Commercial Energy Performance Certificates
An Energy Performance Certificate (EPC) for a non-domestic building is produced by following a set of rules and standard processes which results in the creation of an energy model for the building. The energy model is created using a program called SBEM, the Simplified Building Energy Model which is used to create most of the commercial EPCs in the UK and the Republic of Ireland. The EPC and a Recommendation Report are generated from this energy model.
All buildings that require an EPC must be inspected by an Energy Assessor. During the inspection the energy assessor will collect information about the building which has an impact on its energy performance. This will include plans, dimensions of the building, its uses, the number of floors, the amount and type of glazing (ie single or double glazing), the heating systems and the fuel used. For the inspection, access is required to all parts of the building, and photographs of key parts are taken to act as a record of the process. The data collected is then entered into SBEM to create the energy model
The model is started by entering accurate building geometry into the program. This allows the model to understand the size of the exterior walls, roof and floor through which heating and cooling energy will be lost. L’atelier’s preferred option is to take dimensional data from existing drawings or the floor plans for the property as this improves overall accuracy. Alternatively, a measured survey can be carried out by the assessor, although this approach is really only economic for smaller buildings. L’atelier use a 3D graphical interface for SBEM which allows the building to be visualised and then checked for accuracy. The 3D interface also allows a floor plan to be imported in electronic format which also enhances the accuracy of the energy calculations.
Details of the construction of the building are then added to the model and this can be achieved in a number of ways, depending on the level of information available. Where there are detailed drawings/specifications of the fabric of the building, the actual construction of a wall, for example, can be entered in terms of the materials used or by the U-value of the wall. Alternatively, the date of the building can be used to select the thermal standards used in the Building Regulations in use at that time.
Each heating, ventilation and air-conditioning system is identified and details of the type of system and its performance data is entered. The type of controls fitted to each system is also recorded, as are details of how hot water is generated for washing & cleaning.
Each floor in the model is then divided into zones based on the following characteristics of the zone:
- Activity being carried out in the zone (from a standardised list)
- Heating or cooling system used
- Supply and extract ventilation arrangements
- Provision of hot water
- Lighting type and/or design details
- Lighting controls
Once the model is complete, the data is audited by the Assessor and the software is used to produce the EPC and the accompanying Recommendation Report (RR). The energy assessor will then record the certificate onto the national register via his or her accreditation body and provide the seller or prospective landlord with the EPC. The EPC is now ready to be given to new building owners or made available to prospective buyers or tenants.