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 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. Sensitivity analysis defines the most important input parameters causing this uncertainty. The results for a singlesided ventilation strategy in a single office are discussed.

In this paper a method to solve a design problem of hybrid ventilation system is proposedby building stack pressure around the ventilator using a flat bed, glass-shielded rectangular solarchannel. In support of this idea a CFD (Computational Fluid Dynamics) simulation based ontheoretical calculation is done. Here, natural convection and a k-e two-equation turbulence modelwere used together with the finite volume method.

The authors recently reported the detailed experimental results on that the discharge coefficient of the openings exposed to the wind driven airflow clearly changes depending upon the windangle and consequent conditions. A full-scale building model in a wind tunnel has been used for theexperiment. In this paper, the mechanism of the change is discussed more deeply, and the predictionmethods of the discharge coefficient are tested by the new experimental results for different conditions of opening size and location.

The natural ventilation of a room with a source of uniformly distributed heating at the base andwith vents at multiple heights is investigated both theoretically and experimentally. It is shown that the impact of additional vents can be predicted by determining the height of neutral buoyancy. As a room is heated it heats up to a uniform state and the relative height of neutral buoyancy depends on the ratio of the upper and lower vent areas. When a simple additional intermediate level vent is introduced a unique solution can be used to predict the resulting air flow.

It is difficult to evaluate the effect of cross ventilation quantitatively, because the indoor environment under cross ventilation is uneven and changes with the outside conditions. In this paper, the decay process of tracer gas is measured in uneven space under cross ventilation, and the property of spatial unevenness is examined by the concentration decay and velocity distribution.

We report on a series of measurements of the temperature at Houghton Hall, Luton,over the Spring and Summer of 2003. The data show that the building tracks the externaltemperature, but that the amplitude of diurnal temperature fluctuations typically lies within 2-6 C,while the external fluctuations may be as large as 15-25 C. This buffering of the internaltemperature is largely due to the thermal mass of the space which introduces a time-lag ofbetween 0.5-3.0 hours in the response time of the interior to the exterior space, over the periodof our survey.

This paper discusses the concept and performance of a naturally ventilated building with a double-skin facade in Tokyo. The building incorporates a hybrid ventilation system (natural ventilation integrated with air-conditioning systems) that makes use of buoyancy forces generated in a vertical airshaft in the center of the building. Field measurements were made in order to evaluate the performance of the double-skin facade during the summer and winter and also the performance of the hybrid ventilation system during the spring and autumn.

This paper describes a study on the performance evaluation of a hybrid ventilation systemwith a heat exchanger. This system has two passive stacks and a heat exchange unit, which includes a heat exchange element, a supply fan, an exhaust fan and a bypass route with a damper. In order to evaluate the system performance, the experiments and numerical simulations using a full-scale test house have been performed in winter or mild seasons. In the result, the ventilation rate and the heat recovery rate under the various conditions of the fan and the damper operation were clear.

There has been considerable interest in the interaction between buoyancy and wind pressure gradients on the overall structure of natural ventilation flows. Indeed, it has been shown that when wind and buoyancy forces act in opposition, it is possible that for certain wind speeds, multiple steady states may emerge, with a stable wind dominated and a stable buoyancy dominated regime being possible for identical conditions; while at lower wind speeds, the buoyancy dominated flow develops and higher wind speeds, the wind dominated flow develops.

As ventilation is a significant consumer of energy the rates of ventilation have often been minimized, particularly after the energy crisis in the early 70s, in order to reduce equipment and energy costs. This has caused in many countries indoor air quality problems. It has been shown that ventilation rates have adverse effects on communicable respiratory illnesses; on sick building syndrome symptoms; on productivity and perceived air quality. Often the prevalence of SBS symptoms is higher in air-conditioned buildings than in naturally ventilated buildings.