procurement and construction methods.

The concept of net zero water buildings may not have taken off yet, but it can’t be far behind if the science is anything to go by.

Julie Hirigoyen is chief executive of the UK Green Building Council