ABSTRACT
Museums and art galleries collect, preserve, analyse and display historical artefacts and various achievement of the past. Light is basic requirement in museum design for the appreciation of art work. However, achieving daylight in museum spaces particularly in tropical climate is challenging due to its effect on artefacts and this has resulted to over dependence on artificial light. Daylighting has an important role in sustainable architecture as it affects the energy consumption in a building and also promote work efficiency through promoting good human health. In view of this, it is necessary to improve daylighting in museums in order to reduce electricity demand and increase comfort of the users and also as a tool for advance architectural creativity. Hence, the aim of this study is to test daylight performance of light pipe for optimum lighting in museum design in tropical climate. The study makes use of case study approach and quasi experimental (simulation) to test daylight performance of tubular light pipe. Literature review establishes the level of day light require in museum spaces, while case study find out the types of collections in Nigeria museums and daylight level in the selected museum galleries with light metre readings on sensor points at 900mm above floor level between 1:00pm-3:0pm. To test for the light pipe performance, a standard room of 3mx3mx3.6m was modelled, with light pipe of different aspect ratio (diameter to length) in Ecotect and result visualise in radiance and Daysim. Findings shows that collections in Nigeria museums range from paper paint work to sculpture and natural history collections, however, visual survey shows that some of the collections are not arranged according to the level of daylight requires for each museum space by IESNA guideline for museum light design. The illuminance readings recorde in most of the galleries are not up to standard when compared with the requirement for a museum. However appreciably some sensor points in the galleries fall within the range. Case study of museum of colonial history Kogi shows that 47% percent of the building fully depends on artificial light leading to high energy consumption in the galleries. Also, some galleries fully depend on artificial light. In the second case study the average illuminance level decreases from 335lux to 301lux at distance of 2750mm and 897lux to 301lux at distance of 4500mm from window plane respectively. The test result for the performance of light pipe shows that as the length of light pipe increases with constant diameter, the light level decreases at an average of 15.45% with maximum aspect ratio (D/L) of 1:10 admitting daylight level of between 213.7lux to 195.3lux to 105.2lux at conditions Ac, Ab and Aa respectively on sensor point A, giving optimum performance for most museum spaces. While, the test for effect of increasing diameter of light pipe on daylight performance shows that with increase in diameter of light pipe, there was steady increase in illumination level. For the diameter 300mm the illuminance level is 107.5 lux, while for the diameter 650mm the illuminance level is 177.2 lux at the Sensor B. The average illuminance continues to increase at 24.42% as the diameter increases so that diameter of light pipe has much effect on daylight output. The research recommended that for optimum performance of light pipe in museum in tropical climate the aspect ratio should not exceed 1/10. The outcome of the research work forms the basis for the application of daylight in museum design and the integrating of innovative daylight devices to diffuse and redirect light in museum spaces. Conclusively major findings suggested a comprehensive way that architects can follow in providing a museum that is less dependent on artificial lighting within the tropical wet and dry climate of Nigeria.