Energy Ratings and Energy Performance Certificates.

"The introduction of the Energy Performance Certificate represents a very positive step forward. It means that for the first time people will be given the kind of user-friendly information they need to reduce both the environmental impact of their homes and their energy bills." 

Paul King, UK Campaigns Director of WWF.

Energy ratings for buildings have been evolving since the 1980’s to provide an indication of the energy efficiency of a property.  Since then several energy rating systems have been used eg NHER (National Home Energy Rating), SAP (Standard Assessment Procedure), and RDSAP (Reduced Data Standard Assessment Procedure), all of them are based on BREDEM (The Building Research Establishment Domestic Energy Model).

Energy ratings have often been compared to a car manufacturers fuel economy figures for one of their vehicles.  For instance, two people driving identical cars will not necessarily achieve the same miles per gallon, because the cars are being driven differently.  Therefore the car manufacturers’ fuel economy claims of what can be achieved are based on “standard driving cycle”.  Similarly, energy ratings for dwellings are based on “standard occupancy”, heating pattern and location; so the energy rating software makes assumptions about how many people live in the dwelling, how they use the home and where it is located.  This enables the energy efficiency of two identical properties in different parts of the country to be compared fairly, disregarding how the occupants might use the dwelling.

RDSAP is the energy rating system that the Government has decided to use to produce Energy Performance Certificates (EPC), which is a requirement of the EU Energy Performance of Buildings Directive 2002.  The EPC produced using RDSAP shows the Energy Efficiency Rating (EER) on a scale of A-G (and numerically 100-1), similar to the label on a washing machine or fridge.  The higher the rating is, the more energy efficient the property is, and therefore lower running costs can be achieved. RDSAP also gives the property an Environmental Impact Rating (EIR) in terms of carbon dioxide (C0₂) emissions likely to be produced through use of the dwelling.  This is also presented on a scale of A-G whereby the higher the rating is, the more “environmentally friendly” the property is.   Besides the EER and EIR, the EPC report gives an indication of how much (based on standard occupancy) it is likely to cost to provide heating, hot water and lighting to the property, and suggests improvements that can be made to improve both the Energy Efficiency Rating and the Environmental Impact Rating.

Click here to see an example EPC

About the Assessment

A domestic energy assessment typically takes 45-90 minutes on site to complete, for an average property. Data collected during the assessment includes:

• Property age and type
• Construction of walls and roof to the main property and any extensions, including details of any insulation
• Floor areas
• Lengths of heat loss perimeter walls and any sheltering elements (e.g. garages and conservatories)
• Areas and age of glazing
• Room heights
• The main source of heating and hot water, its controls and any associated equipment (e.g. hot water cylinder), and the fuel used
• Any secondary heaters that are present, and the fuel used

All measurements are taken in accordance with the RICS Code of Measuring Practice.