Fri Jul 10
A well-specified sash window has to do two jobs at once. It has to look right on a Georgian townhouse or a Victorian terrace, and it has to perform to current building standards.
TRC Contracts has spent 30 years building a range of timber sash windows that answers both requirements, from heritage-grade solid glazing bars through to vacuum-glazed units for conservation areas with tight rebate depths.
This piece sets out the products behind that range, the materials and joinery that underpin them, and the performance data architects and specifiers need at the specification stage.
The TRC Contracts sash window range
Heritage sash windows
TRC’s Heritage Box Sash window is built for listed Georgian, Victorian and Edwardian properties where solid glazing bars and putty-fronted glazing are a planning requirement. It operates on a traditional weight-and-pulley system, with a spring balance option available, and achieves whole-window U-values between 1.6 and 2.0 W/m²K depending on the gas fill specified. Anticipated life expectancy is 60 years with regular maintenance.
Traditional box sash windows
Where applied glazing bars are acceptable, the Traditional Box Sash window delivers the same period profile with a whole-window U-value as low as 1.4 W/m²K and acoustic ratings between 29 and 38 dB. Internally beaded for PAS 24 security, it uses the same weight-and-pulley mechanism as the heritage range.
Spring sliding sash windows
For projects that need slimmer sightlines and simpler installation, the Spring Sliding Sash window replaces cords and weights with a pre-tensioned spiral balance. It retains the classic sash profile, reaches U-values as low as 1.4 W/m²K and carries acoustic ratings up to 39 dB.
Easy clean sash windows
TRC’s Easy Clean Sash window combines a traditional profile with a tilt-and-slide mechanism, allowing each sash to tilt inwards by up to 50 degrees for safe cleaning from inside the property. It is tested to Class 4 air permeability, Class 5A water tightness and Class 4C wind resistance, and is PAS 24 and Secured by Design approved.
Vacuum glazed and triple glazed sash windows
Two routes are available where maximum thermal performance is required. Vacuum glazed sash windows use a glazing unit just 8.3mm thick, close to the profile of single glazing, achieving whole-window U-values between 1.1 and 1.2 W/m²K with a fully recyclable cavity that avoids noble gases. Triple glazed sash windows use a 40 to 46mm sealed unit to reach a whole-window U-value of 0.79 W/m²K, suited to exposed or north-facing elevations where rebate depth is less of a constraint.
Acoustic sash windows
TRC Contracts has invested in independent acoustic testing rather than relying on estimated figures. Sash and casement windows are tested and certified to ISO 10140-2:2021 at ratings of 33, 36, 37, 38, 39, 40, and 42 dB, with façade-zoned specifications developed against BS 8233 and local planning conditions rather than a single specification applied across an entire building.
Material and joinery behind every range
Every window in the range is manufactured from engineered laminated softwood, hardwood or Accoya, sourced from FSC or PEFC-certified sustainable forestry. Hardwood cills give exceptional durability in exposed locations, and frames are built using mortise and tenon joints, glued and mechanically fixed, a joinery technique that has stood the test of time for good reason. Wood moisture content is controlled to 12% (plus or minus 2%) on delivery, which limits movement once the window is installed.
Solid glazing bars on the heritage range and applied bars on the traditional range preserve the unique character and original design of the window while the glazing itself is specified to modern thermal and acoustic standards.
Do timber sash windows still perform well in a modern building?
Yes. A properly specified timber sash window, built from hardwood or engineered timber with double, triple or vacuum glazing, meets current thermal and acoustic standards while retaining period proportions. Timber is a natural insulator, giving it a genuine performance advantage over aluminium and uPVC.
Key takeaways
- TRC Contracts manufactures seven distinct sash window products, from heritage solid-bar sash windows through to acoustic and vacuum glazed options
- All ranges use FSC or PEFC-certified timber, mortise and tenon joinery and a controlled moisture content
- Glazing options span double, triple and vacuum glazing, with U-values as low as 1.1 W/m²K
- Acoustic sash windows are independently tested to ISO 10140-2:2021, not estimated
Speak to TRC Contracts about your next specification
Whether you need heritage sash windows for a listed building, vacuum glazing for a conservation area with restricted rebate depth or acoustic sash windows for a noise-sensitive London site, TRC Contracts can support your project from specification through to installation.
Contact the TRC Contracts team to discuss your requirements, or browse the full new timber windows range to find the right product.
