Window energy ratings
As government building regulations become more stringent and heating costs rise, it is becoming ever more important to choose the most effective thermal insulation glass. The British Fenestration Ratings Council (BFRC) has set out an official window energy ratings table, ranging from A to G, with A being the most energy efficient. For more detailed information see Window Energy Ratings section). Windows with a C rating or higher are endorsed by the government-backed Energy Saving Trust.
The energy efficiency of a thermal insulation glass is measured by its U (formerly K value) and its Solar Heat Gain Coefficient (g).
In addition to the low E glass used, energy ratings can be further enhanced by the variety of Spacer Bar, Cavity and Edge Spacing used in the double glazing unit.
U Values
The ‘U’ value of a double glazing window is the measure of its ability to transfer heat – so double glazing windows with the lowest U value are the most efficient insulators against heat loss from a room (see Window Energy Ratings).
Solar Heat Gain
The Solar Heat Gain Coefficient (SHGC), which measures a thermal insulation glass’ ability to transmit solar energy into a room, is measured in value from 0 to 1. The SHGC is commonly referred to as the g-value, or solar factor. The higher the g value, the greater a thermal insulation window’s ability to transmit solar heat (see Window Energy Ratings) and thus increase its energy efficiency.
Types of Low E Solutions
The most efficient thermal insulation glass use a unique manufacturing process which builds up microscopic layers coating, using a technology known as sputtering, under vacuum conditions. (See online and offline coatings). This advanced process builds up a highly resistant, but imperceptively thin coating which gives it a much clearer appearance than other thermal insulation glass. The coating also allows maximum daylight and heat into the room for optimized solar gain. Some products have been shown to reduce heat loss by 24% more than traditional online coated thermal insulation glass, and by 40% compared to standard double glazing window. Further energy savings can be made by using warm edge ‘thermal break’ spacer bars. These can reduce heat lost around the edge of the window by up to 65%.
Combining thermal insulation glass with other solutions
Some ranges of thermal insulation glass can be toughened and laminated and used in double glazing window in various combinations with solar control, self-cleaning, decorative and acoustic glass. (see Which Combination).
No more noise pollution!
Noise reduction
Noise pollution is a growing environmental concern and nuisance, especially in urban areas. Even the background noise of 70 decibels caused by outside traffic can cause disturbance and stress over a continued period of time. Acoustic glass technologies have been developed to combat levels of unwanted noise, whether it be for a translator’s booth, a house located near a busy road or an office next to the airport.
What is acoustic glass ?
Acoustic glass considerably reduces outside noise, especially near busy areas such as motorways, main roads and airports. When used in overhead or roof glazing, double glazing window also provides insulation from rain impact noise. It can be used for interior sound insulation needs, such as office partitions and meeting rooms.
Acoustic glass consists of two or more sheets of glass, bonded together with one or more acoustic inter-layers: Double glazing window. The inter-layers act as a noise dampening core, weakening the sound as it travels through the glass. Interestingly, by varying the thickness of the sheets of glass, even better sound insulation can be achieved. Acoustic laminated glass also benefits from all the safety and security properties of standard laminated glass. For more information see Acoustic Insulation (how does it work).
Combining acoustic glass with other solutions
Laminated acoustic glass can be combined in double glazing window with a variety of Low E, solar control, self-cleaning and decorative glasses (see Which Glass Combinations).
When standard glass breaks, it can form dangerous shards and splinters. To avoid risk of injury caused by broken glass, high tech safety glasses are available in toughened and laminated forms – most of which can be used in double glazing window. Wired glass also qualifies as a safety glass. Less effective, it is only awarded the class C level of the British Safety (BS) standards scale.
Usage of safety glass
Safety glass is now mandatory in some areas of the home (see Building regulations), as well as throughout some types of buildings such as schools. Glass used in roofs must also meet safety requirements in case of an object falling on to the double glazing window which could cause fragments falling below.
