What to remember: facades

Intelligent facades have come of age and are a valuable tool for the specifier in meeting regulations. A range of sophisticated systems are available to help control airflow, heat transfer, light and noise through the facade. Choosing the right combination of elements to do this can be a challenge – specifers should use thermal modelling tools to get a clear idea of energy flows through the facade. Below we take a look at the options.

1 Controls

Thanks to advances in controls technology and falling costs, specifiers can opt for multiple opening and closing parts on a facade. Their position can be varied so that tiny changes have substantial effects on the internal environment. Shading devices, lights and insulation values can also be varied across the facade so they match the sun path and reflect heat to meet the building’s needs.

2 Natural cooling

Night-opening vents in the facade can be operated from a building management system. These open at night to purge the building of stale air and allow the exposed concrete ceiling to cool ready to temper the internal temperature the next day. Problems with earlier models, such as unreliable actuators, have largely been solved.

3 Natural ventilation

A twin-wall facade (two rows of curtain walling separated by a large cavity) can be employed to induce a current of air that vents through the cavity and removes heat and stale air. Twin-wall facades also offer good insulation and acoustic performance.

4 Shading

Shading systems can be built in as part of the facade. They can take the form of external vertical, horizontal or even oblique devices. Control actuators are now reliable enough to install across a facade and strong enough to resist bad weather. This makes possible the integration of passive and active shades that will perform for many years.

5 Solar control

Coatings have been developed that are selective in their ability to absorb or reflect radiation. This means specifiers can opt for glass that rejects more than 60% of the solar energy yet restricts heat loss from the building. Solar energy collection surfaces work in reverse, absorbing nearly all the solar radiation but reflecting very little.

6 Power generation

Photovoltaic cells covering a facade’s opaque areas can be used to generate electricity. However, with current technology, the output is relatively small. Alternatively, the facade can be used as a thermal collector either by direct absorption solar panels or by creating a solar chimney configuration. Energy collected in this way can be converted to cooling by the use of absorption chillers.

7 Insulation

Several manufacturers make highly insulating panels and others provide thermally tuned units that combine mass and thermal insulation. One of the first applications of nano-technology in construction is insulation that contains microscopic particles. Thanks to the tiny particles, the material is 95% air and hence a highly efficient insulator. This is incorporated in facade panels.

8 Acoustics

Use of unequal thickness panes in double-glazing units or multiple laminated glasses achieves very good acoustic performance.

Jointing techniques for glass, framing that leaves no weak points and connectors that are tuned to transfer little acoustic energy have also been developed.

9 Security

“Smart” vents, which allow ventilation but will not allow access to the building and can be invisible when shut, are readily available.

Built-in sensors and wiring loops allow continuous monitoring of the facade.

Check points

• Intelligent facades can be very sophisticated but at a cost
• To ensure success, the whole building will need to be environmentally modelled
• Look at the track record of any system and, if possible, visit an example of it
• It is possible to combine high performance and sustainability
• The facade is only part of the whole. Always specify so it works harmoniously with the rest of the design.