CIBSE TM39 (Technical Memorandum 39) ‘Building Energy Metering’ is a document published by the Chartered Institution of Building Services Engineers (CIBSE) to promote best practice in the design of energy metering and sub-metering in non-domestic buildings. 

One of the key roles of TM39 is to help building services designers meet the requirements of Part L 2010 of the Building Regulations, which puts considerable emphasis on the ability to measure energy consumption. Part L includes a new rule that ‘output of any renewable electrical energy generation system is to be separately monitored’. 

TM39 is designed to help facilities managers and building operators introduce metering and sub-metering in existing buildings. It has been written for designers, owner-occupiers, landlords and letting agents who act on their behalf, managing agents, tenants, office managers, facilities managers, and anyone else who can benefit from the energy data that meters and sub-meters can provide. 

Retrofitting of energy metering is particularly important in an existing building when refurbishment work triggers a requirement for ‘consequential improvements’ under Part L. As in Part L 2006, the 2010 regulation includes energy metering as an acceptable improvement. Metering is also important for those organisations participating in the Carbon Reduction Commitment Energy Efficiency Scheme, where an understanding of energy consumption is essential in the management and improvement of carbon emissions. 

The latest edition of TM39 (published in 2009), offers a cost-effective and practical approach to the procurement of energy metering systems. It should be used to optimise metering strategy against cost, practicality, the value of the information gained and predicted energy savings. A step-by-step method is provided to assist in the selection of appropriate ways of metering energy use. It also provides advice on setting up the prescribed information logbook for use by building owners and occupiers.

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