Elemental boron doping behavior in silicon molecular beam epitaxy

Boron-doped Si epilayers were grown by molecular beam epitaxy (MBE) using an elemental boron source, at levels up to 2×1020 cm−3, to elucidate profile control and electrical activation over the growth temperature range 450–900 °C. Precipitation and surface segregation effects were observed at doping levels of 2×1020 cm−3 for growth temperatures above 600 °C. At growth temperatures below 600 °C, excellent profile control was achieved with complete electrical activation at concentrations of 2×1020 cm−3, corresponding to the optimal MBE growth conditions for a range of Si/SixGe1−x heterostructures

Temperature in housing: stratification and contextual factors

Overheating in new and retrofit low carbon dioxide homes is a growing issue in the UK due to climate change and other factors, with 99% of existing housing predicted to be at medium to high risk if summer temperatures become 1·4°C warmer. A year-long field study in two residential developments in the north of England monitored housing at three different scales: two-storey houses and three- and ten-storey blocks of flats. This revealed significant temperature stratification in the staircase zone, which allows a stack effect, as well as temperature differences between dwellings depending on their location in the building, both for summer and winter conditions even in the low-rise housing. Further investigation revealed that albedo and east–west orientation also contributed to non-linear overheating. Analyses of inhabitants’ thermal comfort and security practices as well as occupancy patterns also challenge the regulatory modelling used to predict building performance. It is suggested that these additional physical as well as user factors in residential developments need further investigation and should now be considered in relation to thermal comfort modelling

Resilience, redundancy and low-carbon living: co-producing individual and community learning

There is an acknowledged need for buildings and communities to be more resilient in the face of unpredictable effects of climate change, economic crises and energy supplies. The notion and social practices involving redundancy (the ability to switch between numerous available choices beyond optimal design) are explored as an aspect of resilience theory. Practice and Social Learning theories are used as a lens through which to explore the available redundancy in housing and home environments to help prevent performance failure through unexpected circumstances or in response to varying user needs. Findings from an in depth UK housing case study show how redundancy is linked with the capacity to share resources and to learn both individually and collectively as a community. Such learning in relation to resilient low-carbon living is shown to be co-produced effectively through participatory action research. The benefits of introducing extra redundancy in housing design and community development to accommodate varied user’s understanding and preferences are discussed in relation to future proofing, value and scalar issues. Recommendations include better understanding of the design, time and monetary contribution needed to implement social or technical redundancy. These costs should be evaluated in context of savings made through greater resilience achieved

Housing performance evaluation: challenges for international knowledge exchange

Developing effective building performance evaluation and feedback processes is a vital part of global efforts to reduce building energy use and gain insight into the actual performance of buildings and technologies. Although attempts have been made to introduce internationally agreed models for these processes, it is clear that various countries are producing different approaches according to their cultural, institutional and policy differences. Knowledge exchange is potentially a key means of developing a shared understanding of values, meanings and practices in relation to building performance evaluation. This paper identifies cultural and institutional barriers in the European Union for international building performance communities of practice utilizing knowledge exchange, from an experiential ‘real-world’ perspective. The preparation of a 30-month research project to help develop building performance evaluation in Poland and an associated bilateral symposium is closely evaluated through an action research case study in terms of the stakeholders, the national contexts in which they operated and the key challenges they faced. Recommendations are then made in terms of the support needed to develop more responsive research programmes in relation to developing international knowledge exchange, and the capacity-building elements required for these international communities of practice