Secondary glazing is a second custom-made window, attached to the inside of your existing window, creating a double glazed effect, with out damaging or changing your existing windows. Clearview secondary glazing is designed to be discreet and compliment your existing window, décor style and property type. See our Quick Guide


The units are manufactured from a combination of a slim seasoned timber perimeter sub-frame and extruded powder coated aluminium profiles, these contain the glass sections, to which numerous options are available. The standard glass is 4mm toughened other glass options are available on request.. All materials are from managed, sustainable abundant sources. See Our Product Guides


The easiest way to explain the difference between the Forte and Classic product ranges is the Forte range is more of a Heavy Duty system capable of being built to larger sizes and take a thicker glass section see our Min/Max size guides

The Classic range is suitable for most domestic properties, a lighter weight and lower cost profile capable of taking upto 6.8mm thickness of glass.

Please see our Product Guides for specific system information.

Yes, we can provide most glass types, based on the specific needs of your project.

The standard glass is 4mm toughened (we do not offer float/annealed glass) Subject to panel size this may default to 6mm toughened. Laminated, Acoustic, Thermal Low-E, and Obscure glass options can be accommodated.

  • The Classic Range can accommodate up to a 6.8mm glass
  • The Forte range can accommodate up to a 8.8mm glass.
  • The Forte Hinge System can accommodate up to a 28mm Sealed double glazed unit.

See our Full Glass Ranges options 


It is difficult to give exact details, as every property and everybody can be affected differently by noise pollution, however the science confirms, Clearview Secondary Glazing can reduce noise by as much as 80% or by over 50 decibels, (a reduction of 3dB is equivalent to halving the noise energy) this is 5 times greater than either double or triple glazing. This is subject to final specification and installation limitations, these details can be clarified during a consultation with one of our advisors. But the number one target is to try and put as much space between the existing glass and new secondary glass, The bigger the air-gap the better the performance. if the space allows try and get 100mm + to an optimum 150mm to 200mm. where space is limited a thicker glass will help. We always recommend starting with a 6mm glass for soundproofing.

Watch Our Performance Video


Predicting the levels of soundproofing you will achieve is extremely difficult due to the many variables concerning you and your property, however following these basic principles will ensure you maximise the potential for the best results.

In order of importance: –

  1. The Airgap
    • This is the gap glass to glass
    • The wider the gap the better
    • Use whatever space is available to an optimum of 200mm+
  2. The Glass
    • The thicker the glass the better the overall performance
    • The combination of glass and airgap will optimise performance.
  3. Refining your choice
    • With a limited airgap consider an acoustic glass option to optimise performance
    • Where larger airgaps are possible acoustic glass will outperform a lower cost option however increases in performance are incrementally smaller.
  4. Choice of System
    • Choose the system best suited to your primary window design and your needs for access.

More information can be found on our Acoustic Page

We have test certification which confirms that Clearview Secondary Glazing can enhance the thermal insulation of a single glazed window by as much as 65% or a U-Value of 1.868 W/m2K (a U-Value is the formula for measuring heat loss the bigger the number the more inefficient the window is, a standard single glazed window has a recognised U-Value of approx. 5.8 W/m2K. This performance is better than a Class C, with some products  this performance can be as much as A+. English Heritage and Historic Scotland carried out research through Glasgow University which showed secondary glazing out performed  double glazed replacement windows. This is subject to final specification and installation limitations these, details can be clarified during a consultation with one of our advisers. see our Thermal Insulation pages

Clearview Secondary Glazing has a proven track record to eliminate or significantly reduce condensation problems to a point where it is no longer a concern. The naturally occurring problem of condensation varies from window to window and property to property and whilst we can’t guarantee a total cure, the fitting of the Secondary Glazing creates a manageable chamber, reducing most of the problem and, where moisture absorption products can be placed, which are then 10 time more effective. see more details on our Condensation pages

Pictures show it best, please visit the Gallery

Virtually all Clearview Secondary Glazing is easy access, and we always recommend considering how to best mange your windows should you install secondary glazing. The idea of taking units out in the summer and replacing in the winter rarely effective and generally causes frustration. Our systems are designed to be in-situ all year round and can simply hinged or slide open for quick and easy access for ventilation or cleaning at any time. Lift-Out semi fixed systems are available and offer a cost-effective solution for seldom accessed windows.

