Feedback This month, a reader discusses the causes of operational failure of buildings and their solutions In discussing Innovate UKs findings in her article, Voluntary DECs can fill the gap (CIBSE Journal, December 2014), Dr Kerry Mashford gives sensible ideas for getting closer agreement between early estimates and later, measured, display energy certificates but one can suggest other causes and solutions. On estimates, the first problem is the lack of a definite brief. This is partly because clients wont decide in detail what they want to do with a building, and partly because in many commercial cases there is no way they can predict how it will be used. The second problem is that the building design and an agreed theoretical use can never be complete when the building is offered to Building Control for approval. Often, the details of the HVAC system and even its type simply cant be thoroughly worked through. The third problem is that the trade does not yet have an agreed energy-use computing program into which accurate building fabric, dimensions, occupancy profiles, use, and building HVAC systems can be fed. Given this program, it would be simple to allow for later, measured occupancy. It would be best to retain a benchmark approach for the imponderables at the approval stage, and to separate all extras such as kitchen and on-floor relaxation stations in the main analysis. The suggested program could then be used to recalculate energy against the actual use. Given adequate benchmarks and honest input at the approval stage there should be much closer agreement with later measured performance. There should be a requirement for much more detailed submetering. On a typical office floor, for instance, power for HVAC equipment, lighting and all client uses such as IT, tea urns, copiers and fax machines should be measurable separately. Simply monitoring a clients so-called small power convinces many to alter their operational approach. As always, the devil is in the detail, because engineering is all about detail, no matter how sensible the concepts may be. John Moss MCIBSE Consultant, building performance and systems, Arup CIBSE Journal welcomes readers letters, opinions, news stories, events listings, and proposals for articles. Please send all material for possible publication to: editor@cibsejournal. com, or write to Alex Smith, editor, CIBSE Journal, CPL, 275 Newmarket Road, Cambridge, CB5 8JE, UK. We reserve the right to edit all letters. CIBSE Journal welcomes readers input, whether it be letters, opinions, news stories, events listings, humorous items, or ideas and proposals for articles. Please send all letters, and any other items for possible publication in the CIBSE Journal, to: editor@cibsejournal.com, or write to Alex Smith, editor, CIBSE Journal, CPL, 275 Newmarket Road, Cambridge, CB5 8JE, UK. We reserve the right to edit all letters. Please indicate how you wish your letter to be attributed, and whether you wish to have your contact details included. "