Windows Buying Guide


Chris Farrington, Cameron Gunn and Lee Manning of ReSolve Advisory Limited were appointed as Joint Administrators of Everest 2020 Limited (“Everest”) on 24 April 2024.

If you have any queries in relation to the business and/or administration, please contact

Chris, Cameron and Lee are licensed to act as Insolvency Practitioners in the United Kingdom by the Institute of Chartered Accountants in England and Wales and, along with their staff, act without personal liability at all times.

Licenced Insolvency Practitioners who are appointed as Administrators, and their staff, act as agents of the company over which they are appointed. A list of ReSolve’s licensed Insolvency Practitioners can be found on our website.

How to choose windows

The Everest guide to everything you need to know about buying new windows for your home. From choosing the right frame style and colour to suit your house to picking the right material and glass for your needs.

Windows buying guide

Buying new windows – where do I start?

There's more to choosing a window than meets the eye. Not only do you have to decide on the window style that will suit your home, but frame material, type of glazing, security features, types of glass and opening options are all important elements to consider.

We've created this guide to help you understand everything you need to know about new windows and walk you through the process of choosing the perfect window for your needs.

Which material should I choose for my new windows?

Deciding on the best window material for your property can be a challenge and certain materials suit some properties better than others (see what is the style of your house below).

Historically, windows were made using timber frames. Steel windows came into use in the early part of the 20th century, followed by aluminium in the post-war period.

uPVC windows were introduced in the 1980s as a more energy efficient type of window, and remain the most popular window material to this day.

Advances in manufacturing technology means that modern windows offer better performance than ever before.

Types of window material

Wooden windows

Offers the lowest thermal conductivity, meaning less heat lost through the frames, and provides a traditional look. Timber is the highest performing material in terms of energy efficiency, as it's a natural insulator that absorbs and retains heat.

Timber frames can be made from both softwood and hardwood. Softwood is faster growing and more plentiful, so it's cheaper. Hardwood grows slower and is more durable, so tends to be more expensive. Modern timber frames are engineered to be stronger, meaning they will not warp or bow, and can also be treated to resist rot and fungus.

Timber offers a traditional look with the benefit that it can have a stained or painted finish. It's the only material that can be repainted a different colour at a later date, so personalising the look of your home becomes even easier.

Wooden windows are seen to be most attractive, but natural materials such as wood require more looking after to keep them at their best and they are more expensive than other options.

uPVC windows

Long lasting and low maintenance, offering high performance at affordable prices. uPVC is a good all-round material that makes smooth and stylish frames which will never rot, flake or rust.

uPVC is a popular choice for windows as it offers fantastic value for money. Although, for some, lacks the unique charm of other materials. However, it is now possible to buy uPVC windows designed to emulate traditional timber frames, to such an extent that it can be difficult to tell them apart.

uPVC windows are still among the most energy efficient available and, with excellent double glazing, can achieve up to an A+ Windows Energy Rating.

Available in a range of colours. uPVC windows can be made with external frames one colour and the internal frame another to match interiors.

Aluminium windows

Aluminium windows are used in structural glazing and other commercial construction projects due to its strength. In domestic properties, this allows for a much thinner window frame and a larger glass surface area, letting more light into the room.

Aluminium windows feature a thermal barrier in the frames, which reduces heat loss through the frames. In the last 10 years, thermal barrier technology has improved massively, and aluminium windows can now achieve almost the same high energy ratings as uPVC windows.

Aluminium windows are extremely weatherproof and low maintenance. Unlike other metals, aluminium does not corrode, so window frames will not rot, flake or rust. A powdered coated finish allows a wide range of colours to be chosen for the frame.

Window Frame Styles

Every window style has its own uses and benefits.

The most important factor for new windows is choosing a style that is in keeping with the age and style of the house. A traditional stone cottage wouldn’t look its best with uPVC tilt and turn windows. And a sleek contemporary new build wouldn’t feature sash windows.

Casement windows are the most popular style of frame and suit most styles of home. However, some houses will require specialist window designs such as period sash window frames.

Types of window styles

Types of window styles

Casement windows

Casement windows have always been the most popular window style. They can be hinged on the side to open left or right, or hinged to open upwards. Extremely versatile, they can be designed to suit a range of properties. The modern technology, with multiple locking points along all sides of the frame, makes a casement window extremely secure.

