BACKGROUND

The traditional design methods has producted, in recent times, buildings that:

• are built with materials characterized by high contents of embodied energy;

• use high amounts of nonrenewable energy sources;

• produce notable quantities of polluting substances;

• set the problem of disposal of material and/or recycling in maintenance, renovation and dismantling phases of buildings.

Environmental considerations related to traditional design methods of buildings urgently need a different approach.

New ‘sustainability oriented’ design criteria have to be set, in addition to new materials, building components, building techniques and technologies.

A meaningful goal may be the design of buildings that require less energy without loss of comfort. That means reducing building services powered from nonrenewable energy sources. Therefore, design and realisation of natural ventilation systems constitute an important subject in the research field on the ability of buildings to respond to climatic conditions.

The ‘passive-type based’ solutions characterized by using components or parts traditionally already existing in buildings seem particularly interesting. This approach avoids the introduction of additional components in the building fabric and, above all, it allows the selected solutions to be inserted in existing buildings.

This study aims to evaluate how the stairwell can be an essential element of natural ventilation systems in low-rise buildings.

This research evaluates how parts of buildings can act as an indoor microclimate control system. Computational Fluid Dynamics (CFD) codes [3] were used in order to design/verify the behaviour of the building components as a natural ventilation system.

This study focuses on building types that are very common, such as the blocks of in-line houses (three — to five-storey with a single stairwell and with two apartments on each floor). The natural ventilation system studied is characterized by easy implementation in energy retrofitting of buildings and by inexpensive installation and management, furthermore, the related operation is quite easy.

In the energy retrofitting of buildings, the finalization of systems with the aforesaid characteristics would allow their implementation on a significant percentage of the building stock in the followings sectors:

— indoor air quality, when the system is designed for only natural ventilation;

— energy savings when the system deals with passive cooling.

In this study, in fact, the main innovation is the different architectural and functional conception of traditional building components, such as the stairwell. In addition, the stairwell is not only used as a chimney in order to increase the air-change rate in the cold season, but it can be used also as a wind-catcher in summer.

The main results of CFD simulations concern the design of the stairwell openings (location, size, aerodynamic characteristics) and the design of an aerodynamics control system.

The behaviour of the examined natural ventilation system is governed by a very large number of parameters. The results shown concern only a certain number of the typical boundary conditions. However, these results can be useful for the designing of other similar natural ventilation systems.

Future research projects will concern the evaluation of different boundary conditions. The further aim is the definition of the most relevant parameters for the designing of similar systems.