The operation and performance of forced-air ventilation systems with the aid of a dynamic modeling and simulation computer program are presented. The functions and features of GEMS (Generalized Engineering Modeling and Simulation), a dynamic modeling and simulation software tool, are briefly described. Using GEMS, the effects of different ventilation airflow rates and sensible and moisture efficiencies on the thermal comfort environment within the conditioned space were analyzed.

The heating degree-days method is widely used for calculation of the air change heating energydemand. However, different countries perceive different values for base temperatures due todifferent insulation levels and internal loads, decreased infiltration rates through tighterconstruction practices, and low temperature settings in efforts to reduce energy consumption.This has always made it difficult to make accurate comparisons for heating energy demandbetween different countries.

Measurements of ventilation rates and internal temperatures have been recorded in a naturallyventilated auditorium with high intermittent heat gains for a wide range of weather conditionsat a UK site. Satisfactory internal temperatures and high ventilation rates have been found forwinter, mid-season and summer external conditions.Simple ventilation and thermal models have been derived from experimental data whichallow the prediction of ventilation rates and internal temperatures within the auditoriumdespite the complex natures of the flow regimes and heat transfer mechanisms present.

This paper presents an experimental study of natural ventilation induced by combined forces of thermal buoyancy and opposing wind in a single-zone building. Experiments demonstrated that for a certain range of buoyancy strength and wind speed, two different stable ventilation modes and thus flow rates exist for a fixed building geometry at given buoyancy and wind strength. In these situations, the final ventilation mode and the ventilation flow rate are dependent on the ventilation history of the building.

This paper outlines work in progress to develop dissemination material to assist the appropriate application of solar and passive ventilation in urban buildings.

Conventional models of building occupants' environmental preferences such as thermal comfort are used to give guidelines for the average environmental conditions that will satisfy large groups of people. The research described in this paper investigates how the preferences of an individual occupant can be modeled to predict their preferred thermal and environmental conditions. A novel, Internet based questionnaire was developed to gather thermal sensation votes.

A number of single tracer gas techniques (decay, step-up, homogeneous constant emission,inlet pulse and homogeneous pulse) suitable for measuring the local mean ages of air in multizonebuildings exist, each having their advantages and drawbacks. The characteristics of thedifferent available techniques are compared from theoretical and practical points of view. Thehomogeneous pulse technique has not been experimentally validated before. This techniquerelies on pulses of tracer gas being injected into the different zones in amounts, which areproportional to the zone volumes.

The Building Air Tightness is an important parameter on ventilation systems performanceand energy losses.Yet, the total amount of leakage is as important on performances as their effective positionin the room.Some calculations have been run according to prEN 13465 from TC156 WG2 for differentbuildings (single house, dwellings and commercial buildings) varying air tightness, valueand repartition for different ventilation systems (natural, mechanical exhaust, mechanicalexhaust and supply).All these calculations have been compared focusing on ventilation losses during heatingseason in Paris.So

Dwellings airtigthness is not well known in practice, in France.When dwellings are equipped with mechanical ventilation systems (which represents about 95% of the new dwellings in France) the airtigthness can strongly influence the performance ofventilation.In the frame of the European Joule Project TIP-VENT (Towards Improved MechanicalVentilation Systems) [1], measurements of airtightness and underpressures were made onthree multifamily buildings.

Before starting to design an HVAC installation for treatment, supply and exhaust of air to and from a building the needs should be listed, transformed to requirements and their consequences analysed. Requirements lead to different amounts of airflow for their fulfilment. These needs for airflow should be calculated. The demand leading to the highest call for airflow will decide the airflow for which the equipment should be dimensioned - the dimensioning airflow.