Perfect balance

Despite the naysayers it’s clear that global warming is becoming a big issue for the world as temperatures soar to uncomfortable levels. As the mercury rises, so too does the temperature inside buildings, which can be extremely dangerous for vulnerable people.

The fact that UK housing stock is the oldest in Europe means that they are amongst the quickest to heat up and they struggle to maintain a comfortable temperature. Within Britain there is some disparity between houses in the north and south, with English homes heating up by 4.7°C, on average, after three hours, whereas Scottish home temperatures rise by 5.6°C in the same conditions.

The most common solution is air conditioning, but the more people use this to cool their homes, the greater the UK’s energy consumption. This will in turn put huge demand on the energy grid. In fact, according to a report from Rethink Energy, global utilities will need to lay on more than 1,500TWh in fresh power resources – collectively about the same amount of electricity that India supplies to its 1 billion citizens.

It’s not just hot summers that need to be considered when it comes to keeping the inside of buildings a comfortable temperature. As we experience more fluctuations through the winter months, keeping homes warm can be an issue for many buildings too.

Thinking ahead

The fact that around 40% of the UK’s total carbon footprint comes from buildings means it’s vital that innovative systems are introduced to help decarbonise the UK.

Although the government has unveiled plans to install 600,000 heat pumps a year by 2028 to improve buildings’ performance, there still needs to be a partnering with other technologies to meet zero emissions targets.

While solutions such as heat pumps and air conditioning are good options for existing buildings, Thermally Activated Building Structures (TABS) are the way forward for new builds, according to REHAU Building Solutions.

“TABS fits the bill here – their larger surface areas mean cooler water temperatures can be used to distribute heat, making structures using the system ideal for integration with low-temperature heat pumps,” explains Franz Huelle, head of technical at REHAU Building Solutions. “Alongside this, TABS reduce the demand for cooling at warmer times as heat is continually regulated throughout the day. In turn, this further increases sustainability. In the right circumstances, TABS can produce up to 80% less operational carbon dioxide than a traditional HVAC system.”

How does it work?

TABS refers to innovative systems of pipework that are embedded within a building’s concrete structure that heat or cool the entire premises. This is achieved by circulating either low-temperature hot water through the pipes to provide space heating, or running an elevated chilled water temperature that enables cooling via radiant and convective absorption.

“As the building’s elements are actively regulated, TABS can help lower peak load requirements, instead using the structure’s dynamic thermal behaviour to offset this demand,” explains Huelle. “This is because the process activates the concrete’s large thermal mass, acting as a buffer for the day’s changing cooling or heating loads.

“An example of this in action can be seen during the evening, when natural cooling takes over as outdoor temperatures fall. This makes the system more cost-effective and energy-efficient when compared to other temperature control strategies.”

What are the benefits?

TABS are thought to be beneficial in a number of ways, including high thermal inertia, large surface areas and radiative heating and cooling that facilitates the use of low-carbon energy sources. Additionally, these systems can also lower construction costs and improve indoor conditions, according to REHAU.

By making use of a building’s existing thermal capacity, TABS have the potential to create more space. As less air conditioning is required in TABS, smaller ventilation air systems are required. This means potentially fewer services are needed, freeing up space between concrete floors and ceilings where they would normally be laid. By reducing this dependency on suspended ceilings, developers using TABS can potentially recover an extra level every 10 floors.

“TABS also eliminates the need for radiators,” explains Huelle. “For high-rise properties in urban centres where space comes at a premium, this is a key concern.”

This technology uses water for thermal transfer as opposed to air, so less energy is needed to maintain environments within a comfortable temperature range. REHAU notes that operating costs are comparatively lower than other HVAC systems because TABS use radiant cooling, which means minimal maintenance costs after installation.

TABS can also be made using off-site modular techniques, which speeds up construction times while lowering labour requirements and costs. According to REHAU, situating the cooling and heating system within a building’s concrete structure, project costs are reduced by between 20-30%, resulting in more cost-effective construction.

“Additionally, occupier health and comfort are enhanced with TABS,” adds Huelle. “This is because radiant exchange means heat from occupants, lighting and other sources flows to the system’s cooled surface. By doing so, air temperature is kept unaffected regardless of the building’s furnishings or occupants.

“The draught-free heating and cooling also means that airborne pathogens, allergens and volatile organic compounds are less able to travel, so those using the premises are better protected against issues such as Sick Building Syndrome.”

What are the typical applications?

Although TABS have been used in Europe for the last 20 years, the technology is relatively new to the UK market, with just a few landmark projects to date.

“Where they are used, it is typically for larger buildings such as offices, educational buildings, hospitals, shopping centres and sports arenas,” says Huelle. “It must be noted that TABS are growing in popularity for these applications, as it is more cost-effective and energy-efficient to counterpart systems used in larger structures. This is because using water flow to influence the temperature of concrete eliminates the need to regulate temperature in individual rooms within large buildings that may have different load requirements. Instead, the building’s mass operates like a living organism to maintain comfortable conditions whilst reducing the demand for cooling systems.”

What are the installation methods?

“There are three main installation methods for TABS,” explains Huelle. “The first, using in-situ concrete slabs, allows for larger circuits and minimal connections within the structure. It can sit anywhere within the structural slab and roughly 300m2 can be installed per day when two people work together. The second method of installation uses pre-cast planks made off-site, allowing for a quicker installation and easier connection with other building services.

“Thirdly and finally, contractors can use pre-fabricated mesh for the same purposes as pre-cast concrete planks to speed up installation. Ideal for reverse return systems, this installation method offers better outputs when near the slab surface. This method is available either for conventional TABS modules, or for near surface TABS, otherwise known as sTABS, which use smaller 14mm pipes situated closer to the soffit for boosted cooling and improved response time.”

With all the benefits that TABS offer it’s clear to see why this method has proved to be extremely popular in Europe. As temperatures become increasingly volatile it’s likely that this type of technology will become more commonplace in the UK as we strive to reach net-zero carbon.

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