Lawrence Berkeley Laboratory is developing a PC-based computer tool, the Retrofit Energy Savings Estimation Model (RESEM) which can provide high-quality estimates of energy savings, based on actual pre-and post-retrofit utility bills. Designed to be used by state and regional energy office staff who have little energy modeling expertise and access to only limited information regarding a building and its retrofits, RESEM hides much of its sophistication behind a simple, intuitive interface.

Building energy analysis programs have undergone a slow evolution since arrival over a decade ago. The frequency of use and number of applications for these sophisticated modeling tools seems to have reached a plateau. Changes are underway that may result in renewed vigor in the field. This paper reviews some of the dominant energy analysis issues. Recent thrust areas are examined for the alternative futures they suggest.

Computers are currently used for a large variety of tasks in building design and analysis. Among the basic software types used are 2-D draughting systems, 3-D modelling systems, spreadsheet and database programs, technical calculation and simulation software. One of the major drawbacks in today's situation is that almost every program uses a unique internal representation of the relevant data describing the building to be designed or analyzed. Consequently it is very difficult to exchange data directly between different programs.

An index of local thermal comfort and pollutant distributions have been computed with the TEMPEST computer code, in a transient simulation of an air-conditioned enclosure with an incomplete partition. This complex three-dimensional airconditioning problem included forced ventilation through inlet vents, flow through a partition, remote return air vents, an infiltration source, a pollutant source, and a thermostatically controlled airconditioning system. Five forced ventilation schemes that varied in vent areas and face velocities were simulated.

Proposed construction of high rise buildings near the U. S. Naval Observatory in Washington D.C. caused astronomers to ask what effect the heat released by these buildings would have on their ability to make accurate observations. Models of the thermal performance of the proposed buildings were developed and used to estimate the rate of heat release to the atmosphere.

Collaborative efforts among building simulation researchers in Europe and the US have resulted in wide acceptance of certain features as necessary attributes of future simulation environments. As identified 'in the Energy Kernel System (EKS), the principal features are those of the object-oriented programming (OOP) paradigm, in which a hierarchy of submodels is readily defined and interconnected to form system models of widely varying purpose, solution methodology, and implementation description.

The heat transfer processes occurring in the earth surrounding a building have a substantial effect on the building's energy consumption. During the heating season, for example, heat loss through ground- contact surfaces may be one of the most significant contributors to building heating load. Equipment sizing procedures and building energy analyses must use some method for calculating heat exchange between the building and the surrounding earth if they are to adequately calculate the building heating and cooling loads.

Modellers ands users of simulation softwares need to agree on a standard way to state the physical bases of their models The proposals presented in this paper are not new; they refer to the very classical way of describing thermodynamical systems. The basic piece of this description is the reference volume which may be "crossed" by mass and energy flows and which may also have some (mass and/or energy) "capacity". R-C networks are nothing more than "degenerate" or "simplified" sets of reference volumes.

This paper describes a general purpose software, Florida Software for Engineering Calculations (FSEC 1.1), that is capable of solving various transport equations used in building science (e.g., combined heat and moisture transfer, fluid flow, contaminant dispersion equations, etc.). The governing equations are solved by finite element methods. General capabilities and an overview of the software structure are given.

Many criticisms have been made about existing software for building energy analysis and simulation. In this paper, we try to show the interest of the model-based approach. The credibility of simulation results is pointed out. Main aspects of the CSTB contribution, in the framework of the GER ALMETH, are presented : the PROFORMA project about model documentation, and the MODELOTHEQUE project aiming to the design of a specific model base and its intelligent management system.