This paper uses a socio-technical building performance evaluation approach to forensically and systematically evaluate the actual performance of two case study dwellings located in a flagship eco-housing development in the UK, during the post-construction/initial occupation stage. The 12-month study captures the ‘as-built’ performance of the building envelope (principally heat loss) and installed equipment along with remote monitoring of energy use and environmental conditions, review of the handover processes and initial experiences of the occupants in relation to the home environment. It is found that actual annual energy use and CO2 emissions of the case study dwellings exceed design predictions by factors of 1.8 and 2.5, respectively. The main reasons for this gap are complex interdependencies that occur across the performance of building fabric and energy systems, usability of controls and occupant expectations and behaviour. Underperformance of mechanical ventilation and heat recovery systems and air source heat pumps results from inadequate commissioning and maintenance procedures and poor occupant control due to complex control interfaces. Furthermore, unclear user guidance and inadequate training during handover lead to poor occupant understanding of the mechanical ventilation and heat recovery systems and heat pumps, resulting in their misuse. The findings have proved that building performance evaluation processes are vital for examining operational outcomes and discovering performance-related issues that would otherwise go unreported and lead to bigger problems in future. Practical application: The methodological approach for evaluating housing performance adopted in this study provides design and construction teams with a practical approach to diagnose workmanship issues with building fabric and any installation or commissioning issues with energy systems and services. Maintenance regime of heating and ventilation system should be clarified at the installation and commissioning stage. Maintenance contracts should be set up for unfamiliar low carbon systems such as heat pumps, MVHR. Occupants need to be trained through graduated and extended handover that involves occupants trying out systems and controls in the presence of trained housing officers, supplemented by visual home user guides (developed by the architects) offering clear guidance on the daily and seasonal operation of systems and controls. Learning from such real-world case studies, from design to early occupation, is helpful in understanding the exact causes of the performance gap and how it can be addressed.

No abstract

This paper empirically investigates the influence of building fabric, services and occupant related factors on actual energy use of six case study dwellings, located in three new low energy social housing developments in UK, covering a variety of built forms and construction systems (timber frame, hempcrete, steel-frame). Physical monitoring of indoor environment and window-opening is cross-related with building fabric and systems' performance, and qualitative data gathered through occupant surveys, review of control interfaces and handover guidance, to understand the causes of the gap between modelled and measured energy use. Actual energy use is found to exceed design expectations by a factor of three, questioning the need for whole-house mechanical ventilation heat recovery (MVHR) systems at measured air permeability rates of 6m³/(h.m²) against the design target of 3m³/(h.m²). Lack of proper commissioning of MVHR and heating systems, combined with inadequate user comprehension about their operation and control leads to occupant 'misuse' wherein systems are de-activated, thereby negatively affecting indoor air quality. This is confounded by occupant factors related to higher demand temperatures, unexpected opening of windows during winters due to under-performance of MVHR combined with habitual behaviours, and over-use of heating systems to compensate for higher than expected air permeability.

This paper uses a forensic building performance evaluation approach to undertake a comparative evaluation of the in-use energy and environmental performance data (collected over two years) of two civic buildings located in Southeast England-a small community centre (<1000m 2) and a medium-sized public library building (~4500m 2), which are designed to high sustainability standards (EPC A rating) and low heating demand met by on-site low/zero carbon technologies. Although both buildings achieved measured air-permeability rates of ~5m3/hr.m2, they encountered similar issues related to poor documentation of 'as-built' drawings, poor handover and guidance, problems with integrating and maintaining new technologies (heat pumps, biomass boilers and solar thermal), lack of calibration of sub-meters, and issues with automatic window controls. However the actual carbon emissions of the community centre are 2 double the predicted, while they are almost five times in the case of library building. This is because the community centre management team overcame some of the issues through their continuous engagement and interest in the building's performance, whereas the management team of the Library building failed to engage with energy management, resulting in disuse of the biomass boiler and solar thermal system. Practical application Comparative building performance evaluation (BPE) systematically reveals the similarities and differences in the actual energy and environmental performance of two 'sustainable' civic buildings. Careful management of heating and electricity loads, good occupant control over the indoor environment and high performance of low-carbon technologies in the Community Centre result in the building performing better than good practice benchmark. Regular changes in FM staff result in inadequate energy management and control over heating, ventilation and lighting, that undermines occupant comfort and leads to excessive energy use in the library building. For civic buildings to perform as designed, it is vital that metering, sub-metering and controls are set up, commissioned and used properly by the FM team. Design teams should ensure that easy-to-understand user guides are made available before handover for FM and occupants.