Natural ventilation with heat recovery: a biomimetic concept

In temperate countries, heat recovery is often desirable through mechanical ventilation with heat recovery (MVHR). Drawbacks of MVHR include use of electric power and complex ducting, while alternative passive heat recovery systems in the form of roof or chimney-based solutions are limited to low rise buildings. This paper describes a biomimetic concept for natural ventilation with heat recovery (NVHR). The NVHR system mimics the process of water/mineral extraction from urine in the Loop of Henle (part of human kidney). Simulations on a facade-integrated Chamber successfully imitated the geometry and behaviour of the Loop of Henle (LoH). Using a space measuring 12 m2 in area and assuming two heat densities of 18.75 W/m2 (single occupancy) or 30 W/m2 (double occupancy), the maximum indoor temperatures achievable are up to 19.3 °C and 22.3 °C respectively. These come with mean relative ventilation rates of 0.92 air changes per hour (ACH) or 10.7 L·s−1 and 0.92 ACH (11.55 L·s−1), respectively, for the month of January. With active heating and single occupant, the LoH Chamber consumes between 65.7% and 72.1% of the annual heating energy required by a similar naturally ventilated space without heat recovery. The LoH Chamber could operate as stand-alone indoor cabinet, benefitting refurbishment of buildings and evading constraints of complicated ducting, external aesthetic or building age

The design and simulation of natural personalised ventilation (NPV) system for multi-bed hospital wards

Adequate ventilation is necessary for thermal comfort and reducing risks from infectious bio-aerosols in hospital wards, but achieving this with mechanical ventilation has carbon and energy implications. Natural ventilation is often limited to window-based designs whose dilution/mixing effectiveness are subject to constraints of wind speed, cross ventilation, and in the case of hospital wards, proximity of patients to external walls. A buoyancy-driven natural ventilation system capable of achieving dilution/mixing was shown to be feasible in a preceding study of novel system called natural personalised ventilation (NPV). This system combined both architecture and airflow engineering principles of space design and buoyancy and was tested and validated (salt-bath experiment) for a single bed ward. This research extends the previous work and is proof-of-concept on the feasibility of NPV system for multi-bed wards. Two different four-bed ward types were investigated of using computational fluid dynamics (CFD) simulations under wind-neutral conditions. Results predict that NPV system could deliver fresh air to multiple patients, including those located 10 m away from external wall, with absolute flow rates of between 32 L·s−1 and 54 L·s−1 for each patient/bed. Compared to same wards simulated using window design, ingress of airborne contaminants into patients’ breathing zone and summer overheating potential were minimised, while overall ward dilution was maximised. Findings suggest the NPV has potentials for enabling architects and building service engineers to decouple airflow delivery from the visualisation and illumination responsibilities placed upon windows

The design and simulation of natural personalised ventilation (NPV) system for multi-bed hospital wards

Adequate ventilation is necessary for thermal comfort and reducing risks from infectious bio-aerosols in hospital wards, but achieving this with mechanical ventilation has carbon and energy implications. Natural ventilation is often limited to window-based designs whose dilution/mixing effectiveness are subject to constraints of wind speed, cross ventilation, and in the case of hospital wards, proximity of patients to external walls. A buoyancy-driven natural ventilation system capable of achieving dilution/mixing was shown to be feasible in a preceding study of novel system called natural personalised ventilation (NPV). This system combined both architecture and airflow engineering principles of space design and buoyancy and was tested and validated (salt-bath experiment) for a single bed ward. This research extends the previous work and is proof-of-concept on the feasibility of NPV system for multi-bed wards. Two different four-bed ward types were investigated of using computational fluid dynamics (CFD) simulations under wind-neutral conditions. Results predict that NPV system could deliver fresh air to multiple patients, including those located 10 m away from external wall, with absolute flow rates of between 32 L·s−1 and 54 L·s−1 for each patient/bed. Compared to same wards simulated using window design, ingress of airborne contaminants into patients’ breathing zone and summer overheating potential were minimised, while overall ward dilution was maximised. Findings suggest the NPV has potentials for enabling architects and building service engineers to decouple airflow delivery from the visualisation and illumination responsibilities placed upon windows

Performance evaluation of natural ventilation strategies for hospital wards: case study of Great Ormond Street Hospital

