With more than 60 years of combined experience in the research, development, manufacture and supply of energy and building related products, Donald Steele and Lawrence Hoagland set out a long term energy efficient ventilation strategy. It would have to provide outdoor air at much higher rates without energy penalty. It would have to control moisture loads as well as heat loads. It would have to be reliable and easily maintained. And it would have to be economically viable for both users and suppliers.