IBPSA1989

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.

Recently, the more accurate comparisons between the existing building behaviour and the simulations have shown that a more realistic model of the whole system has to be considered. In fact, the coupling effects and feedback loops between building, HVAC equipments and the control, are essential and can only be taken into account by a large scale simulation. This observation emerged more and more during the last three years. But, unfortunatly the direct coupling of the existing models in the same simulation software was not often possible.

This paper summarises the objectives and initial achievements of BEPAC, a recently formed club based in the UK which in many respects parallels the stated goals of IBPSA. The mission of BEPAC is "to improve the quality of building performance by encouraging the use and development of environmental prediction methods for buildings".

In recent years. researchers, designers and contractors have begun to investigate the use of new technologies in building construction and operation.The search for more efficient designs has led to complex and difficult to analyze components, systems, and whole building structures. Existing building energy simulation programs were initially conceived in an era when design questions were simpler than they are today. As a result, there are fundamental limitations in the analysis capabilities of these programs.

Today, the development of computer makes the accurate performance analysis of complex system by simulation available for most of the research community, and very soon for every concerned engineer. However, the simulationist approach requires a strong investment on the modelling of the system behaviour. This paper deals with a basic contribution on domestic hot water gas or fuel oil boiler models, usable for large scale simulation involving building and HVAC.

This paper summarizes the results of numerous building energy analysis and design tool evaluation exercises carried out under lEA Task VIII: Passive and Hybrid Solar Low Energy Buildings. These exercises have included: Empirical validation of detailed simulations using passive solar test room data from Canada, Switzerland and the U.S. Code to code comparison of detailed simulations for severa¡ passive solar system types in Copenhagen and Denver.