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Key Environmental Features

Environmental Modelling

Environmental modelling was carried out at the pre construction phase studies, which indicated that the building has excellent energy consumption figures. The design team of BDSP, Arup and Richard Rogers Partnership, led by Taylor Woodrow, believe the design reflects a “green” building whilst not compromising the comfort of those within it.

Ventilation and Lighting

The funnel, wind cowl and lantern are key to ventilation and lighting in the Siambr.

A diagram displaying the natural ventilation in the Senedd building

The roof plane turns down to form a funnel over the debating chamber to allow natural daylight into the space and allow air to be naturally extracted. At the top of the funnel sits the roof cowl and lantern structure. The cowl allows hot air to be exhausted as required and the lantern allows natural daylight into the debating chamber. The roof cowl is designed to rotate with changes in wind direction. This produces a negative pressure on the leeward side of the cowl that allows warm air to be drawn out of the Siambr.

The Lantern

Senedd Lantern

The lantern allows natural daylight into the Siambr. A conical mirror within the lantern reflects additional daylight into the Siambr and this can be lowered to control daylight levels to suit broadcasting requirements. There are a series of concentric aluminium rings with recessed light fittings on the inside of the funnel.

Natural Ventilation

Diagram displaying Natural Ventilation in the Senedd

To reduce the building's overall energy consumption natural ventilation has been incorporated as the primary source of ventilation to virtually all areas of the building. By utilising the structural design (i.e. exposed concrete slabs utilised for their thermal mass), it has been possible to eliminate air-conditioning to all the offices and other similar functional areas. In these spaces, air is introduced into the offices via dedicated floor outlets and is allowed to escape to the atmosphere either via roof vents or openable windows. All of these areas can be controlled individually.

The "normal" mode of ventilation is natural ventilation whereby the purposely designed roof cowl rotates with changes in wind direction to produce a negative pressure on the leeward side of the cowl which then allows hot air to be drawn out of the debating chamber to the outside. During periods when occupancy levels are increased, or when there are increased casual/thermal/solar loads or even whenever the users of the chamber wish to control the temperature to stricter temperature control bands, these areas will have the facility to switch to air-conditioning mode. This pushes cooler air into the space via outlets in the floor.

Through close interaction of the environmental design with the structural design, it has been possible to eliminate air-conditioning to all the offices and other similar functional areas. In these spaces, air is introduced into the offices through outlets in the floor and is allowed to escape through to the outside whether through bespoke roof vents or windows which open.

The Siambr, Committee Rooms and associated public viewing galleries are serviced by a mixed-mode ventilation system, which offers both natural ventilation and air-conditioning. During periods when occupancy levels are higher or when there are increased casual/thermal/solar loads or when members in the siambr wish to control the temperature to stricter temperature control bands, the areas can be switched to air-conditioning mode. This pushes cooler air into the space via outlets in the floor.

Earth Heat Exchanger System

The ground is used as a heat source/sink in the form of earth heat exchangers, coupled with heat pumps to reduce the size of conventional boilers and dispense with the need for chillers. The ground source heat pump system (GSHP) or geothermal heat pump system, will also provide low grade heat which can be used for the underfloor heating system. The attractiveness of the GSHP system lies in its coefficient of performance (i.e. the relationship between how much energy you expend to produce energy, or heat in this case) which is two or three times higher than that of a conventional chiller, so that primary energy consumption and associated emissions are correspondingly reduced.

The system relies on the constant temperature of the earth for heating and cooling through a system of underground pipes. In the winter, heat is transferred from the warmer earth into the water in the underground pipes to provide underfloor heating. In the summer, the system reverses and takes hear from the building and deposits it to the cooler ground.

Biomass Boiler

In order to reduce the carbon-dioxide emissions for heating to a minimum, and consequently achieve the highest Building Research Establishment Environmental Assessment Method BREEAM rating ever achieved in Wales, Taylor Woodrow have utilised wood (biomass) as a combustion fuel source. Being essentially environmentally friendly, it has been recommended that wood chips or wood pellets can be used as the fuel source, both of which are available locally. The boiler installed has the ability to process both wood chip and pellets.

Rainwater Harvesting

One of the water saving measured used on the building is the collection of rainwater from the roof, known as rain water harvesting. Water is collected from the main roofs and stored in two 50,000 litre tanks for use in the building. This is the primary supply of water for flushing the WCs, irrigation and maintenance. Used in conjunction with water saving devices the demand for water has been cut to a minimum.

Benefits to the Economy

Where possible, and subject to EC procurement regulations, indigenous materials and labour have been used. Some 36% of the total contract price of £40.997m has been spent on Welsh labour and materials. Whole life costing was key to the selection of materials. The extensive use of slate in and around the building, illustrated this point. Whereas the use of carpet as a floor covering would have been cheaper initially, over the life of the building it would have proved significantly more expensive than the slate.

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