Electromagnetic Shielding

Electromagnetic shielding is not normally a consideration for architectural applications, but there are projects where the choice of glass is important to either allow signals through the glass or to prevent them. An example of an installation where the transmission is required to be high is the building of an envelope protecting a transmitter. An example of the opposite is where sensitive data is held in a building and there is a concern for electronic eavesdropping.

With uncoated architectural glass there is some opportunity to vary the choices of glass thickness and airgaps to produce some effects such as very low radio reflectivity or very high radio transmission. These effects tend to be at specific frequencies and with radio beams from specific directions. These types of effect can be important in architectural design in the proximity to airports, where unintended reflections of radar beams are a known issue.

For most installations, insulating glass units include at least one pane with a coating to control thermal losses or to provide solar control. The coatings tend to be electrically conductive and affect radio wave transmission. These coating effects can be harnessed to stop electromagnetic signals penetrating into the building through the glass. It can be very difficult to estimate in advance what the overall radio shielding effect will be of a building structure - without a good understanding of what building materials are being used and how they are assembled. A user's perception of the radio shielding effect of a building can be strongly influenced by the strength of the radio signals themselves, for example, how close the building is located to a local radio transmitter.

A common type of product used in buildings is Pilkington K Glass™, the low emissivity coating of which is a transparent electrical conductor. This conductivity is responsible for quite significant radio wave reflectivity. These products are manufactured and specified for their infra-red properties. For products with better specified electrical conductivity and hence radio properties, the Pilkington TEC Glass™ range is available.

Sometimes the radio attenuation effect of conductively coated glass is not noticed due to radio entering the building through walls or even through narrow metal-free slots, for example, PVC-U window frames. It is becoming increasingly common that walls and wall cavities include expanded foam insulation that is foil-coated. The foil on these materials is electrically conductive and very opaque to radio signals. Aluminium and steel exterior cladding are also popular building materials with high reflectivity and high radio attenuation.

Where it is desired that a building has high levels of radio shielding for electromagnetic security or encloses radio interference sensitive instruments like hospital body scanners, the architect will design with conductive materials and connect these to form a ‘Faraday Cage’. Coated glass can be used, and typically the architect will take advice on suitable glass types. Conductive gaskets may be used to electromagnetically connect the coatings on the glass to the ‘Faraday Cage’.

Please contact us for advice on glass used in buildings where either radio shielding is a requirement, or the penetration of radio signals into a building could be an issue.