THE MAHONEY TABLE Applied Climatology ARC 810 Department

THE MAHONEY TABLE Applied Climatology (ARC 810) Department of Architecture Federal University of Technology, Akure, Nigeria ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

OUTLINE q The design process q The Mahoney tables q Example of the use of Mahoney tables ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

q INTRODUCTION The Mahoney tables are a set of tables used in pre-design analysis. The various tables are used: q Data collection, q Thermal stress analysis, q Determination of necessary remedial actions and specification for sketch detail, and q Design recommendation. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

q INTRODUCTION The example of the use of the Mahoney tables shown gives appropriate recommendations for: q Layout, q Spacing, q Air movement, q Size of openings, ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

INTRODUCTION q Protection of openings, q Design of walls, q Roofs and floors, q Outdoor sleeping, and q Rain protection. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

THE DESIGN PROCESS The design process is defined as involving sequential stages using three concepts: q. Analysis q. Synthesis q. Evaluation One of the methods is called the gradual method. This method takes the designer through the following three stages of design: ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

THE DESIGN PROCESS THE PRE-DESIGN ANALYSIS This usually includes a thorough analysis of climatic and other factors affecting design. It is usually necessary to collect data for this analysis. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

THE DESIGN PROCESS THE SKETCH DESIGN This is the stage when, as a result of synthesis, concepts are developed to produce a sketch design. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

THE DESIGN PROCESS THE DESIGN DEVELOPMENT This is the stage when working drawings, details and specifications are produced after evaluation. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

THE MAHONEY TABLES The mahoney tables were designed by Carl Mahoney as a result of studies conducted partly in Nigeria. They relate design decisions to climatic stress and how to relieve it. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

THE MAHONEY TABLES The following steps are followed in the usage of the Mahoney tables: DATA COLLECTION Monthly mean data about air temperature, humidity and rainfall are required for the Mahoney tables. The monthly mean minima and maxima of air temperature, the monthly mean minima and maxima of relative humidity and the monthly mean rainfall are obtained and entered in table 1 of the Mahoney tables. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

THE MAHONEY TABLES THERMAL STRESS The thermal stress both for the day and for the night is obtained for each month of the year. The thermal stress is obtained by comparing the temperature with the comfort limits. The maximum temperature is compared with the day comfort limits while the minimum temperature is compared with the night comfort limits. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

THE MAHONEY TABLES REMEDIAL ACTIONS The thermal stress gives an indication of the remedial action that can be taken to achieve comfort. It can be determined for how many months of the year there is need for ventilation, rain protection and thermal storage. This is specified by the humid and arid indicators. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

THE MAHONEY TABLES The arid indicators deal with thermal aspects of design. The need for thermal storage arises when there are hot days and cold nights. Uncomfortable night temperatures suggest outdoor sleeping while special treatment is required in cold climates. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

THE MAHONEY TABLES DESIGN RECOMMENDATIONS: The design recommendations are made on the basis of the remedial actions needed to be taken to alleviate thermal distress. They deal with separate aspects of design such as: ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

THE MAHONEY TABLES Layout: The layout reduces exposure to the sun when heat is a problem while compact courtyard planning is used when thermal storage is needed. Spacing: The spacing ensures good ventilation in hot and humid climates and reduces breeze penetration in colder climates. Air movement: The decision to use single or double banking is made on the basis of the need for ventilation and thermal storage. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

THE MAHONEY TABLES Size of openings: affects the ventilation rate. Large windows are recommended for hot and humid regions while small windows should be used when high insulation is required. Position of openings may affect the ventilation required for body cooling especially in hot and humid climates. Protection of openings from direct sunlight and rainfall depends on the amount of excess heat and rainfall. Walls and floors may be light or heavy depending on the need for insulation and thermal storage. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

THE MAHONEY TABLES Roofs may be heavy, light and well insulated or light with reflective surface and cavity. Outdoor sleeping is provided when comfortable conditions cannot be maintained indoors at certain periods of the year. Rain protection and drainage is necessary when there is heavy downpour over a period. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

EXAMPLE OF USE OF THE MAHONEY TABLES An example of the use of the Mahoney tables is shown in Table 10. 4 and 10. 5 for Zaria. From the recommendations it can be seen that the climate of Zaria requires a combination of design characteristics to relieve thermal stress. This is a result of the composite nature of the climate with a distinct cold and dry harmattan season, a warm and humid season and a hot and dry period. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

EXAMPLE OF USE OF THE MAHONEY TABLES ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

EXAMPLE OF USE OF THE MAHONEY TABLES q The orientation should protect the building from the western sun; there should be open spacing of buildings adequately protected from the harmattan winds and rooms should be single banked with permanent provision for air movement. q The total area of windows, doors and other openings should not be more than 20 to 35% of the wall area; they should be placed at body height on the windward side and protected from rain and direct sunlight to reduce heat gain. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

EXAMPLE OF USE OF THE MAHONEY TABLES q Roofs, walls and floors should be heavy with high thermal capacity and a time lag of over 8 hours. q Comfort cannot be achieved indoors during the hot dry period thus, space should be provided for outdoor living probably in the form of courtyards. q The intensity of rainfall requires adequate slope of roofs to ensure good drainage. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

EXAMPLE OF USE OF THE MAHONEY TABLES A computer program, MOTOLA, can be used for necessary calculations, print out a report including the climatic data used, the intermediate results obtained and the design recommendations. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

EXAMPLE OF USE OF THE MAHONEY TABLES The Mahoney tables also specify thermal performance of the recommended walls and roofs in greater details as follows| Light walls should have a maximum U-value of 2. 8 W/m² deg C, a maximum solar heat factor of 4% and a maximum time lag of 3 hours. Heavy walls should have a maximum U-value of 2. 0 W/m² deg C, a maximum solar heat factor of 4% and a minimum time lag of 8 hours with a maximum of 14 hours. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria

EXAMPLE OF USE OF THE MAHONEY TABLES Light roofs should have a maximum U-value of 1. 1 W/m² deg C, a maximum solar heat factor of 4% and a maximum time lag of 3 hours. Light and well insulated roofs should have a maximum Uvalue of 0. 85 W/m² deg C, a maximum solar heat factor of 3% and a maximum time lag of 3 hours. Heavy roofs should have a maximum U-value of 0. 85 W/m² deg C, a maximum solar heat factor of 3% and a minimum time lag of 8 hours. ARC 810: Building Climatology Department of Architecture, Federal University of Technology, Akure, Nigeria