VENTILATION | CIBSE DEBATE quality to meet the functional needs of that space. The roundtable endorsed the view that there should be more focus on ventilation that meets the needs of the occupants, rather than a simplistic intention of ventilating a space whether natural, mechanical or both. We really need to move away from talking about ventilating space to talking about ventilating for people, said Julie Godefroy. Systems thinking The panel agreed that provision of ventilation required a systems approach. They concluded that an effective ventilation strategy should consider a range of factors, such as minimum fresh air requirements for hygiene, air quality, acoustics, safety, thermal comfort and avoiding draughts. External conditions may be noisyand polluted, for example, so the ventilation strategy needs to be considered in an integrated way, to mitigate these detrimental factors. Considering various strategies, the roundtable discussed natural ventilation, and debated whether the rules of thumb industry guidance that comes out of the BRE natural ventilation The roundtable agreed a systems approach to guide, and currently used by designers, was too simplistic and ventilation was needed no longer relevant for modern applications. Malcolm Cook, who gave a detailed presentation on ventilation efficiency, said: Its time we challenged these rules of thumb and put some science behind them whether that be computational flow dynamics (CFD) modelling, real-world field testing or experimental work. We have to try to understand this fundamental question: how effective is the ventilation? Henry Pelly had experienced very limited understanding of how natural ventilation works in architects training, and that these [trainee] architects didnt even know these rules of thumb to start with. He said improved rules of thumb should be developed to help architects get a better starting position in the design stage before the building service engineers come onboard. This brought up another important issue for the roundtable the need for engineers to seek early influence to review options and optimise the ventilation strategy. Participants said clients and architects appreciate early advice from engineers on the faade and ventilation strategy, because window design strategy can be crucial to the success of the natural ventilation strategy. In addition, the location and size of plant equipment can have an impact on planning for effective natural ventilation. Clare Murray emphasised the importance of this early input. From an architects point of view, theres a real desire to be having that conversation, she said. Theres some classic relationship behaviour between architects and engineers. Engineers feel like they darent say something to the architects, but, in fact, architects are just wishing someone would say something early, to make it clear what will work and whats not compatible. There is some kind of barrier between architects and engineers, and it doesnt need to be there. Its partly to with language and partly to do with understanding what each other does. Pelly agreed. Definitely, education POINTS FOR DEBATE 1. Focus on ventilation performance: there should be more attention on ventilation that meets the needs of the occupants, rather than the simplistic intention of ventilating a space 2. Systems-thinking approach: an effective ventilation strategy needs to consider a range of factors, such as minimum fresh air requirements for hygiene, air quality, acoustics, safety, thermal comfort and avoiding draughts 3. Engineers should seek early influence toreview options and optimise ventilationstrategies 4. Testing and commissioning of ventilation controls is crucial 5. Post-occupancy evaluation will improve skills and raise awareness of effective ventilation performance. Ashley Bateson said awareness of best practice would help achieve successful integrated ventilation 22 June 2019 www.cibsejournal.com CIBSE Jun19 pp21-23 Ventilation debate Supp.indd 22 24/05/2019 14:52