David Davis is a Director of G&H, a national MEP construction business based in the north of England. He discusses the forecasted growth in air conditioning units, which keep buildings cooler, and how condensate from these units is being used to save fresh mains water on a large scale.
Buildings are getting warmer due to several factors. Climate change is leading to higher outdoor temperatures, combined with the urban heat island effect, and building designs are prioritising energy efficiency with increased insulation and airtightness all of which contribute to increased internal temperatures. In the UK, both new and existing buildings are now failing overheating calculations such as CIBSE TM52 & TM59, and in most situations, natural ventilation cannot be used as mitigation, so installing air conditioning is becoming more prominent as a solution.
As a result, we are seeing a year-on-year increase in the use of air conditioning (AC) units. As volumes increase, the unit costs reduce, making them more affordable, and their sales continue to rise. A report from the International Energy Agency as far back as 2018 predicted that the number of AC units worldwide would triple to 5.6 billion in the next 25 years. While this is a global figure, the UK is certainly not excluded from this market growth; AC units are being used in most new building developments and as retrofits in urban residential schemes to combat heat issues and make buildings altogether more comfortable.
Installing AC units in a large commercial building brings its own challenges, one of these being the requirement to ensure that the condensate water produced by these units is efficiently removed to prevent water damage to the equipment and the building structure. Typically, a 1.75kW air conditioning unit, one of the smallest on the market, can produce over 1 litre of condensate per hour when in use; routing the pipework through buildings to remove it is therefore an important consideration. Poorly designed condensate systems can lead to water-stained ceiling tiles or, in the worst case, a collapsed ceiling. In most cases, this AC condensate drains into a drip pan and then runs into a hose connected to the drainage system.
When you consider that today, all this condensate water is currently channelled to the drainage system of a building, that’s a huge amount of water that could serve as an alternative water source for non-potable applications. With fresh water being a scarce resource that is very likely to become more expensive, using condensate is a really beneficial solution for saving water on a large scale.
Across the globe, both physical and economic water scarcity issues are well documented, but even in the UK, despite higher-than-average rainfall, the problem still exists, and sanitation issues with our water resources feature regularly in the news. In 2019, the UK Environment Agency warned that England may not have enough water to supply its needs by 2045 if it continues on its current course and uses mains fresh water for all its water needs. Our shortage of fresh mains water is well publicised; we use too much, and we need to find new solutions to save it.
As a commodity, water is underpriced, leading to excessive use and waste, as it’s cheaper than investing in water-saving technology. A tangible example of high usage was highlighted in a recent BBC documentary featuring the management of Heathrow Airport. The presenter confirmed that each toilet, using on average 5 litres of water, costs approx. 2p per flush. If all the expected 16,000,000 airport visitors over the summer used the facility, it would equate to 80 million litres of fresh water used at a cost of £320k.
Condensate is essentially distilled water, and while not suitable for drinking, it is a perfectly reliable source of grey water that could be used for a number of applications, with flushing toilets being an obvious one.
A great example of using condensate water at scale is eco-cistem®, a toilet cistern that uses condensate water for flushing. It has already been installed in several commercial hotels and office facilities and is saving up to 64% of fresh water. One such project was the Majestic office complex in Leeds, home to Channel 4 TV. The building had 49 eco-cistem® cisterns fitted and is now saving 1.1 million litres of mains water per year, as the toilets are flushed with condensate water.
The eco-cistem™ unit features a patented 18-litre, twin-chamber cistern that can store up to 12 litres of ‘free’
condensate grey water above a standard 6-litre chamber dedicated to flushing the toilet. The unit prioritises using the condensate for flushing and only pulls in fresh water when no grey water is available. This ensures an efficient flush each time with no reduction in performance. In an eco-cistem™ installation, the condensate water is redirected to the toilet cistern and used to flush the toilet(s).
There are estimated to be circa 60m toilets in operation in the UK across both domestic and commercial premises, if they all use an average of 5 litres per flush*, just twice a day, and if we could save even a quarter the water by using condensate, it results is a substantial saving equivalent to 600 Olympic size swimming pools.
This is just one example of how condensate from the growing number of AC units installed can save fresh water. There will be others, and I hope that by highlighting the issues and sharing the eco-cistem™ example, it inspires others to consider new uses of condensate for saving fresh water and making a difference in our sustainable journey.
*-which they don’t as many will use more as they are pre-2001 when the UK aligned to EU directives mandating the use of dual flush toilets.
This article appeared in the May25 issue of Specify & Build Magazine.
