Tall, slender columns punctuate the internal valley. These burgeon into a canopy-like covering of leaf-shaped panels inspired by China’s native ginkgo trees. The columns support a flat, slender roof that overhangs the 150m x 150m square building. A series of skylights punctuates the roof, flooding the interior with daylight filtered through the ginkgo-leaf canopy.

A 16m-high glazed façade wraps around the giant building to ensure its spectacular interior is on display to passers-by. The glazing is self-supporting, without so much as a steel strut or glazed fin to mar its transparency. The façade’s designers, Eckersley O’Callaghan (EOC), say this is the largest self-supporting glass façade in China and the tallest of its type ever completed.

It was an achievement recognised by the judges of the Society of Façade Engineering Façade 2024 Design and Engineering Awards, when the scheme won the International New Build category. The judges described it as: ‘A beautiful, sculptural yet highly technical and complex design – superbly detailed.’

EOC’s involvement with the project started in 2018, when it was appointed as façade consultant to the scheme’s architect, Snøhetta, after it won the international design competition with its scheme to ‘reinstate the library’s relevance in the 21st century’.

The firm’s role was to develop the façade concept to ensure it would perform as intended, while rationalising the detailing so the scheme could be built by local teams. ‘We helped steer the design direction and, by liaising with contractors and fabricators, were able to understand the costs and buildability of the various façade proposals,’ says Minxi Bao, associate at EOC.

The architect’s initial concept was based on a glazed façade formed from a series of vertical, 3.2m-wide, curved glass panels – like giant, semi-circular sections of transparent channel stood on their ends. The glass was positioned so that it curved in opposite directions on adjacent panels, to give the walls a rippling, corrugated appearance.

The benefit of this solution, from a structural perspective, was that the curve helped the panels to resist loading, says Bao: ‘We liked the idea, because it gave the façade significant geometrical  stiffness, but we understood it would be a challenge to fabricate curved units at this scale.’

EOC went to the world’s leading glass suppliers to find a potential manufacturer for the curved panels. The engineer asked for feedback on the manufacturing feasibility of the panels at two heights: 16m and 20m. This showed that, while it was possible to realise the concept at both heights, the cost of doing so would have been ‘prohibitively expensive’, according to Bao.

Developing an economical solution

EOC set about developing a more economical façade solution that would not compromise the architectural concept. It changed the glazing from curved to a more pragmatic flat panel, which it arranged in a zig-zag fashion. ‘We came up with a pleated solution using flat panels that would be cheaper to manufacture and easier to build,’ explains Bao.

Working with the architect, the engineers also opted for the lower roof height of 16m, to ensure a buildable design that would keep the scheme within cost and buildability constraints.

In-depth structural analysis was carried out on the folded plate proposal to establish the depth and modulation of the plate, the relative stiffness of joints and the required thickness of glass. Specific areas of the façade – such as the building’s corners and its interaction with the portal frames spanning the entrances – also required detailed investigation to ensure the solution’s viability.

To accommodate the vertical movements of the roof, the top connection to the main structure features a slotted hole, allowing the roof to deflect downward by 50mm and upward by 30mm, without loading the glass

The flat, insulating glass units that make up the zig-zag walls are 15.8m high and approximately 2.5m wide. They are assembled from a laminated outer glazed unit comprising five panes of glass bonded together by SentryGlass interlayers. This is backed by a slimmer, two-ply inner unit. The interlayer allows the separate glass plies to act as one. The gas cavity is created by a spacer bar and sealant around the perimeter of the glass panes.

Mechanical connections were investigated for the glass-to-glass connections between adjacent panels, potentially involving cast-in inserts within the glass.

Ultimately, for visual clarity, a simple structural silicone-bonded joint was adopted to attach the vertical edge of one unit to that of its neighbour. ‘The units don’t have any intermediate support along their vertical edges, so all the load needs to be resisted by the glass,’ says Bao.

The panel’s zig-zag arrangement is highly beneficial, enabling the giant glazed panels to work together to efficiently resist wind loading on the façade. Bao explains: ‘If we’d designed a completely flat façade, the glass would have had to be really thick, because we’d end up having to use a significant number of layers [to give it sufficient stiffness]; by adopting a pleated solution, we are able to use the in-plane stiffness of the adjacent glazed units.’

Accommodating roof movements

The glass façade’s design and detailing was engineered to accommodate both vertical and horizontal movements of the main structure, caused by dead loads, wind loads and seismic loads. EOC’s relatively simple solution was to accommodate roof movement in the steel retaining channels at the top and bottom of the glazed units.