Tilt and turn windows

Tilt and turn windows possess a dual hinge design that tilts and open inwards using hinges at the bottom and side. Tidy and efficient, these windows have been designed for flats, apartments and other upper storeys, providing secure ventilation and an easy way to clean the glass inside and out.

Sash windows

Amongst the most traditional window styles. Historically made from timber, sash windows can now be made from uPVC, for a classic design that fulfils modern day performance requirements.

There are several different styles of sash window available, modelled on designs from the Georgian, Victorian and Edwardian periods. Designs vary depending on the era, but tend to have a thicker frame depth and a deep bottom rail.

Cottage windows

Georgian bars can be added to either casement or sash windows to add a traditional finish to your property. Internal glazing bars sit between the glass panes and keep your windows easy to clean, whereas external bars sit on the surface of the glass.

Another option is diamond or square leaded glass designs to replicate traditional window styles.

How to choose a window style that's right for your home

Many people decide to replace their existing windows like-for-like, but with so many window designs, frame styles and other decorative features, there is an option to suit your property.

First, think about the window's functionality. Standard casement windows are well suited to most projects, but if ventilation, security or maintenance are a concern, consider other styles.

One way to make sure your house looks its best is to ensure that each individual window appears balanced. We call this 'window framing'. Choosing a symmetrical window will enhance the aesthetics of your property and create a lasting impression.

Most importantly, consider the original style of your house to influence the frames you choose.

What is the style of your house?

Traditional houses

Houses built before the 20th century originally had wooden windows, and still suit these today. Georgian houses, 1930s semis and Victorian terraces are all period properties built with wooden sash windows or period detailing. Modern uPVC windows can sometimes replicate these styles, but there's no replacement for timber. In some cases, replacing period windows with uPVC can devalue a property, so take care when replacing windows on traditional houses.

Suburban housing

Properties in housing developments built from the 1960s onwards can be replaced with white uPVC. Depending on the colour of the house brick or render, coloured frames can add a unique touch.

Modern Architectural

For that stylish contemporary look, there's no better choice than sleek aluminium frames. Used in structural glazing, aluminium is a strong material that can hold larger glass units to increase the amount of natural light. Aluminium frames sit flatter than uPVC frames and have slim profiles that allows for an increased glazed area with an unobtrusive frame.

Window Glass & Glazing Types

Originally, windows only had one job, and that was to let light into a building. The first windows were made with pieces of glass held together by lattice leading. Soon after, the invention of thinner and flatter plate glass led to larger squares of glass held together by wooden glazing bars.

Float glass was invented in the late 1950s, allowing for the quicker production of large, flawless glass sheets. This helped the development of more advanced glazing. Double glazing became the norm from the 1970s onwards, as energy efficiency, comfort and security became more important to homeowners.

Glazing options

Single glazing

Installing single glazing is still a requirement on occasion where planning or conservation regulations apply. Along with timber frames, single glazing helps a property retain its period look. To improve insulation under these circumstances we recommend secondary glazing.

Double glazing

Double glazing is one of the most effective ways to improve the insulation of a home, creating a warm and comfortable living environment.

In a double glazed window, two panes of glass are joined by a spacer bar. The gap between the panes traps warm air, slowing the escape of heat from a building. In addition, the best windows introduce an inert gas, such as argon, which further limits the movement of cold air.

In the UK, all new buildings must install at least 1.4 U-value or C rated double glazed windows as standard, but many companies are offering double glazing that can achieve an A or even A+ rating.

Triple glazing

Triple glazing contains a third pane of glass, creating an extra cavity which traps warm air and reduces heat loss through the sealed unit.

A common misconception about triple glazing is that the improvement in thermal performance is due to the extra pane itself. However, it's more about the types of glass and coatings used, the gas filled sealed unit and the distance between the panes.

Is triple glazing really any better than double glazing?

Everest triple glazing is one of the highest performing glazing units on the market with an industry-leading lowest U-value making it ultra energy efficient. Choosing energy-efficient Everest windows can help lower your energy bills and reduce your carbon footprint.

If your priority is noise reduction, we recommend noise-reducing double glazing because the middle pane in triple glazing can increase sound vibration and amplify sound transference.

As the Future Homes Standards are introduced, the energy efficiency of a home and U-values for windows will become more important. At Everest, we believe that triple glazed windows will become a requirement in all new build houses as the standards for the fabric structure of buildings keep increasing.

