Glazing Upgrades | Timber Sash Windows

Laminated Single Glazing upgrades For Period Windows

Can sash window glass be upgraded?

Yes, energy efficient laminated glass or acoustic glass can be retro fitted into your existing period windows.

Regardless of the temperature outside a window with good insulation properties will help to improve the comfort of your home.

Upgrade Glass in period windows & doors. Laminated

Upgrade glazing with laminated glass

Replace glass and upgrade glazing in heritage windows with laminated glass to make your home warmer, quieter and more secure.

Replace Glass with Standard Laminate

Laminated Glass is manufactured by bonding multiple panes of glass together with a thin, single layer film sandwiched between the glass layers. Laminated glass has many benefits including greatly reduced ultra violet (UV) light ingress. to protect your interior furnishings from fading; Grade A safety rating; Greatly improved security and noise reduction of up to 24% over existing 3mm float glazing .

Glazing upgrade with “Hush” glass

Acoustic Insulating Glass provides all the benefits of standard laminate plus a special 3-layer acoustic PVB laminate interlayer that is specifically designed to reduce sound transmission. Reductions of up to 40% in comparison to similar thickness float glass may be achieved.

Upgrade glazing with “Comfort” glass

A Factory applied  low e coating to one of the glass surfaces improves energy efficiency. This low-e coating reflects heat, helping to keep your home cooler in summer and warmer in winter. Up to 39% better thermal insulation than ordinary window glass.

Upgrade glazing with “Comfort” + “Hush”

Hush glass with a low-e coating results in a quieter more comfortable home with energy savings.

Retrofit double glazing into sash frames?

In some instances it is possible to install double glazed units into existing timber sash frames.  The thickness and condition of your existing sashes are the deciding factors.  As your original window glass is only 2-4 mm thick and a double glazed unit is 14+mm thick obviously some sash frame alterations are required.  Deepening the glass rebate to install double glazing is only possible with sashes 42mm or thicker as otherwise the mortise and tenon joints will be considerably weakened. 

With the advances in single glazing, laminated glass is often the best solution. 

Pilkington Spacia™ is a recent innovation which provides similar energy efficiency performance as a standard unit, but in a much thinner profile. Instead of being gas filled a vacuum separates the panes.  These sealed glazing units are only 6.5 mm thick, but currently they remain an expensive option. 

Glazing upgrades in a double hung sash window | sash Window Specialist Midlands UK

Upgraded glazing benefits include:

  • An energy efficient home is a comfortable home
  • Low E glazing reduces your homes carbon footprint.
  • Reduced UV prevents furnishings from fading
  • Reduced condensation on glass
  • Low friction draught proofing strips aid smooth window operation and stop annoying rattles.
  • Air borne noise, dust and other pollutants that are suspended within draughts are also greatly reduced.

Sash Weather & Draft Seals.

Our Glazing Upgrades Include:

  • Draughtseal & Overhaul Service
  • Removal of existing glazing
  • Cleaning and preparing rebates
  • Installation of new glass
  • Traditional putty pointing
  • Balancing the weight system with lead.

Counterbalancing Heavier Glazing

Lead Sash Window Weights For Double Glazing Sash Windows.

Additional weight is required to counterbalance the heavier replacement glass.  The original cast iron weights must be supplemented or replaced with lead weights.  The additional weight requirement makes up a considerable part of the total service cost.

An important consideration is that the additional weight will be carried by the pulley.  Whilst the majority of pulleys in British sash windows are sturdy axle pulleys, occasionally some may require replacing.  Many Australian sash windows have cheaper pulleys that frequently need to be replaced, at additional cost.  Our standard replacement sash cords are more than sufficient to carry the additional weight.

Can you fit a pet door into a heritage window?

Yes, we can fit cat flaps into sash window glass.  Dog doors can be fitted into period doors and french windows.

Low Emissivity glazing should reduce heating bills by around 14%.

Traditional double-hung sash windows are not regarded as being very energy efficient.  The thin single glazing and draughty gaps, that allow the sashes to slide, can both be significantly improved.

Draught-stripping your existing period sash windows can reduce the draughts by almost 90%, and is always the first step to improving energy efficiency in period windows.

Heat loss through standard single glazed windows is in excess of 25%.​

Single glazed monolithic glass contributes to energy loss conducted directly through the glass.  Low E glass has a special insulating surface that reduces the amount of radiant heat transfer. 

How Does low-emissivity glass work?

low e glass for period casement and sash windows

Low-e glass has a special coating which is a poor radiator of heat and does not allow heat to be transferred through the glass. In winter, heating is reflected back indoors; in summer heat from the
sun is reflected away, keeping the room cooler. 

Inefficient windows make air cooling and heating systems work harder and make occupants feel uncomfortable, often adjusting room thermostats to compensate.  


At Sash Window Specialist we understand the charm of traditional wooden windows which is why all of our work is designed to be as sympathetic as possible.

Laminated glass upgrade with Comfort Hush in a sash window
Comfort Hush Laminated Glass

Historic Glass

Before choosing this service some consideration should be given to the benefits of your existing glazing.  Heritage window glass was hand made resulting in an uneven surface with flaws and distortions.  Historic glass adds to the windows character in a way that modern float glass can not match.  If your property has unique historic value then first consider if our Draught Seal & Overhaul Service might be sufficient . 

We have been using the same top quality British made draught seals for over 20 years.  Brush draught seals are the best option for long life in a sliding sash window.

Obscured / patterned sash glass

Float Glass – the standard glass that has been fitted for many years is often only 2 or 3mm thick. Simply increasing the thickness will reduce the amount of noise & improve energy efficiency slightly. 

When a wide range of decorative glass is required, such as bathrooms, this is the best solution. Patterned and etched glass is available in a range of thicknesses, dependent on the design.

Laminated window Glass.Standard Laminated Glass - manufactured by bonding multiple panes of glass together with a thin inter-lay film sandwiched between the glass layers. Laminated glass has many benefits including greatly reduced ultra violet (UV) light ingress, Grade A safety glass, improved security as well as improved noise reduction. Improvements of up to 24% can be achieved over existing 3mm float glazing.  In our experience standard laminated glass often offers a cost effective solution. A limited range of patterns are available.

Accoustic Laminate Window Glass.‘Hush’ and 'Comfort' – laminated glass that incorporates a ‘hush' interlayer or 'çomfort' low-e coating'; or both. The interlayer is designed to dampen noise and may reduce noise by up to 40% in comparison to similar thickness float glass. Comfort is an advanced low e coating that reflects heat.  Hush and Comfort glass are more expensive than standard laminated glass.

double glazed unit for sash window.

Double Glazing –  the thermal improvements are a welcome benefit to every home.

  • Argon filled for better energy efficiency
  • Acoustic DGU configuration.
  • ‘Low E’ energy efficient glass.
  • Etched or patterned glass.
  • Safety Glass.
  • Slimlite units or duplex bars.
  • 5 – 16 mm spacer bars depending on the sash thickness.

  logo. logo.

Window Security & Hardware

Sash Window Renovation. | Double Glazed Timber SashDouble Glazed Wooden Sash Window. Double Glazed Sash Window.


Various catches effectively bring the sashes into a locked position, however the screws holding these in place are small and these catches should not be considered an effective security measure. We have a range of sash window security options available.  We also supply a wide range of sash window furniture, available in variety of finishes.