Each integrated glazing unit (IGU) has a stainless-steel profile, factory bonded to its top and bottom edges. The profiles slot into steel channels at the top and bottom of the units. These are attached to the building’s structural steel frame. Polytetrafluoroethylene (PTFE) bearings line the sides of the steel profiles to enable the IGUs to slide smoothly up and down, left and right (for the in-plane horizontal) within this channel restraints.

It was not wind loading, but seismic movement that provided EOC with one of its biggest challenges – and, in particular, the interaction of the glass wall with the roof.

‘Beijing is at the junction of three seismic zones, the capital city does have a really high safety factor for earthquake action in the Building Codes,’ says Bao.

Under the worst-case seismic scenario, the building’s sizeable roof, which is held aloft on the grid of slender vertical columns, was predicted to sway by up to 120mm horizontally.

To accommodate this in-plane lateral displacement, steel hemispherical rockers positioned at the centre point of the bottom of a glazed panel allow the IGUs to rock left and right.

Vertical deflections of the main structure are either caused by dead loads, or wind loads. To accommodate the vertical movements of the roof, the top connection features a slotted hole, allowing the roof to deflect downward by 50mm and upward by 30mm, without loading the glass.(see diagram) .

EOC worked closely with the structural engineer in developing the supporting solution to ensure the building’s structure wasn’t over designed and that the architect’s vision was maintained.

To comply with Chinese code requirements, EOC used Finite Element Analysis to model the facade in detail and quantify its performance and capability to accommodate the main structure’s movements.

Controlling solar gains

The architectural requirement for the façade to be self-supporting and free from framing precluded the use of openable vents to allow passive ventilation of the giant reading room.

To keep the interior comfortable in Beijing’s hot summers and cold winters, the glazed panels have a U-value of 1.6W/m²K. Solar gain is controlled primarily by overhanging the roof, shading the façades. In addition, a bespoke high performance low-E coating applied to the glazing gives it a g-value of 0.24, to further limit the amount of heat transmitted through the glass. ‘The glass fabricator customised a specific coating for this project to ensure performance parameters would be met,’ says Bao.

On the east and west elevations, the façade varies in height from 15.8m to 8m, where it rises over a plinth of terracotta blocks, which provide a decorative facade. The 30mm-thick blocks, which are 450mm high and 2,100mm wide, appear to be bonded to the glass, but are actually attached to a subframe hidden behind.

In addition to extensive digital modelling, visual mock-ups of the façade were made to assess the quality of light transmitted to the reading room, which Bao says, ‘is quite subjective’.

The engineers were fortunate that there was no requirement for fire-rated glazing or for fire compartmentation within the glass façade. There was, however, a requirement for 120-minute separation at the glazing interface with the terracotta. This was provided using a steel plate and fire-stop detail.

From an acoustic perspective, the mass of the giant laminated glass units meant the façade’s acoustic requirement of 30dB Rw+Ctr (where Rw is the weighted sound-reduction index in decibels and Ctr is an adjustment factor to account for low-frequency noise) was satisfied for the reading room without additional acoustic treatment.

The façade developed by EOC, also helped to reduce both embodied and operational carbon.

The pleated facade provides the glass with additional stiffness, reducing the amount of material required, which cuts embodied carbon. Furthermore, additional heat energy is required to curve a glass panel, and so, moving from a curved panel arrangement to a flat panel arrangement, meant that the embodied carbon could be further reduced.

With regards to operational carbon, the use of a curved panel would have limited the number of available coatings that could have been applied compared to a standard flat panel. Hence, making use of flat panels meant that the glass could have a better thermal and solar performance, allowing the building to use less energy to heat and cool the library.

The façade also contributed to the building achieving three stars, the highest level, under China’s Green Building Evaluation Label.

The spectacular library opened its doors to the reading public in December 2023, reaffirming the library’s relevance in the 21st century. No wonder the SFE Awards judges were impressed.

The post A new chapter in façade design: Beijing’s unique new library appeared first on CIBSE Journal.

The property company manages a portfolio valued at £13bn – of which it owns £8.9bn – and is aiming to achieve net zero carbon by 2030. Central to this ambitious goal is the replacement of gas boilers with heat pump systems in its properties.

The transition from fossil fuels started in 2012 with the installation of a hybrid heat pump system at 350 Euston Road, where heat pumps work in tandem with gas boilers to meet peak heat demand. In its latest project, British Land has replaced four gas boilers with heat pump chillers at its York House headquarters in London and says it will be the blueprint for future energy retrofits.

