Velux Roof Windows for London Victorian Loft Conversions: Specification, Planning, and Costs

OPENING TYPES FOR LOFT CONVERSION ROOF WINDOWS: VELUX AND OTHER MANUFACTURERS (FAKRO, ROTO, KEYLITE) PRODUCE TWO PRIMARY OPENING TYPES FOR PITCHED ROOF WINDOWS: 1. CENTRE-PIVOT (THE MOST COMMON UK LOFT CONVERSION CHOICE): - THE SASH PIVOTS AROUND A CENTRAL HORIZONTAL AXIS — THE BOTTOM HALF OF THE GLASS SWINGS INTO THE ROOM WHEN OPENED, THE TOP HALF SWINGS OUT. - REQUIRES APPROXIMATELY 600-700MM OF CLEAR HEADROOM IN FRONT OF THE WINDOW FOR THE SASH TO SWING IN — NOT SUITABLE FOR VERY LOW-PITCHED ROOFS WHERE HEADROOM AT THE EAVES IS LIMITED. - VELUX PRODUCT CODES: GGL (PINE FRAME), GGU (POLYURETHANE COATED — MAINTENANCE-FREE EXTERIOR), GPL (PINE CONSERVATION ROOFLIGHT — GGL EQUIVALENT), GPU (POLYURETHANE CONSERVATION ROOFLIGHT). - CLEAN POSITION: CENTRE-PIVOT VELUX WINDOWS CAN BE ROTATED 180° TO ALLOW CLEANING OF THE OUTER PANE FROM INSIDE — A KEY PRACTICAL ADVANTAGE FOR A LONDON VICTORIAN LOFT WHERE EXTERNAL CLEANING VIA LADDER IS DANGEROUS.

2. TOP-HUNG (RECOMMENDED WHERE HEADROOM ALLOWS AND A BETTER VIEW/LIGHT DISTRIBUTION IS WANTED): - THE SASH IS HINGED AT THE TOP — THE BOTTOM OF THE GLASS SWINGS OUTWARD WHEN OPENED. - PROVIDES A CLEANER UNOBSTRUCTED VIEW (NO PIVOT BAR AT CENTRE OF GLASS) AND BETTER UPPER-ZONE DAYLIGHT DISTRIBUTION — THE TOP OF THE GLASS IS ALWAYS VERTICAL EVEN WHEN THE WINDOW IS CLOSED ON A SLOPING ROOF. - REQUIRES EXTERNAL CLEANING FROM OUTSIDE (LESS PRACTICAL) OR A SPECIALIST CLEANING SYSTEM. - VELUX PRODUCT CODES: GHL (PINE), GHU (POLYURETHANE EXTERIOR), GHS (MANUALLY OPERATED THROUGH CENTRE PIVOT BUT MARKETED AS TOP-HUNG LOOK).

FIRE ESCAPE GLAZING REQUIREMENTS: IN A LONDON VICTORIAN LOFT CONVERSION WITH MORE THAN TWO STOREYS: - PART B OF THE BUILDING REGULATIONS REQUIRES AT LEAST ONE OPENING ROOF WINDOW IN EACH HABITABLE ROOM ON THE LOFT STOREY THAT CONSTITUTES AN EMERGENCY ESCAPE ROUTE. - THE ESCAPE WINDOW MUST HAVE A MINIMUM CLEAR OPENING OF: 450MM HIGH × 450MM WIDE (MINIMUM DIMENSIONS) AND 0.33M² MINIMUM CLEAR OPENING AREA. THE OPENING MUST BE NO MORE THAN 1.1M FROM THE FLOOR LEVEL. - VELUX ESCAPE WINDOWS: VELUX GGL AND GGU WINDOWS IN SIZES MK04 (78×98CM) AND ABOVE SATISFY THE MINIMUM ESCAPE REQUIREMENTS — BUT THE POSITION ON THE ROOF AND DISTANCE FROM THE FLOOR MUST BE VERIFIED BY THE BUILDING CONTROL OFFICER. - PRACTICAL IMPLICATION: FOR A TYPICAL LONDON VICTORIAN LOFT CONVERSION, THE BUILDING CONTROL OFFICER WILL REQUIRE AT LEAST ONE VELUX (OR EQUIVALENT) OPENING ROOF WINDOW OF MINIMUM MK04 SIZE IN THE LOFT BEDROOM — SPECIFY THIS AS A MINIMUM IN ANY LOFT CONVERSION SCOPE OF WORKS.

THERMAL SPECIFICATION: VELUX ROOF WINDOWS HAVE IMPROVED SUBSTANTIALLY IN THERMAL PERFORMANCE IN RECENT YEARS: - STANDARD DOUBLE GLAZED VELUX GGU (POLYURETHANE EXTERIOR): U-VALUE APPROXIMATELY 1.4 W/M²K (WHOLE WINDOW, INCLUDING FRAME). COMPLIES WITH PART L (CONSERVATION OF FUEL AND POWER) FOR REPLACEMENT WINDOWS (MINIMUM U-VALUE 1.8 W/M²K) BUT IS OUTPERFORMED BY THE TRIPLE GLAZED OPTION. - TRIPLE GLAZED VELUX ENERGY (PREVIOUSLY "THERMO PLUS"): U-VALUE APPROXIMATELY 0.57-1.0 W/M²K (WHOLE WINDOW) — RECOMMENDED FOR LOFT CONVERSIONS IN LONDON WHERE THE ROOF IS THE MAIN THERMAL ENVELOPE AND HEAT LOSS THROUGH ROOF WINDOWS IS SIGNIFICANT. - ENERGY RATING: VELUX USES AN ENERGY RATING SYSTEM (A++ TO E) SIMILAR TO WHITE GOODS — LOOK FOR A+ OR ABOVE FOR A LOFT CONVERSION ROOF WINDOW. - RAINWATER OPERATION AND RAIN SENSOR: VELUX INTEGRA (SOLAR POWERED, NO WIRING) AND VELUX ELECTRIC ROOF WINDOWS CAN BE FITTED WITH A RAIN SENSOR — THE WINDOW CLOSES AUTOMATICALLY WHEN RAIN IS DETECTED. USEFUL FOR A LONDON LOFT WHERE THE OCCUPANT MAY NOT ALWAYS BE IN THE LOFT TO NOTICE RAINFALL.

