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                    Windows

                    Natural light permeating the inside of a room in CH2
                    CH2’s windows have a number of features that assist in the heating and cooling processes in the building, control glare, and enhance use of natural light.

                    ​The following features are designed to provide a barrier to heat gain into the building in the summer and heat loss from the building in winter:

                    • double-glazing
                    • timber window frames, which are a low conductor of heat when compared with aluminium, reducing the 'heat bridge' effect
                    • external sunshade from balconies (from the floor above) and from fabric shades above doors to each balcony
                    • chilled beams over the window cooling the air and creating a protective curtain of falling cold air across the window when heat gain is an issue
                    • underfloor hydronic heating grilles, located adjacent to the window, providing a protective curtain of rising warm air when heat loss is an issue.

                    Window features

                    Timber window frames

                    All window frames to the north, south and east elevations are timber, rather than aluminium.

                    When resourced correctly, timber is a more sustainable material than aluminium, as well being a product with low embodied energy and well-understood performance and maintenance regimes. In addition, timber is a lower conductor of heat and therefore reduces the ‘heat bridge’ effect that occurs with metal frames.

                    Other features of the timber frames include:

                    • finger-jointed construction used for less waste
                    • windows designed for repair and disassembly (screw construction) and with an anticipated life-span of more than 100 years
                    • laminated fabrication used to ensure a well-sealed and air-tight system.

                    Upper and lower windows and blinds

                    Each window has an upper and lower section, each with a separate blind. This allows the use of blinds to be optimised, which has the following benefits:

                    • The upper section is well-protected from the sun by the balcony above and blinds are only needed in the winter when the sun is very low in the sky. The upper blind also is raised rather than lowered and can therefore be set in an optimum position.
                    • The lower blind is required for sun protection more often than the upper blind. In this instance, the use of the blind is optimised by having only a partial blind, 900mm high. The blind can therefore be set at the optimum level up the window to protect from the direct rays of the sun, without unduly reducing the amount of natural light entering the building.
                    • Staff can control the use of the blinds to optimise the protection from the sun’s rays and the amount of natural light entering the building at any time.

                    Glare control

                    Glare is caused by sharp contrasts and is often treated by brightly lighting inner walls or using blinds. Both of these methods waste energy.

                    CH2 reduces glare while preserving energy by framing external views with leaves on the northern balconies and vertical planters on the south.

                    Additional features to control glare include the use of reveals, external and internal plants:

                    • Reveals (splayed framing) mitigate the contrast between the very bright outside light and the internal, relatively dark wall. This is an old device used particularly in Georgian interior architecture. On CH2, the air supply and exhaust ducts are located on both sides of the windows on the south (supply air) and the north (exhaust air) facades. These ducts give the external wall enough thickness to form reveals to the windows. The half-light on the reveal helps to reduce glare.
                    • External plants: each of the windows on the northern facade has a balcony with trellised planting on each side, running the full height of the building. These plants provide lateral protection from the sun’s direct rays and help control glare by diffusing light.
                    • Internal plants: plants were successfully trialled in the existing Council House for glare control and have been installed in moveable internal planters on each side of most windows on the south elevation which can be subject to glare reflected from buildings across the street.

                    Western timber shutters

                    Exterior view of CH2’s western timber shutters CH2’s western facade features a system of recycled timber shutters that protect the building from the late afternoon sun, while also enabling views out of the building and natural light to enter the building. The shutters are open when the sun is in the eastern or northern sky, closing only when the sun is in the west.

                    As well as providing a responsive sun shade system for the office, the shutters, constructed from reused scraps of Australian hardwood timber, show how materials weather and age over time. Untreated, the shutters will be left to age and go grey naturally.

                    The timber was sourced by Nullarbor Timbers from 200 derelict and demolished houses made from Australian native hardwood species, such as jarrah, ironbark, red gum and blackbutt.

                    The shutters are slatted to maximise the amount of daylight that can be admitted, while still performing their protective function. They move automatically to a pre-set program based on the seasonal position of the sun, regardless of whether the sun is hidden by overcast skies.

                    In summer, the shutters fully close fairly quickly and when the sun is nearly square-on to the building, they then open slightly to stop the sun from penetrating through the slats.

                    In winter, the shutters close more slowly and do not need to close completely as the sun does not get square-on to the building. In winter, the main purpose of the shutters is to protect staff from the glare of the sun’s rays.

                    The movement of the shutters is hydraulically operated using vegetable oil. Power required to operate these is produced by solar photovoltaic cells on the CH2 roof.

                    Natural light

                    CH2 maximises the amount of natural light penetrating the building, reducing the need for artificial lighting.

                    The building’s north and south facades comprise alternate vertical bands of glass and thick concrete walls containing supply-air ducts (on the south side) and exhaust-air shafts (on the north side). The shafts widen towards the upper levels in order to facilitate air supply and exhaust.

                    The windows are at their widest at street level, narrowing at the upper levels. This enables more light to be admitted to the lower levels of the building, where light access is restricted by surrounding buildings and there is less air demand at the end on the air ducts.

                    CH2 takes advantage of natural light by:

                    • locating windows at the highest point of the curved concrete ceilings
                    • having an external ‘light shelf’ on the northern windows that, while protecting the windows from the direct rays of the sun, also bounces natural light into the building
                    • having moveable timber shutters that remain open to catch the morning sun, closing when the sun is in the western sky in the afternoon
                    • careful positioning and use of blinds to the northern windows. These windows are divided into upper and lower sections, each with its own blind. The upper blinds are only needed when the sun is low in the sky in winter. The lower blind is a partial blind (900mm high), to protect from the direct rays of the sun, while still letting in natural light.
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