The paper gives an outline of existing modelling capabilities as well as an overview of current developments in integral modelling of hygrothermal conditions for whole buildings as presented within IEA Annex 41. Such models deal with the heat, air and moisture conditions of most relevant elements of buildings: The indoor air, the building envelope, inside constructions and furnishing. These building elements interact with each other and they are influenced by the use of the building, the building services, and the outside climate.

Combined heat, air and moisture (HAM) simulation at the envelope level and building simulation havebeen two separate activities for many decades now. In HAM-models, inside temperature and inside relative humidity are handled as known boundary condition, while all building simulation tools predict inside temperatures and net energy demand without any consideration for relative humidity.Things started to change when airflow modeling became doable.

At the conceptual design stage, one needs to pay considerable attention to both the energy as well as indoor air quality (IAQ) requirements. Often, designers tend to overlook ventilation and IAQ issues and conceptualise the HVAC design more from energy considerations. An energy efficient design of airconditioning system in hot and humid climates is quite challenging in view of the high humidity levels prevailing all-year round. This paper outlines some of the key factors that could lead to inadequate or inefficient ventilation and, thereby, poor IAQ.

This paper presents an analysis of energy and comfort performance of typical office buildings for summer cooling in five climate zones in China using the natural ventilation assessment tool, which is developed based on the integrated thermal and airflow model. Harbin, Beijing, Shanghai, Kunming and Guangzhou are selected as the five representative cities for Very Cold, Cold, Hot Summer and Cold Winter, Mild and Hot Summer and Warm Winter zones respectively. The cooling energy consumption with air conditioning system is compared to that with natural ventilation system.

An earth-air heat exchanger (EAHX) has been implemented in a low-energy office building in Kortrijk,Belgium. An extensive monitoring campaign was conducted to define the energy consumption in the building and the contribution of the EAHX to energy savings. This paper presents the results of the measurements and compares the measured performance of the EAHX to the building energy use and to results of a simulation model for 3D transient heat transfer.

A multi-disciplinary study to comprehensively measure and analyze operational performance and indoor environmental conditions in a sample of typical, commercial office buildings in the United States is described. The study will provide data that are currently not available. The indoor building factors that will be investigated during this study have never been formally studied in a comprehensive and systematic manner.

Natural night ventilation is an energy efficient way to improve thermal summer comfort. Coupled thermal and ventilation simulation tools predict the performances. Nevertheless, the reliability of the simulation results with regard to the assumptions in the input, is still unclear. Uncertainty analysis is chosen to determine the uncertainty on the predicted performances of natural night ventilation. In addition, sensitivity analysis defines the most important input parameters causing this uncertainty.

With the exception of a few analyses of the impacts of ASHRAE Standard 62-89 and energy use in specific buildings, the energy use in commercial building due to infiltration and ventilation flows has received little attention. However, as improvements have been made in insulation, windows, etc., the relative importance of these airflows has increased. Previous work at NIST described a research plan to quantify, and assess opportunities to reduce, the energy and indoor air quality impacts of building airtightness and ventilation system control in office buildings (Emmerich et al. 1995).

Measurements of spoiler aerodynamic noise, generated in a low velocity flow duct and radiated from an open exhaust termination, have been made in the form of sound power spectra. The individual 1/3 octave power measurements are satisfactorily collapsed with the aid of derived theoretical scaling laws. Non-dimensional spectra are presented which permit generalized predictions of flow noise for bluff bodies, including splitter attenuators, mounted in low speed flow ducts.

On the basis of a method devised by Nelson and Morfey, measured sound power levels generated by a variety of induct spoiler configurations have been collapsed. A method of determining the duct clear area ratio and magnitude of the characteristic dimension coefficient from the measurement of the pressure loss has been devised. The non-dimensional spectra produced have been used to predict the sound power levels generated by single-vane dampers. The predicted levels are in good agreement with measured levels.