Secondary glazing

A practical alternative to double glazing for conservation areas

If you live in a listed building or conservation area it may not be possible to replace your windows. In this instance secondary glazing would be the perfect option to reduce noise and cold draughts.

With secondary glazing an additional window installed directly inside of the existing frame. It can help your home achieve thermal, security and noise reduction benefits, whilst remaining invisible to the outside.

Types of glass

New technologies have been developed that make window glass stronger, shatterproof, clearer and quieter. It's important to consider what type of glass would be best suited to your requirements.

Low-E glass

Low emissivity glass has an invisible, thin coating applied to its surface that reflects heat. It is strategically placed on the inner pane of glass to help keep heat indoors and to maintain a comfortable temperature.

Low iron glass

Windows that contain low iron glass are noticeably clearer. They allow a higher level of light to pass through compared to older glass types, which sometimes have a slightly green tint.

Security glass

Security glass is available in a range of sizes and thicknesses depending on your security needs. Typically, laminated glass is 6.4mm thick (compared to 4mm for standard glass), and contains a thin plastic interlayer that prevents the glass from breaking. Toughened glass is up to five times as strong as ordinary glass of the same thickness.

Used as an outer pane in a double glazed unit, this provides an extra level of security to the window as a whole. Toughened glass must also be used for fixed lights in side panels to doors, as well as in windows close to the ground.

Noise reducing glass

Noise reducing glass contains an inner pane that is 6.8mm thick supported by an outer pane that is an incredible 6mm thick. Together, they provide excellent sound insulation. A thin and lightweight solution to noise problems.

Coloured glass

Add coloured shapes, patterns and bevelled designs into the glass itself. Decorative glass looks beautiful in top hung fanlights – the top sashes of casement windows – as well as feature windows in halls and stairwells. Coloured glass is similar to stained glass windows, but it doesn't require leading to hold the glass together.

Leaded glass

Stylish strips of lead are a purely visual benefit that can be added to your window in order to make it more aesthetically pleasing.

Obscure glass

Obscure glass creates a 'cloudy' effect, also known as privacy glass. There's a variety of textures available, such as leaves and flowers, as well as grainy patterns.

How much do new windows cost

How much do windows cost?

Our guide to the cost of new windows to help you budget.


Do I need planning permission for windows

Do I need planning permission for windows?

The planning rules and building regulations for windows explained.


How to choose glass for windows

How to choose glass for windows

There are many different types of glass tailored to different needs in a home.


Window furniture & fittings

Whether you're after a sleek modern look or a sculptured classical appearance, the right frame styling, handles and other accessories create a superior level of authenticity.

Weather tight seals

Until very recently, window seals were thick, black and rubbery, and stood out starkly against white frames. Seals are now slim and discreet, offering better insulation and contributing to much higher energy performance.

Rubber seals tend to flatten once it is subject to repeated pressure, altering their shape and ultimately hindering their performance. Eventually, they can collapse and this is one of the main reasons why older windows fail after a number of years.

Everest seals are made from a soft PVC and will spring back to their original shape every time. Because the seal is co extruded, it will never pull out of the groove, ensuring consistent weather performance for the lifetime of the window.


Window handles come with key locking as standard and are usually available in a range of colours and metallic finishes to match the frame colour.

Sash window furniture

The key to achieving an authentic-look sash window is in the furniture. Small metal hook pulls sit at the foot of the sash, with fasteners locking the window together.

Traditional ironmongery

Modern windows can be made to look exactly like their traditional counterparts with traditional style handles, such as monkey tail or tear drop handles. Windows can also be decorated with peg stays, the period version of modern-day friction stay hinges, that keep a window casement open at the angle you want.

Other ways to accessorise your new windows include different frame colours (including two-colour frames), decorative glazing and period features, such as sash horns and Georgian bars.

Window security

Installing secure windows in your home is important on a couple of fronts. Firstly, strong frames and locks can protect your home against intruders, significantly reducing the risk of break-ins and burglaries. Secondly, restrictive window openings can create a safe environment, opening just wide enough to ventilate a room without the risk of falling out.

The best way to compare security of a window is to research the credentials. Windows must achieve the British Standards certification PAS 24:2022 – the minimum security standards required for residential properties.

