Facades contribute to controlling heat loss and gain.Active, ventilated facades afford high thermal performance and can respond to daily or seasonal changes. Natural ventilation through the building via opening windows in the facade can reduce the internal temperature. will achieve a cool interior. Such facades reduce energy costs.
Active facades also improve comfort levels. They enable sufficient light to enter whilst minimising glare for occupants and neighbouring buildings, and also reduce noise ingress.
In 2006 the refurbishment of a 1960's tower block, the highest building in Ireland, owned by Cork County Council was completed.Along with a complete internal refit and the provision of additional office accommodation including a new concourse and council chamber, this tower was re-clad with a Colt active glass louvre secondary façade system covering over 1400 m2 of facade, for the east and west facades.
In this case, the installation of the active façade not only met all of the above mentioned objectives, but also avoided the need for air conditioning. It also dramatically improved the appearance of the building.
Working with Shay Cleary Architects, who won a design competition for the building, the consultant Arup and Main Contractor Rohcon, Colt was able to demonstrate expertise with such façade systems, and could meet the design specification following extensive in-house testing at its Havant test facility. Such tests were essential to prove both dynamic effectiveness and structural stability, and included tests of windloads, impact, wind resistance and glass louvre structural integrity.
The secondary façade consists of pre-assembled sub-frames measuring the height of one floor x 1.2m wide.These were lifted into position in a similar manner to a unitised curtain walling system, and were fixed to adjustable support brackets off the perimeter walkway supports. Each louvre blade of the Colt glass louvre system consists of 12mm laminate glass supported on extruded aluminium brackets, which in turn are pivoted on the supporting mullions. Each bank of louvres is automatically controlled by actuators, connected back to the buildings BMS with manual overrule.All moving components are stainless steel on teflon impregnated bushes with a design life of twenty-five years.
Key building fabric elements have been designed in order to facilitate effective natural ventilation of the main areas.At the same time the scheme achieves maximum energy efficiency by controlling the façade elements so that the building is in unison with the climatic environment.
In summer the elevation opens up and provides shading, while in winter the elevation can wrap up, collecting solar gains and protecting the occupants against the wind. Natural ventilation is facilitated primarily by high and low level openable windows. Draughts associated with natural ventilation are addressed by controlling the tilt angle of the external louvres. On cold windy days these act as a buffer to pacify the wind and create a cavity space that allows the air to pick up solar energy before entering the office. On warm summer days the louvres are opened fully so that the air is not overheating the occupied spaces.
The efficiency of the ventilation is further enhanced by relatively shallow office depths and high clear ceiling heights.As in any naturally ventilated non air conditioned building a crucial issue is the control of solar heat gains.Thus in summer the louvres are angled to reflect unwanted solar gains away from the interior. In winter the louvres are adjusted so that beneficial solar gains can be harnessed to reduce heating requirements.