In order to provide an integrated building design system that easily can be adapted by building designers, the Danish Building Research Institute has developed such system. It is based on experience gained as participant in the European COMBINE projects and from development of building energy simulation tools. The intention is that a number of computer tools for building design and analyses shares information about the buildings that they analyse, and that data for the building geometry can be provided by a CAD system.

Simulation tools are not yet used as much and as well as they should all along building life cycle ( BLC ). Most important decisions are still taken almost without using these tools. The work done in the frame of IEABCS Annex 30 consisted in identifying and eliminating as much as possible the main bottle necks encountered in the use of simulation tools.

Models used for forecasting of future energy demand are often econometrically based and do not attempt to look in detail at end uses of energy. It has become clear in recent years that 'this approach to energy forecasting can produce more realistic estimates of future demand in the building sector if it is used in conjunction with models which-cover important physical and social parameters and the contraints which these impose (Grubb 1990; Grubb 1991). Such complementary models provide insights which would otherwise be missed.

This paper concerns reasons - and solutions – for the time lag in the uptake and use of building simulation in the Czech Republic relative to many other countries. Following a brief introduction, several barriers to the use of simulation are identified. Barriers can be classified as cultural, economical or technical but there are many interactions. The paper then concentrates on recent work and activities, which aim to reduce these barriers.

The premise underlying this work is that introducing uncertainty considerations into simulation will facilitate risk assessment and that this, in turn, will help to improve designer confidence in simulation. Sources of uncertainty abound in building simulation and must be factored into the solution process. These sources have been identified and useful techniques for quantifying the effects of uncertainties are presented. Two approaches are described: the use of traditional statistical methods, and the use of alternative arithmetical methods.

Typical Meteorological Years obtained from observed meteorological records have become the de facto data source when evaluating thermal performance of buildings. However, this data source has various drawbacks, and alternative TMY assembling methods based on statistical and stochastic models seem to have been perfected to a point where they become sound alternatives. Numerical simulations of test cells were performed for a mid-latitude temperate climate, Lisbon.

This paper describes use of building energy performance modelling and simulation in design process at the early conceptual level of architectural design. Based on the architect’s initial ideas, four alternatives of building facade solution and airconditioning system operation were developed and simulated in real climate conditions, represented by typical winter and typical summer week. Results in terms of heating and cooling energy consumption and flux and air temperature in the double facade cavity course are discussed, and a recommendation for further design process is made.

New thermodynamic energy “water potential” based on the chemical potential of a component of mixture gases is defined as the driving force of gaseous phase water flux. Adhesive power, which is a kind of stress called “capillary attraction” and a part of the water potential, is proved as the driving force of liquid phase water flux. Then numerical model of coupled heat and water transfer using the water potential is introduced and influences of stress such as gravity and stationary pressure on water flux are indicated from the viewpoint of thermodynamics.

Coupled heat and moisture transfer equations which describe temperature and moisture fields in the building walls, the earth ground and so on are nonlinear. Due to the nonlinearity, the complicated analysis has to be performed in each time under the different boundary values. If linearization of the system with adequate accuracy can be achieved, a solution can be obtained simply by applying the superposition principle.

Object-oriented or modular simulation methods represent a concrete alternative to present monolithic building simulation technology. Modular methods have previously been used primarily for component based systems modeling, while envelope models have remained monolithic. In this paper, the advantages of the new technology are reviewed and an equation-based models library for systems as well as envelope modelling is introduced. The new library has been developed within IEA SHC Task 22 and is available as NMF source code. Airflow network models are combined with thermal.