Template for transition: York House retrofit

Screenshot of the dashboard view of the new heat pump

The retrofit of York House involved the replacement of four gas boilers and chillers with two parallel 4-pipe air source Climaveneta heat pumps, which concurrently supply chilled water and heating to the low-temperature heating system. Climaveneta is part of Mitsubishi Electric.

‘The benefits of using 4-pipe heat pump chillers is that there’s a year-long cooling load, and we get to use some of the rejected heat from that process to heat the building,’ says Daniel Valente, head of projects at Nationwide Air Conditioning.

Other improvements to the HVAC system included the introduction of indoor air quality (IAQ) controls for ventilation, a full validation of the fan coil units, and confirmation of water flow rates and temperatures.

The previous gas boilers had 1.3MW of heating capacity, while the new heat pumps have a heating capacity of 600kW, with a duty standby arrangement and a combined cooling capacity of 1.2MW.

The project has resulted in a 57% annual decrease in HVAC energy usage, and electrical energy use has reduced from 982MWh in 2019 to 419MWh for the 12 months up to September 2024, even with heating and cooling moving from gas to electric.

An advanced building model, in line with the Nabers UK standard, was built to identify what the peak loads would be.

‘We came up with a proof of principal that we could actually utilise a 95% peak load design to minimise the equipment size, but also to optimise the project costs. It enables us to start controlling the building on a demand-driven strategy,’ says Draper, of Twenty One Engineering. The design was validated by the operational gas profiles of the building, he adds.

The system maintains a temperature of 17°C when the building is unoccupied, says Draper. This reduces the time needed to heat up the building, which maximises the efficiency of the heat pump.

One challenge was to ensure that a flow temperature could be maintained that was hot enough to heat the building at all times, says Valente. ‘We needed to ensure that we were able to increase the flow temperature at periods of high load, so we installed a second-stage water-to-water heat pump,’ he adds.

The unique aspect was that there was no hydraulic separation in the LTHW system, and a much lower heating capacity. ‘The water-to-water heat pump only injected heat when needed to meet the building heating load required during the winter months,’ Valente says.

The benefits of this were higher operational efficiencies, lower initial capital costs, and a simpler installation.

Key to British Land targeting net zero carbon is the adoption of ISO standards 50001 Energy Management and 14001 Environmental Management, as well as the Nabers UK rating scheme, which provide frameworks for measuring and reducing energy use. ISO 50001 Energy Management is used to monitor and improve the energy performance of its buildings, and ISO 14001 Environmental Management to measure and continually improve other areas of sustainability.

‘ISO frameworks demonstrate that we are operating in line with our commitments, and that we have clear objectives and goals that we are working towards,’ says John Gentry, British Land’s head of technical services and sustainability. 

CIBSE Certification offers UKAS-accredited certification for ISO 9001, 14001, 45001 and 50001 and, last year, took over from the BRE as the scheme administrator for Nabers UK, the operational energy rating scheme. CIBSE Certification certified British Land’s environmental and energy management systems. 

One of two four-pipe heat pump chillers installed at York House. Credit: Mitsubishi Electric

Nabers UK, which has its roots in Australia, has two UK products – Design for Performance (DfP), which drives energy efficiency in new offices, and Nabers Energy for Offices, which measures the energy efficiency of existing offices. British Land is keen to use Nabers Energy for Offices to monitor the performance of existing buildings, including retrofits such as York House. It is using Nabers DfP to accurately predict energy performance of new buildings such as 1 Broadgate. 

The strength of the rating is that energy data has to be validated annually, allowing the continuous monitoring of plant, says Matthew Beales, British Land’s head of technical project delivery. 

British Land has long invested in sub-metering. This has been key for ISO 50001, which requires metered data to be submitted annually. ‘The system gave us the granularity of data to be able to really drill down into the profiles of our buildings and see how they were being operated – and where we were using energy unnecessarily,’ says Gentry. 

British Land’s Credit 360 data management system records, tracks and analyses building data, including energy and water consumption. It can identify anomalies in performance – so, if an occupier’s energy or water use spikes, the system flags it, allowing for investigation and resolution of the underlying issue.

Geoffrey Brophy, British Land technical services manager, is responsible for data quality. ‘I like to know what’s going on in the building that I’m responsible for from an energy point of view,’ he says. ‘I don’t want to sit in front of an occupier and not know what I’m talking about.’

Phil Draper, managing director at Twenty One Engineering, says British Land’s metering and data systems made meeting the ISO requirements relatively straightforward. ‘Most were already within British Land’s culture. It already had internal auditors, for example,’ he says.

Meet the Nabers UK

British Land has a long association with Nabers UK, having been on the working group that established the rating scheme in the UK. 

