Ventilation strategies for urban housing: lessons from a PoE case study

Mechanical ventilation with heat recovery is still not widely used in UK housing, but with insulation and air-tightness standards becoming increasingly strict, it is likely to become more common. Operable windows are almost a given for housing and the UK climate is rarely extreme enough to restrict people's use of those windows for natural ventilation. This is a potential problem for the use of heat-recovery systems and could greatly reduce their energy efficiency. The paper takes the Iroko housing scheme at Coin Street, London, as a post-occupancy evaluation (PoE) case study to investigate the questions raised with respect to how well the occupants of the houses cope with balancing both natural ventilation and mechanical systems to achieve thermal comfort energy efficiently. First, the optimum balance of mechanical and natural ventilation is estimated and used to determine the maximum potential saving it could give when compared with natural ventilation alone. Short-term monitoring of the building in question together with the results of questionnaires showed why this theoretical balance is not achieved and that the energy consumption is likely to be worse than for natural ventilation alone. Noise, perceived control, perceived freshness and misunderstanding are all discussed as possible causes for the apparent disjunction. Misunderstanding on the part of residents was shown to be a critical determinant, so information about the heat recovery system was distributed to the residents and the paper ends by looking at what theoretical energy savings might be made as a result of this act.