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Our Triple Glazed Timber Sash Windows combine the appearance of a classic sash with the performance of modern glazing. Each unit is factory-fitted with 40–46mm sealed triple-glass, achieving a whole window U-value of 1.1 W/m²K. This high level of insulation makes them ideal for projects where energy efficiency is a priority.
The windows are built with engineered timber frames, available in redwood, hardwood, Accoya or oak, and finished with a durable three-coat microporous paint or stain. A traditional weight-and-pulley system ensures smooth operation, with optional child restrictors and locks for added safety.
From concealed trickle ventilation to a wide choice of RAL colours, every detail can be specified to suit the building. These windows provide long-term durability, tested weather performance, and the reassurance of TRC’s 30 years of sash window expertise.
Product Guidance
| Frame | 100 x 192 mm (lining width x frame depth), manufactured using mortise and tenon joints, glued and mechanically fixed |
| Sash | 39 x 71 mm top rail and stiles, 90 x 71 mm bottom rail, 45 x 71 mm meeting rail |
| Mullion/transom | 39 x 71 mm top rail and stiles, 90 x 71 mm bottom rail, 45 x 71 mm meeting rail |
| Sill projection | 35 mm, 50mm, 60mm, 70mm |
| Staff / parting beads | Timber |
| Wood moisture content | 12-19% |
| Glazing beads | Internally beaded with the external rebate up stand to give the appearance of putty glazing |
| Air Permeability | 600 Pa (Class 3), EN1026 EN12207 |
| Water Tightness | 200 Pa (Class 5A), EN1027 EN12208 |
| Wind Resistance | 1600 Pa (Class 4), EN12210 EN12210 |
| Whole Window U-Value | 1.1 W/m²K EN ISO 10077-1 |
| Whole Window Acoustic rating Rw, dB | BS EN ISO 10140-2:2021 29 dB (-2; -4) 4mm/16mm spacer/4mm/16mm spacer/4mm 30 dB (-1; -2) 6mm/14mm spacer/4mm/14mm spacer/8.8mm (44.2 laminated acoustic) |
| Anticipated Life Expectancy | 60 years with the regular maintenance |
Product Specifications
| Material | Frame and sash in engineered redwood, bottom cill in solid hardwood (standard), engineered hardwood, Accoya, or 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 | Triple glazed, 4/14/4/14/4 Low-E top sash – 4tgh/14/4/14/4tgh bottom sash - Standard, Ug-value: 0.6 W/m²K; g-value: 0.52-0.55 |
| Perimeter spacing bars | White warm edge perimeter spacer with white warm edge integral spacers - Standard. Silver and Black spacer optional |
| 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 | Windows to be factory fitted with 40-46mm thick sealed triple-glazing unit Tested to BS EN1279. Composition of glass units is to be (from outside): 4mm float with Low-E coating – 16mm argon filled cavity - 4mm float-16mm argon filled cavity - 4mm float glass with Low-E coating. Perimeter spacer in white or black |
| Glazing Bars | Applied bars are used to achieve the slim section of traditional glazing bars. These are applied with double sided glazing tape to both faces of the sealed unit and capped with clear silicone |
| 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 |
| Ventilation | A controllable trickle ventilator can be fitted to the window dependant on width of frame EA 2000, 4400mm² |
| 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-2901, 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
A whole-window U-value of just 1.1 W/m²K.
Weight-and-pulley operation for smooth, traditional action.
Optional restrictors limit opening to 100mm for safety.
Any RAL colour or stained timber finishes available.
FSC or PEFC-certified timber from managed forests.
60-year lifespan with regular maintenance.
Browse completed installations showcasing TRC’s craftsmanship across a range of properties.
Discover the exceptional blend of classic elegance and advanced performance in our triple glazed sash windows. Designed for professional environments, these windows combine the timeless appeal of traditional design with the latest in insulation technology.
Our windows are meticulously crafted to enhance any professional setting. The triple-layered glass optimises thermal efficiency and noise reduction, making them ideal for various applications where both aesthetics and functionality are paramount.
– Heritage Design, Modern Glazing
– Classic Look, High Performance
– Traditional Sash, Triple Glazed
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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