How SAP ratings are used to measure the annual efficiency of a biomass boiler
Posted by Laurence Jones on 23 September 2011 at 10:15 am
A: What is SAP?
Standard Assessment Procedure (more commonly known as SAP), is a home energy rating that is recognised by the British government.
In brief, SAP provides an indexed rating of the overall energy efficiency of a building and is based on consideration of space and water heating, ventilation and lighting. These are calculated taking account of the shape and fabric of the building, its thermal insulation, the fuel used, the performance of the heating system and other energy using devices.
The SAP rating is expressed on a scale of one to 100. The higher the number, the better the energy rating. SAP also delivers an Environmental Impact rating on a scale of 1 to 100 based on carbon dioxide emissions.
How does SAP work for a biomass boiler?
Biomass boilers will run at various loads throughout the course of the year. A typical UK household will run up to “full load” throughout the winter months and “part load” during warmer seasons. The combination of these two figures (x0.5) is known as the seasonal efficiency.
Using this seasonal efficiency of a boiler, you can add it to the other SAP considerations such as insulation, the thermal conductivity of the walls etc to calculate your households rating.
SAP is, by its very nature, designed to consider all of the energy that a property consumes. Accordingly, it is regarded by many as the definitive procedure for measuring home energy ratings.
You can find more information on SAP here.
Photo by iied.org
About the author: Laurence Jones was marketing support officer at HETAS
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