Standard requirements for safety glass
Safety glass must conform with the BS 6206 standard requirements in order to qualify as safety glass. Three levels of impact resistance exist under the BS specifications – A, B and C – with class A being highest. For glass to be awarded the class A safety standard, it must be able to resist an impact of 45 kg without breaking, or break safely. However those with projects for safety glass should be prepared for the more stringent European safety standards that are currently coming into effect for the UK (for more information see Standards)
Laminated glass
Laminated glass is comprised of one or more inter-layers, sandwiched between two or more sheets of float (or annealed) glass. The inter-layers are composed of a PVB (polyvinyl butyal) laminate, or cast resin.
Cast resin laminated glass is manufactured by pouring liquid resin into the cavity between two glass sheets. This method of laminate is often used where heavily textured or patterned glass is to be used.
PVB laminated glasses tend to have a higher safety performance and are the more commonly used variety. One or more sheets of glass are bonded together with one or more PVB inter-layers. If the glass suffers an impact, it may eventually fracture, but the broken fragments will remain bonded to the inter-layer.
Other benefits of laminated glass
Safety grade laminates also act as a deterrent against burglary and vandalism. Depending on the composition of the laminate and thickness of the glass, different levels of performance are also possible for acoustic insulation and protection against firearms and explosions. (Also see Security Glass).
Toughened Glass
Toughened, or tempered, glass is four to five times stronger than ordinary float glass. If it is broken relatively harmless fragments, known as ‘dice’, are formed which are unlikely to cause injury. Toughened glass that meets with the highest British Safety Standards, Class A, is suitable for use in structural double glazing window where the glass is to be fixed by bolts or clamps.
Toughened glass is made by heating prepared and processed glass sheets to a temperature of 700°C (just above the softening temperature of glass) The sheets are rapidly cooled by blasts of cold air to both surfaces, resulting in the outer surface contracting and solidifying before the interior of the glass. This process increases the tensile strength of the glass and gives it safe breakage characteristics.
Combinations
Toughened and laminated safety glass can be combined with other double glazing windows such as decorative, easy clean, thermal insulation and solar protection glass within the same double glazing window. (See Which Glass Combinations).
Benefits and regulations
A good thermal insulation glass saves money with low energy bills
As heating costs continue to rise at an alarming rate, installing double glazing window with thermal insulation properties (Low E) is a shrewd investment for reducing heating bills. The latest Low E thermal insulation glass solutions work in two ways – by reflecting heat back into the room, rather than allowing it to escape and by allowing the home to benefit from free solar energy.
By using the most energy efficient Thermal insulation glass solutions (with an A rating on the Window Energy Ratings scale), it is estimated that over a 20 year period as much as £ 9000 can be saved on heating costs for an average sized semi-detached home – and as fuel costs rise, probably much more. Double glazing window can halve the amount of energy lost by single glazing.
Thermal insulation glass plays a vital role in increasing comfort to your home by stabilizing the internal temperatures. Importantly, thermal insulation glass also helps reduce energy costs for heating and cooling which is good for the family budget and the environment. Using less energy in the home helps reduce greenhouse gas emissions via double glazing windows.
Double glazing window keeps you cool by acting as a barrier from the heat in summer. The inside temperature of your home can be up to 8°C to 12°C cooler than an un-insulated without thermal insulation glass. Thermal insulation glass keeps you warm as it acts as a barrier against heat loss. They work just as effectively in winter as they do in summer. Your home will be warmer or cooler, more efficient to heat and much more comfortable to live in.
Triple Glazing
Triple glazing has become synonymous with efficiency in home insulation and responsible energy use. As the name suggests, triple glazing is a window that is made up of 3 layers of glass with 2 gas-filled cavities between the layers. Where double glazing, with its 2 panes of glass, was a significant improvement in insulation, triple glazing is the next evolution, improving window insulation by a further 50%.
But how does triple glazing work exactly and why does its installation guarantee such an increase, not only in domestic energy efficiency, but also in your home’s selling price?
