natural ventilation

In contrast to mechanical ventilation, natural ventilation's performance is usually impacted by uncertain factors, including wind fluctuations, outside air temperature variations, and occupants' behaviours. These factors require a stochastic evaluation process for natural ventilation at the design stage such as quantifying the effective ventilation rates and optimising control strategy.

Windcatchers are roof mounted devices that use the action of the wind to provide top down natural ventilation to a room. Here, fresh air is channelled into a room while, at the same time, stale air is drawn out. This provides a simple but attractive natural ventilation methodology that is increasing in popularity in U.K. schools. However, an analysis of system performance has largely been limited to laboratory based measurements and the use of CFD to generate predictions.

This work investigates the impact of space planning, interior porosity and variable occupancy on the energy use in offices that is attributable to ventilation/infiltration and air movement. TAS, Lightscape, and Excel software packages were used to simulate and analyse airflow and thermal loads in different office layouts. These layouts were created by varying the internal configurations of a base case shell.

Wind catcher systems have been employed in buildings in the Middle East for many centuries and they are known by different names in different parts of the region. Recently there has been an increase in the application of this approach for natural ventilation and passive cooling in the UK and other countries.

In a hot-humid climate, comfort ventilation involving air movement over the skin of the human body is a prime consideration for thermal comfort. In developing countries with such a climate, the use of an air conditioner is not economically feasible by a majority of the population. Therefore, ceiling fan assisted cooling strategies hold significance. Fans increase the air movement inside rooms, thereby causing the layer of sweat over the occupant's body to evaporate. This paper aims to assess the evaporative cooling effect of a ceiling fan in a naturally ventilated house.

This paper presents a study aimed at evaluating the effectiveness of natural ventilation strategies used in government dwellings in the Egyptian desert climatic design region. Three government housing blocks, built in the New Al-Minya city, were employed as case studies. Autodesk-Ecotect and FloVent CFD software were used to simulate the internal air movement and air temperatures. Theoretical analysis shows that there is considerable cooling potential by natural ventilation, with the thermal comfort potential being improved by up to 52% peak and 33.5% average.

It is only comparatively recently, since the development of mechanical ventilation and refrigeration, that it has become possible to completely control the air quality and thermal environment inside buildings, irrespective of outdoor conditions. However, such control is an energy intensive process that requires reliable energy supply. Concerns about future security of conventional supply, combined with the impact of fossil fuel emissions on global warming, has resulted in renewed emphasis on building energy efficiency.

An experimental study of the phenomenon of buoyancy driven natural ventilation through single-sided horizontal openings was performed in a full-scale laboratory test rig. The measurements were made for opening ratios L/D ranging from 0.027 to 4.455, where L and D are the length of the opening and the diameter of the opening, respectively. The basic nature of airflow through single-sided openings, including airflow rate, air velocity, temperature difference between the rooms and the dimensions of the horizontal openings, were measured.

Designing for natural ventilation became permissible across an extended range of climate zones in 2004 with the incorporation of an adaptive model into ASHRAE's comfort standard (ASHRAE, 2004). This mainstreaming of adaptive comfort was further reinforced with the introduction in 2007 of a European standard (EN, 2007) that mirrored ASHRAE's precedent. Despite broad international acceptance and application of the concept, there remains a gap in the fundamental theoretical underpinnings of the adaptive comfort approach.

Solar chimneys may provide enough ventilation to buildings when properly designed. Although many design tools, theoretical models and experimental studies have been reported, the impact of many design parameters such as the construction thickness, the thermal resistance of the walls, the absorptivity of the internal surfaces of the chimney, the thermal mass of the chimney and the type of glazing, is not well known. This paper aims to provide information on the optimum sizing of the above parameters.