Denali HD's between 11-15 and LTZ silverado HD's (12 or 13)-15 are 100% peltier cooled. 15.5+ GM changed the literature to ventilated seats and I didn't pay attention the last time I was in one to tell if they're still peltier(however, other members have said they are on other forums). If the seat feels cold to the touch while the fan is on then it has a peltier - I want to say they try to maintain a delta of around 15-25f of cabin temp if memory serves.