BUILDING OPERATION IN PRACTICE


The actual energy use and CO2 emissions from a building will often differ from the figures calculated for Part L compliance using the Simplified Building Energy Model (SBEM), or by using more sophisticated design modelling packages, such as Integrated Environmental Solutions (IES).


There are two main reasons for the disparity between actual and calculated performance:


The accuracy of the modelling package used,


The difference between the actual in-use conditions and those used in the modelling calculation.


The SBEM compliance modelling tool assesses building performance under a number of standard operating conditions, defined in the NCM. The calculation methodology is much simpler than more specialist software, which will affect the overall accuracy. In addition, buildings seldom operate under precisely the


same conditions as those modelled in the NCM.


More complex DSM packages tend to be more accurate. They allow the designer to input the building’s proposed operating conditions and hours of operation, which results in more accurate calculations. Most DSM packages also incorporate a Part L compliance module. This allows designers to assess the building’s performance under NCM conditions for regulatory compliance.


Energy consumption will be higher if the building’s operating hours increase, or if lighting use or operating temperature rises. Poor operational control of external doors, windows and heating ventilation and air conditioning (HVAC) systems will also increase energy consumption.


Many buildings now display energy certificates (DECs), which show where and how much energy the building is using. These can be invaluable when developing energy consumption reduction plans.


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