Natural ventilation is attractive due its potential to lower energy consumed by healthcare environments but maintaining steady/adequate airflow rates and thermal comfort is challenging in temperate countries. Although many contemporary hospitals use traditional windows for natural ventilation, there are alternative strategies that are largely under-utilised probably due to lack knowledge of their ventilation performances. Each alternative has design implications and airflow characteristics – both of which affect thermal comfort and heating energy. This study evaluates the performance of buoyancy-driven airflows through four selected natural ventilation strategies suitable for single-bed hospital wards. These strategies are: single window opening, same side dual-opening, inlet and stack as well as ceiling-based natural ventilation (CBNV), a new concept. These strategies have been explored via dynamic thermal simulation and computational fluid dynamics, using a new ward of the Great Ormond Street Hospital (GOSH) London as a case study. Results reveal that 25% trickle ventilation opening fraction is required to achieve required airflow rates and acceptable thermal comfort in winter, and with exception of window-based design, other strategies minimise summer overheating to different extents. The CBNV concept uniquely shields fresh air and delivers it to isolated parts of wards or directly over patients (i.e. personalisation). This provides higher air quality at such locations and creates mixing which aids comfort and dilution. The findings demonstrate how quantitative data from simulations can be used by designers to meet qualitative or sensory design objectives like airflow direction and thermal comfort with respect to the energy consumed in space and time

Natural personalised ventilation: a novel approach

The need to protect susceptible patients from cross-infection resulting from airborne pathogens is essential in hospitals, especially when patient immunity is either suppressed due to medical procedures or compromised by ailment. Personalised ventilation (PV) is a method of creating a local zone of high air quality around such patients. However, contemporary PV techniques are based on mechanical ventilation, which adds to the energy burden of healthcare buildings. In single-bed wards, a potential source of infection could be other occupants such as visitors and healthcare workers. Threats may also come from airborne pathogens migrating from adjacent zones, especially if the single-bed wards in question are not positively pressurised. While the World Health Organisation (WHO) has issued guidelines on using natural ventilation to control infectious bio-aerosols in hospital wards (with flow rates of up to 60 l/s/patient), how to achieve this rate without high energy and carbon costs, remains unanswered. The objective of the research reported here is to demonstrate a novel approach of using low-energy, buoyancy-driven natural airflow for personalised ventilation of single-bed hospital wards. The investigation has been carried out by undertaking dynamic thermal simulations (DTS) and computational fluid dynamics (CFD) simulations. Findings demonstrate that given appropriate design, it is possible to achieve personal protection for vulnerable patients using a natural mode of ventilation alone. Co-occupants could also benefit from the mixing characteristics offered by the proposed system, which does not occur in typical buoyancy-driven displacement ventilation

Natural personalised ventilation for hospital wards: experimental validation

Personalised ventilation (PV) systems are useful in protecting vulnerable hospitalised patients from airborne infection due to localised delivery of clean air. A natural personalised ventilation (NPV) system has previously been shown to be a feasible, natural and low-energy alternative to mechanised PV systems. The original NPV system was investigated using three conceptual designs which used dynamic thermal modelling and steady-state computational fluid dynamics to simulate a single-bed hospital ward. Findings from these designs led to optimisation of the NPV system components (stack and ducts) which also serve as the basis for this experimental validation. The objective of this research is to validate the flow characteristics of the optimised NPV system using scaled model experiments in addition to computational fluid dynamics (CFD) studies. Water-bath modelling (WBM) was carried out in a large Perspex tank and a scaled version of the single-bed ward was also constructed in Perspex. Results improve our understanding of the proposed NPV strategy, in particular showing that different locations of heat sources within the model leads to considerably different internal temperatures at steady state. Close similarities between CFD and WBM simulations were also observed

Virtual collaboration in the built environment

Throughout the 2013 to 2014 academic year, three institutions have been collaborating in the education of three cohorts of students through the BIM Hub project ; these are Coventry University and Loughborough University in the UK and Ryerson University in Canada. Students formed groups of six individuals, two from each university, including architects, construction engineers and project managers. The project was designed to create an authentic simulation of industrial collaboration and practices. At Coventry participation was optional (students had the alternative of forming collaboration with other Coventry students). At Ryerson and Loughborough participation was mandatory. They were set a project to design and plan a building for a particular site in Coventry through forming online collaboration, and reflect on their experiences. The study was funded by the Higher Education Academy in the UK with the intention of identifying which success factors led to effective online collaboration and is a follow-up to a previous project sponsored by the Hewlett Packard Catalyst Program (Soetanto, et al, 2014). Focus groups were conducted with the students at the institutions, the following analysis focuses on the issues faced and solutions identified in terms of the technologies involved and the strategies for successful collaboration. The analysis focuses on two of the universities and offers reflections based on their experience

