Offseason is a perfect time to inventory vacant homes in Aspen and Pitkin County. Itinerant owners are gone during iffy weather, so their blinds are closed, their doors are locked. Even when they’re empty, however, energy flows unabated through second homes. Many consume far more energy than smaller residences — by a magnitude of three times — because of energy-gulping amenities such as pools, spas and heated outdoor areas. Such was the recent conclusion of an independent energy study: “Energy use per square foot of home increases as the home size grows — by three times.