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Secondary Glazing FAQ's

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As industry leaders we have put together this FAQ section to share our knowledge of secondary glazing and answer any questions you may have.

General Information about Granada Glazing

Tell me more about Granada Glazing

Granada Glazing is a designer, manufacturer and installer of aluminium secondary glazing products. We have manufactured high quality, bespoke glazing products since 1984. Our 40,000 square feet manufacturing facility houses CNC and metal forming machinery, supported by a state of the art powder coating line.

As industry leaders, we specialise in manufacturing glazing products that boast exceptional acoustic and thermal properties. Working with over 500 trade partners across the UK, we can install secondary glazed units for both residential and commercial markets. Granada supports both supply only and supply and install.

Our in house capabilities have allowed us to manufacture products that are of the highest quality and best performing. With internal designers, we can provide a solution which will overcome any problem whilst playing close attention to the aesthetics and functionality.

As we manufacture arched frames and powder coat in house, we can ensure a high level of quality and a product suitable to stand the test of time.

Does Granada install secondary glazing?

Granada Glazing designs and manufactures bespoke aluminium secondary glazing. Our products are widely used within both homeowner and commercial markets.

We have partnered with over 500 industry leading tradesmen who install our products for homeowners. Our elite trade network installs secondary glazing products throughout the whole of the UK. We often receive homeowner/residential orders where these are passed to a local tradesman who will survey and install our products. Our approved trade network is trained to the highest standards and adhere to Granada’s customer care guidelines.

At Granada, we pride ourselves on the quality of our product, which is matched by high levels of service given by both our approved tradesman and our internal sales team.

Since 1984 Granada Glazing has been the industry leader. We offer technical support and can recommend a product that is suitable for most budget requirements, performance and functionality. For technical support, or help with selecting the right product to cure your noise or thermal issue, please speak with us directly by telephoning 01909 499 899 or click here to email our internal technical support team.

For commercial installations, Granada has an in house surveying and installation team. We have designed, manufactured and installed secondary glazing within some of the most iconic buildings situated in England, Scotland, Wales and Ireland. Notable projects include:

• Bush House – London
• Edinburgh Castle – Scotland
• Stirling Castle – Scotland
• Parkinson Building – Leeds
• Gradbach Mill – Derbyshire
• Great Northern Hotel – London

About Secondary Glazing

What is Secondary Glazing?

Secondary glazing is a discreet window that is installed to the interior side of the room. Available in different styles to suit all window types, secondary glazing will decrease noise levels breaching your primary windows and increase thermal efficiency.

As it doesn’t change the fabric of the building secondary glazing can be installed within Conservation areas and Grade I and Grade II Listed Buildings. All of Granada’s products are manufactured from durable aluminium and can be powder coated in over 200 RAL colours.

Secondary glazing is often installed to combat 2 main issues; Acoustic and Thermal performance. No other form of glazing can reduce noise levels by up to 80% (which is the equivalent of 54 dB). Another benefit of secondary glazing is that it offers an increased level of security. If your primary windows are forced open, secondary glazing acts as a second barrier as it can’t be opened from the outside.

All of Granada’s products are manufactured in durable aluminium and are powder coated in house which allows them to stand the test of time. Often used in conjunction with single, double, and triple glazed uPVC or timber windows, secondary glazing boasts unique performance that is unmatched by any other window system.

I have windows in varying sizes and shapes, is secondary appropriate?

Granada’s secondary glazed units are manufactured to order in bespoke sizes and colours. We can bend/arch frames in house to suit any window size, shape or style.

As our products are made to order, we can manufacture units that match both transoms and mullions to reduce sightlines and make the secondary glazing even more discreet. For larger windows, typically commercial applications, we can stack or couple single units to achieve the required coverage.

What colours are the frames available in?