Horizontal Sliders, panels sliding left and right (all panels will slide), the panels can also be lifted out of the frame. Panels can be equally split across the width of the frame or offset to match the existing glass sections if required. With a 2 pane slider, both panels will slide. LH = Left Hand, RH = Right Hand, i.e. If the side you are likely to open most often (from inside looking out). is the Left side. the LH version should be selected, this means the Left Hand panel will slide in front of the Right Hand Panel, the Right sliding behind the left.

With a 3 panel standard slider (SS3) this enables the left and right sides to individually slide  in front of the centre panel, there will always be a pane of glass covering the centre, panels can be lifted out. If access to the centre panel of the primary window is required, a CO3 unit should be selected (Centre Opener). LH or RH versions an LH version means the panel will slide from the Left over the right.

Vertical Sliders, Panels sliding up and down, both panels slide, the standard configuration is the bottom panel will slide up in front of the top panel, this can be switch on request. Panels can be equally split of offset to match the primary window if required. Panels cannot be removed, but on some systems can be tilted out of the frame for easy cleaning. The panels are supported by hidden springs so will be held at a desired open position. The panels will not fully slide to the centre point.

Operational Video Examples can be viewed in our Video Library

Secondary windows, or glazing, offer all the benefits to double glazing- improved heat retention, lower heating costs, lower greenhouse emissions, improved noise reduction and improved property security, as well as significantly reducing draughts and condensation. It is a lower cost option to full window replacement, and there if no disposal to landfill, it’s quick and easy to install and generally does not require any post-installation decoration. Most importantly, secondary glazing gives an improved living environment. In addition may existing windows have lasted 100 years or more, with little maintenance can last, for many more, protecting the character, charm  and heritage of a property for future generations to appreciate. They will outlast many replacement options without any disposal to landfill and with the enhanced performance they offer a very environmentally responsible solution.

Yes. In most cases, secondary glazing meets the requirements of Buildings and Conservation regulations associated with both Grade II & I listed buildings, as it is a completely reversible installation that does not effect the fabric of the building. However, subject to your property listing status, we recommend liaising with your local conservation officer who will be able to give you further advice.

See examples of our Listed Building project portfolio 


Clearview Supply Only standard systems are normally dispatched within 15 working days from customer approval this would be for rectangular style units but includes splayed reveals and bays if required. More complex requirements, e.g. arched windows. would take a little longer, details would be confirmed at the time of order.

See our Delivery Details

Installation: (if you are using our installation service), This is subject to location, and the specification of your order, but we endeavor to complete within 4-6 weeks from formal survey.

How much does the delivery cost? Delivery is free to most parts of England and is confirmed on submission of the delivery point postcode. However, we need to charge for delivery to the following areas: Check your Postcode here

  • Scotland: Most of Scotland is Price on Application to the following locations postcodes starting:   PA / PH / AB / DD / IV / KW / £P.O.A. A Charge of £75.00 + VAT per drop to KY / FK & parts of East DG. A £100.00 + VAT charge to KA & Central DG. A £150.00 + VAT charge to West DG.
  • North West: A £75.00 + VAT to all CA.
  • Wales: A Charge of £75.00 + VAT is applicable to East LL & SY. A £100.00 + VAT to Central LL & SY.  A £150.00 + VAT to West LL /SY & All SA. 
  • Cornwall: TR / PL / TQ A Charge of £75.00 + VAT.
  • South East: CT A Charge of £75.00 + VAT
  • This is a single charge per drop (not per unit), and confirmed on quotation or verification.

The delivery is a dedicated service (not a mainstream courier) , shipping only the secondary systems, using a small fleet of Mercedes  Sprinter vans (or equivalent). Delivery dates will be notified shortly after approval, Times and dates cannot be selected or specified.  

