近年来，人们对能源短缺问题进行了大量研究，认为美国对能源的需求将很快超过其发电能力和化石燃料供应。根据斯坦福研究所（Stanford Research Institute）一份被广泛引用的报告，住宅和商业建筑的空间供暖和制冷约占美国总能耗的20%，1968年美国的总能耗为每年60万亿Btu。此外美国东海岸地区频繁停电和停电是夏季空调用电需求超过预期的良好迹象。在某些时候，电力公司的供电和配电能力会受到影响。正是在这种背景下，建筑物的设计最需要精确的热负荷和冷负荷计算方法，以最小化能源需求。 人们普遍认为，如果建筑物的隔热性能得到提高，就可以设计成节能型建筑；窗户尺寸、漏风和照明水平降低；正确安装遮阳设备；充分设计、安装和维护加热和冷却系统；它们的蓄热能力得到了最充分的利用。然而，这些节能功能必须考虑到许多限制因素，例如材料、施工和维护的额外成本、符合当地建筑规范、居住生活方式、美学、施工实践和设备可用性。尽管存在这些限制，但目前仍有足够的工程信息和技术基础，足以保证对建筑物加热和冷却的各种设计方案进行广泛研究，以最大限度地减少能源浪费。 例如，基于常规稳态计算的加热和冷却系统的设计和运行通常会导致设备尺寸过大，以及待控制空间过热或冷却。过度设计的系统通常运行效率较低，需要更多的材料（因此需要更多的能量）来生产，从而形成恶性循环。从能耗、峰值功率需求和上述许多实际约束的角度来看，设计最佳供暖和制冷系统的一个有效方法是通过精确的模拟研究建筑物的热性能。由于计算机模拟的使用使得评估各种设计方案对净能耗的敏感性成为可能，因此它们可以成为设计过程中的有效工具。 然而，为了在计算机上进行此类设计研究，所使用的计算机程序应全面，并应表明对与能源使用有关的许多参数变化的正确响应。ASHRAE能源需求工作组推荐的方法可以满足这些要求，因为它旨在解决建筑结构、占用空间中空气之间的精确传热关系。居住者、照明设备和其他内部设备，如下所述。引文:德克萨斯州达拉斯ASHRAE交易会第82卷第1部分研讨会

Numerous studies in recent years on the matter of energy shortage lead one to believe that the U.S. demand for energy will shortly outstrip her power generating capacity and fossil fuel supply. According to a well quoted report of the Stanford Research Institute space heating and cooling for residential and commercial buildings amounts to approximately 20% of the total energy consumed in the U.S which was 60 trillion Btu per year in 1968. Moreover. frequent blackouts and brownouts in the east coast region of the U.S. are good indications that the electric power demand for summer air conditioning exceeds. for certain times, the capability of supply and distribution by the power companies.It is under this context that accurate methodology for heating and cooling load calculations is most needed for the design of building which is to minimize the energy requirement. It is generally accepted that buildings can be designed to be energy-effective if their thermal insulation is increased; window size, air leakage, and lighting levels decreased; shading devices properly installed; heating and cooling systems adequately designed, installed, and maintained; and their heat storage capability most fully utilized. These energy saving features, however, must be considered with reference to numerous constraints, such as added costs for material, construction and maintenance, conformance to local building codes, occupancy life styles, aesthetics, construction practices, and availability of equipment.In spite of these constraints, sufficient engineering information and technical basis exist today to warrant extensive studies on various design alternatives for heating and cooling the building to minimize the wasteful use of energy. Design and operation of heating and cooling systems based upon conventional steady-state calculations, for example, usually result in oversizing of equipment and overheating or cooling of the space to be controlled. An overdesigned system usually operates at lower efficiency and needs more material (consequently more energy) to produce it, thus creating a vicious cycle.One effective way to design the heating and cooling systems which is optimum from the standpoint of energy consumption, peak power demand and many practical constraints mentioned above, is to study the building thermal performance by using accurate simulations. Because the use of computer simulations makes it possible to evaluate the sensitivity of various design alternatives on the net energy usage, they can be an effective tool in the design process. In order for such design studies to be conducted on the computer, however, the computer program to be used should be comprehensive and should indicate the proper response to the change of the many parameters which are pertinent to energy usage. The methodology recommended by the ASHRAE Task Group on Energy Requirements can meet these requirements, because it is designed to solve exact heat transfer relationships among the building structure, air in tne occupied space. occupants, lighting fixtures and other internal equipment as described hereafter.