Balanced Vertical Sliding

Designed to work seamlessly with traditional sash windows, providing a discreet internal solution

Balanced Vertical Sliding

Vertical sliding secondary glazing is designed to work seamlessly with traditional sash windows, providing a discreet internal solution that preserves the character of the original frame. The slim aluminium unit sits neatly within the window reveal and features self-supporting panes that can be securely held at any chosen position, allowing controlled ventilation.

Smooth spring-balance operation ensures ease of use in both commercial and residential settings. The range also incorporates a unique tilt-in facility, allowing each secondary sash panel to be independently released from the outer frame and pivoted inwards through almost 180°, making cleaning and maintenance simple. A slide-past option is available, allowing both panels to fully slide past one another for unrestricted access to the whole secondary glazing unit.

Get In Touch

Specify with NBS Source

Balanced Vertical Sliding

Tilt In Balanced Vertical Sliding Unit

Technical Performance Data

Full panel sizing, acoustic and thermal performance data for the Balanced Vertical Sliding range. All figures are for specifier guidance - contact our technical team to discuss project-specific requirements.

Up to 50 dB Noise Reduction (Rw)
1.49 W/m²K Best U-value (BVS)
1,500mm Max Panel Width
6 Glass Types Available

Values are Rw (dB) measured to BS EN ISO 717-1. All tests performed with a 200mm air gap (glass-to-glass) and a 6mm single-glazed toughened primary window in a hardwood frame. Deduct 1 dB for a 150mm air gap; deduct 1–4 dB for a 100mm air gap.

BVS - Balanced Vertical Slider

Secondary GlassRw (dB)
Weighted		Rw+C (dB)
Traffic weighted		Rw+Ctr (dB)
Low-freq weighted
4mm Toughened484642
6mm Toughened504843
6.4mm Laminate504944
6.8mm Laminate504944
8mm Toughened504944
8.8mm Laminate505044
10.8mm Laminate505045

TBVS - Tilt-In Balanced Vertical Slider

Secondary GlassRw (dB)
Weighted		Rw+C (dB)
Traffic weighted		Rw+Ctr (dB)
Low-freq weighted
4mm Toughened474543
6mm Toughened494744
6.4mm Laminate494845
6.8mm Laminate494845
8mm Toughened494945
8.8mm Laminate494945
10.8mm Laminate494946

Rw data extrapolated from physical tests at Element High Wycombe (23/06/22 & 12/07/22). Test configuration: 1,200 × 1,200mm unit, 200mm air gap, 6.87mm standard laminate secondary glass, 6mm single-glazed toughened primary in a hardwood frame.

Data extrapolated from physical testing at Element High Wycombe (23/06/22 and 12/07/22).

Download Performance Data Sheet: GSG-DS002 Rev A — Acoustic

U-values shown are combined whole-window system Uw values (primary window + air gap + secondary glazing), calculated to BS EN ISO 10077-1:2017 and BS EN ISO 10077-2:2017 with a 50mm air gap. These are not the centre-of-glass Ug values of the secondary unit alone. Values marked * are indicative figures calculated internally by Granada Glazing Ltd. and have not been externally verified — all other values are from calculations by Windata Ltd.

Hardwood primary - 4mm float glass, 60mm hardwood frame, Uw = 4.7 W/m²K | Steel primary - 3mm float, steel Crittall frame, Uw = 6.0 W/m²K

BVS - Balanced Vertical Slider

Secondary GlassHardwood Primary
U W/(m²K)		Steel Primary
U W/(m²K)
4mm K Glass1.49*1.6*
6mm Toughened1.64*1.77*
4mm Toughened1.64*1.78*
6.4mm Laminate1.64*1.78*
6.8mm Laminate1.64*1.77*
6mm K Glass1.51.59*

TBVS - Tilt-In Balanced Vertical Slider

Secondary GlassHardwood Primary
U W/(m²K)		Steel Primary
U W/(m²K)
4mm K Glass1.5*1.61*
6mm Toughened1.64*1.77*
4mm Toughened1.64*1.78*
6.4mm Laminate1.64*1.78*
6.8mm Laminate1.64*1.77*
6mm K Glass1.51.6*

* Indicative values calculated internally by Granada Glazing Ltd. - not externally verified. All other values from Windata Ltd. calculations per BS EN ISO 10077-1:2017 & BS EN ISO 10077-2:2017.

Download Performance Data Sheet: GSG-DS003 Rev B — Thermal

All dimensions in mm. Sizes are for guidance only and depend on glass type, subframe, and installation method. Contact us to discuss units outside the listed parameters.

For the Balanced Vertical Sliding range, Max Height shows the overall frame height. Each individual sash panel is a maximum of 1,800mm tall — the full unit comprises two sashes within the frame.

