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Home Glossary Fenestration
Finishes noun

Fenestration

/fen-eh-STRAY-shun/

Also known as: glazing, window arrangement, window layout, glazed openings

The arrangement, sizing, and design of windows, doors, and other glazed openings in the facade of a building. Fenestration affects daylighting, ventilation, thermal performance, structural integrity, and the visual character of the building.

Fenestration is a key consideration in planning applications - local planning authorities assess whether window proportions, positions, and materials are appropriate for the area. Building Regulations Part L sets limits on the total area of windows and glazed doors relative to floor area to control heat loss. Energy-efficient glazing such as double or triple glazed, low-emissivity coated units is required in new and replacement windows.

Approved Document L - Conservation of Fuel and Power

Max. U-value (replacement windows)1.4 W/m2K
Max. glazed area (new dwellings)25% of floor area (guideline)
StandardBS EN 14351-1 (windows and doors)

Part L limits the area of new windows and doors relative to floor area to control fabric heat loss. U-values for replacement windows must meet minimum standards. FENSA or Building Control sign-off is required for replacement windows.