E-stack technology mixes cold air with internal warm air providing a low-energy ventilation solution.
Most natural ventilation systems introduce fresh air into sealed offices without difficulty in summer. But once temperatures drop below 15oC they are either switched off, or use heaters to warm the cold air – a solution which demands a lot of energy.
Now, a Cambridge University spin-off, Breathing Buildings, thinks it has a better solution. It involves mixing the fresh (but cold) incoming winter air with the interior air. The latter is of course much warmer. Combining the two can produce air which is fresh, but does away with the cold draughts typical of many ventilation systems in winter.
“Most companies just throw more energy at the problem”, says David Wilkinson, Finance and Operations Director. “[But] there is a huge amount of heat gain from occupants in commercial buildings. Why not use that energy?”
The company’s e-stack technology, funded in part by BP, uses a roof stack (an opening that can be part-closed when outside temperatures drop) to allow the cold air in, and two (low-energy) 45W fans to mix it with internally generated heat. First commercialised in 2007, it’s now in operation in 65 buildings across the UK, including the zero-carbon Crouch Hill School in north London, designed by architects Penoyre and Prasad LLP, which opened in January 2013.
The system costs the same to install as mechanical ventilation, but energy consumption in use is about half that of standard industry benchmarks. Indoor air quality improves, too.
Breathing Buildings has been shortlisted for Ashden’s 2013 Energy Innovation Award. As Ashden Founder-Director Sarah Butler-Sloss puts it, “building products and services that make reducing CO2 emissions realistic and affordable are essential for combating climate change”.
It is part of a trend which could be catching on more widely. Costly but pioneering designs, such as PNC Bank’s new headquarters in Pittsburgh, are helping to raise the profile of natural ventilation systems. The skyscraper, due for completion in 2015, has two layers – an outer one which works as a weather barrier, and an inner one that has automated air vents, a wood curtain wall, and manually operated sliding doors to open the building for air.
But it’s not simply a matter of green design. “It’s hugely about the follow through”, says Penoyre and Prasad partner, Ian Goodfellow: “There’s no point in having the greenest building in the world if it’s too complicated to operate or people override the systems.” For him, end-user training, as offered by The Building Services Research and Information Association’s Soft Landings project, is “equally important”. – Lizzie Rivera
Photo: Penoyre Prasad