In high temps 'district cooling' is alternative to wasteful AC For many, rising temperatures are a cue to crank their home AC units or fans. In greater Paris, some neighbourhoods are signing on to get relief from heat spells with a collective solution called "district cooling." In Boulogne on the French capital's southwest border, an underground heat-and-refrigeration unit uses the local groundwater to reduce the energy needed to produce heat and cooling for nearby buildings. "District cooling" advocate Guillaume Planchaud says that in addition to being more energy efficient, the collective method emits fewer pollutants and doesn't add to the heat of the city by blowing hot air into the environment. IMAGES AND SOUNDBITES