Terminology - Ratings & Values
The energy efficiency of a window, giving a rating
between A - G (A being best) taking into account the
solar gain “g” value, U-value of the window and the BFRC Rating
amount of air leakage. The energy rating of the
product is indicated on a colour coded labeling
system.
The measurement of heat transmission through the
building element, in this case the window or door.
U - Value The lower the U value the better the insulation properties.
Measures the solar radiation (Heat) transferred Solar Heat Gain
through a window to the interior of a house. The
lower the Solar heat gain “g” value, the less heat is ( g Value )
transmitted into the house.
The SAP rating provides a means of calculating the
energy efficiency of each dwelling. The SAP rating is
based on the energy costs for heating space and water
and provides an understanding of running costs of the
dwelling. The SAP rating is measured on a numerical
scale of 1 to 100, the higher the number the better the
rating. The average house in the UK has a SAP rating
of 40 to 50, whereas most new dwellings are aiming to
achieve 80 or above. The calculation uses factors such
as the building size, floor area, solar gain factors,
ventilation, materials used to create the new dwelling
(i.e brick / block type, roof tile, insulation, plasterboard),
it also includes the appliances within the dwelling (i.e
boiler specification, radiators etc) and the fuel used to
run the appliances and heat water. The suppliers of S.A.P Rating
these items must all be able to produce documentation
providing the relevant information regarding the energy (Standard Assessment Procedure)
efficiency of the product. Within our particular industry
the window and door frames as well as glass energy
ratings and ventilation values are applied to the
calculation.
The SAP rating is usually calculated by either an
architect, the house builder or an approved SAP
consultant. The calculation must then be submitted to
the local authority building control officer for review. The
SAP rating notice must then be clearly displayed for all
to see on the dwelling.
The SAP calculation is predominantly for new build
certification.
Issue: 2 (January 2008) 7.4
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