Double Glazed Casement Windows

Double Glazed Casement Windows

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Who are Core Sash Windows?




We’re a window and door installation company based in East London. Core Sash Windows install all types of timer or aluminium windows & doors, giving us extensive experience in every part of the installation process. Customer service is one of our main selling points and our most common way of getting new business is word-of-mouth referrals.

Some terms you’ll need to know before going any further

Casement Sash or Window Sash: The part of the window that actually moves – i.e, the bit on hinges with the glass.

Opening: The opening in the wall that we create when installing your new windows.

Surrounds: The walls that surround the window on the inside. This is the area that is typically disrupted the most by window installation, which will need to be repaired by our painters (if you’ve ordered the comprehensive fit).

Fanlight: The small window at the top that is attached to the main product.

Double glazing: The two panes of glass in your frame.

double glazed casement window glazing









Engineered Timber: The type of wood we use as standard. The grains in the wood are set against each other in order to resist the typical stresses of timber, i.e bending, bowing, breaking.

double glazed casement window engineered timber






Argon or Krypton: The two kinds of inert gas most commonly used in windows. Krypton is generally seen as the most efficient gas for the job, but is more useful is extremely cold climates like Scandinavia or Russia as opposed to the UK. Argon is more than enough for most properties in the UK, so there’s generally no need to be spending your money on something that is more efficient that you need it to be.

What is a double glazed casement window?

A double glazed window is any window that has two glass panes instead of the older, traditional single pane. A double glazed hinged window, or ‘casement’ window, is essentially any window that operates on hinges. As you can imagine, this gives it an enormous amount of scope and almost any type of design is possible. These windows can be very simple, i.e a single opening casement, or they can be very complex, i.e a large bay of many opening casements.

double glazed casement window example

History of double glazing and casement windows

Casement Windows

Since casements windows are one of the most obvious ways to build a window, they’ve been around longer than the typical sash window. Hinges have been used to operate windows and doors in your average home for centuries, meaning that you can find historical examples of hinged windows and doors through many different ages. Using traditional glazing methods, the glass would be held in with lead strips, which is why you see that same glazing method on many older properties. Although the energy saving properties of single glazing aren’t that great, they’re definitely better than the alternatives people had at the time – i.e, either having a shuttered opening or no opening at all.

Double Glazing

Double glazing was invented in the 30s, and became popular in the 50s and 60s as an efficient way of saving energy in the home. People typically had single panes of glass which let a huge amount of heat escape, but with the gradual rise in popularity of double glazing, people stared to move away from the traditional sash window and move onto more modern double glazing.

What benefits do casement windows have that double glazed sash windows don’t have?

Casement Benefits

casement window benefits










Energy efficiency, noise exclusion and cost are the big ones. Since sash windows have a sliding sash that needs to actually move up and down within their openings, they need a certain amount of ‘play’ so they have enough room for the sliding sash to move up and down freely. Casement windows are not burdened by this design requirement and so simply plug the opening as snugly as possible. This means the energy efficiency and noise exclusion are both improved, and since it’s a simpler type of window design, the cost is kept to a minimum.

Sash Window Drawbacks

Sash Windows look great, but they weren’t designed to be that efficient. The sliding sash needs to be able to move snugly within it’s opening which means that it’s a little less energy efficient than casement windows. Most people have their focus on energy efficiency when they purchase new windows, which is why sash windows aren’t as popular as casements in many areas of the UK. Sash windows, even with double glazing, are still a mandated replacement in many parts of London or other historic towns & cities which is why they continue to be popular. Indeed, if city councils didn’t mandate this replacement, it’s likely that the sash window might have disappeared from the UK altogether. Sash windows are also more likely to have snagging issues with the weights or the fitting as the process is much more complex than your typical double glazing, meaning that there’s more room for error.

Benefits of timber windows compared to plastic windows

Environmental Benefits

double glazed casement window environmental impact






Plastic windows and white upvc are extremely environmentally unfriendly. Not only are the windows difficult to maintain over time, but when disposed of they produce an acrid fume that is often simply pumped into the atmosphere. The fabrication process also leaves waste products and produces pollution, whereas timber is produced from renewable sources. Although timber is more expensive, it will look much better over time (since plastic starts yellowing after a few years) and is simpler to maintain yourself. Apart from all that, timber looks a lot better than the same old white upvc that every else has!

Aesthetic Benefits

double glazed casement window in home










Timber windows have a much more natural and homely feel. Instead of the cold, rigid, edged plastic you can have a beautiful historic timber window with painted brush strokes. The more relaxed feeling you get from products like this is what you’re really paying for. We can produce timber windows in hardwood, softwood or accoya depending on your preference.

Maintenance Benefits

timber maintenance benefits








Timber, although more vulnerable to water, is easier to keep looking good over time. No matter what you do with your plastic windows, they’ll always look cheap and nasty after getting yellowed over time. Should you chip or break the window you won’t be able to carry out a seamless repair either, as plastic will have to be glued on. With timber, you can use wood filler to fill the gap perfectly before sanding and repainting to make the chip repair as seamless as possible.

Casement windows & the design of other windows in your home

Your new windows should look the way you want them to, which is why we recommend casement windows over sliding sashes in certain cases. Sash windows are somewhat limited by their design, but casement windows can be made to follow any design rule you want, so long as the new windows sash can still operate on hinges. Having said that, you can also choose a ‘direct glazed’ window, where the glazing goes directly into the window frame itself.

How will my double glazed windows be installed?

Comprehensive Fit

A comprehensive fit aims to cover all aspects of window and doors installation from start to finish. You shouldn’t need to bring in any other contractor to support our work. We always aim to keep your home as clean and dust free as possible, so dust protection and disposal is included in this service.

Carpentry Phase

  • Make sure the home is properly dust protected.
  • Measure up to ensure the new window matches the old size.
  • Remove the old window.
  • Plane the new window as necessary and fit with anchoring screws.
  • Fit any necessary architraves or timber wrap.

Painting Phase

  • Double check dust protection in the home and make sure it’s all correct.
  • Fill any gaps on the window.
  • Fill any gaps on the surrounds.
  • Paint the window itself, using neat brushstrokes.
  • Paint the surrounds using customer supplied paint or standard Core paint.

Basic Fit

A basic fit is the simplest and quickest installation procedure, generally for people who have already contracted someone else to complete for extensive painting work in the home.

Carpentry Phase

  • Measure up to ensure the new window matches the old size.
  • Remove the old window.
  • Plane the new window as necessary and fit with anchoring screws.
  • Fit any necessary architraves or timber wrap.

Aftercare of your new double glazed windows

Care of timber

All our products come with a 10 year guarantee if you maintain the window properly over it’s lifetime. Part of that means that you do not allow mould or damp to build up in the home and negatively affect the windows. Please ensure that your windows are wiped clean of excessive moisture whenever it occurs to avoid build up and ingress. Any defects with workmanship will come under our 10 year guarantee.

Care of glazing

The glass should be wiped clean of moisture whenever necessary. We guarantee the glass units for 2 years, excluding breakages, so if you notice that any moisture is building up inside the glass unit then just give us a call and we’ll get that fixed for you.

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Enjoy being warm and comfortable!

call us: 020 3302 2060 or email: [email protected]

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