Tests for Software Accreditation and Verification

In recent years there has been a significant growth in the market for software to support building services design. These tools are now widely used for a range of tasks in the building services industry by consultants and contractors. In 2002 the Building Services Research and Information Association, supported by CIBSE and the Association of Consulting Engineers, published Design checks for HVAC.This quality control framework for building services design specifically addressed issues of verification and validation of design data. It particularly noted the need for software packages to be validated prior to use and warned of the possible professional indemnity implications of using software packages without validation. In one example a consulting engineer was held to be 90% liable for design failures that occurred due to errors in the design software used, which had not been checked or validated by the engineers.This new edition arises from a need for the UK regulators to have a mechanism for the technical accreditation of detailed thermal models as part of their formal approval for use in the National Calculation Methodology. To do this it has been necessary to extend the range of the tests described in the previous edition, in particular to include tests to predict annual heating and cooling demand and overheating risk. The conversion of demands to energy consumption has also been taken into consideration with one of the tests requiring the prediction of the performance of an air handling unit.These tests do not however provide a 'truth model' and so to demonstrate that the models can give credible results a test using the experimentally measured performance of a simple test cell has been added. Further changes have been made necessary to ensure that where appropriate calculation methods meet the relevant British (European) Standards.The preparation of software tests is not a trivial task and the ground work carried out by the University of Strathclyde in their development of the original set of tests has been invaluable. Similarly this document could not have been written without the aid and patience of the software houses who 'tested the tests'.During this development period it became clear that to succeed with the simplest of tests required great care and therefore the CIBSE recommends that the tests be used as part of the user training that is necessary to satisfy the CIBSE QA procedures described in chapter 5 of the 2006 edition of CIBSE Guide A. Such a QA system is part of the requirement for using a calculation tool as part of the National Calculation Methodology.CIBSE market research on publications and design software suggests that many members and nonmembers believe that the software they use accords with CIBSE methods. Some also believe the software they use is accredited by CIBSE, although this is not the case. Section 4 is therefore devoted to tests associated with CIBSE calculation methods. These are intended to provide a means by which members can test for themselves that the software they use is producing results consistent with those produced by CIBSE methods, and with good practice.Software users will be able to test their software to assure themselves that it is consistent with published CIBSE methods and practices. The tests will enable software users to carry out a range of basic checks on the software they use, and to demonstrate that they have undertaken basic initial validation of the software to quality assurance and professional indemnity insurance practitioners. This set of simple tests is intended to develop a culture of software testing and validation in the industry. CIBSE intends to expand and update the range of tests in the future.Initial validation alone is not sufficient to demonstrate that use of a particular software package was appropriate to the needs of a specific project. Accurate software is a prerequisite of, but does not guarantee, design quality. Design quality is also a function of, amongst other things, the input data and assumptions used, and of the way in which outputs from the software are used. It is always the responsibility of the designer to ensure that whatever software design tools are adopted, they reflect and are appropriate to the contractual obligations accepted in the appointment by the client. Further guidance on design quality is given in Design checks for HVAC.