PLANNING FOR VELUX ROOF WINDOWS IN LONDON CONSERVATION AREAS: MOST LONDON VICTORIAN TERRACES ARE IN CONSERVATION AREAS. THE PLANNING RULES FOR ROOF WINDOWS IN CONSERVATION AREAS DEPEND ON WHICH ROOF SLOPE: - REAR SLOPE (FACING THE GARDEN OR AWAY FROM A HIGHWAY): VELUX-TYPE ROOF WINDOWS ON THE REAR SLOPE OF A LONDON VICTORIAN TERRACE ARE PERMITTED DEVELOPMENT (NO PLANNING PERMISSION REQUIRED) IF THEY DO NOT PROTRUDE MORE THAN 150MM ABOVE THE ROOF SLOPE AND ARE NOT THE HIGHEST PART OF THE EXISTING ROOF. THIS APPLIES EVEN IN CONSERVATION AREAS. - FRONT SLOPE (FACING THE STREET): ANY ALTERATION TO THE ROOF SLOPE VISIBLE FROM A HIGHWAY REQUIRES PLANNING PERMISSION IN A CONSERVATION AREA. A STANDARD VELUX (WHICH PROTRUDES 150MM+) ON THE FRONT SLOPE OF A CONSERVATION AREA PROPERTY WILL ALMOST CERTAINLY BE REFUSED. A CONSERVATION ROOFLIGHT (FLUSH OR NEAR-FLUSH) ON THE FRONT SLOPE MAY BE GRANTED IF THE FRAME COLOUR AND STYLE IS ACCEPTABLE. - CONSERVATION ROOFLIGHTS (VELUX GIL, WHITESALES EM-GLAZE, THE ROOF LIGHT COMPANY): WHERE THE CONSERVATION OFFICER REQUIRES FLUSH OR LOW-PROFILE ROOFLIGHTS, THE VELUX GIL (CONSERVATION INTEGRA) SITS FLUSH WITHIN THE ROOF SLOPE (APPROXIMATELY 16MM ABOVE THE SURROUNDING TILES). THE GIL IS A FIXED (NON-OPENING) UNIT — FOR VENTILATION IN A CONSERVATION AREA, A SEPARATE VENTILATED ROOFLIGHT ADJACENT TO THE GIL IS SOMETIMES SPECIFIED. - ARTICLE 4 DIRECTION: SOME LONDON CONSERVATION AREAS HAVE AN ARTICLE 4 DIRECTION REMOVING PERMITTED DEVELOPMENT RIGHTS FOR ROOF ALTERATIONS — EVEN REAR SLOPE VELUX WINDOWS MAY REQUIRE PLANNING PERMISSION UNDER ARTICLE 4. CHECK WITH THE LOCAL PLANNING AUTHORITY.

LOFT CONVERSION ROOF WINDOW POSITIONING: - HEAD HEIGHT FROM ROOF WINDOW TO FLOOR: VELUX RECOMMENDS THAT THE BOTTOM SILL OF A ROOF WINDOW SHOULD BE BETWEEN 700MM AND 900MM FROM THE LOFT FLOOR LEVEL FOR COMFORTABLE STANDING USE. FOR A FIRE ESCAPE WINDOW, THE CLEAR OPENING MUST BE NO HIGHER THAN 1.1M FROM THE FLOOR — CHECK POSITIONING CAREFULLY ON LOW-PITCHED ROOFS. - DAYLIGHT DISTRIBUTION: THE POSITION OF THE VELUX ON THE ROOF PLANE AFFECTS DAYLIGHT DISTRIBUTION IN THE LOFT ROOM. ROOFLIGHTS HIGHER ON THE PITCH (CLOSER TO THE RIDGE) DISTRIBUTE DAYLIGHT MORE EVENLY ACROSS THE ROOM; ROOFLIGHTS LOWER ON THE PITCH (CLOSER TO THE EAVES) GIVE MORE LOCALISED ILLUMINATION NEAR THE WINDOW.

COSTS (SUPPLY AND FIT, LONDON 2025-2026): VELUX GGL CENTRE-PIVOT (PINE) MK04 78×98CM — SUPPLY ONLY: £250-350 VELUX GGU POLYURETHANE CENTRE-PIVOT MK04 — SUPPLY ONLY: £350-500 VELUX GGU TRIPLE GLAZED ENERGY MK04 — SUPPLY ONLY: £550-750 VELUX INTEGRA SOLAR ELECTRIC MK04 — SUPPLY ONLY: £700-1,200 FITTING A ROOF WINDOW (LABOUR, FLASHING, INTERNAL REVEAL LINING — PER UNIT): £300-600 CONSERVATION ROOFLIGHT (VELUX GIL OR EQUIVALENT, SUPPLY AND FIT): £600-1,500 FULL LOFT CONVERSION VELUX PACKAGE (2 × ROOF WINDOWS WITH FLASHING AND INTERNAL LINING, SUPPLY AND FIT): £1,500-4,000