Birling Consulting Ltd
Birling Consulting Ltd

Controllability - The Knowledge Gap

There is excellent guidance from CIBSE, BSRIA, etc. on many aspects of building services. However there is very little guidance on controllability and control strategies necessary for modern plant and bivalent systems.

Recent CIBSE guidance includes the following:

  • AM14 Non-domestic hot water heating systems – includes a fair degree of detail on system design and control strategies with some areas of excellent advice. However, it has limited advice on hydraulic arrangements and control strategies for the increasing use of bivalent systems, thermal storage to enhance lead heat source operation and/or meet peak loads, control of high differential temperature heat networks, interfacing with manufacturer’s packaged controls, etc. It also does not include heat load based control strategies which can be instrumental in effective system control.
  • AM15 Biomass heating - includes guidance on system design and control, but is primarily for biomass, some principles can be applied to other systems but care needs to be taken in understanding the differences.
  • CP1 Heating networks – this establishes procedures and principles as a Code of Practice and includes design principles but does not detail control strategies in association with relevant schematics, only one generic schematic being included with some hints at control, but no detail.

BSRIA control strategies and CIBSE Guide H have not been updated in recent years to include relevant issues. The Building Regulations Part L and associated guidance has limited controls guidance and some of this is simplistic and potentially confusing IMHO.


Most building services engineers have a limited understanding of controllability and control strategies necessary for modern systems. Most control systems integrators have a limited understanding of building services, particularly the effects of different hydraulic arrangements on control strategies. What is needed is better understanding between the different disciplines of all issues relevant to a successful controllable system.


BRECSU General Information Report 40 Heating systems and their control endeavoured to bridge this knowledge gap and was produced to accompany a series of seminars across the UK including many CIBSE regional events. However, despite the increasing complexity of systems there has been limited guidance in intervening years on overall system design and controllability.

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