LET’S LOOK AT THE COMPOSITION OF A TYPICAL TRIPLE GLAZED WINDOW
A triple glazing window comprises 3 glass panels with 2 gas-filled chambers between the panels, encased in a sealed frame. The unit functions as an insulated whole, where the type of glass, its thickness, the distance between the glass panels, the type of gas in the cavities as well as the air pockets in the frame’s design contribute to its superior insulation capabilities.
The typical triple glazing unit is made up of 3 panes of 4 mm glass, with the optimal gap size being 16 mm between them. The thickness of the glass has an influence on the unit’s thermal insulation capabilities, but ultimately, it’s the size and fill of the cavity that has the most impact on preventing heat loss through the window.
Triple glazing uses Krypton [Kr] gas to fill the 2 cavities between the glass panes. Krypton gas has a 34% lower conductivity than air, which aids in heat loss prevention as well as providing sound insulation from outside noise. Because a triple glazed unit has 2 of these gas pockets, its heat conductivity is greatly reduced when compared with double glazing that has only 1 gas-filled pocket. Double glazing also makes use of Argon gas [Ar], which while being more cost effective, is not as thermally efficient.
The frames of triple glazing units are made up of 1 of 4 materials, being u PVC, wood, aluminium and composite frames that consist of a softwood core with aluminium cladding.
Click here to read more about the different window materials and for information on how to choose the right triple glazed windows for your home.
The style of window that will suit your home will typically dictate which material will be most appropriate, although most window styles can be manufactured in any of the materials. Even homes in conservancy areas and ones that have to comply with strict building codes, can upgrade their windows to triple glazing. Council requires that the aesthetic of a property in a conservancy area remains unchanged or at the minimum, sympathetic to the original. u PVC, with its highly customisable finish and texture options, is a great choice for these types of windows.
HOW IS THE GLASS DIFFERENT FROM OTHER WINDOWS?
Triple glazing makes use of different treatments and types of glass to increase its efficiency.
Low iron glass is the preferred glass type to use in triple glazed windows. This type of glass doesn’t have the blue-green tinge seen in standard glass panels, making it appear whiter and more clear. This allows the most amount of short wave solar, or light, to pass through the 3 panels to the interior of the home.
Low E-glass (low emissivity glass) is coated with a microscopic film that reflects long wave infrared energy, otherwise known as heat. The interior pane of a triple glazing unit is coated with this low-E film, which then reflects heat back into the room instead of allowing it to escape to the outside. This ensures that any heat generated inside, remains inside.
The central glass panel comprises toughened glass. Because of its position in the unit, this pane is particularly prone to thermal stress cracking since it is exposed equally to hot temperatures from inside the home, as well as cold temperatures from outside. By toughening the glass pane, the risk of thermal stress cracking is reduced 4 -5 times compared with untoughened glass.
3 reasons why triple glazing is superior to any other window
- Home owners across the UK are quickly warming up to the idea of triple glazed windows for their homes, with many of them choosing to upgrade their double-glazed windows to more energy efficient triple glazing. Experience has shown that triple glazed windows do not just improve the comfort levels inside a home and lower the energy bills; they also give a healthy boost to the market value of the property.
- Triple glazing is durable, eliminates cold spots that could be present in insufficiently insulated homes, enhances security, and reduces energy bills. The UK government has a very aggressive 2050 target, committing to cut the country’s carbon emission levels by 80% by 2050. The domestic housing market contributes roughly 30% of the greenhouse gasses produced in the UK, which means it is the responsibility of every home owner to do their bit by upgrading their home to be more energy efficient.
- As more and more people become aware of the benefits that triple paned windows offer, many are opting to have it installed. While the initial installation cost is higher than double glazing, the return on investment is far greater. Triple glazing also greatly improves a property’s Energy Performance Certificate (EPC) which has a direct influence on the market value of that property. Here’s a look at the different options in domestic glazing and why triple glazing is the most efficient and constructive solution in home improvement.
