Sebastian Macmillan trained and practised conventionally as an architect before forming Eclipse Research Consultants in partnership with Ian Cooper in 1984. Through Eclipse he undertook a wide range of research and technical writing commissions for leading research organisations in the built environment. He was responsible for researching and writing a number of case studies and good practice guides for the government’s Energy Efficiency Best Practice programme and its successor Action Energy. He monitored the operation and achievements of the Energy Design Advice Scheme, the Low Carbon Design Initiative (Northern Ireland), the Scottish Energy Systems Group, and (jointly with Faber Maunsell) Design Advice.
He has undertaken commissions for the Construction Research and Innovation Strategy Panel on the added value of good design and, for the Strategic Forum, identified key messages for small and medium organisations from the rethinking construction agenda. As well as strategic research, he has written best practice guides and case studies for Constructing Excellence and the IT Construction Forum. In 2002 he won funding under the DTI Partners in Innovation programme to lead a study into better designed buildings (2004-2005) and edited Designing Better Buildings (Spon Press, 2004).
In 2006 he wrote The Value Handbook for CABE (the Commission for Architecture and the Built Environment) launched at the 2006 RIBA Annual Conference in Venice. For the Specialist Engineering Alliance, he wrote Sustainable Buildings Need Integrated Teams which was launched in the House of Lords in March 2009 by Lord O’Neill.
As Sector Programme Manager for Construction with the Engineering and Physical Sciences Research Council (1999-2001) he managed a portfolio of academic research projects across the UK. Between 2004 and 2009 he was part-time Consortium Manager for ‘Carbon Reduction in Buildings’ a university consortium supported jointly by the Carbon Trust and the Engineering and Physical Sciences Reseach Council under the Carbon Vision initiative; and was appointed secretary to the joint Carbon Trust/EPSRC Carbon Vision Buildings Engagement Group.
In 2009, he led a major review of the construction industry in one of the Emirates of the UAE.
Between 2006 and 2017 he was the Director of the Interdisciplinary Design for the Built Environment programme when it was offered jointly by the Departments of Architecture and Engineering at the University of Cambridge. Since 2017 it has been offered by the Cambridge Institute for Sustainability Leadership. He continued to support the course as a tutor, supervisor, lecturer and examiner. He has also supervised and examined PhD students in both Departments, as well as at other universities such as University College London, the University of Manchester, and the University of Central Lancashire.
In 2016-17 he was a Visiting Professor at Turin Polytechnic.
He was an External Examiner in Architecture at Leeds University (2018-2021) and Heriot-Watt University Dubai Campus (2017-2021). He advised several universities about their submissions to the Research Excellence Framework 2021.