Since the start of the Industrial Revolution there has been a general improvement in working conditions. As part of this process, light in the work place was recognised as an important environmental factor. In the early years of the 20th century it was also recognised that in providing adequate lighting for a particular working environment, there was a need to avoid the potential negative effects of too much, or inappropriately distributed, light. One of the negative effects of light in the work place was glare. Holladay (Holladay, (1926)) attributed the negative effects of glare to impairment of vision caused by light scatter. Stiles (Stiles, (1929)) refuted Holladay's case by arguing that only a small proportion of the reduction in task visibility could be attributed to light scatter effects (where task visibility is a measure of how far above the visual threshold a task's contrast is). Stiles distinguished disability glare, a light scatter effect, from discomfort glare which was glare that could not be attributed to light scatter. The distinction made by Stiles resulted in the separate development of discomfort and disability glare models. Very few, if any, studies since Stiles have re-evaluated the potential association between subjectively rated discomfort glare, and physically based disability glare. In the study reported here, subjects were asked to set the appearance of a 2° glare source so that it appeared at the Borderline between Comfort and Discomfort, or BCD (Guth, (1963)). Each subject's visual threshold for a 4 cycle per degree spatial grating was measured under BCD and control conditions, and a comparison made to assess if light scatter effects from the glare source influenced threshold contrast, C_th. The results of the study indicate that C_th, can be lower in the presence of the glare source set to BCD. This anomaly may be explained by improvement in image quality caused by the glare source driving the pupil to a smaller diameter. More significantly, there was found to be a strong correlation between subjective BCD settings and age, and also between BCD settings and control condition C_th. Both of these results suggest an influence of light scatter on BCD settings of discomfort glare. This conclusion was further supported by the fitting to the data of the independently reported stray light function of Ijspeert et al (Ijspeert et al, (1990)). Thus the results strongly suggest a correlation between subjective BCD settings of a glare source and light scatter function. A conclusion that substantially weakens Stiles' argument that discomfort glare is not dependent on light scatter effects. Using the results of the study, a new threshold type model for assessing discomfort glare is proposed, which explicitly includes age as a parameter. However, much variance remains to be explained in the glare data. Therefore, a second theme investigated in the dissertation is the possible association between scene visual structure and visual discomfort. The results of this study indicate that there is a small but significant difference in the image structure of natural and man made environments. This difference may contribute to visual discomfort, but will require further investigation.

Para vegetação esparsa e de porte alto a determinação dos parâmetros de rugosidade é comprometida pela dificuldade em se observar condições que satisfaçam a lei logarítmica da velocidade do vento. Estimou-se o comprimento de rugosidade (z0) e o deslocamento do plano zero (d) por alguns métodos com medidas micrometeorológicas e da estrutura física de arbustos esparsos em região semi-árida, durante o experimento HAPEX-Sahel. A velocidade do vento foi medida em quatro alturas acima da superfície (3,0; 4,1; 5,3 e 8,5 m), e os fluxos determinados por correlações dos turbilhões a 9m de altura. Métodos baseados no perfil logarítmico foram aplicados em condições de atmosfera neutra. A altura média da vegetação era h = 2,06 ± 0,47 m. O método convencional (ajuste estatístico) resultou em estimativas satisfatórias de d e z0 em condições nas quais a validade do perfil logarítmico foi satisfeita. Com uma única altura de medida localizada acima da subcamada inercial as estimativas resultaram em valores ou fisicamente inconsistentes ou que não caracterizam a rugosidade da superfície. Quando se utilizou a velocidade de fricção dada pela correlação dos turbilhões na solução do perfil logarítmico, as estimativas melhoraram. A combinação do perfil logarítmico com a relação z0 = λ (h - d) proporcionou estimativas satisfatórias para os valores de λ = 0,188 e 0,190 determinados em função da estrutura física da vegetação, o que não foi observado para o valor médio da literatura (0,166). Relações entre a estrutura física da vegetação e o transporte de momentum estimaram apropriadamente d e z0. A rugosidade da área foi melhor descrita por d = 0,95 m = 0,46 h e z0 = 0,204 m = 0,1 h, sendo λ = 0,185. As velocidades horizontal do vento e de fricção foram mais sensíveis a variações em z0 do que em d. / For sparse and tall vegetation the estimate of roughness parameters is compromised by the difficulty in observing conditions that satisfy the windspeed logarithmic law. The roughness length (z0) and the zero-plane displacement (d) were estimated by some methods with micrometeorological measurements and the physical structure of sparse shrubs in semi-arid region, during the HAPEX-Sahel experiment. The wind speed was measured at four heights above of surface (3.0, 4.1, 5.3 and 8.5 m), and the turbulent flows determined by eddy correlations at the height of 9m. Methods based on the logarithmic profile have been applied in neutral atmosphere conditions. The average height of the vegetation was h = 2.06 ± 0.47 m. The conventional method (statistical fit) resulted in good estimates of d and z0 only under conditions of validity of the logarithmic law. Only one height of measurement located above of the inertial sublayer is enough to result in physically inconsistent values. When the friction velocity, given by eddy correlation, was used in the logarithmic law, the estimates improved. The combination of the logarithmic law with z0 = λ (h - d) provided satisfactory estimates of the surface roughness for λ = 0.188 and 0.190 determined in function of the physical structure of the vegetation; but for λ = 0.166, the average value of literature, the estimates where not good. Relationships between the physical structure of the vegetation and the momentum transfer estimated appropriately d and z0. The area roughness was better described by d = 0.95 m = 0.46 h and z0 = 0.204 m = 0.1 h, being λ = 0.185. Wind speed and friction velocity were more sensible to variations in z0 than in d.

