When it comes to choosing the right glazing, having the right information to hand goes a long way to helping you make an informed decision. There are so many options to choose from and if you own sash windows it is especially important to make the right choice.
If you’re not sure where to begin, we’ve listed some of the most common options below to help get you started.
Single glazing
Single glazing is the most common type of glass type found in sash windows. The reason for this is either because it is cheaper to replace the glass like-for-like, rather than upgrading to double glazing.
What single glazing can’t provide, however, is adequate levels of heat insulation and soundproofing. The various types of single glazing available include:
– Architectural salvage glass: Typically around 3mm thick and featuring a number of imperfections and blemishes, this type of single glazing is found in older, listed buildings. As it is a more specialist replacement glass, it is also one of the most expensive to use.
– 4mm float glass: By far the most common single glazing used in London is 4mm float glass. The reason for its popularity is due to the relative lightweight that enables sash windows to still work without issue. Its heat insulation properties are at an acceptable level, while the cost remains low. 4mm float glass also performs well when a draught-proofing system is installed. In terms of security, it helps prevent break-ins as when the glass is broken the pointed shards make it difficult to pass through without receiving a nasty cut.
– 4mm obscured glass: The use of obscured glass is a little more specialized and is preferred for homes or businesses that want to increase privacy. The use of patterns or textures on the glass makes it less transparent to distort the view into the other side. This can range anywhere from completely hiding the items in question or only revealing silhouettes.
– 4mm toughened glass: If you want to retain single glazing but need to enhance security measures, then installing 4mm toughened glass is a good option. While more expensive it also proves extremely resistant against breakage. This type of glass doesn’t offer great levels of heat insulation, but it does fit perfectly into a sash window and has no negative impact on the weighting system.
What also has to be taken into account with any glazing is the U-value. This relates to the rate of heat transfer that occurs through the glass. The lower the value, the slower the rate of heat loss.
Inside a timber window, single glazing has a U-Value of 4.8 – this decreases by 0.1 per millimeter, so replacing 4mm glass with 10mm will produce a U-Value of 4.2. While this will improve acoustic performance, the same can’t be said for thermal performance, so you will still have a significantly higher energy bill to contend with.
You can also read: 5 Advantages of Traditional New Sash Windows
Laminated glass
When more than one pane of glass is connected together using a thick inter-lay film then laminated glazing is created. Where needed it can help to reduce UV light, while significantly reducing noise pollution. Two of the best option for sash windows glass are:
– Laminate safety glass: 6.4mm laminated glazing ticks all the right boxes in terms of security, safety, and heat retention, although it is not always possible to use because of the weight and thickness. This is the standard option that is available from fitters but its usage will depend on the dimensions of the window frame itself.
– Acoustic laminated glass: To get the most out of this type of glass, it tends to work best when paired with a double glazed unit. In many cases, it can be as thick as 10mm, which adds to the weight and expense due to the counterbalancing that is required. However, it will increase security and acoustic performance, depending on the requirements of the specific installation.
Solar Glazing
Another glazing option available is solar glass. This can be installed to absorb heat transfer and reduce solar glare. This is done by tilting the glass to absorb the sun’s rays or coating it to reflect the heat back outside of the property. In more extreme cases the glass can be tinted and coated to achieve maximum effect.
The type of glazing used will depend on the requirements for a property as there are a number of different types available, typically ranging between 4-12mm. Laminated options are available, which will further enhance the already high levels of thermal insulation this glazing offers.
Double Glazing
Whenever is new sash windows double glazing is installed in any property, draught-proofing is also included as standard. Price-wise this also strikes a good balance between performance and cost and there is no shortage of options when it comes to installing this type of sash windows glazing:
– 4mm-16mm-4mm: 4-16-4 doubled glazed units are the most commonly installed into timber windows. When it is only the sashes that are being replaced and the existing boxes are remaining, then the unit thickness will be determined by the thickness of the sash.
Slimline double glazing units: The requirements of the unit will dictate the thickness of the double glazing to be installed. The wide range of pane glass types (laminated, patterned, etc.), combined with the choice of filler gas (Krypton or Xenon) and warm edge spacer colors will help achieve varying levels of thickness and thermal insulation.
The use of Xenon gas will create higher levels of thermal efficiency, but it is much more expensive as a result. Although, if the cavity is widened from 4mm to 6mm and Krypton gas is used instead, the same thermal efficiency rating can also be achieved.
Listed building double glazing: installing new windows into listed buildings can be tricky, although the creation of slimline double glazing units has allowed them to be installed in older, single glazed rebates. Of course, this does come with a higher price tag, although considering the improvement in heat and sound insulation it provides, it will ensure long term energy bill cost savings.
Triple glazing with high performance
Triple glazing is formed simply by using three panes of glass rather than two, with the cavity between each one filled with an inert gas such as argon, krypton or xenon. When it comes to reducing noise pollution there is no better option as even double glazing finds it hard to compete.
As you might expect, the cost of this type of glazing is considerably higher, adding as much as 25% to the price in some cases. However, it will prove worth it if you need to block out external noise and also increase the heat insulation properties of the building.
