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Our Heritage Box Sash window is specifically crafted to serve as an enhanced replacement for original period windows commonly found in listed Georgian, Victorian, and Edwardian historic properties and conservation areas. This window is double glazed with ultra slim double-glazed units, solid glazing bars, putty fronted and incorporating concealed draught exclusion to keep the aesthetics of the original window but with much greater performance, typically achieving U values of 1.8 -1.4 and acoustic ratings of 38-30db depending on the make-up of the glass unit.
Constructed with slim frame and sash profiles, the Heritage Box Sash window functions with a classic system of cords, weights, and pulleys. A spring balance option is also available. These windows are typically installed within a check reveal, allowing the box to remain largely concealed behind external brick or stonework, although it can also be fitted flush with the brick face, where the box remains visible and is often finished with an architrave.
TRC’s Heritage Box Sash can be supplied fully finished with a 3-coat spray applied microporous water-based paint system or can be supplied primed only for a topcoat to be applied on site by others.
All of our windows come with a choice of sash lifts, fasteners, locks and pulley wheels with a wide range of finish options including antique brass sash, polished chrome, satin nickel, polished brass, matt bronze and polished nickel.
Product Guidance
| Frame | 100 x 140 mm (lining width x frame depth), manufactured using mortise and tenon joints, glued and mechanically fixed. |
| Sash | 39 x 45 mm top rail and stiles, 90 x 55 mm bottom rail, 45 x 55 mm meeting rail. |
| Mullion / transom | 200 mm wide (130 mm for triple sash with fixed outer sash). |
| Sill projection | 35 mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm. |
| Staff / parting beads | Timber. |
| Wood moisture content | 12-19%. |
| Glazing beads | External Traditional putty glazed. |
| Air Permeability | 450 Pa (Class 3), EN 12207: 2017 |
| Water Tightness | 200 Pa (Class 5A), EN 12208:2002 |
| Wind Resistance | 1600 Pa (Class 4C), EN 12210:2016 |
| Whole Window U-Value | Softwood window with: U-value 1.8 W/m²K with 4mm/6mm Krypton/4mm Softcoat(14mm O/A) U-value 1.6 W/m²K with 4mm/6mm Special Gas/4mm Softcoat (14mm O/A) U-value of 1.5 W/m²K with 4mm/6mm Xenon/4mm Softcoat (14mm O/A) Hardwood window with: U-value 1.9 W/m²K with 4mm/6mm Krypton/4mm Softcoat(14mm O/A) U-value of 1.7 W/m²K with 4mm/6mm Special Gas/4mm Softcoat (14mm O/A) U-value of 1.6 W/m²K with 4mm/6mm Xenon/4mm Softcoat (14mm O/A) |
| Whole Window Acoustic rating Rw, dB | Acoustic rating is Laboratory tested to BS EN ISO 10140-2 : 2010 (Airborne Sound Insulation) 4mm / 6mm /4mm Softcoat (14mm O/A) – 31[-1; -3] dB; 6.8mm (33.2)/ 8mm Krypton/4mm Softcoat (18.8mm O/A) – 36[-1; -2] dB |
| Anticipated Life Expectancy | 60 years with the regular maintenance |
Product Specifications
| Material | Frame+Sashes Engineered redwood, Bottom Cill in Solid Hardwood - Standard. Engineered hardwood, Accoya, European oak. |
| Finish | Three coat spray applied factory finish using water based micro-porous paint / stain. |
| Colour | White - RAL 9016 - Standard. Any RAL - from RAL classic range. Stain - from TRC stain range. |
| Glazing | Double slimlight glazed, 4/6/4 Low-E top sash – 4toughened/6/4 toughened bottom sash – Standard. Single Glazing of 4 mm or 6mm thick toughened - Optional. |
| Perimeter spacing bars | White perimeter spacer - Standard. Black spacer optional. |
| Solid Bar | Ovolo 24 x 45mm. |
| Trickle ventilation | Concealed through frame head trickle ventilator. EA 1700, 4400, 5000 mm². |
| Child restrictor | Angel lock standard. Traditional Sash Stop optional. |
| Operation | A traditional box sash window uses an Iron (occasionally Lead) weight, attached to a cord, passed over a pulley and fixed to the glazed sash frame. As the window is operated the weights travel upwards or downwards concealed inside the frame. |
| Timber Species | Manufactured in selected engineered laminated pine, hardwood or Accoya, sourced from sustainable and managed forestry (FSC or PFEC certified). |
| Moisture Content | 12% +/- 2% on delivery |
| Glass | The windows to be factory fitted with 12, 14 or 16mm thick sealed double “slimlight” glazing unit Tested to BS EN1279 Parts 2 & 3. Composition of glass units is to be (from outside): 4mm float – 6mm argon, krypton or Xenon filled cavity /4mm float glass with Low-E coating. Other glazing combinations are available on request. The height of the sidelight of the DGU is not less than 8.5mm. Perimeter spacer in white or black. |