Some windows also boast 'Secured by Design' accreditation, a flagship UK Police initiative to help 'design-out' crime through the use of high-quality innovative products.

Some safety features for windows include:

Internally beaded windows

Window glazing is held in place against the frame with a small strip called a 'bead' which runs along all the edges of the window sash.

Early uPVC windows had the option of external beading, but this has largely been dropped due to security concerns. Window beads used to be a lot weaker and offered an easy opportunity for burglars to simply peel them away and remove the glass.

Most windows nowadays have internal glazing beads, which is the most secure option.

Multi-point locking

There are many more options regarding locks, offering varying levels of safety and security.

Technically, a window with just two locking points can be considered "multi-locking." The more points that can be locked, the more secure it is. There isn't a standard number of mechanisms, but if you can find a window that has eight or more locking points, you have yourself an incredibly secure window.

Bi-directorial locking adds a layer of complexity in the frame that prevents the intruder from being able to jemmy your window out of place.

Key lockable handles

All modern window handles are key lockable, making it difficult for potential intruders to simply wriggle your windows open. It also adds an extra safety feature for top storey rooms accessible by children and vulnerable. It is recommended that you leave your key inside the lock, however, so it is accessible in event of an emergency.

Hinge-side security brackets

Some uPVC window frames incorporate tough, interlocking brackets that secure the outside of a window sash when fully shut and locked. This means that if an intruder tries to lever the window on the hinge side, the brackets will prevent them from being able to lever the window out of place.

Egress hinges

Used for fire escapes, egress hinges allow a casement window to open fully outwards in order to provide an emergency exit.

Opening restrictors

Opening restrictors limit how much a window opens, either by connecting the sash and the frame via a cable, or by fitting key-lockable restrictors that allow windows to open no more than a couple of centimetres wide for ventilation purposes.

The Royal Society for the Prevention of Accidents reports that 4,000 children under the age of 15 are injured falling from windows every year. Something that could easily be prevented by using window restrictors.

Lockable ventilation & night vents

Windows have the option of leaving a small, one inch gap when closing known as the night vent position that many people use as a means of ventilation. However, leaving a window on the latch is far less secure than shutting a window fully, and can present an opportunity for a potential burglar to prise open the window.

New windows can be provided with 'trickle vents' instead, which provide background ventilation without compromising the security of your home.

Energy Efficiency

Up to a third of heat in the home is lost through single glazing. By upgrading to energy efficient windows you can make a saving in your energy use. Thermally efficient windows are at least double glazed, with low emissivity glass and an inert and non-toxic insulating gas like Argon between the panes.

Combined with energy efficient frames, new double glazed windows can achieve an A+ Window Energy Rating (WER), and triple glazing can achieve an A++ Window Energy Rating (WER). Upgrading your windows could enable you to make a significant saving on your household bills every year.

WER rating

The British Fenestration Rating Council (BFRC) created the WER rating (Window Energy Rating) in order to simplify how effective a window is. The rating system offers grades from A-G (with A being the highest rating). If the window is rated higher than an A it will be followed by a number, and anything above an A10 becomes A+. In October 2015, the BFRC introduced the A++ rating for windows that achieve higher than A20.

The WER rating is made up of three key elements: U value, solar gain and air loss through leakage.

1. Thermal efficiency (U value)

A window's U value is the technical way to measure heat loss through a type of building material, such as a brick wall or tiled roof. U values are calculated by the equation W/m2k, which measures heat loss in watts (W) per square metre of material, when the temperature (k) outside is at least one degree lower.

The lower the U value, the better the insulation provided by the material. Single glazed windows have a typical U value of 4.8-5.6W/m²K. Modern double glazing can achieve a U value as low as 1.4W/m²K, and triple glazing is even more energy efficient, reaching 0.6W/m²K.

As the Future Homes Standards are introduced, the energy efficiency of a home and U-values for windows will become more important. At Everest, we believe that triple glazed windows will become a requirement in all new build houses as the standards for the fabric structure of buildings keep increasing.

Everest uPVC triple glazed windows and double glazing windows have an ultra-low U-value.

2. Solar gain (G value)

Solar gain is another factor that can boost a window's energy rating. Not only are windows now designed to reduce heat escaping, but they can also let heat in by capturing the sun's rays. Solar gain is measured by the G value, on a scale between 0 and 1, with a high number indicating high solar gain.