Our products are manufactured from durable aluminium and powder coated in house. Our standard, and most popular colour, is Standard White with a high gloss finish. In addition to standard white, we hold stock colours which include:

Van Dyke Brown (BS08B29, Gloss)
Cream (RAL9001, Satin)
Grey (RAL7016, Satin)
Ivory (RAL1015, Satin)
Black (RAL9005, Satin)
Traffic White (RAL9016, Matt)
Pure White (RAL9010, Satin)

To offer our customers short lead times Granada purchased a powder coating line allowing us to finish all products in house. This investment has given our customers a level of customisation as we can powder coat frames in over 200 RAL Colours to suit all taste and preferences.

Are there any guarantees or warranties?

In the unlikely event of a malfunction, our secondary glazing is backed up with a five year warranty on frames and glazing; and a two year warranty no moving parts.

The majority of our elite trade network are members of FENSA. FENSA is a governing body where tradesmen and installers can self certify that their installations comply with current building regulations.

In the unfortunate event of malfunction, please speak with our customer care team by telephoning 01909 499 899.

Which Glass type should I choose?

Secondary glazing is normally specified to combat 2 main issues; acoustic or thermal performance. In conjunction with the air cavity, the type of glass specified plays a vital role in rectifying your issue. As standard, all of our products are manufactured with 4mm toughened glass for enhanced security and safety. (Please be aware that other secondary glazing providers may supply float glass which is brittle and can be easily broken. If broken, it can leave large dangerous shards, often resulting in injury).

Here at Granada, we provide several types of glass ranging from different thicknesses to different coatings. Each type of glass has specifically been designed and selected for optimum performance.

Sound – Selecting the correct glass and installing the secondary glazed unit with an air cavity of 150mm to 200mm, can drastically reduce noise issues by up to 80% (54 dB). Most traffic noise problems can be rectified with the installation of either 6.4mm or 6.8mm clear acoustic glass. Where noise is a real nuisance, and loud in nature, we suggest the specification of 8.8mm clear acoustic glass.

Thermal – Cold draughts breaching your primary windows can make a room feel uncomfortable and makes it uneconomical as the loss of heat will result in higher energy costs. Where thermal performance is required, we advise the installation of either 4mm, 6mm or 8.8mm clear laminate low E glass. Low E glass has a specifically designed coating that reflects heat waves back into the room thus keeping your it warm in the winter, and cool in the summer.

The type of glass specified can increase or decrease your quoted price. It is best practice to speak with us directly as you may over specify the glass type. Some of our customers, and commercial clients, specify the highest performing glass which in turn adds cost. Often we can provide a tailored solution to rectify your issue which is both cost efficient and practical for your specific requirements.

Will secondary glazing work with double and triple glazing?

Secondary glazing can be used in conjunction with all types of windows. Traditionally, secondary glazing was utilised to increase the thermal properties of single glazed timber windows. Modern advancements in specific glass types and frame material have given secondary glazing a new lease of life.

Its acoustic performance is unmatched by any other glazing product and can drastically reduce noise breaching single, double and even triple glazing. If you live in an area with high noise pollution, only secondary glazing will reduce noise levels by up to 54 dB, turning the sound of a diesel bus into a whisper.

Manufactured from durable aluminium, Granada’s secondary glazing is slimline and can be powder coated in over 200 RAL colours to suit all tastes and preferences.

Slimline by nature and durable by design, Granada’s secondary glazing will enhance the thermal and acoustic performance of your windows, whilst standing the test of time.

What materials are used for the frames?

As market leaders within the glazing industry, it is important that our secondary glazing is high performing and aesthetically pleasing. The key to our approach is to use the best raw materials available and manufacture to the highest standard possible.

All of our frames are manufactured in house from slimline, durable aluminium. We cut, powder coat, arch and fabricate our aluminium frames in house under one roof. Utilising high tech machinery such as CNC machines, we can ensure all frames are built to size as sealed units.