| Glazing Bars | Solid traditional framed glazing bars with individual glass units |
| Ironmongery | A lockable Fitch fastener and two finger pulls to the bottom sash with options in colour and finish. |
| Cill | Manufactured in Hardwood with options of Projections: 35 mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm. |
| Horns | Solid feature horns to top sashes are included as standard (See Drawing No H-001) |
| Ventilation | A controllable trickle ventilator can be fitted to the window dependant on width of frame (See Drawing No HERITAGE-140/06) EA 1700, 4400, 5000 mm². |
| Finish as Delivered | Window supplied factory finished, externally and internally with Teknos Water-based micro porous opaque to specified RAL colour, or stained finish. Aqua prime 1410, Aqua mid-5200, Aqua top 2600. |
| Restrictors | Restrictors which allow the opening of the sash to be restricted to 100mm is an option |
| Fixing | Installation to be carried out using best building practices and in conjunction with recommendations of TRC windows |
| Warranty | Manufacturing and Material Defects: 10-year guarantee. Finishes: The standard three-coat opaque finished joinery guaranteed for 10 years. The stain finishes guaranteed against blistering or flaking for six years. Seals: The seals on double-glazed units are guaranteed for 10 years (from the date of delivery). Ironmongery: Functional failure is guaranteed on ironmongery for two years. |
Technical Drawings
U-values between 1.8 and 1.4 W/m²K
Slim frames, sashes, and authentic period proportions
Choice of weight-and-pulley or spring balance operation
Available in any RAL colour or classic stains
Cill projections available from 35mm up to 110mm
Timber from FSC-certified, responsibly managed forests
Browse completed installations showcasing TRC’s craftsmanship across a range of properties.
TRC heritage sash windows use a classic weight and pulley mechanism, and are ideal replacement windows for listed buildings as well as architect-led new developments.
We use traditional putty to secure thin, high-performance Slimlite glass (single- or double-glazed). Slimlite ensures an authentic appearance, and satisfies demand for modern acoustic and thermal performance.
Solid glazing bars come as standard. Each window comprises a number of individual glass panels, giving our heritage sash windows genuine character.
When it comes to safety, angel locks and sash stops are fitted as standard. And restrictors can be fitted 100mm above the mid rail to ensure child safety and the security of your property.
All windows are finished with three coats of spray-applied microporous water-based paint, which ensures the smooth operation and optimum performance of the window.
Heritage sash windows are a traditional style of window that can add character and charm to any home. These windows are made up of two movable sashes that slide up and down vertically, allowing for easy ventilation and access to the outdoors. They have been a popular feature of British architecture for centuries and are often found in historic buildings and period homes.
Here at TRC Windows, we are passionate about preserving the heritage and character of these windows while also improving their performance and energy efficiency. Our expert craftsmen use traditional methods and materials to create beautiful, bespoke sash windows that are tailored to your individual needs and preferences.
Our windows are made from high-quality, sustainably sourced timber and are designed to blend seamlessly with the original architecture of your home. We offer a range of glazing options, including double and triple glazing, to improve energy efficiency and reduce noise pollution.
We also offer a range of additional features, such as draught-proofing and security locks, to ensure that your heritage sash windows are not only aesthetically stunning but also supremely functional and secure. Our team of experienced TRC fitters will install your new windows with care and precision, ensuring a perfect fit and a long-lasting finish.
Whether you are looking to restore your period home to its former glory or simply add some traditional charm to a modern property, TRC Windows has the expertise and experience to create the perfect heritage sash windows for you. Contact us today using the form below to discuss your requirements and to arrange a consultation with one of our friendly team members.
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