Replacing windows or doors in England touches several parts of the Building Regulations. Here's what each one covers, and how our Reynaers systems are specified to meet them.
Approved Document L (2021 edition) — in force from 15 June 2022. Sets minimum thermal performance for replacement windows and doors in existing dwellings in England. This is the single most important regulation for window & door replacement — failure to comply is a Building Regulations offence.
When replacing windows or doors like-for-like in an existing home (not an extension), the minimum performance requirements are:
Our Reynaers systems achieve Uw values as low as 0.64 W/m²K — well exceeding these requirements.
Special rules apply. Always check before replacing windows or doors:
Always consult your Local Planning Authority before replacing windows in a listed or protected building.
| System | Type | Best Uw | Part L |
|---|---|---|---|
| SlimLine 68 | Window | 1.1 W/m²K | ✓ Pass |
| SlimLine 38 | Window | 0.8 W/m²K | ✓ Pass |
| MasterLine 8 | Window / Door | 0.64 W/m²K | ✓ Pass |
| SlimPatio 68 | Sliding door | 1.4 W/m²K | ✓ Pass |
| MasterPatio | Sliding door | 1.47 W/m²K | Check |
| CF68 / CF77 | Bi-fold | 1.1 W/m²K | ✓ Pass |
In England, replacing windows or doors is notifiable Building Regulations work. You must use either a FENSA-registered installer or notify your Local Authority Building Control.
2Rsystems is a FENSA-registered installer. This means we can self-certify our window and door installations comply with Building Regulations without you needing to involve Building Control.
If not using a FENSA-registered installer, the homeowner must submit a Building Regulations application to their Local Authority Building Control (LABC) or an Approved Inspector.
Installing windows without notification is a Building Regulations offence and can cause problems when selling your property.
Approved Document F (2021 edition) — in force June 2022. Adequate ventilation is essential for indoor air quality and preventing condensation. If the existing windows have trickle vents, replacement windows must also have trickle vents of at least equivalent size — you cannot remove ventilation when replacing windows. In practice, most habitable rooms need background ventilation fitted even where the originals didn't have it, to meet whole-dwelling ventilation targets.
Continuous, low-level ventilation via trickle vents in window frames. Cannot be switched off.
Rapid ventilation for clearing pollutants, cooking smells etc. Provided by openable window sections.
Mechanical extraction required in wet rooms to remove moisture and pollutants at source.
We factor ventilation requirements into every quote, so there are no surprises once your FENSA certificate is issued.
Approved Document B (2020 edition) — all habitable rooms must provide a safe means of escape in case of fire. Windows play a critical role as secondary escape routes.
Fire escape windows must open outwards or be top-hung. Bottom-hung (hopper) windows that open inward are not acceptable as a sole means of escape. Above 4.5m from ground, a protected stairway with fire-resisting construction becomes mandatory instead of a window escape.
Approved Document K. Safety glazing must be installed in critical locations to prevent injury from glass breakage. All safety glazing must be permanently marked with the BS 6206 Kitemark.
Within 1,500mm from floor level in all door glazing — BS 6206 Class B required.
Within 300mm of door edge and within 1,500mm from floor — BS 6206 Class B required.
Any glazing with its lowest point within 800mm of floor level — BS 6206 Class C required.
All glazing in shower enclosures, screens and wet areas — safety glazing required.
For double-glazed units, safety requirements apply to both panes if both sides are accessible. Trickle vents must not compromise safety glazing integrity.
Approved Document Q (2015, updated) — mandatory security standard for all new residential buildings. PAS 24 tests the complete window or door assembly — not just the lock or glass — against common burglary techniques. The standard was amended in 2024 (PAS 24:2022+A1:2024) with a stricter test targeting lock-cylinder attacks; products certified to the previous version remain valid during a transition period until January 2027.
Resistance to forced entry with common tools for a minimum of 3 minutes.
Withstands physical pressure and repeated impact.
Resistance to lock picking, bumping and cylinder attacks.
BS 6375 weather-performance compliance, plus corner strength and glazing bead security testing.
Replacement windows in existing homes: Part Q does not strictly apply, but PAS 24 is still strongly recommended for ground-floor openings.
Speak to our team — we'll walk you through exactly what your installation needs to comply with, at no cost.
Call 01794 721 100