Factors that influence the solar factor include the number of panes, the type of gas between them, and also the type of coatings added to the windows, as they dictate whether the glass absorbs or reflects the heat.

Contrary to what you might think, solar gain windows do not always lead to overheating. The UK has a relatively cool climate and relatively little sunshine, so overheating is rarely a problem. For rooms where sun streams in during the afternoon, it could be worth considering upgrading to triple glazing. The level of solar gain is actually less than double glazing, due to the extra pane of glass and cavity.

3. Air leakage (L value)

Air leakage occurs when there is a weak point around the window frame, such as the seals. Most modern windows are fully airtight, and should have an air leakage factor or L-value of zero (0.00W/m²K).

Air leakage is not to be mistaken with ventilation. Ventilation is a controlled system, letting in small amounts of fresh air to reduce stuffiness and improve air quality, whereas air leakage will compromise the energy efficiency of your window.

Questions to ask before you buy new windows

  • +
    How do I know if I need a new window?

    The lifespan of a window depends on the quality of the product and workmanship. A well-made and well-fitted window won't have to be replaced for decades.

    Warning signs for needing to replace a window are:

    • Misted windows due to blown double glazed unit (failure of glazing seals)
    • Timber frames have warped or started to rot
    • Plastic has perished, is peeling or discoloured
    • Windows rattle, or let in draughts and the cold
    • Sashes don’t open or close properly
    • Broken hinges, handles and locks
  • +
    How do I find out if I live in a conservation area?

    Conservation areas are in place to protect architectural and historical buildings or places of interest, and are more common for properties built before the turn of the 20th century.

    You can find out if you live in a conservation area by contacting your local planning authority (LPA), and you can find out if you have a restrictive covenant by checking the title deeds for your home.

    Before you replace windows or start any building work, always check to see is you have any restrictions on your property.

  • +
    Which window material is the easiest to maintain?

    uPVC and aluminium frames are the easiest material to maintain, and only require cleaning occasionally by wiping down the frames with a damp cloth.

    Timber windows are the highest maintenance frames and need to be recoated every couple of years.

  • +
    What kind of guarantee do the windows come with?

    Everest 10 & 20 operates alongside and in addition to the protection afforded by our membership of FENSA. This provides consumers in England and Wales, who use Everest to fit their windows and doors important cover. It means that your windows are installed by a certified installer, that the work complies with building regulations, and importantly that you will have an insurance backed guarantee – which covers the cost of any required servicing of your products in line with our standard 10 year guarantees.

    Read more: Everest guarantees...

  • +
    How long will the installation take?

    Typically, you can expect to have your new windows installed about 4-6 weeks after ordering, but this is subject to a variety of factors, including arranging any planning permission and seasonality.

    The time it takes to install a window depends on how many windows and other home improvements you're having installed at the same time. A single window can take anywhere from 3 hours to install, to a day for a full house of windows.

  • +
    What double glazing accreditations and standards should I look for?

    Building regulations apply to double glazing window replacement so you must use a reputable company that is registered under the competent person scheme. At Everest, we can give you a certificate of completion that states your windows pass regulation.

    The accreditations to look out for include:

    • Competent person scheme CERTASS
    • Fenestration Self Assessment Scheme FENSA
    • British Standard Institute BSI
    • The Glass and Glazing Federation GGF
    • Secured by Design, the official police security initiative SBD

What you should expect from your new windows

Finally, when considering new windows, these are all the requirements your new windows should have:

  • Be easy to maintain and clean
  • Let in a good amount of light
  • Look good and be aesthetically in-keeping with your home
  • Be highly secure with multi-point locks and mechanisms
  • Have glass that can't be removed from outside of the home
  • Have a high energy rating (A++ is currently the highest) to reduce energy bills
  • Be made-to-measure, therefore fit perfectly into the aperture of your home
  • Keep out draughts
  • Not move or rattle when the wind blows
  • Long lasting guarantees that cover all areas of the window (not just the glazing)
  • Add value to your home

Everest Customer Reviews

Start Your Project Today...

Book your free quotation appointment with one of our local expert consultants who will:

  • Provide an accurate, no-obligation quote
  • Offer ideas and practical solutions
  • Show you samples of our products
  • Take all necessary measurements

Sorry, something you've entered isn't correct. Please check the form.



    By providing your details above you agree to be contacted under the terms of our privacy policy.