Heating, cooling and dehumidifying air in buildings currently consumes one sixth of all the energy used in the world. With the “Cleanair” system Professor Matthew Johnson of the University of Copenhagen has created a device that cuts building energy use by up to 25 percent. Saving that much energy is good news for landlords, and even better news for the climate. But CleanAir is about more than saving energy and CO2. It’s also about securing better health.