ABSTRACT

The debate on the best way to design for the warm humid climate is ongoing among researchers as it is agreed that it is the most difficult climate to design for. The ongoing dilemma is whether to build lightweight or heavyweight structures in order to achieve optimum thermal comfort levels. Heavyweight construction
already exists at the East African coast, which experiences warm humid climate, and Lamu is no exception.
Lamu Old Town is a UNESCO World Heritage Site with its architecture consisting of the traditional, densely clustered, heavyweight Swahili buildings. However, a change has been observed within Lamu old town recently by UNESCO/ICOMOS/ICCROM and the Lamu council of elders where new individual lightweight
buildings are coming up, which do not adhere to the conservation regulations laid down by UNESCO. The aim of this research therefore, was to contribute to the ongoing discussions by carrying out a comparison of the thermal performance of the newer individual buildings, the refurbished buildings and the traditional
buildings and making recommendations on the best way of putting up new buildings in the warm humid climate of Lamu old town. 

The author carried out this research by reviewing the existing literature on design for warm humid climate, as well as, on the history and architecture of Lamu old town. This formed the basis of the visit to the area of study where field work was carried out in terms of monitoring the hygrothermal performance of the selected
case study buildings which represented the traditional, refubished and new typlogies. The research data was presented in the form of photographs, analytical notes, tables, graphs and architectural sketches. The findings of the study revealed that the recorded average indoor temperatures of all the buildings studied were above the recommended upper comfort limit of 27oC. However, the traditional Swahili buildings performed better than the new buidings with the traditional verandah building (Mwana Arafa Jambeni building) being the best thermally performing building and the new verandah building (Stop Over Guest House), which was built in 2008, being the worst thermally performing building. The new verandah building studied had an average relative humidity reading of 62.15%, which was above the recommended upper comfort limit of 61%. All other buildings studied had average humidity readings which were below the recommended upper comfort limit.

The author therefore recommended architectural parameters for putting up new buildings within Lamu old town in order to create indoor thermal conditions that are within the recommended indoor temperature and relative humidity comfort range. This includes the use of passive design strategies in both the urban planning and building design such as shading the building against direct solar radiation and allowing for permanent flow of air, among others. The author also recommended for a similar study to be done for the thermal performance of traditional, refurbished and new buildings in other Swahili coastal towns as the thermal performance may vary with the altitude of the town.

CHAPTER 1:  BACKGROUND OF THE STUDY

Thermal comfort is defined by British Standard EN ISO 7730 (2005) as the condition of mind that expresses satisfaction with the thermal environment and is assessed by subjective evaluation. There exists a problem in controlling man’s thermal environment and creating conditions favorable to his activities (Olgyay V. (1963) Design with Climate). The effect of climate on man is an important  factor in building design as it is essential that the mind and body recovers from the mental and physical fatigue resulting from the activities of the day through recreation, rest and sleep. However, this is often impeded by unfavourable climatic conditions with the resulting stress on body and mind leading to discomfort, loss of efficiency and an eventual breakdown of health (Koenigsberger et al., 975). Therefore, one of the main tasks in building design, according to Koenigsberger et al, is to provide the best possible indoor climate. This can be achieved by responding to climatic conditions and the environmental factors experienced within the building location such as air temperature, humidity, radiation and air movement.

The climatic conditions experienced in the area of study, Lamu Old town, is warm and humid. Warm humid climates are found in a belt near the equator extending to about 15oN and 15oS and are characterised by very little seasonal variation throughout the year with the only punctuation being that of periods with more or less rain and the occurrence of gusty winds and electric storms (Koenigsberger et al., 1975). The town is located 2 oS of the equator, at an altitude 0f 308m above sea level, in Lamu Island, which is part of Lamu County (Fig 1.2). The environmental factors experienced include high temperatures throughout the year, with an average of 27.1 °C, while the annual mean relative humidity is 78.2%. The average amount of rainfall recorded annually is 895 mm with the highest recorded amount in May and the least amount in February. The predominant wind direction being North-East

Thermal Performance of Traditional, Refurbished and New Buildings in Lamu Old Town Introduction from December to March (Kaskazi winds) and South-West (Kuzi winds) from April to September (UN-Habitat, 2016). 

In addition to the climatic conditions experienced due to its location along the East African coast, another important factor in building design is that Lamu Old Town is rich in history and culture with it being the oldest and best-preserved Swahili settlement in East Africa. The architecture and urban structure of the town demonstrate the cultural influences that have come together there over several hundred years from Europe, Arabia, and India. It is due to this reason, among others, that the old town was gazetted as a UNESCO World Heritage Site (Fig 1.3) in 2001. Other factors that contributed to its gazettement as a heritage site include its important religious function as a significant centre for education in Islamic and Swahili culture and its representation of a significant phase in the history of the region as a major seaport which led to the interaction between the Bantu, Arabs, Persians, Indians and Europeans.

The town is characterized by narrow streets and coral stone buildings (Fig 1.4) with impressive carved
doors, influenced by a unique fusion of Swahili, Arabic, Persian, Indian and European building styles.
The buildings on the ocean with their arcades and open verandas provide a unified visual impression
of the town when approaching it from the sea. The vernacular buildings are internally decorated with
painted ceilings, large niches (madaka), small niches (zidaka), and pieces of Chinese porcelain  (whc.unesco.org, 2020). This research therefore focuses on studying not only the design solutions in Lamu old town in response to the climatic conditions experienced, but also in response to the rich historic and cultural value of the town.