The Internal Environment of Buildings

The ways in which the internal environments of buildings are controlled have become very sophisticated as the needs of occupiers have evolved. The degree to which we are able to moderate the internal environmental conditions using the building enclosure and building services is great. However, it is easy to take for granted some of the features of buildings that affect the internal environment and to overlook the basis of the evolution of these features. Dwellings are generally designed to be aesthetically pleasing. Many of the details that we associate with building style and aesthetics have their origins in the need to satisfy functional needs. As buildings have developed, the role of building services to control heat, light and ventilation has become more significant. It is easy to forget that these services rely on the existence of an appropriate building envelope in order to achieve the required level of performance. The dwelling as we now know it has its origins in the simplest form of building enclosure, created by people to protect themselves from the extremes of the environment. The factors that led people to develop such enclosures in historic times are still evident today, and the function of dwellings, although now much more sophisticated, is still essentially the same as it was then. One of the primary functions of the building fabric is to create an environmental envelope.

Historically people have sought to modify and control the environment in which they live. In prehistoric times caves and other naturally occurring forms of shelter were used as primitive dwellings, providing protection from the external environment. As civilisation has developed, so the nature of people’s shelter has become more refined and complex, developing from caves and natural forms of shelter to simple artificial enclosures, such as those used throughout history by nomadic peoples worldwide. The ways in which the structures created by humans developed have depended upon the nature of the climate in specific locations and the form of building materials available locally. This resulted in the development of vernacular forms of building, based on the use of readily available local materials. As a consequence, identifiable styles of buildings developed in different areas, each adapting the form of the building to satisfy functional requirements with available materials and technologies. The ability to transport building materials over relatively large distances is a recent development. In Britain, for example, this was limited prior to the Industrial Revolution by the lack of effective transport networks. The advent of canals and rail links allowed materials to be transported over relatively large distances. Hence the extent of vernacular architecture has reduced, with materials from a wide variety of locations being incorporated into more modern buildings to satisfy functional requirements in the most efficient and cost-effective way possible. Examples of vernacular architecture are found in the UK and throughout the world. In areas such as the Middle Eastern desert regions, where diurnal temperatures vary considerably, being very hot during the day and cool at night, buildings of massive construction are common. Such buildings are referred to as ‘thermally heavy’ structures. The intense heat of the day is partly reflected by the use of white surface finishes, and that which is not reflected is absorbed by the building fabric rather than being transmitted into the occupied space. As a result of the slow thermal reaction of the building this stored heat is released at the times of day when the external temperatures may be very low, acting as a form of storage heater. The effects of direct solar gain are reduced by the use of a limited number of small window openings.

In areas where the climate is consistently warm and humid, such as in South East Asia, a very different approach to building design is required. In such situations, rare breezes may be the only cooling medium that can remove the oppressive heat and humidity of the internal environment. Since this cooling and dehumidifying effect takes place in a short period, the building must be able to react quickly to maximise any potential benefit. Hence, a ‘thermally light’ structure is essential to transmit external changes to the interior with minimal delay. The nature of buildings in such areas reflects these requirements, with lightweight building fabric and many large openings to allow cooling breezes to pass through the building.