Our knowledge, expertise and skills in manufacturing ensure a high quality and the best performing product. Our competitors have tried to reduce the amount of aluminium within the frames to reduce the cost of raw materials but we found this has a negative effect on the product quality. Reducing the amount of aluminium does decrease the cost. The implications of this make frames and sashes unstable and unable to take the weight of the glass, creating health and safety issues. This also decreases the acoustic and thermal performance of the product.

Granada’s head office holds a team of product developers where they can often be found designing and manufacturing glazing products using new materials and manufacturing techniques. All of our products are quality tested before they leave our facility ensuring a high level of quality and function.

Will I lose the functionality of my windows?

Granada’s secondary glazing is available in many styles, complimenting all window types. We have a range of windows that slide horizontally and vertically for easy access and cleaning.

Our hinged unit operates on a hinged mechanism that can be placed on the side of the window for conventional opening, or on the top or bottom dependent upon your requirements. Other window styles include fixed windows or lift outs which can easily be lifted out of the frame.

Our in house design team have designed a range of products that are discreet, functional and high performing. Our product range is suitable for all types of windows and can be tailored to meet most budgets.

The Benefits Of Installing Secondary Glazing

What are the main benefits of secondary glazing?

Secondary glazing is unique due to the fact it can be customised to meet your functional requirements and dramatically improve upon acoustic, thermal and security issues. Available with a range of glass types, secondary glazing can; decrease noise levels by up to 80% (54 dB), increase thermal efficiency by up to 65% and make your home more secure.

Secondary glazing is often used in conjunction with single glazed timber windows however, due to its unique capabilities at blocking sound, we have seen a substantial increase in secondary glazing been used with double and triple glazed uPVC windows.

Sound – If you live on a noisy street where noise from passing traffic and trains is causing a nuisance secondary glazing will help. Granada advises the installation of 6.8mm acoustic glass with the secondary glazed units installed with an air cavity of 150mm to 200mm glass to glass. This installation type is referred to as reveal fix. The slimline and discreet secondary glazing is simply installed within the window cavity enhancing the acoustic performance.

Thermal – Old, single glazed timber windows can leak vital warm air causing draughts leading to an increased energy consumption. If your windows are currently underperforming, secondary glazing can decrease heat loss through your primary windows by 65%. To achieve a 65% reduction in heat loss, we advise the installation of 6.4mm Low E glass. Low E glass has a specifically designed coating that reflects heat back into your room. When installing secondary glazing to enhance thermal performance, the best installation type is face fix. Face fixing is where you install the secondary glazed unit to the inside face of the primary unit. To gain the best performance results we advise an air cavity of 80mm glass to glass.

Security – As secondary glazing can’t be opened from the outside, it adds an extra barrier to forced entry. If an intruder forces or breaks the glass of your primary windows, they will have to try and force the secondary glazing to gain access to your property.

Secondary glazing is a popular choice for homeowners who live in a conservation area or Grade I and Grade II listed buildings. Secondary glazing can be installed without planning permission and prevent the issues old windows have which can’t be changed. Historic England recommends the installation of secondary glazing as it does not change the original fabric of the building.

For homeowners that can change their original timber windows but don’t want to lose the character of their property, secondary glazing which is discreet in style and design is an option which is often specified.

How to achieve the best thermal performance?

Draughty windows can make a room feel uncomfortable and will result in higher energy costs as heat is escaping. Secondary glazing, with either 4mm, 6mm or 8.8mm Low E glass, can reduce heat loss by up to 65% and instantly prevent draughts. We often recommend the installation of Low E glass as it has a specifically designed coating that reflects heat back in to the room.

For optimum performance, we recommend that the secondary glazed unit is face fixed to the interior side of your primary window. With an air cavity of no more than 80mm. Secondary glazing will decrease the amount of heat loss when installed with single, double or triple glazed timber or uPVC windows.

Here at Granada, we can manufacture our secondary glazed units with or without a hardwood subframe. We advise the installation of a hardwood subframe as this acts as a thermal barrier, preventing the aluminium frame and glass cooling due to the temperature of the fabric of the building.

