A project was formulated for the purpose of studying the possibility of improving indoor climate in hot countries without the use of fans and/or air conditioners. This climate regulation technique is here termed passive climate regulation. In the present report the results of the first stage in a series of studies are presented and discussed. In this stage the principles involved are outlined and the computational techniques are demonstrated for relatively simple cases. These are then supported by experiences from practical applications to one of a number of similar construction projects carried out in Saudi Arabia. The important conclusion to be drawn from this project is that passive climate regulation is a technique which can easily bring about comfortable indoor climate, especially for buildings in hot-dry regions.