Farooq, Faisal
2024.
MVHR system evaluation based on ventilation effectiveness and human comfort in bedrooms of low-carbon UK dwellings.
PhD Thesis,
Cardiff University.
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Abstract
Energy efficiency measures require contemporary housing in the UK to be built to higher air tightness levels than ever before. As infiltration levels reduce, the adoption of ‘propose-provided ventilation’ strategies, such as Mechanical Ventilation with Heat Recovery (MVHR) become paramount for maintaining a healthy indoor environment. In-situ evaluation studies suggest that due to improper design, installation, commissioning, maintenance, and use of MVHR, a gap in performance exists. These issues have a negative consequence on ventilation effectiveness and occupant comfort especially in sleeping environments. Existing literature investigates these issues from a qualitative perspective and studies were conducted at a time when MVHR was at its early stage of deployment, when knowledge on system design and installation was not there. This thesis takes a case study approach using mixed methods to present the current practice of MVHR in the UK and quantifies the impact of having an MVHR supply vent on ventilation effectiveness and comfort in sleeping environments. Two case studies were chosen, both of which were social housing developments located in South Wales, UK. Semi-structured interviews were conducted with eight building professionals to verify literature findings, and to present project management and policy-based recommendations. Monitoring work was carried out to (i) calculate ventilation effectiveness via tracer gas experiments in three bedrooms of different sizes and layout, (ii) iii quantify acoustic comfort by taking sound and frequency measurements in different bedrooms with the system on, off and in boost mode, and (iii) predict thermal comfort by setting up a Predict Mean Vote (PMV) experiment in one bedroom for four nights during winter months. A Computational Fluid Dynamics (CFD) model of one bedroom was created to simulate worst-case scenarios that could not be evaluated by monitoring alone. These included simulating the effect of decreasing the distance between supply vent and door undercut on short-circuiting, and predicting the effect of seasonality, furniture, increased flow rates, and decreased heat exchange efficiency on night-time thermal comfort. The methodological approach of combining interviews, monitoring and modelling proved useful in answering the research questions. Results from the study led to three main conclusions: (i) proper mixing of air is achievable as long as a distance of 600 mm is kept between the supply vent and door undercut; (ii) a low frequency roar can be heard with the system on boost; and (iii) thermal discomfort is unlikely to occur even in worst-case scenarios. This thesis highlights the need for stricter procedures to ensure that compliance with building regulations is met, and provides recommendations for good practice for MVHR designers, installers, and manufacturers to ensure adequate provision of ventilation and minimum disruption by noise and draught in sleeping environments.
Item Type: | Thesis (PhD) |
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Date Type: | Completion |
Status: | Unpublished |
Schools: | Architecture |
Date of First Compliant Deposit: | 18 September 2024 |
Last Modified: | 21 Oct 2024 13:55 |
URI: | https://orca.cardiff.ac.uk/id/eprint/172233 |
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