Describes how a Wisconsin engineer is using basic thermodynamic principles and readily available equipment to design innovative heating, ventilating and air conditioning systems. The hybrid HVAC designs offer two crucial elements: supply ventilation composed of 100% outdoor air and significantly reduced energy consumption. The new systems are both competitive in price to conventional systems and also less expensive to maintain. In one case study the hybrid system ventilates a 33 year old school building with 100% outdoor air and reduces building energy costs by at least 21%. The system is a regenerative double-duct system. The heat recovery units have 92% efficiency and use the bulk of heat emanating from lighting, human occupants, the kitchen, computers, and solar gains to help condition the building. (Normally heat recovery efficiency is in the low- to mid-80th percentiles.) States that traditional HVAC systems work by brute force and are incredibly inefficient. They miss opportunities for efficiencies under at least five laws of thermodynamics. The engineer employs an adiabatic conversion of sensible-to-latent energy to change the psychometric properties of the air without refrigeration through both direct and indirect evaporative cooling. Evaporating or condensing water - changing it from a gas to a liquid state or back - is the only process that can convert sensible energy to latent energy and produce a heating or cooling effect without having to consume additional energy resources. This is the only truly 'free' energy, and this system captures and uses it, when traditional HVAC systems cannot.