6 of the Most Common Issues with Glass Specification

There can be many issues with glass specification that are easily avoided by working closely with a professional glazier

Common issues with glass specification can include overheating, high noise levels and misunderstandings. This guide will help identify and offer solutions for some of these issues, with the main solution being to always use an architect for a project and work closely with your glazier to ensure the right systems are specified and everything is clear. 

The design specification is the most crucial and critical part of the architectural process. This provides the architect, contractor and subcontractors with an understanding of what is required with clear instructions indicated in the spec.

Glass specifications can be highly technical and complicated for some projects. A proper specification for the glazing on a project requires a detailed description of the installation including dimensions, glass thickness, performance requirements and is structural supports are needed.

In this article, we explain the 5 most common mistakes that are made in glass specification and what can be done to minimise or even prevent this from happening altogether.



thermal break, insulated sliding glass windows in cold snow environment

Large elevations of glass are great for increasing the influx of natural light within buildings such as structural glass facades, glass roofs and glass links. However, common issues with glass specification include these large surface areas of glass allowing direct sunlight to penetrate into the building which brings with it high levels of solar radiation if a solar control coating hasn’t been applied during manufacture.

This is particularly important in international projects, where the sun’s rays are stronger and weather conditions can be more extreme. If solar control coatings aren’t considered at the glass specification stage, then the building will be at risk of becoming too hot. Trying to tackle overheating from the solar gain as an afterthought can damage the overall architectural design of a building, by trying to bolt blinds or louvres onto structures that weren’t originally designed to have them. 

Solution: Solar control options

Solutions for solar control can be integrated into the architectural design and glazing package, but these need to be thought about early on in the design and specification stage.

Other methods of solar protection can be achieved with the use of automated external blinds or automated louvre roof structures. If considered at the design specification stage, external storage areas for the blinds can be hidden within the building structure for a minimalistic aesthetic.

Aluminium louvre roof structures not only provide a solar shading solution but also create a watertight roof to offer shelter to an outdoor entertainment space throughout the year. The louvres can be tilted via automatic controls to varying degrees to provide the desired level of shading to glazing and outdoor environments. The flexible nature of the systems makes them suitable for use in any climate, whether hot or cold.


Thermal Insulation

minimal framed sliding glass doors over looking infinity pool

Traditionally, glazing systems have been considered a real weak point in the thermal envelope of a building due to single glazing and poor thermal performance. However, due to impressive advances in glass technology, glass coatings and framing systems the thermal insulation available from glass units has greatly improved meaning thermal efficiency is no longer a common issues with glass specification.

The glass is just one element of a glazed installation, the thermal performance of an installation will need to be considered including the configuration of any doors, the Uw value of the framework and the finishing details around the frames. In colder climates, subject to extreme snow and freezing temperatures, the glazing systems will need to meet enhanced thermal performances to keep the cold out.

Solution: Consider the whole glazing installation

When trying to meet the thermal performance requirements of the building, it isn’t just the glazing that needs to be considered, it is also the frame of the system and where the unit is going to be installed. A typical DGU will now give you an Ug value of 1.0 W/m2K, using argon gas fillings and low e coatings to insulate the glass and reflect radiant heat back inside.

If you know the thermal performance you require from your glazing installation, you should tell the architectural glazing subcontractor at the specification stage. They can then assist you in selecting the glazing system that will best achieve your performance goals and the aesthetic required.

Triple glazing should be considered to achieve enhanced thermal performances in extreme climates and prevent the risk of uncomfortable living temperatures. The slim framed sliding door systems, as well as our Invisio structural glazing system, have profiles specifically engineered to accommodate triple glazed units.


Noise Levels

Common Issues with Glass Specification for double height glazing

Another area of performance to consider early in the specification stage is what level of acoustic reduction is required from the glazing. Many large developments, especially in city centres, will have a target for acoustic reduction. Background noise caused by machines, cars, people, aircraft, music performances or trains is not only a great nuisance but is scientifically proven to cause stress for occupants within a building. 

If the acoustic performance required from the glazing isn’t considered at the right time in the specification timeline it may not be possible to include an acoustic reduction interlayer into the glass. This is because the increased thickness of glass might not be suitable for all glazing systems. It is best to get those performance requirements in at the initial stage so that the right systems can be recommended for specification.

Solution: Acoustic Reduction

Glass has a natural acoustic reduction value and you can ask your glazing subcontractor for the specific value. To improve the acoustic performance of your glazing there are various factors that can be controlled to the glass specification to reduce sound transference. Your architectural glazier will be able to advise you on the best specification of glass for the acoustic value you need, it isn’t always a case of increasing the glass thickness.

Different glass thicknesses and specifications can help increase the acoustic performance without adding much to the cost, however, if further improvements are required to the acoustics of the glass it is worth investing in acoustic reduction glass. This interlayer improves the acoustic performance by reducing the transmission of sound through the glass between 35Db to 49Db. Acoustic reduction glass dissipates the sound wave, reducing noise pollution from the outside.


