Fox, J.; (2008) A study of occupant controlled ventilation within UK dwellings. Doctoral thesis , University of London.

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Abstract

This thesis tests the hypothesis that the ventilation systems installed in UK dwellings, constructed in 2003/04, are adequate to control indoor pollutants and provide acceptable indoor air quality. The debate regarding recommended levels of airtightness for UK dwellings, and the question 'can a limit be established', is also addressed. The theoretical requirements to achieve health, comfort and energy efficiency within dwellings, is reviewed and how the current strategy of 'Build tight and ventilate right' is being achieved in practise compared to theory. The thesis examines in detail the evidence that, in practice we are ventilating right, and explores the concept being applied: 'to control ventilation heat loss, by reducing uncontrollable air infiltration, at the same time as providing adequate indoor air quality by controllable background ventilation'. This study revisits this concept and questions the validity of building tighter buildings only to add 'designer holes' in the name of energy efficiency. The thesis examines the installed performance of the ventilation systems' component parts, as found in UK dwellings. In addition to questionnaires and interviews with residents, the ventilation system 'in-situ' is inspected and tests carried out. The operation of peoples' window habits is also monitored by visual inspection over a one year period. Laboratory measurements of the ventilation system are taken for both ideal installations, and as found in reality on site. The results of this empirical data are then entered into computer models representative of the dwellings, to discover the impact of how buildings really perform. Empirical evidence suggests that occupants control their windows predominantly in response to external temperatures. Installed extract fans can provide as little as 30% of the Building Regulation requirements when manufacturers data suggests that they should comply. This is primarily due to the poor installation of the fan into a real building system. Airflow through background (trickle) ventilators was also found to be compromised by 38%, due to inferior routing of the slot through the window system. Anti-weathering techniques applied by the window manufacturers further inhibited the air flow through the ventilators by as much as 46% compared to the ventilator manufacturers' performance data. The results from the software models indicated that tightly constructed dwellings would provide a reduction in ventilation heat loss, but at the expense of IAQ if ventilation systems were not performing as designed or used as intended. No evidence from either academic studies or from manufactures could be found which measured the installed performance of domestic ventilation systems, in particular the performance of the component parts used to form the basis of a natural ventilation system generally found in most UK dwellings. This thesis provides much needed information on the "real" performance of ventilation systems as "installed" in the UK. The study found there was a need for the installation and performance of ventilation systems to be tested 'in-situ'. There would appear to be a case to call for a legislative regime to inspect and if possible test the ventilation systems of new dwellings as they are completed.

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