Double Glazing

Double Glazed Wooden Sash Windows in Brighton & Sussex.


The double glazing of traditional sash windows is now very common. There are a few things to consider before deciding on what is the best option for you.

Victorian Sash Windows Brighton

Double Glazed Victorian Sash Windows

There is more to double glazing than just two panes of glass, intricate details need to be copied to make sure your new sash or even casement windows look original and authentic.

Another point to consider is planning requirements. Your property may be in a conservation area, article 4 direction will usually mean a planning application is required just to upgrade to double glazing.

Sash Windows in Listed buildings are abundant and many of our clients live in a listed property. Double glazing in listed buildings is becoming more common, but this will defiantly require some kind of planning application listed building consent.

Timber types need to be considered, although we are now predominantly using Accoya. Hardwoods and redwoods are available also and can make the joinery more affordable.

  1. Contact us to speak to surveyor about your best options.
  2. Upgrade your sashes whilst retaining your existing box frames can save thousands on multiple windows.
  3. Glass and glazing options for double glazing 
  4. Listed buildings Slimlite glazing will be your only option for double glazing.

Fensa Approved Window Installer FAQ’s


Traditional timber sliding box sash windows and doors have always been glazed with crown and later float glass, this was set in with linseed oil putty. This method of glazing dates back hundreds of years. Since the late 1970s double glazing has been at the fore front of the window industry. However the traditional joiner was slow to pick up on this, mainly due to the lack of an effective glazing method that did not allow the double glazed unit mist up.

In April 2002 (Updated 2016) the government made it law that all new windows and doors had to be double glazed (Document L of the building regulation). Listed buildings are exempt from this law. This is when the modern age of timber windows really started.

The main issue with timber windows and doors is how bulky they are. Authentic sleek and narrow profiles are what make traditional windows look traditional. To achieve this look, new high performance double glazed units have been developed. We are at the fore front of this technology with our double glazed sash windows using low emissive glass (Low e) with an inert gas such as Argon, Krypton or Xenon. Dependent on the thickness of the double glazed unit, the addition of gas can double the heat retention. Planitherm low e glass is the market leader. To compliment the double glazed units, all parts of our sash windows come with draught proofing fitted as standard.

For a free quotation for new double glazed sash windows – Click Here or call our office 01273 855 546 9am – 5pm.


Traditionally  windows and doors were made from seasoned softwoods. The timber was originally sourced (mainly) from the Baltics. Today all of our timber comes from FSC approved sources.

FSC – Forestry Stewardship Council works to improve the management of forests worldwide, certification creates an incentive for the owners of these forests to adopt the best social and environmental practices. So basically timber is now imported from all over the world.

Traditional double glazed sash upgrades are made from treated softwood. The original boxes are softwood so the additional expense of hardwood or Accoya is not necessary.
Completely new traditional windows and doors can be made from either treated softwood with hardwood sills, hardwood throughout or Accoya with Hardwood sills.

All of our new double glazes sash windows and doors come with a 10 year insurance backed warranty, so piece of mind is not an issue.

Double Glazed Wooden Sash Windows

Benefits of treated soft wood: Soft wood has a reputation for rotting; this should not be the case. If joinery grade timber is used to manufacturer you’re your windows, which is far superior to the wood you would find in your local DIY stores skirting board, rotting should not be an issue. Obviously the wood needs to be looked after and a high quality preserver topped off with a microporus water based primer will enhance the life of that piece of wood by many years. The downside is that the joinery will need decorating every few years, but so long as this is done, many soft wood windows are over 150 years old. We recently worked on some soft wood windows that were 250 years old in Fulham, West London.

Benefits of Hardwood windows: Hardwood is the preferred choice of windows and doors but the cost has a major factor in this. The labour time to manufacturer hardwood windows is twice that of using soft woods. Plus the material cost is more than double. Also hardwood doors and windows are heavy, heavy to open and heavy to close and this can be noticeable if you are older. However hardwood does not need to be decorated, it is very durable, it does not have the same movement as soft wood as does not swell as much which can cause sticking. Hardwood windows are quite common on the large Victorian seafront Mansions in Brighton Sussex.

