The Senedd - A Landmark Building

Published 01/03/2021   |   Last Updated 17/02/2024   |   Reading Time minutes

The Senedd and Sustainability


The Senedd Building from a front facing view including the boat statue


The Senedd

The Senedd, this iconic building, is home of the Welsh Parliament.

We are the democratically elected body that represents the interests of Wales and its people, makes laws for Wales, agrees Welsh taxes and holds the Welsh Government to account.

Designed by Lord Richard Rogers and Ivan Harbour and officially opened on St David’s Day in 2006, the Senedd was immediately recognised as a landmark building. The Welsh Parliament is committed to transparent democracy and the Senedd was designed to reflect this.

Find out more about the vision for the Senedd and see Ivan Harbour’s early architectural sketches of the building in our Design at its Heart display in the Pierhead.


Design and Architecture 

With a hundred-year design life, the Senedd features a range of hard-wearing, inert materials. Welsh slate steps bring the visitor upwards from the waterfront and encases the private spaces of the building. A lightweight gently undulating roof shelters both internal and external spaces, and is drawn down to form the funnel over the Siambr. This funnel has a dual function, introducing daylight into the Siambr while a wind cowl at its head draws fresh air through the Siambr space.


The Senedd building from a left fron view.


On either side of the Siambr are two internal courtyards, formed by two deep slots cut into the plinth, which provide daylight for a sequence of committee rooms and offices on the ground floor. These courtyards also add to the transparency of the building allowing views into the private spaces from the public levels above.


Group of people sitting in the Senedd


The building

The Senedd stands on a concrete plinth, featuring columns, beams and slabs.

Over 16,700 tonnes of concrete make up this solid foundation. Chosen for its robust quality and thermal properties, the concrete was cast on site and has a high quality finish. There are many areas of the building where it has been left exposed as part of the buildings aesthetic.

The glass walls of the Senedd represent the transparent nature of the work that goes on inside the building.

The glazing allows natural light in, meaning the ceiling lights, operated by automatic lux meters, are off for most of the day. Some of the windows open automatically; in order to moderate the internal temperature of the building. In more enclosed areas, this ventilation is provided by vents in the floors and ceilings.

 People sitting on sofas in the Oriel of the Senedd


Sustainability features

The Senedd was designed to be a sustainable building from the outset, even achieving BREAAM’s ‘Excellent’ rating at design stage for many of its sustainable features.

The design brief also required the following sustainable criteria to be met:

■ design life of 100 years;

■ use of indigenous materials;

■ minimise energy consumption and waste;

■ application of renewable technologies; and

■ to be “exemplar” in terms of sustainability.



The funnel at the centre of the Oriel is an important part of the buildings ventilation system. The cowl at the top changes direction with the wind, producing negative pressure inside the funnel; drawing warm air out of the chamber and replenishing it with cooler, fresh air from below.


View from inside the chamber looking into the funnel


Above is the view of the funnel from inside the chamber. The lantern at the top of the funnel allows natural daylight in. 

The outside of the funnel and the ceiling are covered in red cedar wood. The wood contains a natural self-preserving oil, meaning it won't need treating for at least 100 years.

On the outside canopy the weathering process has changed this into a pleasant grey colour; contrasting with the wood inside the building. 


The funnel in the center of the Oriel


The design of the building includes a ground souce heat pump, which utilises the temperature of the earth for heating and cooling. This allows some heat to be brought into the building in late summer when the earth is still warm, and reversed in spring when it helps with cooling on sunny days. 

A drawing of how the water pumps work

For extra heating in the winter, a biomass boiler is used. This uses near-zero-carbon wood chips from sustainably-sourced timber as a fuel and keeps the carbon dioxide emissions of the building to a minimum.


Image of the biomass boiler


The roof of the Senedd is also designed to collect rainwater, used for flushing toilets and maintenance activities. It is collected into two 75m3 tanks under the building (that’s 75 tonnes in each tank!) and cleaned using ultraviolet light. Along with other water-saving devices such as waterless urinals and automatic taps, rainwater collection keeps demand for mains water to a minimum. Our monthly supply of mains water is similar to a large domestic property!


A picture of the roof of the Senedd building taken from the Pierhead roof


The Senedd in figures

The Senedd represented a significant stage in the story of devolution in Wales – a story that can be traced back many centuries.


A building of such importance is made up of some pretty impressive figures:

■ Over 1,200 people helped construct the building.

■ The steel roof is made from 421 tonnes of steel with 21,900 bolts and 2,088 connections.

■ The ground source heat pump is made up of 27 boreholes drilled 100 metres into the ground.

■ The area of the building is 5,000m2.

■ There are 89 reflective tubes on the inside of the funnel.

■ The building uses more than 1,000 tonnes of Welsh slate, covering approximately 10,000m2.

■ If all of the timber slats used in the Senedd were put end to end they would stretch for 45 km.

■ The conical mirror that sits inside at the top of the funnel weighs 150 kg.

■ We’ve retrofitted a lot of the lights in the Senedd with LEDs now. So far, they’ve saved more than 60 tonnes of carbon being produced.


All are welcome to visit us here, to see the Welsh Parliament at work.


An image of Cardiff Bay including the Senedd and Pierhead buildings.