Upgrade Your Old Single Glazed Timber Sash Windows to Double Glazing.

It is a misconception that you are going to lose the character or charm of your property by installing double glazed sash windows. Our traditional timber sliding box double glazed sash windows replicate your original windows enhancing the warmth in your property without losing that traditional look. Pembroke & Nash specialise in this area and we are proud to be recommended by professional clients such as architects and local planning officers. We have installations of double glazed sash windows across the south throughout London, Surrey, Sussex & Brighton with hundreds of happy customers.

double glazed sash windows Brighton

Double glazed sash windows Brighton Hove & Sussex

We have 2 options for new double glazed sash windows.

Option 1 – New double glazed sash windows to fit into your existing sash box frames.

The box frame is the part of the window where the weights are kept and all of the mouldings are attached. The sashes are the windows that slide up and down. Replacing ONLY the sashes is a lot more cost effective than replacing the whole box sash window. This saves hugely on materials, labour & mess.

Option 2 – Complete double glazed box sash windows.

New box frames are required when there are no original part of your window left or a new opening has been created.

Styles of sash windows – We can supply & fit new double glazed timber windows of any style bespoke to your requirements

1. Georgian Sash Windows – multiple glazing bars.
2. Victorian Sash windows – with a vertical glazing bar (Or no glazing bars at all).
3. Edwardian Sash Windows – with ornate sashes and glazing bars.

(The double glazed sash windows cost varies on the type of windows required, the more glazing bars, generally means higher cost).

Listed building specifications are different than those in a conservation area. Where applicable all of the windows supplied and fitted by The Pembroke & Nash sash window company will be certified under FENSA (Document L)

Please see our gallery for 100s of examples of Double Glazed Sash Upgrades


For a free quotation for new double glazed sash windows – Click Here or call our Brighton & Sussex office 01273 855 546


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 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.

Sash Window Repair Brighton

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.

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. www.accoya.com

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%. Please see Glass Options for further information. Other glass manufacturers products such as Pilkington energikare are also available for double glazed sash windows.

Gas Chart

Inert gas between glass panes for double glazed sash windows.

Inert gas u value chart Argon, Krypton  & Xenon / Pembroke and Nash double glazed Sash Windows

New double glazed sash windows within your existing box frames / gas options. New box sash windows will have either 24mm argon units (16mm cavity) to achieve an overall U value of 1.6 or less to comply with Document L of building regulations. Narrow units on New box sash windows are available with Krypton gas and thermal spacers. Replacing the sashes only does not come under building regulations.Thermal spacers will reduce the U values further. Please contact us for details on thermal spacers.

The chart  lists the U value of a double glazed unit with Planitherm glass with – No gas (Air), Argon, Krypton & Xenon. For instance a double glazed unit with a 6mm cavity (Space between the two panes of glass) has a U value of 2.5 if you add Argon then this is reduced to 2 and reduced again to 1.5 with Krypton gas. For reference a single glazed traditional sash window has a u value of around 5.5. The lower the U value the higher the thermal rating. Is Krypton gas worth the extra cost over Argon? Krypton adds around 10% to the cost of new sashes, over and above the cost of Argon. If you are upgrading form a single glazed window to a double glazed window with Planitherm glass and Argon gas then the difference from single glazing is immense. Argon is fitted as standard. If Krypton inert gas is within your budget then the answer to the additional cost is yes, but if it is not  then Argon and Planitherm makes a huge difference from single glazing and you probably would not notice the additional 25% in performance that krypton may add. Please see the chart below to give you further information.

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