This British Standard gives recommendations on the principles which should be observed when designing for the natural ventilation of buildings for human occupation.

Indoor air quality ventilation airflow rates and HV AC capital and operating costs usually are closely related. Auxiliary energy loads for supply air heating or cooling sometimes can substantially reduce the need for dehumidifying or humidifying by using air-to-air heat or energy exchangers. The most important factors in reducing HVAC capital and operating costs are ventilation airflow requirements, climatic parameters, exchanger recovery system performance factors and duration of operation.

A Japanese electronics company has developed a new type of gas-to-gas heat exchanger, called the Ductron. The heat exchanger has a simple structure composed of aluminium or stainless steel pass partition plates stacked with a gas passage (1 cm wide) between each plate, Heat exchange duct- Ductron and can be installed as part of an air duct system. It is applicable not only to HVAC systems but also to various industrial applications. The efficiency level is over 5 0%.