Sustainability at the Senedd: Keeping Bills and CO2 Emissions Down

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The Senedd, the Welsh Parliament building in Cardiff Bay, might conjure up images of debates and politicians. But beyond the world of policy, the Senedd boasts some seriously impressive sustainable features.

The Senedd building is constructed with eco-friendly materials in mind. Recycled and low-carbon content materials were used whenever possible, minimising the environmental impact. They even incorporated durable and sustainable options like using local materials such as 1000 tonnes of Welsh slate for the floor of the building. Canadian western red cedar was also used as a responsible choice that reduces the need for harmful chemical treatments as the wood contains a natural self-preserving oil, meaning it won’t need treating for at least 100 years.

The sustainability features of this building are very impressive, but to explain simply, let’s split the building’s feats into four main sections: water, lighting, cooling and heating:

Cloud with raindrops


Did you know that the Senedd has a 6,000-square-meter steel roof? This rooftop acts as a natural insulator, keeping the building cool in summer and warm in winter. Rainwater is collected from the roof and stored in a large tank which holds as much as 100,000 glasses of water. This is known as ‘grey water’, which is used for flushing toilets and maintenance activities. The water is stored in two huge tanks under the building and cleaned using ultraviolet light.



The Senedd’s architects were all about maximising natural light and ditching overhead fluorescents. Strategically placed windows help to bathe the Senedd building in the sunshine, creating a bright and airy atmosphere that’s proven to boost mood and productivity – a benefit for both staff and visitors.

While some lights are necessary, the Senedd doesn’t settle for outdated bulbs. Their system is high-tech, with built-in sensors that adjust brightness based on natural light. Sunny day? Lights dim automatically. Overcast? They provide a little extra illumination. It’s a smart and efficient way to keep the space well-lit without wasting energy.

Thermostat with snowflake


The Senedd has a unique funnel-shaped feature. It’s not just there to look cool (although it does that too). There is a large circular window at the top of the funnel in the Siambr. A conical mirror reflects daylight inside. In the funnel, attached to a steel frame, are 89 reflective aluminium tubes that help to do this. This funnel also cleverly helps circulate air throughout the building naturally. In the summer, it acts like a giant chimney, pulling warm air up and out. This means less reliance on energy-guzzling air conditioning.

Thermostat with sunshine


The building includes a ground source heat pump, which uses the temperature of the earth for heating and cooling. For extra heating in the winter, the Senedd uses a biomass boiler, which uses recycled, near-zero-carbon wood pellets from sustainably sourced timber as a fuel and keeps the carbon dioxide emissions of the building to a minimum.

Fancy a visit?

If you’re keen on tackling climate change, supporting local business, or architecture, a visit to the Senedd is an absolute must. Take a look at our handy guide to the Senedd for help planning your next trip there.

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