Can you deliver overseas? No, we can deliver to any mainland UK port or address, for the customer to arrange their own onward shipping arrangements. In line with the standard delivery statement above.

Can the driver assist with unloading? Standard delivery is to kerbside onlyDrivers are only insured to unload to the threshold of the property, we advise that customers make arrangements to assist and to handle the units thereafter.

Please visit the following page for additional ordering and delivery information: Order & Delivery Services

  • Unfortunately, we are unable to offer export arrangements, support or assistance, units can be delivered in standard packaging format to any UK Mainland port or distribution centre based on standard order processing. The customer must make all freight Management and forwarding arrangements with their chosen provider. VAT is applied in full and in accordance with HMRC regulations, it is the customers responsibility to make any VAT reclaim or recovery should it be applicable.

Most of our business is to the DIY market, Units are supplied fully assembled, predrilled and glazed, easy installation ready.

If you follow the simple step by step Measuring Guide, the units will easily lift into position, with a few adjustments to get level, all of which is fully explained in the Installation Guide, the units can be fixed in place and the supplied finishing trim applied to cover, seal and hide any gaps and inaccuracies between the wall and frame.

If DIY is not for you, why not call on friends, family or neighbours to assist, anyone who can wield a screw driver can tackle this process.

If you haven’t got a contact you can rely on we can suggest using the Which Trusted Trader search service, just enter your postcode and search for Carpenter /Joiners, you should get a list of qualified and verified tradesmen in your area and whilst we can’t offer Personal recommendations, they will be more than capable of carrying out the work.

It varies. It’s dictated by the size and complexity of the order. Based on a  window approximately sized 1000mm x 1200mm, installation should take under an hour. On an average order size of 8 windows, installation can be complete within a day, it is relatively simple for anyone with basic DIY skills . Clearview secondary glazing is pre-assembled, pre-glazed and pre-drilled for ease of installation. 

see our Installation Guide


No, we can only offer this service with our installation option. Following our measuring guidance is easier than you may think.

We do have specialist installation team and can provide a fully comprehensive Survey, Supply and Installation service, this is a highly qualified City & Guilds trained team covering all certification requirements for both domestic and commercial projects.

However, this service is limited by size and location of project, and generally limited to an approximate 50-mile radius of our Sheffield Head Office for most domestic sized property. details are discussed and evaluated via a telephone consultation service.

[Click here] to see if we can fit in your area

Commercial work is evaluated on a project by project basis

Site assessment visits are only arranged following a consultation with one of our advisers Contact Us 

Where we are unable to offer an installation option, why not consider our Supply Only service for a DIY approach or using a local tradesman, this is easier than you may think and very cost effective.  see our Help Centre for more details.

Unfortunately we cannot recommend fitters, it is not possible to keep an up to date national database of installers where we know they are accepting work of this nature or their quality of customer service is appropriate. we prefer the customer to vet and verify their own installer.

The DIY approach can be easier than you may think, if you are not DIY confident, you may have friends, family or neighbours who are and could be called on for help.

If you are still struggling to find assistance, we can suggest using the Which Trusted Trader service, just enter your postcode and search for carpenter / joiners, this should give you a list of tradesman in your area who would be more than capable of carrying out the work. If you advise you have found the system, but need help, to fit or to both measure and fit.

Primary windows are rarely square and parallel sided, so you need to ensure the widest part of the secondary unit (including the sub-frame) will fit into the narrowest part of the area it is being fitted. Any gaps around the frame are then covered and sealed with the edging trim supplied with the units. It is particularly important that the units are not too tight, and most problems occur because of this,  whilst some adjustments can be made to the Sub-Frame, if the unit is too tight it won;t fit and cant be used, if squeezed in it can distort and cause operational and performance problems. a small gap around the units ensures maneuverability and position to ensure the perfect fit.

See our measuring guide

The recommended 10mm tolerance deduction is for guidance only as the aperture/reveal distortion will dictate unit size/fit adjustments  and requirements.

No, we are unable to determine what fixings and packing requirements may be needed due to the vast range of differing window styles and materials. All  fixing material requirements screws, packers etc are detailed in the installation guide.