Please speak with us directly where we can advise which type of glass, product and installation type will yield the best results.

What is the benefit of the subframe?

All of Granada glazing’s products are manufactured and supplied with a hardwood subframe (please note: insert panels are not supplied with a subframe). As standard, the wooden subframe and aluminium window frame are pre drilled and countersunk for ease of installation. The hardwood subframe which surrounds the secondary glazing unit increases the rigidity of the whole window, aiding installation.

As aluminium is a great heat conductor, the wooden subframe acts as a thermal barrier which prevents cold bridging from the fabric of the building onto the aluminium. In turn, this can help reduce condensation, as the temperature of the aluminium frame and glass is not cooled by the temperature of the building fabric.

As standard, (on most products) we supply aluminium secondary glazing with a subframe, pre-drilled and countersunk. As we manufacture in house we can supply secondary glazing to your specification, please advise at the point of quotation if you do not require a subframe or pre-drilled units.

How to achieve the best acoustic performance?

Correctly specified and installed, secondary glazing will acoustically outperform all other types of glazing. It is not uncommon to see secondary glazing where double or triple glazing is installed. To achieve up to an 80% acoustic performance, Granada advise the specification of either 6.4mm, 6.8mm or 8.8mm clear acoustic glass and an air cavity, no less than 150mm – 200mm glass to glass.

The key to reducing noise levels is to break up the sound waves that pass through the glazed units. The installation of secondary glazing adds an extra barrier and air insulation prevents noise transference. By selecting the correct glass, and a secondary glazed unit that is expertly manufactured with tight seals and no visible gaps, you will hear a substantial decrease in noise levels.

Acoustic reverberation is when multiple panes of glass vibrate at the same time. This can increase noise levels and is often a result of having the same thickness of glass within your primary and secondary windows. We advise the installation of a different thickness in the glass, which will help block noise of varying frequencies and help prevent acoustic reverberation.

It is important that the secondary glazed units are correctly installed and no gaps are visible between the fabric of the building and the wooden subframe provided. This is why Granada work with the best tradesmen within the UK and often provide detailed training on how to install our products.

Reports indicate that a passing diesel bus often creates 85dB of noise. Correctly installed, Granada’s secondary glazing can reduce noise levels by 54 dB. A reduction of 54 dB will reduce the noise level to 31 dB which is the equivalent of a whisper.

Please speak with us directly where our technical sales team will be able to recommend a product and glass type suitable to rectify your problem. Often customers over specify glass types which increase the cost of the secondary glazing. Our sales team can offer a solution which will suit most budgets whilst curing your issues.

How does secondary glazing increase security?

As secondary glazing can’t be opened from the outside, it adds an extra safety barrier to forced entry. If an intruder forces or breaks the glass of your primary windows, they will have to try and force the secondary glazing to gain access to your property. All of our secondary glazed products are manufactured from durable aluminium where toughened, security glasses are available to offer extra protection.

How to minimise condensation?

Secondary glazing, installed with a trickle vent, can help minimise the level of condensation. The trickle vent aids air circulation within the air cavity which, in turn, can minimise condensation. Granada can install an acoustic trickle vent which has been specifically designed to aid air circulation whilst preventing noise waves passing through it.

A hardwood subframe can act as a thermal barrier, as aluminium is a great heat conductor, the wooden subframe prevents cold bridging from the fabric of the building onto the aluminium. In turn, this can help reduce condensation as the temperature of the aluminium frame and glass is not cooled by the temperature of the building fabric.

Condensation is caused when hot air makes contact with a cold material and where the air is then cooled, where water droplets appear. Minimising the temperature of the glass within your primary units, should help to minimise the level of condensation.

Installation & Aftercare

How is secondary glazing installed?

Secondary glazing is installed to the interior side of the room creating little to no mess and often installations can be completed within 1 hour. Secondary glazing can be installed within the reveal of the window or can be fixed to the face of the primary window, dependent upon the application. To achieve a neat finish, we supply PVC trims as standard, which you can scribe in. To view video tutorials on how to install secondary glazing please click here.

