Natural ventilation specialist Breathing Buildings has successfully defended the University of Cambridge's Passive Stack patent for low-energy e-stack ventilation technology.

Breathing Buildings grew from the University of Cambridge as a spin-out company in 2006. It was formed to develop and commercialise low-energy e-stack mixing ventilation technology, which was developed as part of a research programme at the university’s BP Institute.

A patent for the e-stack system was filed by Breathing Buildings in 2006 and granted in Europe in 2012. Managing director Shaun Fitzgerald (pictured) said the company knew it was “onto a big thing”.

The university’s patent was recently opposed by the parent company of natural ventilation specialist Passivent, which filed papers with the European Patent Office (EPO). However, the opposition was rejected in a hearing at the EPO in Munich on 11 March 2014, meaning the patent was maintained and only Breathing Buildings is allowed to manufacture products covered by the patent.

E-stack products are designed to allow natural ventilation to be used in winter and mitigate cold draughts by using the heat gains in a building, rather than requiring the use of radiators.