T101%20Thermal%20performance

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• T101 Thermal performance

Window energy rating
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Energy rating schemes

• NFRC
• National Fenestration Rating Scheme, USA
• BFRC
• British Fenestration Rating Scheme
• EWERS
• European Window Energy Rating Scheme

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FENSA

• FENestration Self Assessment
• Approved by ODPM as complying with Part L1
• Self certification by dealer/installer
• Administered by the GGF

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FENSA

• Self certification
• Frame type
• Thermal break
• Low e-coatings
• Gas filling
• Part L1 U-values

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Part L2 2002
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Part L2 2002
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Part L2 2002
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NFRC

• Operating for 15 years in the USA
• Rating scheme showing
• U-value
• Solar Heat Gain Coefficient
• Air leakage
• Factors combined differently for different
  climates

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NFRC

• 6 climatic regions cover USA
• Heating climates
• Cooling climates
• Sunny climates

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NFRC
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BFRC

• Independent UK body
• Spun out of UK Government funded research
• Partners were Trade Associations, Laboratories,
  Analysts and Universities
• Establishing links in Europe
• May feature in the next version of the Building
  Regulations

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BFRC rating

• Takes account of
• U-value
• Conduction, convection, radiation
• SHGC
• Solar Heat Gain Coefficient
• Air leakage
• Air leakage at 50Pa, L50

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Original BFRC label
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BFRC rating

• DWERS
• Domestic Window Energy Rating Scheme
• Ratings in the range G - A
• A is most energy efficient, DWER gt 0
• Todays good windows normally fall in band C, -20
  lt DWER lt -10

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DWER

• DWER 218.6 x Window Solar factor -
  68.5 x (Window U-value Air infiltration
  factor)
• Factors of 218.6 and 68.5 recognise the influence
  of Window Solar factor, U-value, and air leakage
  in the UK
• Windows will perform differently in different UK
  climates but will always be ranked consistently

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BFRC rating

• Separate values given for
• Window U-value, Uw
• Window solar factor, gwindow
• Window air infiltration factor, 0.0165L50
• To allow for fuller consideration

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Light transmittance

• A good DWER can be achieved by selecting right
  SHGC
• This can be achieved by using a tinted glass
• Heavily tinted glass will affect light levels in
  a building and may lead to an increased energy
  use for artificial lighting
• The light transmittance value is given to allow
  specifiers to avoid this problem

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EWERS

• European Window Energy Rating Scheme
• Adopted in Denmark
• Uses scale of A,B,C,D,E
• Similar to rating schemes for domestic appliances
• May be taken up in UK with BFRC as the operating
  agent
• Will use a common label but each state will set
  its own classification on the basis of climate
  and window styles!

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EWERS labelling
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Linking rating to regions
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BFRC rating label