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The WEP rating is provided for a standard window to represent typical window sizes. This enables a comparison between different products. Each WEP rating label is specific to a unique window frame and glazing assembly from a single manufacturer. This WEP label is non-transferable and both the window assembly name (1) and the manufacturer (2) will appear on the WEP Certificate.  The WEP Certificate Energy Index(3) combines the following characteristics to allow consumers to determine how well each window assembly will perform.

Energy Performance Criteria

  • The termal transmittance (4) (Uwindow or Uw) is a measure of the insulation properties of the window assembly and allows the consumer to compare how effective each window assembly is at containing and conserving heat within a building in the winter. The lower the U-value of the window assembly, the greater the thermal performance of the window. The published U-value combines the thermal transmittance for both the glazing and the window frame.

  • The solar factor (5) (gwindow) or Solar Heat Gain Coefficient (SHGC) measures how well a product blocks heat caused by sunlight.  Heat gain can be beneficial in winter months but can also present consumers with additional cooling loads in summer months.  The Solar Factor is expressed as a number between 0 and 1. A lower Solar Factor means less heat gain.

  • The air leakage (6) (Lfactor) is a measure of the air tightness of a specific window assembly.  The weakest point in any window arrangement will tend to be around the seals on an opening section of window.  To qualify for the NSAI WEP Scheme, manufacturers must first demonstrate that their window arrangements achieve a Class 4 air tightness rating when tested at 600 Pa to I.S. EN 12207:1999 Windows and doors - Air permeability - Classification.  As a result well-made windows should have little or no air leakage. The lower the air leakage value of the window assembly, the greater the overall efficiency of the window assembly.
For further information download:

Apply for WEP

Manufacturers who wish to have a NSAI Agrément Window Energy Performance certification their products should review the application process which outlines the terms and conditions of the WEP scheme and WEP application forms

Click on window type links below to view energy rating label of each certified window.


Certificate Number
[website listed]
Window Type Description WEP
Rating New
Rating Index
IAB/W003/007 Senator Windows Senergy Plus PVC U A3 5.47
IAB/W003/008 Senator Windows Senergy Premium PVC U A2 11.41
IAB/W003/009 Senator Windows Senergy Elite PVC U A1 21.68
IAB/W004/003 O'Grady uPVC Ltd Eco-Elite Plus PVC U A3 0.15
IAB/W004/004 O'Grady uPVC Ltd Eco-Elite Triple PVC U A3 5.53
IAB/W004/005 O’ Grady uPVC Ltd Eco Elite Passive PVCU A3 4.48
IAB/W005/006 Earthkind Window Systems Ltd Earthkind Passive PVC U A3 2.30
IAB/W005/007 Earthkind Window Systems Ltd Earthkind Energy Double PVC U A2 10.14
IAB/W005/008 Earthkind Window Systems Ltd Earthkind Energy Triple PVC U A2 17.44
IAB/W007/003 Grogan & Currid uPVC Ltd. Futurespec+ PVC U A1 31.40
IAB/W007/004 Grogan & Currid uPVC Ltd. Futurespec PVC U A3 0.42
IAB/W008/007 Sean Doyle Windows Ltd Odyssey C70 28 PVC U A2 9.58
IAB/W008/008 Sean Doyle Windows Ltd Odyssey C70 36 PVC U A1 19.76 
IAB/W008/009 Sean Doyle Windows Ltd Odyssey C70 44 PVC U A1 31.40 
IAB/W008/010 Sean Doyle Windows Ltd Energy Plus External PVC U A3 -0.27
IAB/W009/005 Maher Windows Maher Eco Rated PVC U A3 6.16
IAB/W009/006 Maher Windows Maher Eco Triple PVC U A3 -0.31
IAB/W012/009 Profile Systems C70 A3 1.40 PVC U A3 -0.40
IAB/W012/010 Profile Systems C70 A2 1.0 PVC U A2 18.39
IAB/W012/011 Profile Systems C70 A3 1.42 PVC U A3 0.42
IAB/W012/012 Profile Systems C70 Triple Seal Passiv PVC U A1 31.40
IAB/W012/013 Profile Systems Kommerling C76 Casement 0.79   PVC U A3



Profile Systems

Kommerling C76 Flush 0.78 PVC U A3 8.66
IAB/W013/002 O'Rourke Windows & Glass Limited Fox & O'Rourke C70 A-Rated PVC U A3 0.55
IAB/W014/001 Kells Window Restoration Systems Kellwin Energy Plus Timber A3 -0.14
IAB/W014/002  Kells Window Restoration Systems  Kellwin Heritage Eco Timber  A3 2.73
IAB/W015/003 Wright Window Systems Eco-Wright Platinum PVC U A2 12.91
IAB/W015/004 Wright Window Systems Eco-Wright Platinum II PVC U A3 7.85
IAB/W015/005 Wright Window Systems Eco-Wright Passive PVC U A1 31.40 
IAB/W015/006 Wright Window Systems Eco-Wright Platinum 1 PVC U A2 17.02
IAB/W015/008 Wright Window Systems Wright Legacy 1.2 PVC U A3 1
IAB/W015/009 Wright Window Systems Wright Legacy 0.8 PVC U A2 14.60
IAB/W015/010 Wright Window Systems Eco-Wright Diamond 3 PVC U A3 6.52
IAB/W017/002 Moloney Windows Platinum 36 PVC U A2 9.90 
IAB/W017/003 Moloney Windows Platinum 28 PVC U A3  1.23
IAB/W019/002 Forde Bros Ballinlough Forde Windows A-Rated PVC U A3 0.42
IAB/W019/003 Forde Bros Ballinlough Forde Bros 1.2 Window PVC U A3 2.66
IAB/W024/002 Larkin Aluminium Ltd Larkin Double A Rated Window  PVC U A3 6.03 
IAB/W024/003 Larkin Aluminium Ltd Larkin Triple A Rated Window PVC U A2 12.64
IAB/W026/001 TSL Windows Liniar Sculptured Section PVC U A2 10.27
IAB/W029/001  Dalgan Windows Ltd        Ultra Passive   PVC U                    A3  5.17
IAB/W029/002  Dalgan Windows Ltd  Ultra Double      PVC U  A2    12.32
IAB/W029/003 Dalgan Windows Ltd  Ultra Triple


A3 2.43
IAB/W030/001 Mahon Windows Eco Energy Plus PVC U A2


IAB/W030/002 Mahon Windows Eco Energy PVC U A3 0.42
IAB/W030/003 Mahon Windows Eco Energy Passive PVC U A1 31.40
IAB/W031/001 WISNIOWSKI Sp. z o.o. S.K.A. T/A DEVELO  DEVELO A PVC U A3 3.17
IAB/W031/002 WISNIOWSKI Sp. z o.o. S.K.A. T/A DEVELO DEVELO A+ PVC U A2 9.81