Technical Booklet F2 Conservation of Fuel and Power in Buildings Other Than Dwellings·Page 58·3.59
Alternative performance standard for replacement windows in buildings requiring external appearance preservation
Where replacement windows must maintain the building's external appearance and cannot meet Table 3.2 standards, they must have a centre pane U-value of no more than 1.2 W/m2.K, or single glazing combined with low-E secondary glazing with weather stripping.
Where, because of the need to maintain the external appearance of a building, replacement windows are unable to meet the standards given in Table 3.2, the replacement windows should have a centre pane U-value of not more than 1.2 W/m2.K. Alternatively, single glazing may be used in combination with low-E secondary glazing with the weather stripping on the secondary glazing to minimise condensation risk between the primary and secondary glazing.
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