Useful Information about Architectural Glazing
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Useful Information about Architectural Glazing
The term 'wind loading' refers to the amount of pressure caused by wind that the glass must be able to resist. When calculating wind loads for architectural glazing projects there are many factors that need to be considered, including the buildings height, shape, relationship to surrounding buildings and the terrain. The local wind speeds and gust durations also need to be taken into account as these forces all put pressure on the building.
Wind can generate enough pressure to damage architectural glazing, therefore, it is imperative that wind loading is allowed for in the design stages of a project. The in-house team of IQ designers are experts at designing architectural glazing for wind loading and know which variables need to be carefully considered.
Building Regulations Approved Document A details many aspects of building construction that should be considered in line with its location and positioning in the landscape. It dictates the maximum height of buildings depending on its location and associated average wind speeds.
It helps architects and designers create a building that will be able to withstand the natural environment within which it will sit.
Various aspects of the building design will be determined by this including the building shape, height, and location of any openings.
In addition, ‘BSEN 1991-1-4: 2005 – UK National Annex to Eurocode 1 – Actions on Structures – General Actions – Wind Actions’ will also be used by architects to determine the wind loading on a structure. This will apply to both vertical and sloped glazing.
There are actually three types of wind forces that would be exerted on a building, these are the following:
Uplift Wind Load is an upwards force of the wind that would affect roof structures or similar horizontal structures in a building, such as canopies or awnings. The wind flow under a roof structure pushes the roof upwards, the wind flow over the horizontal structure pulls the roof upwards.
Shear Wind Load is a horizontal pressure or force that can cause walls or vertical structural elements to tilt or crack, causing a building to tilt.
Lateral Wind Load is another horizontal wind pressure that can make a structure move off its foundations or overturn.
Architects take the basic wind speed for the site, the site terrain category, the wind loading at sea level and the corrections for the height of site and topography to determine the design wind loading.
When this is provided to your glazier (such as IQ) they can then determine the glass specification required for each element of glass on the project. The key is to design an architectural glazing installation that perfectly suits the project’s performance requirements and design preferences without over-specifying. Over specifying glass leads to an increase in project cost and does not add value to the project.
The GGF (the Glass and Glazing Federation) provides guidance on wind loading for glass installations. They recommend a minimum wind loading of 600 N/m2 (0.6 kN/m2) be applied to glazing in any location as a basic. Due to IQ’s experience in high specification glazing projects, we typically design to 0.65 kN/m2 as a standard (higher than most glaziers) to ensure that our glazing installations are robust and have longevity.
All structural glass assemblies are designed bespoke to suit each project's requirements, this includes the wind load requirements. Different areas or locations throughout the UK will have different design wind load requirements depending on the basic wind speed of the area and the size and shape of the building as well. These wind loadings should be provided to IQ by the architect so that we can design a glass installation that suits the project’s requirements.
Our Invisio structural glazing system has been tested under various wind load environments to provide confidence in the system’s ability to protect against high wind loads.
The frameless structural glazing system was tested at typical wind loads of 0.8 kN and 1.6 kN loads with a maximum deflection of 1/175. This provided a table of maximum recommended sizes at these wind pressures.
Structural glazing installations outside of these parameters are more than possible with bespoke engineering and design. Our team can determine the required glass specification and fixing methods to create a frameless glazing installation for any wind load.
Framed glazing systems, such as aluminium and steel windows and door glazing products, can be pre-tested to determine what their wind load strength is. These tests are completed using EN standard testing method 12210, Windows and Doors - Resistance to Wind Load. The resulting classifications are broken down into two parts;
For example, our slim framed sliding doors have a wind tightness classification of Class C5. This means the system was tested to a maximum of 3000 Pa of wind pressure (5) with a relative frontal deflection of < 1/300 (C). This is a very high level of tested wind resistance.
High wind load areas therefore tend to opt for sliding systems or rebated casement windows and doors.
Coastal properties or sites that are set out of a sheltered town environment may be subject to higher wind loads and therefore will have to be designed to withstand these additional forces.
A ‘town’ location is defined as an area where more than 15% of the surface is built on.
A ‘country’ location is anything that is not a ‘town’ as well as coastal areas that are more than 100m above sea level and inland areas more than 200mm above sea level.
Sliding doors tend to provide a higher level of wind resistance than pivot windows or bifold doors. This is due to the sliding pane being captured within the outer framework on all sides whereas pivot and bifold openings just sit within the outer framing using brush seals as a weather seal.
Ensuring that architectural glazing installations are designed and installed with the required wind loading's is extremely important to ensure that windows and doors operate properly throughout their lifetime. You also need to ensure that those structural glass assemblies are designed with the correct glass thicknesses and relevant strengthening interlayers.
An architect or engineer should be able to work out the designs wind load that we will need in our calculations for glass specifications and fixing details. This wind load is generally calculated using BS EN 1991-1-4:2005+A1:2010 regarding wind actions on buildings.
These wind loadings should then be given to your architectural glazier for them to consider when designing your architectural glazing designs. If this is not done then a standard wind load will be used which may not be suitable for the project.
When specifying architectural glazing it is always best to speak to the experts. Our in house designers will detail all glass specifications and fixing requirements for the project. Get in touch with a member of the team to find out how to appoint IQ to your project.
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