How do I measure my windows?

Before you measure your window for the installation of secondary glazing, normal practice is to select a design that compliments your existing primary window. The key is to select a design that does not add additional site lines and can give you access to your primary window for maintenance, cleaning and ventilation.

We ask that all measurements are given in mm and are formatted width x height. Please click here to view a short video which covers all aspects of measuring your windows.

How to look after secondary glazing?

Granada’s secondary glazing is manufactured from aluminium and is powder coated to give a durable and aesthetically pleasing finish. From time to time, you may need to wipe the aluminium with a damp cloth to de-dust. Cleaning the glass is no different than any other glass product. As our products are manufactured from high quality aluminium they are self sustaining giving many years of trouble free service.

In the unlikely event of a malfunction, please speak with either the tradesman who installed the secondary glazing or speak with our after sales care team who you can contact on 01909 499 899.

What depth of air gap is best for my windows?

The installation of secondary glazing boasts many unique benefits. One of these benefits includes an 80% reduction in sound (54 dB) and a 65% decrease in heat loss. The installation of secondary glazing requires a small air cavity which acts as insulation between your primary windows and the secondary glazing. The air cavity plays a vital role when reducing noise levels or increasing thermal efficiency. (We advise a different air cavity based upon the issue you are trying to cure.)

Sound – We advise an air cavity of between 150mm to 200mm. This type of installation is referred to as reveal fix. The secondary glazing unit is installed within the window reveal and can reduce noise levels by up to 80% (54 dB). For optimum performance, Granada recommends the specification of clear acoustic glass which is available in thicknesses of 6.4mm, 6.8mm and 8.8mm.

Thermal – To achieve optimum thermal efficiency we recommend an air cavity of up to 80mm. This type of installation is commonly known as face fixing as the secondary glazed unit is fixed to the internal face of your primary window. Specified with a Low E glass correctly installed secondary glazing can reduce heat loss by up to 65%.

Please speak with Granada directly, where we will be able to recommend a solution, tailored to your requirements.

Can I install secondary glazing myself?

A skilled tradesman can install secondary glazing within 1 hour. Our products are supplied as standard with a hardwood subframe. The subframe serves 2 purposes; It enhances the rigidity of the aluminium window for ease of installation and acts as a thermal barrier between the fabric of the building and aluminium window frame.

Installation and finishing videos can be viewed by clicking here.

What is the difference between face fix and reveal fix?

Secondary glazing is installed by either reveal fixing or face fixing each installation type will increase either acoustic or thermal performance.

Reveal Fix – To achieve the optimum acoustic performance we recommend acoustic glass where the secondary glazed unit is installed with a 150mm to 200mm air cavity glass to glass. The secondary glazed unit is installed within the window reveal enhancing acoustic performance by up to 80% (54 dB).

Face Fix – Face fixing is recommended to increase thermal performance. The secondary glazed unit should be installed no more than 80mm away from the primary window. It is installed to the internal face of the primary window and when taking advantage of Low E glass, customers often see up to a 65% decrease in heat loss.

Planning Permission & Listed Buildings

Do I need planning consent to have secondary glazing installed?

As secondary glazing does not change the original fabric of the building, it can be installed without planning permission. It is good practice to notify your local conservation officer and make them aware of the modification to the listed building. The installation of aluminium secondary glazing is often advised by the English Heritage as the fabric of the building is not changed.

Can secondary glazing be installed within conservation areas and Grade I & Grade II listed buildings?

Secondary glazing is often installed within conservation areas, Grade I and Grade II listed buildings. Its unique benefits include increasing acoustic and thermal performance, thus making it a popular choice within the heritage market.

English Heritage advises the installation of secondary glazing, as the installation process doesn’t change the original fabric of the building.

Sectors Granada support

Horizontal Sliders

Vertical Slider

Hinged Casement

Lift Out Windows

Fixed Windows

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