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Thermabronze™ System

The Thermabronze™ system has been designed as a solution to the current energy saving requirements within Building Regulations, featuring a double thermal break within our characteristic slim frame for enhanced thermal performance. The frame incorporates a decorative bronze bead that secures the glass in place, double weather seals and will accept 18mm double glazed units. A range of decorative ironmongery complements the handcrafted, bespoke nature of the product

System Features

Traditional Bead Option
Contemporary Bead Option
Double Glazing (18mm)
Thermally Broken Windows
Side Hung Unit
Top Hung Unit
Fixed Unit
Fixed Unit Over 1.2m2 (24mm Glazing)
Rebated Leg Profile
Equal Leg Profile
Vertical and/or Horizontal Glazing Bars
Leaded or Plain Units
Security Options Available
Optional Trickle Ventilation
Double Weather Seal
Part Q Compliant

System Drawing

Opening Frame

Thermabronze opening system drawing

Fixed Frame

 Thermabronze fixed system drawing

Equal Leg Fixed Frame

Thermabronze fixed equal leg system drawing

Recommended Design Limits

Side Hung Casement

Max O/a Width 650mm
Min O/A Width 300mm
Max O/A Height 1700mm

Casements over 1100mm high will require 2 handles. Where width is greater than height, casement sash must be top hung.

Top Hung Casement

Max O/a Width 1200mm
Min O/A Width 300mm
Max O/A Height 500mm
Min O/A Height 350mm

Fixed Lights

Max O/A Width 1200mm
Max O/A Height 2400mm

The inclusion of opaque glazing and abutment details may alter the above performance data and design limits.
Please contact our sales team to discuss any requirements outside of the standard size limits detailed above.


U-value performance based on an 18mm double glazed unit made up of 4mm float/10mm 90% Krypton filled cavity/4mm Planitherm total + with warm edge spacers.

Fixed casement overall value 1.4W/m2K
Opening casement overall value 1.5W/m2K
Centre pane value 1.1W/m2K

When incorporating a genuine Georgian bar add 0.4 to the U-value.

U-values calculated in accordance with BS EN iso 10077-1:2006 based upon a single fixed light sample 1230mm x 1480mm and a single opening light sample 1230mm x 1480mm.

Weather Rating

BS 6375 Part 1

Exposure categories measured in pascals

UK Exposure category 2000

Air Permeability

Class 4
Maximum Test Pressure 600 Pa


Class 8A
Maximum Test Pressure 450 Pa

Resistance to wind load

Class A5
P1 2000
P2 1000
P3 3000

The above tests are carried out on side-hung outward opening windows measuring 1700m x 650mm and are tested excluding any additional security features.

Part Q Security

Tested with scroll handles, plain backplates, manor stays and Part Q casement locks. Below test carried out on windows measuring maximum 1700mm x 650mm.

Side opening and fixed casements. Pass