BVS - Balanced Vertical Slider

Glass TypeMin WidthMin HeightMax WidthMax HeightAspect Ratio
(W:H)		Max Panel
Weight
4mm Toughened175mm175mm (lower) / 240mm (upper)1,500mm3,325mm1.5 : 145 kg
6mm Toughened175mm175mm (lower) / 240mm (upper)1,500mm3,325mm1.5 : 145 kg
6.4mm Laminate175mm175mm (lower) / 240mm (upper)1,500mm3,325mm1.5 : 145 kg
6.8mm Laminate175mm175mm (lower) / 240mm (upper)1,500mm3,325mm1.5 : 145 kg
8.8mm Laminate175mm175mm (lower) / 240mm (upper)1,500mm3,325mm1.5 : 145 kg
10.8mm Laminate175mm175mm (lower) / 240mm (upper)1,500mm3,325mm1.5 : 145 kg

TBVS - Tilt-In Balanced Vertical Slider

Glass TypeMin WidthMin HeightMax WidthMax HeightAspect Ratio
(W:H)		Max Panel
Weight
4mm Toughened175mm175mm (lower) / 275mm (upper)1,500mm3,325mm1.5 : 145 kg
6mm Toughened175mm175mm (lower) / 275mm (upper)1,500mm3,325mm1.5 : 145 kg
6.4mm Laminate175mm175mm (lower) / 275mm (upper)1,500mm3,325mm1.5 : 145 kg
6.8mm Laminate175mm175mm (lower) / 275mm (upper)1,500mm3,325mm1.5 : 145 kg
8.8mm Laminate175mm175mm (lower) / 275mm (upper)1,500mm3,325mm1.5 : 145 kg
10.8mm Laminate175mm175mm (lower) / 275mm (upper)1,500mm3,325mm1.5 : 145 kg

BVS:

Product RangeGlass OptionsMax. Window Size
(Including 16mm Timber)		Installation Options
Width (mm)Height (mm)Area (m²)Face Fix
Through Timber		Reveal
Fix Through Frame		Reveal
Fix Through Timber		Optional Deep
Reveal Fix Through Timber		BevelsSpecials
Classic4.0mm tough157530253.0TIM-43x16TIM-43x16TIM-62x16TIM-70x16TIM-62x50TIM-90x90
Enhanced6.0mm tough157533256.0TIM-43x16TIM-43x16TIM-62x16TIM-70x16TIM-62x50TIM-90x90
Enhanced6.4mm Laminate157533255.6TIM-43x16TIM-43x16TIM-62x16TIM-70x16TIM-62x50TIM-90x90
Enhanced6.8mm Laminate157533255.3TIM-43x16TIM-43x16TIM-62x16TIM-70x16TIM-62x50TIM-90x90
Enhanced8.8mm Laminate157533254.1TIM-43x16TIM-43x16TIM-62x16TIM-70x16TIM-62x50TIM-90x90
Enhanced10.8mm Laminate157533253.3TIM-43x16TIM-43x16TIM-62x16TIM-70x16TIM-62x50TIM-90x90

TBVS:

Product RangeGlass OptionsMax. Window Size
(Including 16mm Timber)		Installation Options
Width (mm)Height (mm)Area (m²)Face Fix
Through Timber		Reveal
Fix Through Frame		Reveal
Fix Through Timber		Optional Deep
Reveal Fix Through Timber		BevelsSpecials
Classic4.0mm tough158330253.0TIM-50x16TIM-50x16TIM-62x16TIM-70x16TIM-62x50TIM-90x90
Enhanced6.0mm tough158330256.0TIM-50x16TIM-50x16TIM-62x16TIM-70x16TIM-62x50TIM-90x90
Enhanced6.4mm Laminate158330255.6TIM-50x16TIM-50x16TIM-62x16TIM-70x16TIM-62x50TIM-90x90
Enhanced6.8mm Laminate158330255.3TIM-50x16TIM-50x16TIM-62x16TIM-70x16TIM-62x50TIM-90x90
Enhanced8.8mm Laminate158330254.1TIM-50x16TIM-50x16TIM-62x16TIM-70x16TIM-62x50TIM-90x90
Enhanced10.8mm Laminate158330253.3TIM-50x16TIM-50x16TIM-62x16TIM-70x16TIM-62x50TIM-90x90

Our Sheffield-based manufacturing base is home to our very own painting plant, allowing you to choose from a comprehensive palette of more than 200 powder-coated RAL colours to achieve a precise match with your Granada secondary glazing system. Suitable for new developments, heritage buildings, and complex commercial environments, our finishes are specified to meet the requirements of each project.

Stocked colours available from short lead times

White
RAL 9003
Cream
RAL 9001
Van Dyke Brown
BS 08 B29
Anthracite Grey
RAL 7016
Black
RAL 9005
+200 RAL
custom colours

Dimensions

All sizes given in mm.

