natural ventilation

This paper describes the development of a simplified tool which should be used at the early design stage for predicting air ventilation rates in a building. The method is based on the assumption that the air flow rate may be calculated as a function of two independent parameters. The first, called effective pressure difference, takes into account the local weather data, surrounding terrain, and building typology. The second is the overall building permeability, and accounts for permeable components (geometry and permeability), including vents.

The basic mechanism for natural ventilation in a building involves air flowing through purpose-made ventilator openings. These ventilators must be carefully designed as natural ventilation driving forces are weak compared to the dynamic forces created by mechanical systems. This paper describes a series of experimental parametric studies that investigated how components within a ventilator (in this case louvers and wire mesh screens) interacted. Air flow measurements through the individual louver and mesh components were compared to the air flow through mesh / louver combinations.

It is well known that iterative solution processes can lead to divergence when dealing with coupled airflow and thermal analyses for buildings ventilated either naturally or by a mixed-mode system. The Newton-Raphson method or its variants are used in almost all existing multi-zone airflow models. This paper discusses the qualitative features of the iterative solution processes of the Newton-Raphson method when used for coupled thermal and ventilation analyses of a simple one-zone building with two openings.

Global Information Systems (GIS) are being used to provide data on a wide range of environmental issues, and in the area of climate studies they are being used to determine zones of towns and cities where there are good or poor external environments. From this analysis, planning guidelines can be drawn up to ensure that developments either enhance or do not deter from the environmental quality of the surrounding area.

Natural ventilation, which may provide occupants with good indoor air quality and a high level of thermal comfort, and reduce energy costs, has become an important sustainable strategy in building designs. This investigation used three computational fluid dynamics (CFD) models: steady Reynolds averaged Navier-Stokes equation (RANS) modelling, unsteady RANS modelling, and large eddy simulation (LES) to study both wind-driven and buoyancy-driven natural ventilation.

This paper presents an overview of systems that utilise thermal mass in conjunction with night ventilation. It discusses the concepts behind and development of a system (CoolDeck) to improve the performance of systems where air is ventilated through false ceiling and floor voids to access hidden mass. The system improves thermal interaction between the circulating air and the thermal mass of the slab. A case study is presented demonstrating the effectiveness of the system in a refurbishment application (Stevenage Borough Council (UK) offices).