Amoako-Attah, Joseph (2015) Impact of climate change on newly detached residential buildings in the UK passive mitigation and adaptation strategies. Doctoral thesis, University of West London.
Joseph Amoako-Attah Thesis Final (October 2015).pdf
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The global increase in demand for dwelling energy and implications of changing climatic conditions on buildings require the built environment to build sustainable dwellings. The aim of this thesis is to apply passive mitigation and adaptation design strategies to newly detached residential buildings in the UK with the view to identify the key building envelop and systems parameters to secure the right balance of energy consumption and thermal comfort in dwellings. In addition, currently, acceptable robust validation process for validating space temperatures is required, as existing simulation software validation is geared toward energy consumption. The thesis further aims to apply an effective validation method to the validation of building simulation indoor temperatures.
This thesis comprised of six case studies. In the first study, Bland-Altman’s method of comparison is used as a validation technique in validating space temperatures in building simulation application. This is a newly developed knowledge in civil and construction engineering research in validating thermal analysis simulation software. The relevance of this approach is due to the emergent understanding that the goodness of fit measures used in current building simulation model validation are inadequate coupled with that fact that the current simulation software validation are geared toward energy consumption.
In the second study, global Monte Carlo sensitivity analysis is performed on two differing weather patterns of UKCIP02 and UKCP09 weather data sets to compare their impact on future thermal performance of dwellings when use in thermal analysis simulation. The investigation seeks to ascertain the influential weather parameters which affect future dwelling indoor temperatures. The case study when compared to literature affirms the mean radiant temperature and the dry bulb air temperature as the key parameters which influence operative temperatures in dwellings.
The third study, the extent of impact of climate change on key building performance parameters in a free running residential building is quantified. The key findings from this study were that the average percentage decrease for the annual energy consumption was predicted to be 2.80, 6.60 and 10.56 for 2020s, 2050s and 2080s time lines respectively. A similar declining trend in the case of annual natural gas consumption was 4.24, 9.98 and 16.1, and that for building emission rate and heating demand were 2.27, 5.49 and 8.72 and 7.82, 18.43 and 29.46 respectively. This decline is in consonance with the range of annual average temperature change predicted by the GCM based on the IPCC scenarios (IPCC, 2001) which generally shows an increase in temperature over stipulated timelines. The study further showed that future predicted temperature rise might necessitate the increasing use of cooling systems in residential buildings. The introduction of cooling to offset overheating risk, the trend of heating and cooling demand shows progressive increase variability with an average percentage increase of 0.53, 4.68 and 8.12 for 2020s, 2050s and 2080s timelines respectively. It is therefore observed that the introduction of cooling cancels out the energy gains related to heating due to future climatic variability.
The fourth, fifth and sixth case studies consider the integrated passive mitigation strategies of varying future climatic conditions, variable occupant behaviour, building orientation, adequate provision of thermal mass, advance glazing, appropriate ventilation and sufficient level of external shading which influence the potential thermal performance of dwellings and a methodology that combines thermal analysis modelling and simulation coupled with the application of CIBSE TM52 adaptive overheating criteria to investigate the thermal comfort and energy balance of dwellings and habitable conservatories.
In the fourth study, the impact of four standardized construction specifications on thermal comfort on detached dwellings in London, Birmingham and Glasgow are considered. The results revealed that the prime factor for the variation of indoor temperatures is the variability of climatic patterns. In addition, London is observed to experience more risk of thermal discomfort than Birmingham and Glasgow over the time period for the analysis. The total number of zones failing 2 or 3 CIBSE TM52 overheating criteria is more in London than in Birmingham and Glasgow. It was also observed that progressive increase in thermal mass of the standardized construction specifications decrease the indoor temperature swings but increase in future operative temperatures. The day ventilation scenario was seen not to be effective way of mitigating internal heat gains in London and Birmingham. The opposite was observed in Glasgow. Night ventilation coupled with shading offered the best mitigation strategy in reducing indoor temperatures in London and Birmingham.
In the fifth study, Monte Carlo sensitivity analysis is used to determine the impact of standard construction specifications and UKCP09 London weather files on thermal comfort in residential buildings. Consideration of London urban heat island effect in the CIBSE TM49 weather files leading to the generation of three different weather data sets for London is analysed. The key findings of the study indicated that in the uncertainty analysis (box and whiskers plots), the medians for the day ventilation scenarios are generally higher than those of the night ventilation and further higher than the night ventilation with shading scenarios. This shows that applying mitigation scenarios of night ventilation and shading have a significant impact on reducing internal operative temperatures. In addition, the sensitivity analysis shows glazing as the most dominant parameter in enhancing thermal comfort. The sensitivity of glazing to thermal comfort increases from Gatwick, with London Weather Centre having the highest sensitivity index. This could be attributed to the urban heat island effect of central London, leading to higher internal operative temperatures. The study thus shows that more consideration should be given to glazing and internal heat gains than floor and wall construction when seeking to improve the thermal comfort of dwellings.
Finally, the sixth study considers the use of passive solar design of conservatories as a viable solution of reducing energy consumption, enhancing thermal comfort and mitigating climate change. The results show that the judicious integration of the passive solar design strategies in conservatories with increasing conservatory size in elongated south facing orientation with an aspect ratio of at least 1.67 could progressively decrease annual energy consumption (by 5 kWh/m2), building emission rate (by 2.0 KgCO2/m2) and annual gas consumption (by 7 kWh/m2) when the conservatory is neither heated nor air-conditioned. Moreover, the CIBSE TM52 overheating analysis showed that the provision of optimum ventilation strategy depending on the period of the year coupled with the efficient design of awnings/overhangs and the provision of external adjustable shading on the east and west facades of the conservatory could significantly enhance the thermal comfort of conservatories.
The findings from these case studies indicate that thermal comfort in dwellings can be enhanced by analysis of future climatic patterns, improved building fabric and provision of passive design consideration of improved ventilation and shading. They also confirm that the utilization of appropriate mitigation strategies to enhance thermal comfort could contribute to the reduction of the environmental implications to the built environment and facilitate the drive towards the attainment of future sustainability requirements.
|Item Type:||Thesis (Doctoral)|
|Subjects:||Construction and engineering > Civil and environmental engineering
Computer science, knowledge and information systems
|Depositing User:||Marzena Dybkowska|
|Date Deposited:||08 Jan 2016 10:33|
|Last Modified:||26 Jul 2016 15:05|
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