Passive hollow tubes consist of a light pipe transport section with, at the upper end, some device for capturing natural light and, at the lower end, a means of distribution of light within the interior. The wider use of the systems is currently limited by the lack of quantitative design methods other than those based on empirical data. This paper presents results of laboratory and field measurement of luminous flux output and luminous intensity distribution for various configurations of passive solar light pipes. The results indicate quantitative performance and form the basis of a number of methods of performance prediction for a wide range of passive light pipe system configurations.

This paper reports daily and seasonal patterns of lighting use in offices where occupants were able to vary the level of illuminance falling on their working areas. The results show that occupants set a wide range of illuminances, many of which are significantly below CIBSE Code recommendations leading to significant energy savings throughout the year. Although users report use of controls for a variety of reasons, the results of the long-term monitoring of switching behaviour reveals that very few in fact use them for anything other than to switch on upon arrival at work, with further use of systems during the day being rare. Evidence suggests that the way in which systems are configured exerts influence over the level of electric light occupants work under. There is some evidence of an effect of daylight availability on levels set but little evidence to suggest pervasive and consistent user preferences for levels of electric light.

The use of locally addressable dimmable lighting systems has been examined in 14 open-plan office buildings. This paper discusses user attitudes toward control systems and the luminous conditions they produce. The majority of users are satisfied with both the quantity and quality of light on their workstations and are generally positive towards systems. This is despite large numbers of them working in illuminances significantly below current CIBSE recommendations. This indicates a significant potential for energy saving, since increased personal control leads to the use of lower lighting levels without detriment to occupants’ perceived lighting quality and visual comfort.

A study of 14 open-plan offices equipped with occupant controlled general lighting recorded achieved workstation lighting conditions at a number of times of the year. The results confirmed the occurrence of a wide range of workstation lighting levels, many significantly below CIBSE Code recommendations, with average electrical loadings due to lighting in the order of 55% of maximum. System con-figuration had a significant influence on luminaire output, illuminances and energy consumption. In general the lowest luminaire outputs were in buildings where the default reset level was to a low output, with the highest outputs being in buildings having high reset levels and large control groups. In addition locally sited control devices were associated with lower luminaire output.

This paper reviews developments in hybrid light guidance systems. In these daylight and electric light are simultaneously delivered into a building where they are combined and distributed via luminaires. The technology used in hybrid systems, both conceptual and realised, is discussed. The review speculates as to their likely performance in terms of daylight delivery; capital and running costs; user reaction to the systems; potential impact of the systems on the building which they light; and suitable design methods. It is noted that a substantial amount of work remains before the potential of hybrid systems may be realised, notably on their long-term economics and feasibility in different geographic locations.