How should we teach BIM? A case study from the UK

Growing industry demand and the United Kingdom (UK) government’s 2016 ‘BIM deadline’ have provided a clear impetus for enhanced BIM teaching in UK HE institutions. This paper reports on the approach taken in a large multi-disciplinary School of Civil and Building Engineering. From a number of options, the approach to embed BIM into existing modules was chosen and three categories of BIM Learning Outcomes (BIMLOs) were identified including: knowledge and intellectual aspects; practical skills; and transferable skills. A three-year implementation plan (2014 – 2016) was developed in which 26 priority modules had their existing learning outcomes upgraded to meet the BIMLOs. Partnership with BIM technology providers and practicing professionals, contemporary and research-driven topics as well as guidance and strategy documents e.g. BS1192-2007, PAS1192, BIM Protocol and Government Soft Landings determined the contents of these BIMLOs. Many priority modules were taken by mixed cohorts of students drawn from various programmes, so group work via problem-based coursework was typically used for assessment. Guided self-learning through web-based video tutorials has been adopted across the School using commercially available and in-house produced content. These have helped students with problem-solving and modelling skills. New BIM-dedicated modules were developed on collaborative working through common data environments (shared workspaces) as well as the auditing and coordinating of BIM models. This approach required long-term vision, leadership, BIM championing and the cooperation of academic peers who were extensively consulted. A feedback mechanism was put in place to capture students’ experiences regarding BIMLOs, access to computing facilities and effectiveness of video tutorials

Single-sided natural ventilation strategies for healthcare buildings

Control of airborne pathogens, while achieving comfort and energy efficiency, places strains on typical mechanical air-conditioning systems of hospitals. These buildings expend over 40% of their energy for heating of air and spaces (DoH, 2006) while still being challenged by the problem of airborne infection. Natural ventilation remains a largely unexplored alternative which could alleviate this problem; however, achieving acceptable indoor air quality (IAQ), thermal comfort and energy efficiency from this technique is challenging and requires careful design and modelling. Many hospitals appear to use same openings (windows) as both inlets and outlets, making the air exchange process inefficient. The aim of this study is therefore, to demonstrate the feasibility of using dual opening single-sided, buoyancy-driven natural ventilation for achieving low-energy comfort and reduction of airborne pathogens in 1-bed and 4-bed hospital wards that are designed or refurbished according to the Department of Health’s Activity Database (ADB). Conceptual design conditions were based on provisions of HTM-03 guidelines and openings were sized through empirical methods. The design conditions are tested using dynamic thermal simulation (DTS) to demonstrate the long-term airflow and comfort implications. Computational fluid dynamics simulations (CFD) are then used to provide an indepth steady-state prediction of the distribution and quality of air as well as pathogen dispersal, with respect to airflow patterns/directions for the selected strategies. These research findings provide insights into the airflow, and comfort performances of 1-bed and 4-bed wards for both existing and proposed healthcare buildings whose design or retrofit calls for single-sided natural ventilation

A framework for quality evaluation of university housing facilities

Campus housing facilities are a major investment for any institution. Accommodating staff and faculty within the premises of a university access to the work place for such special employees, but also establishes belonging, essential to retain high caliber staff within their institutions. However, this might sequence an adverse effect if the quality of place or quality of life of such facilities were compromised, as occupant's satisfaction of the quality of their housing can be directly linked to their work performance. This paper presents a framework for evaluating the quality of university family housing facilities. The framework entails carrying out a walkthrough investigation; conducting focused group meetings; interviewing the executives of campus maintenance and planning departments; developing and administering a questionnaire survey; conducting a public hearing session; analysing the data gathered from the above; and recommending a range of time-phased solutions for housing improvements. The framework has diversified its investigation techniques. It is capable of measuring the performance of a network of buildings rather than a single building. Most of the earlier Post Occupancy Evaluation studies concentrated on the level of single buildings. © 2010 Macmillan Publishers Ltd