Nickel Sulphide Inclusions

corner opening slim framed sliding glass doors create indoor outdoor space

A glass breakage due to a nickel sulphide inclusion is a rare occurrence but it is something that all specifiers of glass should consider. It is a phenomenon that naturally occurs in glass where small particles of Nickel Sulphide can still be present in the glass at installation. Visually you won’t be able to see these tiny impurities and they are benign until they become aggravated. A simple way to see if a glass breakage was caused by a Nickel Sulphide Inclusion is to watch out for the ‘Butterfly Effect’ pattern on the glass.

Solution: Heat Soaking

The chances of glass breakage from nickel sulphide can be considerably reduced by specifying Heat Soaked glass.  

The tempered glass is put into a kiln held at the temperature of 555 degrees for about 2 hours to detect any glass units that may have an NSI within them. During the process, any glass that may have an NSI breaks due to stress within the glass, which means the glass that survives the Heat Soak Testing (HST) has a much lower chance of having a nickel sulphide inclusion within it.

Heat Soaked Glass should be specified for any panel of glass that is going to be inaccessible once construction is finished. This will reduce the chance that you will have to figure out how to replace it should breakage occur. In commercial projects, this is particularly recommended for any glazing on skyscraper buildings.


Condensation on Glass

anti condensation glass

Have you ever seen water droplets and fog on windows, even when no rain has occurred? This is condensation! Condensation is caused by the glass surface (has a low temperature) coming into contact with the warm air within a building. This often happens in the cold months of winter and is not always a bad thing as this reduces the majority of humid and warm air to leave, which is what you expect from a good window. Particularly in international climates, where the inside and outside climates are likely to be vastly different or air conditioning units are in use, condensation is likely to occur.

Did you know activities like bathing or cooking means an individual can produce about 4 litres of water vapour in just one day? This does not only provide the inconvenience in wiping the surface constantly and lessening the lifespan of the window but can cause greater problems such as mould forming and growing, which will in time damage the frame. There are no cost-effective solutions in getting this repaired, which means even more money will be spent to get the windows replaced.

Solution: Anti-condensation Glass

IQ Projects offer anti-condensation glass- this stops dew forming on the glass surface. You may recognise the warmth of the glass when you touch it, this is due to the heat of the roof temperature reflecting back, preventing any warm air from leaving. This is another great way to save your energy bills while reducing your carbon footprint.

All our glazing systems are fully thermally broken, helping to prevent heat loss and tackle condensation simultaneously. another way to tackle condensation is to create spaces that are well ventilated. This can be achieved by specifying opening elements within a glass façade, such as an opening rooflight system like the M.A.R.S (Modern Automated Rooflight System).



Common Issues with Glass Specification for sliding glass doors

Air permeability tests of our glazing installation is a very important factor but mistakes can easily happen. Around 40% of heat is lost from a building due to poor glazing systems and poor installation. Air leakage can happen due to cracks and openings of the window, which means too much unwanted air enters the building contributing to problems such as heat loss and cold draughts.

Solution: Air Permeability testing

Check that the Air Permeability of your chosen glazing systems have been tested according to the building test EN 12207, which clearly shows it fulfils UK standards and regulations. Generally, UK glazing standards will be higher than international locations, thus offering peace of mind that the building standards are up to scratch. If you are unsure, always ask the glazing subcontractor for this information. Fully certified FENSA can be provided by IQ Projects for approval on installation to give architects peace of mind providing a lasting investment.


Avoid these common issues

slim framed sliding glass doors and windows create light filled space

There is a lot of responsibility for architects designing a project or building. The architects wants and needs are our biggest focus here at IQ Projects and we will help every step of the way, incorporating their desires in the glazing specification to ensure our clients are happy with the overall project whilst surpassing building regulations.

Architects are confident in specifying products from IQ Projects because they know we will deliver, we also share the same passion and desire as architects for delivering projects, no matter big or small, that exceed all expectations within the expected time frame. When specifying architectural glazing products from IQ Projects we will ensure architects are provided with the best advice. The expert installation will happen according to the plans lasting many years to come.

Our hardworking team is here to serve you before building or installation begins, solving common glass mistakes before they even occur!

IQ have been working as professional commercial glazing contractors for over 15 years. With the IQ headquarters being based just outside of London, the majority of our specialist commercial glazing projects have been in South East England, although over the last few years QI’s work around the UK has broadened. With 5 main regional offices we have the capacity to work throughout the UK; working in all areas of non-residential, offices are also in our extensive portfolio. One of IQ’s earlier projects, Great George Street, specified IQ to design and installed a large structural glass atrium in the modern office in Bristol, as well as fire-rated glazing.


What Next?

For help in designing your next project and avoiding these common issues with glass specification, contact the IQ team today at hello@iqprojectsuk.com or call 01494 722880.


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Shannon Normoyle

As one of the Senior Marketing Executives, Shannon oversees the website and SEO management for IQ and can often be found working on SEO strategies or writing content for the websites. 

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