Keeping Tabs

Franz Huelle, Technical Manager for Building Solutions at REHAU, explains how new technology is helping maximise energy efficiency and keep buildings cool.

As scientists ramp up warnings of unprecedented heatwaves and climate change, new solutions are being sought to improve the thermal modulation of buildings’ fabric. In 2023, the UK experienced the climate phenomenon known as El Niño. Bringing record temperatures to much of the UK, buildings and infrastructure were put under unprecedented levels of structural stress. We must adapt quickly to deal with new extreme levels of heat.

Building specifiers and contractors who want to tackle the heightened risk of buildings overheating are turning to thermally activated building structures (TABS). TABS utilise the large thermal mass of concrete building structures as a buffer for the changing temperatures during the day. It achieves this by running hot or cold water through pipes within the slab. Used on various excellent-rated BREEAM and Passivhaus certified projects across the UK, the technology is proving itself an efficient low-energy cooling system.

This kind of concrete core tempering (CCT) applies the principle of using the thermal storage mass of building components for constant heating/cooling. The thermal energy absorbed by the building component in the case of cooling is dissipated via integrated pipes. In the case of heating, the pipes heat up the building component, which can release the heat to the room again via the surface. Thanks to the high insulating standard of the building shell and the large-area energy exchange in CCT primarily due to radiation, only slightly higher or lower surface temperatures are required compared to the room temperature to modify internal temperatures.

There are three installation methods: in situ concrete slabs, which can sit anywhere within the slab and make large circuits possible; precast concrete planks, which are created off-site but are quick to install on-site with easy connections to building services; and prefabricated mesh, which offers fast installation and better outputs when near the slab surface, and can be used for post-tensioned (PT) slab applications.

Smart controls

The technology has low investment and operating costs and makes use of alternative energy sources to increase comfort levels and reduce drafts. The individual room control requires the separate control of the heating surface of a room, as well as a strict thermal separation of the heating surfaces of the individual rooms from each other. The aim of individual room control is to reduce the energy consumption of buildings and prevent overheating in rooms.

TABS can be enhanced by pairing with smart control systems that help increase energy efficiency and reduce carbon emissions, especially with predictive smart controls based on weather forecasts. The large thermal mass of TABS demands a non-standard control strategy, as a mismatched control strategy can lead to overshooting of a room’s temperature, particularly when starting the system or when conditions are changing by a large margin. However, it is now possible to achieve the perfect match of TABS and controls to deal with high thermal mass. As well as being able to cope with standard radiant heating and cooling systems in the floor or ceiling, this new technology provides a holistic solution to entire building temperature control and makes more efficient heating a reality.

By pairing radiant cooling systems with smart controls, the performance and efficiency of new buildings can be maximised. The Met Office recently said that the number of extremely hot days in the UK could increase fourfold from ten days to 37 days a year with a 4°C increase in global warming. While these figures are worrying, they explain why more building specifiers are searching for technologies that reduce the consequences of overheating.

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Image credit | Adam Coupe Photography



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