Frame and panel tolerances: ±1.5mm

Maximum delivery sizes: 2,100 × 4,400mm

Glass Thickness Tolerances

  • Toughened: ±0.2mm
  • Laminated: ±0.4mm
  • Laminate interlayer: ±0.1mm

Acoustic Test Conditions

All windows tested at 1,200 × 1,200mm with a 200mm air gap and 6.87mm standard laminate, against a wood-framed primary with 6mm single-glazed toughened glass.

Notes on Sizing

Sizes are for guidance only and depend on glass type and subframe. Units outside the listed parameters are sometimes possible - please contact us for advice.

Technical Specification Documents

Know everything you need to confidently specify our secondary glazing systems. Our downloadable documents include detailed performance data, drawings, U-value and acoustic figures, installation guidance, and product compliance certificates to support building regulations requirements.

Filter Downloads

File NameDocument TypeFile TypeAction
Certificates
Social Value CertificateCertificatePDF
Once For All Health & Safety CertificateCertificatePDF
SafeContractor Sustainability CertificateCertificatePDF
ISO 9001:2015 Quality Management SystemCertificatePDF
FORS Bronze CertificateCertificatePDF
Constructionline Gold CertificateCertificatePDF
CHAS SSIP CertificateCertificatePDF
Builders Profile CertificateCertificatePDF
View All Downloads →

Looking For More?

To view the coupling guide and other documents available, please use the technical downloads.

Go To Technical Downloads

Product Case Studies

Reuben College, Oxford

Reuben College, Oxford

Secondary glazing was specified as part of a complex refurbishment of multiple historic buildings at Reuben College, including the Grade II listed Radcliffe Science Library. The system was designed to improve thermal and acoustic performance across teaching, study, and office spaces while retaining the original windows, their detailing, and means of operation. The solution improved energy efficiency, reduced noise intrusion, and supported the University of Oxford's broader decarbonisation strategy.

Read full case study
Premier Inn, Llandudno

Premier Inn, Llandudno

Granada Glazing's secondary glazing enhanced comfort at the Premier Inn in Llandudno, built on the Grade II listed Tudno Castle Hotel site. 46 units of Balanced Vertical Sliders and Hinged Units with Low-E glass reduced heat loss by up to 65% and cut external noise by up to 80%, creating warmer, quieter guest rooms while preserving the historic timber windows and façade.

View case study

Our Other Secondary Glazing Options

I have windows in varying sizes and shapes, is secondary glazing appropriate?
Granada secondary glazing units are made to order, allowing bespoke sizes and colours to suit any window. Frames can be bent or arched in-house to match any shape, style, or opening. Custom manufacturing also allows units to align precisely with transoms and mullions, minimising sightlines for a discreet appearance. For larger windows, single units can be stacked or coupled to achieve full coverage without compromising performance or aesthetics.
Which glass type should I choose?
Secondary glazing is typically specified to address two main challenges: acoustic or thermal performance. Alongside the air cavity, the type of glass chosen plays a crucial role in resolving these issues. All Granada units are manufactured as standard with 4mm toughened glass, offering enhanced security and safety. Unlike some providers who use float glass, which can shatter dangerously, toughened glass minimises risk and meets high safety standards.

We offer a range of glass types, carefully selected for optimal performance, including variations in thickness and coatings.

Acoustic performance: When installed with an air cavity of 150–200mm, the correct glass can reduce noise by up to 80% (54 dB). Typical traffic noise can often be managed with 6.4mm or 6.8mm clear acoustic glass, while louder environments may require 8.8mm acoustic glass for maximum sound reduction.

Thermal performance: Draughts through primary windows can make spaces uncomfortable and increase energy costs. For improved thermal efficiency, we recommend 4mm, 6mm, 6.4mm, or 8.8mm toughened Low-E glass, which reflects heat back into the room, keeping interiors warmer in winter and cooler in summer.

The choice of glass can affect the overall cost. We advise speaking directly with our team to ensure the specification is tailored to your requirements, delivering both practical performance and cost efficiency without unnecessary over-specification.
What depth of air gap is best for my windows?
Secondary glazing offers a range of benefits, including up to 80% reduction in noise (54 dB) and a 65% decrease in heat loss. A small air cavity between the primary window and the secondary glazing plays a vital role in both acoustic and thermal performance. The recommended cavity varies depending on the issue you are addressing.

Acoustic performance: For optimal noise reduction, we advise an air cavity of 150–200mm. This reveal-fix installation positions the secondary glazing within the window reveal and, when combined with clear acoustic glass in 6.4mm, 6.8mm, or 8.8mm thicknesses, can reduce sound by up to 80% (54 dB).

Thermal performance: For improved energy efficiency, we recommend a face-fixed installation with an air cavity of up to 80mm. When combined with Low E glass, this can reduce heat loss by up to 65%, keeping interiors warmer in winter and cooler in summer.

Granada's team can advise on the most suitable glass, cavity, and installation method, providing a tailored solution to meet your specific acoustic or thermal requirements.