Para vegetação esparsa e de porte alto a determinação dos parâmetros de rugosidade é comprometida pela dificuldade em se observar condições que satisfaçam a lei logarítmica da velocidade do vento. Estimou-se o comprimento de rugosidade (z0) e o deslocamento do plano zero (d) por alguns métodos com medidas micrometeorológicas e da estrutura física de arbustos esparsos em região semi-árida, durante o experimento HAPEX-Sahel. A velocidade do vento foi medida em quatro alturas acima da superfície (3,0; 4,1; 5,3 e 8,5 m), e os fluxos determinados por correlações dos turbilhões a 9m de altura. Métodos baseados no perfil logarítmico foram aplicados em condições de atmosfera neutra. A altura média da vegetação era h = 2,06 ± 0,47 m. O método convencional (ajuste estatístico) resultou em estimativas satisfatórias de d e z0 em condições nas quais a validade do perfil logarítmico foi satisfeita. Com uma única altura de medida localizada acima da subcamada inercial as estimativas resultaram em valores ou fisicamente inconsistentes ou que não caracterizam a rugosidade da superfície. Quando se utilizou a velocidade de fricção dada pela correlação dos turbilhões na solução do perfil logarítmico, as estimativas melhoraram. A combinação do perfil logarítmico com a relação z0 = λ (h - d) proporcionou estimativas satisfatórias para os valores de λ = 0,188 e 0,190 determinados em função da estrutura física da vegetação, o que não foi observado para o valor médio da literatura (0,166). Relações entre a estrutura física da vegetação e o transporte de momentum estimaram apropriadamente d e z0. A rugosidade da área foi melhor descrita por d = 0,95 m = 0,46 h e z0 = 0,204 m = 0,1 h, sendo λ = 0,185. As velocidades horizontal do vento e de fricção foram mais sensíveis a variações em z0 do que em d. / For sparse and tall vegetation the estimate of roughness parameters is compromised by the difficulty in observing conditions that satisfy the windspeed logarithmic law. The roughness length (z0) and the zero-plane displacement (d) were estimated by some methods with micrometeorological measurements and the physical structure of sparse shrubs in semi-arid region, during the HAPEX-Sahel experiment. The wind speed was measured at four heights above of surface (3.0, 4.1, 5.3 and 8.5 m), and the turbulent flows determined by eddy correlations at the height of 9m. Methods based on the logarithmic profile have been applied in neutral atmosphere conditions. The average height of the vegetation was h = 2.06 ± 0.47 m. The conventional method (statistical fit) resulted in good estimates of d and z0 only under conditions of validity of the logarithmic law. Only one height of measurement located above of the inertial sublayer is enough to result in physically inconsistent values. When the friction velocity, given by eddy correlation, was used in the logarithmic law, the estimates improved. The combination of the logarithmic law with z0 = λ (h - d) provided satisfactory estimates of the surface roughness for λ = 0.188 and 0.190 determined in function of the physical structure of the vegetation; but for λ = 0.166, the average value of literature, the estimates where not good. Relationships between the physical structure of the vegetation and the momentum transfer estimated appropriately d and z0. The area roughness was better described by d = 0.95 m = 0.46 h and z0 = 0.204 m = 0.1 h, being λ = 0.185. Wind speed and friction velocity were more sensible to variations in z0 than in d.

Mould growth affects a significant proportion of dwellings in the UK and Europe. The house dust mite is also known to inhabit most dwellings and is one of the key factors affecting the health of the occupants. One of the key variables affecting mould growth and house dust mite populations is relative humidity. The relative humidity in a dwelling is dependent upon both the moisture levels and the temperature. The ability to assess the impact of different interventions on the relative humidity depends upon the ability to model both the internal temperature and the internal vapour pressure. This thesis develops, tests and assesses the impact of four combined moisture and thermal models which predict micro-environmental relative humidity. Two thermal models are tested, the BREDEM-8 monthly model, and the BREDEM-12 seasonal model. To each of these, two moisture models have been integrated including Loudon's steady-state moisture model and Jones' admittance moisture model. The BREDEM-8 Loudon model has been shown to be the most accurate model for predicting the airspace relative humidity in 36 dwellings during the heating season. The BREDEM-8 Loudon model has then undergone further development and testing and the applications of the model are investigated. A variable infiltration calculation has been implemented and tested within the BREDEM-8 Loudon model and the results show no improvement in the model prediction accuracy. Surface relative humidity calculations have also been incorporated for all dwelling surfaces, including cold bridges, and the significance of predicting surface conditions has been evaluated. The impact of fuel poverty is tested using simple versions of the BREDEM-8 Loudon model which have been adapted to account for situations where the expenditure available for fuel is limited and where the heating system is inadequately sized. Finally, a Mould Index has been developed which indicates the risk of mould growing on the coldest surfaces in a dwelling and various interventions in dwelling design and use are tested against this index and against the Affordable Warmth Index which defines the affordability of a particular dwelling. The results demonstrate a number of significant limitations in the current British Standard for condensation in buildings, BS 5250: 1989. It has been shown that the geographical and seasonal variations in internal relative humidity are significant, and that the highest relative humidity is unlikely to coincide with the coldest period of the year. It has also been shown that the modelling of surface conditions is critical in the assessment of mould growth in dwellings. Sensitivity studies carried out on the BREDEM-8 Loudon model have shown the most significant variables affecting the relative humidity predictions are the demand temperature, the heating pattern, the number of occupants, the ventilation rate and the level of insulation. The adequate sizing of the heating system and the ability of the occupants to afford to heat the dwelling to a comfortable temperature have been shown to be essential. It has also been shown that a change in the dwelling design or use may improve the affordability but may also lead to an increased risk from mould growth.