Understanding occupants: feedback techniques for large-scale low-carbon domestic refurbishments

Abstract

How can occupant feedback methods inform the management and design of low-carbon and whole-house refurbishment of dwellings? This is particularly relevant for large-scale, whole-house refurbishment programmes tasked with achieving deep cuts in carbon dioxide (CO₂) emissions. Evidence from pre-refurbishment occupancy can influence which interventions are chosen and increase their efficacy. A critical review is undertaken of a portfolio of short- and long-term occupant feedback techniques for evaluating occupants' perception of comfort, satisfaction, behaviour, and expectations. A number of these occupant feedback techniques are then tested empirically at the pre-refurbishment stage for two discrete case-study house types as part of ongoing research. The evidence reveals wide gaps between modelled and actual energy consumption; poor indoor CO₂ and daylight levels, low operating internal temperatures, as well as problematic noise transmission. Such findings influence the selection of suitable user-centred low-carbon refurbishment interventions and ensure that there is a robust learning process for building owners, occupants, designers, and building managers. To optimize time, cost, and occupant involvement, it is important that feedback from occupants on building performance focuses on ‘need-to-know’ rather than ‘nice-to-have’ factors.

Comment les méthodes de feedback des occupants contribuent-elles à la gestion et à la conception des opérations de rénovation complète et bas carbone des logements d'habitation? Ceci s'applique tout particulièrement aux programmes de rénovation complète à grande échelle, auxquels il est donné pour tâche de réaliser de fortes réductions des émissions de dioxyde de carbone (CO₂). Les données probantes obtenues auprès des occupants avant rénovation peuvent influer sur le choix des opérations et accroître leur efficacité. Il est entrepris un examen critique d'un portefeuille de techniques de feedback des occupants à court terme et à long terme, permettant d'évaluer le confort perçu, la satisfaction, le comportement et les attentes des occupants. Un certain nombre de ces techniques de feedback des occupants sont ensuite testées empiriquement lors de la phase préliminaire à la rénovation sur deux types de maisons faisant l'objet d'études de cas distinctes dans le cadre des recherches en cours. Les données probantes obtenues révèlent de gros écarts entre les consommations énergétiques modélisées et réelles; de mauvais niveaux intérieurs de CO₂ et de lumière du jour, des températures intérieures de fonctionnement basses, ainsi que des problèmes d'insonorisation. De telles constatations influent sur la sélection d'opérations de rénovation adaptées, bas carbone et centrées utilisateurs, et garantissent l'existence d'un solide processus d'apprentissage pour les propriétaires des bâtiments, leurs occupants, leurs concepteurs et leurs gestionnaires. Afin d'optimiser la durée, les coûts et l'implication des occupants, il est important que le feedback des occupants concernant les performances des bâtiments se concentre sur les facteurs de type «need-to-know» (indispensable à savoir) plutôt que de type «nice-to-have» (accessoire).

Mots clés: rendement énergétique, logement, rénovation bas carbone, feedback des occupants, évaluation après occupation, remise à niveau

Keywords:

• energy performance
• housing
• low-carbon refurbishment
• occupant feedback
• post-occupancy evaluation
• retrofitting

Acknowledgements

The authors gratefully acknowledge the residents of the case study dwellings in Oxford and Rosyth for their cooperation during the study and for regularly completing the questionnaire, diaries, and heating log sheets. The authors are also grateful to Technology Strategy Board for providing funding for Phase 1 of the ‘Retrofit for the Future’ programme. Thanks are also due to Home Group Housing and Oxford City Council, owners of the two case study dwellings. Finally, the authors thank the journal referees and editors for constructive comments and suggestions.

Notes

To address this human aspect of energy efficiency in buildings, the UK Research Councils, as part of their ‘Energy Programme’, have recently launched a number of funding calls, which include: the Engineering and Physical Sciences Research Council (EPSRC) and EDF's joint call on ‘People, Energy and Buildings’ in 2009; the ongoing ‘Energy and Communities’ call by the Economic and Social Research Council (ESRC); and the ongoing TSB's sandpit call on ‘User-Centred Design for Energy Efficiency’ in (non-domestic) buildings: ‘User-Centred Design for Energy Efficiency in Buildings. Competition for Sand-Pit Participants’(TSB, 2009b).

Both the selected case studies have been successful in receiving funding for the implementation of low-carbon interventions, and they will undergo detailed monitoring and post-occupancy evaluation, post-implementation. This will allow the authors to correlate and substantiate the approach and findings of occupant surveys during pre-refurbishment with that of post-refurbishment.

A co-heating test involves heating a dwelling to a constant internal temperature (typically 25°C) and tracking daily heat input (watts; W) and the daily mean internal–external temperature difference over an extended period. A range of weather data are collected to enable corrections for solar gain and to enable the impact of other weather characteristics (principally wind) to be taken into account during the analysis. Typical test periods can be from two to three weeks (or even longer) depending on dwelling characteristics, temperature stabilization, and the objectives of the testing within overall project requirements. In order to enable clear results, relatively uncluttered by the noise of experimental error, it is necessary to ensure a strong internal–external temperature difference (10°C or more). For this reason, testing can only be undertaken during the colder months, usually October–November to March–April.

See http://www.diykyoto.com/uk/.

SAP is the government's Standard Assessment Procedure for Energy Rating of Dwellings. It is used to demonstrate compliance with building regulations for dwellings.

See http://www.bsria.co.uk/news/performance-funding/.

‘Soft Landings’ is an initiative for better briefing, design, handover, and performance in use. It involves a graduated handover wherein project teams stay engaged after practical completion to hand-hold clients during the initial period of occupation, and to stay involved for up to three years providing professional aftercare.