Head-to-Head Specification & Cost Comparisons
Independent side-by-side audits compiled by Tarquin Barnsby (trading as uPVCWindowCalculator.co.uk) (ICO Reg: ZC136598). Every comparison includes full 2026 cost bands with zero email or phone gate.
Local FENSA Installer vs National Chains (Anglian, Everest): 2026 Price & Warranty Audit
In 2026, commissioning a vetted local FENSA or Certass installer reduces turnkey uPVC window and door replacement costs by 42% to 56% (£4,400 vs £9,800 for a standard 8-window 3-bed semi) because you avoid 25% self-employed canvasser and showroom sales commissions while receiving the exact same Rehau, Liniar, or Veka A+ profile.
A+ Argon Double Glazing (1.2 W/m²K) vs Triple Glazing (0.8 W/m²K): 2026 UK Payback
Under Approved Document L1B (2026), replacement windows must achieve a whole-window U-value of 1.4 W/m²K or WER Band B. Upgrading from A+ Argon double glazing (1.2 W/m²K) to triple glazing (0.8 W/m²K) adds 18% to 22% (£85–£125 per window) and is primarily justified for north-facing elevations, flight paths, and Busy A-road acoustic damping (38–42 dB Rw).
Casement vs Flush Sash vs Vertical Sliding Sash Windows: 2026 UK Cost Matrix
In 2026, standard lipped uPVC casement windows cost £380 to £520 installed, heritage flush sash casements (where the opener sits flush within the outer frame like 19th-century timber) cost £540 to £720 (+35%), and spring-balanced uPVC vertical sliding box sash windows cost £680 to £920 per aperture (+75%).
GRP Composite Front Doors vs Solid Timber Core & Aluminium Bi-Fold Door Costs (2026 UK)
In 2026, a PAS 24 / Secured by Design GRP composite front door costs £1,050 to £1,350 fully fitted, a 48mm solid timber-core composite door (Solidor/Endurance) costs £1,380 to £1,790, and a 3-pane 3.0m thermally broken aluminium bi-fold patio door costs £2,750 to £3,450 including trickle vents and Part Q multipoint locking.
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