English

In order to assess the applicability of a more modular approach to the development of building thermal analysis programs, this paper begins with a review of some of the basic numerical methods used in simulation. These are discussed with some observations from other fields of study besides building simulation. Two major examples of advanced simulation methods are presented: the use of sparse matrix methods for heat transfer simulation and a modular calculation of building airflows.

This paper describes a design tool, 'Condensation Targeter', for assessing condensation risk in dwellings and the effect of remedial measures thereon. The BREDEM energy model is augmented by a moisture model to determine mean internal relative humidity (MIRH). This measure of condensation risk is calculated for two zones in a dwelling from mean internal temperatures, moisture generation and ventilation rates. Primary input data relate to occupancy (fuel expenditure and moisture production) and dwelling characteristics (thermal and ventilation).

Mathematical models of various kinds are important in many disciplines. Unfortunately, it is often difficult and time-consuming to develop models. This paper considers the possibilities to reduce model development work as far as possible by supporting reuse of models. Two basic ideas are discussed: First, use of symbolic descriptions (equations) to describe behaviour and second, concepts for modularization to make reuse of models both flexible and safe. The results presented are parts of project to develop computer aided engeneering tools for model development and simulation.

In 1937, Congress created the Bonneville Power Administration (Bonneville) to serve as transmission and distribution agent for electricity generated by the Bonneville Dam. Today, Bonneville, as a part of the United States Department of Energy, also distributes hydroelectricity from twenty-nine other federal dams in the Pacific Northwest to its "wholesale customers", the majority publicly-owned utilities. Bonneville's full service area covers approximately 300,000 square miles in the states of Oregon, Washington, Idaho, and Montana west of the Continental Divide.

Commercial building owners and managers face a complex array of HvAc technology options. Economicanalysis of the options requires consideration of technology characteristics, equipment operatingstrategies, and utility rates. The interaction among these factors is complicated, requiring structured analysis tools that go well beyond simple spreadsheets. To provide a uniform and well-tested approach, the Electric Power Research Institute (EPRi) has developed COOLAID, COOLGEN and COMTECH, which are PC analysis tools for commercial building technologies.

In a paper presented at the 1985 predecessor of this conference, I maintained that current PC microcomputer technologies provided the opportunity to develop a new generation of graphically oriented, interactive building modeling programs. Our efforts to implement one such program, called TAKEOFF, have not been an unqualified success but do provide lessons about this type of program. Generally, the technical proficiency required by interactive graphic programming is in another realm when compared to that required for "simple" building modeling.

Building simulation software alone can sometimes fall short of providing a reliable building model. The user can improve the fit by using empirical data to fine tune the simulation and properly reconcile the building's loads and it's systems' operations. The empirical data may take various forms but will generally include metered utility data and information from site visits and load monitoring. This entire process can be assisted using computerized techniques which in themselves model the building's energy balance.

Much effort has been devoted over the years to advance Building Performance Simulation (BPS) by improving algorithms and by extending the simulation domain to daylighting, acoustics, and indoor air quality. Yet in several recent relevant ASHRAE forums many attendees asked for transparency, useability, and flexibility of computer programs. The issues of flexibility, transparency, and ease of use are categories commonly associated with the user interface. Moreover, they relate fundamentally to software architecture. A good user interface is the foundation of a program, not a finishing touch.

At the present time several powerful simulation models exist for the assessment of building environmental performance at the design stage. However when used as design tools these models suffer from several fundamental limitations. Typically they fail to tackle the problematic issues surrounding data preparation in the face of uncertainty. Invariably models are functionally orientated, containing little knowledge of the application domain. This means that they cannot direct a users' line of enquiry, allowing 'Why do you ask' type responses for example.

The most common use of building energy simulations, by far, is in the design of buildings, especially non-residential ones. It is a common perception that the simulations ought to be useful for many other applications, such as commissioning, control and diagnostics. A distinguishing feature of the latter applications is that they require linking with monitored data, and this link must be addressed before the applications can be realized.