Benefits of Accoya sash windows: Accoya is now becoming the preferred choice by architects and clients alike. The main benefits of this timber is the fact that it does not absorb moisture, thus it does not swell or warp. Secondly no known parasites or fungi will attack this timber. It is highly durable lighter than traditional hardwoods and machines well. This timber is quite brittle so care needs to be taken when it is being installed but generally this timber is rated second to none. This timber comes with a 50 year supplier’s guarantee from Accoya (Subject to their terms and conditions). We have recently fitted Accoya windows in Properties in Chelsea, Shepherds Bush, Guilford and Brighton. Double Glazed Sash windows in accoya are the ultimate option.

Accoya wood

Accoya wood(Sourced form Accoya website). Accoya is a high technology wood. Created via acetylated wood modification process, using sustainably grown timber, the Accoya process is non-toxic. It is a wood that matches or exceeds the durability, stability and beauty of tropical hardwoods. The Accoya wood production process takes fast growing softwood and creates a new product. Accoya wood gives environmental advantages over slow-growing hardwoods (which might be unsustainably sourced), woods treated with toxic chemicals, and non-renewable carbon-intensive materials such as plastics, metals and concrete. Accoya wood is FSC and PEFC certified.

Glass type for double glazed sash windows

PLANITHERM is a new generation of energy saving window glass that uses advanced coatings to retain more internal warmth whilst capturing free energy from natural daylight. That means you home will be warmer and your energy bills lower compared to standard windows. By specifying PLANITHERM as your energy efficient window glass you can cut your energy bills by up to 28{081cee51a18d029ade5a6055a6465995b508a6f285db27102d119684b054bff9}. Please see Glass Options for further information. Other glass manufacturers products such as Pilkington energikare are also available for double glazed sash windows.

Draught proofing & window furniture are fitted with new double glazed sash windows as standard.

Noise reduction in double glazed sash windows

Noise pollution can be our client’s biggest issue when looking at replacing their windows especially if noise is stopping you from sleeping. The best way to reduce noise is to disrupt the vibration, if the double glazed sealed unit is constructed using two different depths of glass i.e. 6.4mm and 4mm this will cut down the audible sound. Also a non-metallic spacer bar will absorb some of the sound vibration thus further reducing noise.

Comfortable sound levels are around 35 decibels in daytime and 30 decibels at night. Our acoustically insulating glass units will cut out excess noise and is particularly effective if your house is near too busy roads, train stations or airports. There are specific double glazed units that are designed to reduce noise. The best way of reducing noise with double glazed units is to use a noise reductive laminate glass in the outer pane such as Pilkington optlilam. Then use a dense gas inside the unit such as Krypton or Xenon. The inner pane needs to be of a different thickness than the outer pane and the unit gap different from them all. A recent job we have just completed in Chelsea has a 6.4mm laminate outer pane an 8mm cavity filled with Xenon gas and a 4mm Planitherm inner pane. These units are very expensive so cost can be an issue. Please see Pilkington’s noise pamphlet for further details. Noise levels are measured in decibels – Read more……….

Security for double glazed sash windows

• Security is an issue that we all need to be aware of whether you live in London or a rural Sussex village. We can make our windows to a Secure by Design standard. This is a standard that new buildings have to comply with if the window is in a basement, reachable form a flat roof or near an accessible balcony.
• Windows are a popular point of entry for burglars through breaking glass or just being left open. Security stop locks can make a the difference between a burglar gaining entry or leaving empty handed.
• Using laminated glass in ground-floor and accessible windows such as those above a flat roof will stop the easy shattering or breaking of glass. However a standard double glazed unit is hard to get through.
• Laminated glass holds together when shattered or when someone attempts to break it, it has the same properties as a car windscreen, it cracks but holds together.
• Security glazing tape is used to hold the double glazed unit in place. Once fixed the double glazed unit is near on impossible to remove. Windows can be made so that they are internally beaded also.

For a free quotation for new double glazed sash windows – Click Here or call 01273 855 546

Covering Brighton & Hove and all of Sussex.

Office Telephone 01273 855546

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