What SAP?

"This ole house is gettin' shaky, this ole house is gettin' old. This ole house lets in the rain, this ole house lets in the cold." - This Ole House by Shakin' Stevens

If you’ve recently moved house, you’re probably familiar with Energy Performance Certificates (EPC). They provide a concise summary of the energy and environmental performance of domestic properties, specifically, an estimate of CO₂ emissions and energy consumption. 

These are used to apply a colour coded performance rating to the dwelling. EPCs must be provided whenever a property is sold or rented and provide useful information to the new occupier as a starting point to estimate the likely environmental impact and energy bills associated with the dweling.

The calculations underpinning an EPC require a standardised methodology for assessing energy and environmental performance of dwellings. This is where the Standard Assessment Procedure or SAP comes in. In addition to EPCs, the SAP is used for a number of policy initiatives including the Green Deal and to ensure compliance with building regulations.

SAP was originally developed by BRE (Building Research Establishment) in 1992 and has since undergone several revisions and developments. It provides a standardized method to assess energy consumption per unit area for space heating, hot water, lighting and ventilation based on factors such as the construction materials used, the degree of insulation and the installed technologies.

Since SAP makes a number of assumptions about typical occupancy and householder behaviour, estimates cannot be used in design calculations or to make precise estimates of energy consumption or CO₂ emissions for a given dwelling. However, it does provide a standardised method allowing the performance of homes, the specifics of which vary hugely across the housing stock, to be compared.

The latest version of SAP was released after consultation in 2012. SAP 2012 includes a number of changes compared to SAP 2009 including an allowance for regional climate and height above sea level, revised values of CO₂ emission factors and fuel prices as well as more detailed consideration of heat losses from primary pipe work. 

These changes can have interesting knock-on effects, including regional differences in the estimated savings from installing solar technology, for example, which could have direct financial implications.

As low carbon technologies become more sophisticated and diverse, SAP will have to evolve to deal with ever more complex scenarios. One direct challenge is the way in which ‘off-site allowable solutions’, likely to be a key part of the 2016 zero-carbon new homes target, may be represented within SAP. Hence, look out for some further significant revisions to SAP in the near future.

Image courtesy of Joel Abroad