We do offer optional fixing kits, these can be added to your quotation at the point of creation or you can visit our online store

Trim: With white units the standard trim supplied free of charge, it is white 28mm wide uPVC, this is easy to work with, matches the colour of the unit and is maintenance free. 

With colour units a 27mm wide timber painted trim is supplied as standard to match the units.  this may  require painting and upkeep at some future point.

The trim supplied is in sufficient lengths to cover the front face only, sealing off gaps between the reveal wall and the frame. Additional trim for back trimming or side covering is available as an optional extra.

The customer must satisfy themselves that the standard trim supplied is sufficient for their needs.

Alternative sizes are available as an optional extra and can be added to the quote / order as required..

Please note, the trim is an industry standard product, if you find that an alternative trim is required after delivery, this can be purchased from local DIY merchants or a variety of online retailers. we are unable to supply trim as a standalone item.

We always recommend that the sub-frame is included, this is pre-attached to the system at the point of manufacture. This has several benefits and is hidden by the edging trim on completion. It enables gaps around the frame in out of square apertures to be easily covered and give a better blended and unobtrusive finish. It enables minor adjustment to be made on installation and to notch out around lumps, bumps or cables etc. it also enhances insulation performance with expansion and contraction during seasonal changes.

The sub-frame is a value engineered product, designed to be hidden from view on completion, it is designed to protect the unit in transit and can arrive marked, with nicks scratches and knots, joints in the sub-frame will move in transit. All these aspects are perfectly normal and will not deteriorate the performance or final appearance of the unit when fitted. 

Units can be supplied without the sub-frame, this is a special-order requirement and Clearview need to apply this on behalf of the client. It does not alter the price, but measuring becomes far more critical as onsite adjustments can’t be made and gap filling around the unit must be considered. See our Quick GuideInstallation Guide

Face Fixing is where the Secondary Glazing unit is attached directly on to the face of the primary window frame, screw fixing through the front to the back of the secondary glazing.

Reveal Fixing is where the unit is attached to the side walls of the window reveal (the reveal is the depth of the window sill area) the screw fixings going in side to side / up and down. This is usually required if, (a) there is not enough frame on the primary window available to attach the unit to or (b) you want to increase the air-gap between the primary glass and the secondary glass to increase the sound-proofing performance.

See Face & Reveal Fixing

Other than drilling several small fixing holes into the existing window frame or surround, your primary window remains untouched and fully intact when you install Clearview secondary glazing. You will still be able to access your primary window all year and in most cases with a hassle free sliding or hinging option instant opening for ventilation cleaning and maintenance is assured.

Yes. In most cases Clearview can provide glazing units to fit most existing profiles, even complete circular designs, alternatively we can design a bespoke solution. if you send us some images we can offer advice, but in most arched cases we require a template for manufacturing.

View our Product Guides these show what shapes each system can accommodate

Skylight or Velux style windows, we also advise caution if trying to secondary glaze a window with a sloping or roof setting. it is critical to consider the safety and securing of both the frame and any moving/removable panels. Most sliding options do not perform well. We would advise a lift-out unit is probably best suited fitted with a locking bolt to secure the panel.

Clearview frames are available in a wide range of colour options. Clearview Secondary Glazing systems are supplied in White as standard. However, there are a number of stock colour options, Off-White, Cream, Dark Brown, Grey & Black, these carry an additional charge over the standard finish.  200 Bespoke colour options are also available, price on application. see our Colour Range details 

No – in most cases, unless your room is already undergoing decoration, the installation of Clearview Secondary Glazing does not require your room or area to be cleared or covered, other than allowing access to the window area. Your room will be left in a comparable condition to before the installation.

Clearview secondary glazing is a bespoke product tailor made to the customer’s specific needs, each unit is built to meet the most effective solution for Appearance, Performance, Practicality and Price. As there are many options available so there isn’t a simple off the shelf price. As specialists in this field our consultation service is a great place to start. However, our online Supply Only Fastquote service can give you an instant price and is customisable to get your perfect design. For installation services please contact us

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