Energy shortages in urban areas and rapidly rising energy costs will soon make building energy consumption an important element in architectural design. Previously, this factor had been given consideration only in the latter stages of design, and then by the consulting engineer. Now, the architect will have to use it as one of the criteria in evaluating alternative solutions. To aid the architect in this analysis, ENERPAC has been developed. ENERPAC is a computer program for building energy design. It is designed especially for the architect to use in the early stages of a project by using variables of the type and scale appropriate to this level of design. The program is written in conversation language, mainly in the form of questions directed to the user. After interrogating the user to obtain the necessary data, calculations are made to determine the building energy load. The user may then change the variables, as desired, to evaluate their effect on the load. In addition to its use in new building design, the program has also proven useful for obtaining a quick determination of building loads for cost estimates, such as adding air conditioning (cooling) to existing buildings. The five areas of investigation and documentation covered by this thesis were (1) existing programs, (2) program requirements, (3) methodology, (4) results, and (5) conclusions. A listing of the program and a User's Manual are included in the Appendix. / M.Arch.