在过去几年中，居住建筑的供暖、通风和空调（HVAC）系统以及这些系统的运行方式对其服务的建筑能耗的影响都有了很大的增长。最近在这些系统燃料供应方面经历的“能源危机”只强调了一个事实，即一些建筑/系统设计比其他建筑/系统设计消耗更多能源。在某些情况下，选择性设计标准要求选择具有固有高能耗的HVAC系统类型。其他系统的选择基于最低安装成本或易于操作，而不考虑维护和操作成本。 “能源危机”只是让我们意识到自然资源的物理限制，并迫使我们意识到，为了持续提供能源，我们必须保护这些资源。完全有可能，最终的解决方案将在于开发替代能源，但这种解决方案将在未来数年内实现。因此，保护现有能源供应是我们近期能源计划的一个重要方面。

The past few years have seen a great growth in the area of heating, ventilating and air-conditioning (HVAC) systems of occupied buildings and the manner in which the operation of these systems affects the energy consumption of the buildings they serve. The recent "energy crisis" which has 'been experienced with regard to the supply of fuel for these systems has only emphasized the fact that some building/ system designs consume more energy than others. In some cases, selective design criteria have dictated the selection of HVAC system types with inherently high energy consumptions. Other systems have been selected on the basis of minimum installation costs or ease of operation, with no consideration given to the cost of maintenance and operation.The "energy crisis" has simply made us aware of the physical limitations of our natural resources and forced us to realize that in order to have a continuous supply of energy we are going to have to conserve these resources. It is entirely possible that the ultimate solution will lie in the development of alternative sources of energy, but such a solution would be years in the future. Thus, conservation of existing energy supplies is an important facet of our energy program for the immediate future.