‘We need to look beyond modelled theoretical certifications, such as EPCs and Breeam, and look at actual operational rating targets, such as Nabers UK,’ says Matt Webster, the property company’s head of environmental sustainability. 

British Land was the first in the UK to receive a Nabers UK DfP target rating certificate for the 1 Broadgate office in London, which is due for completion this year. ‘In projects such as Broadgate, we can see the benefit of Nabers UK in terms of efficiency, the collaboration between the design team and the property management team, and supply chain,’ says Webster.

The refurbished interior at York House

The detailed energy modelling required by Nabers UK means that British Land has the confidence to use more efficient plant and more sophisticated control philosophies in new and existing buildings, he adds.

While British Land is leading the efficiency drive, there is a growing awareness among its customer base about Nabers UK and building performance, Webster continues.

‘At York House, there are some pretty big occupiers that have set their own climate goals and climate strategies to which the building can then respond,’ he says.

Webster is ‘really pleased’ that CIBSE is now running and administering Nabers UK. ‘The technical capabilities of CIBSE Certification as an independent organisation are fundamental to the integrity of standards such as Nabers UK. It ensures the ratings are properly verified and understood,’ he says. l

For more on Management Systems Certification at CIBSE Certification, including ISO 50001, go to: cibsecertification.co.uk/management-systems

For details of Nabers UK, visit:
cibsecertification.co.uk/nabers-uk

The post British Land’s heat pump retrofit at York House appeared first on CIBSE Journal.

Although local authorities have generally adopted a ‘fabric first’ approach to their housing decarbonisation strategies, we felt there was a need for greater focus on the importance of rapidly decarbonising heat, and how to do this in an affordable way.

With this in mind, we recommend, as the first step, retrofitting a heat pump alongside basic fabric efficiency improvements, adequate ventilation, and photovoltaic panels. This delivers an immediate emission reduction of around 80% to 90%, while operational costs should be similar to, or much lower than, a fossil fuel boiler.

We recommend further fabric efficiency improvements over time, as parts of the building naturally need to be repaired or replaced, to eventually reach levels recommended by LETI.

This approach mirrors that of the Association for Environment Conscious Building’s (AECB’s) step-by-step retrofit programme, the Superhomes programme in Ireland, and the UK Passivhaus Trust in its recent paper The right time for heat pumps.

How much, how fast?

Required rates of heat pump deployment were modelled by applying the Climate Change Committee’s (CCC’s) Sixth Carbon Budget recommendations to Cornwall’s housing stock. These include an end to the replacement of off-gas grid boilers from 2028 and on-gas grid boilers from 2033. We did not apply the CCC’s assumption that 11% of homes will use hydrogen boilers, as we could not find evidence to support this approach.

We also reduced the proportion of district heating to account for the lower density of heat loads in Cornwall, compared with the national average. There could be a future role for geothermal heat via heat networks, if it turns out to be cheaper than individual heat pumps.

We also expect individual heat pumps connected to ambient temperature borehole arrays to play a role. The modelling indicated that, by 2030, 16% of existing fossil fuel heating systems will need to be replaced with heat pumps, increasing to 46% by 2035, and 77% by 2040.

Understanding heat pump readiness

A key question with a heat pump-led approach to retrofit was whether existing homes would be ‘heat pump ready’. A common misconception with heat pumps is that they won’t work efficiently, or at all, in poorly insulated homes.

The reality is that a heat pump is indifferent to its surroundings; it just moves heat from one place to another and will work as long as it, and the heat emitters, are large enough to meet the dwelling’s peak heat load at the design flow temperature.

For each retrofit, three levers can be applied to achieve heat pump readiness: reduce the peak heat demand through fabric efficiency; increase the heat emitter size; and increase flow temperatures. The optimum balance between them will be different for each home, depending on the desired split between upfront cost versus operating costs.

The main physical constraint facing most homes in Cornwall is their electrical supply capacity. This is determined by the electricity cable that runs from the street to the house, the electricity meter, and the main fuse. While a domestic single-phase supply can, in principle, supply a maximum of 24kW of electrical capacity, some distribution network operator (DNOs) only offer up to 19kW as standard, and older homes may have as little as 7kW. Upgrades are often paid for by the DNO, but can take some time to complete, which can be an issue in the case of emergency boiler replacements.

The largest single-phase heat pumps draw about 6-8kW of electricity under peak demand conditions, which corresponds to a heat output of around 14-18kW. This means that, even with a modern electrical supply, homes with a peak heat load of more than 16kW will need fabric retrofit work, a secondary heating system, and/or a three-phase supply.

Heat pump readiness in Cornwall’s housing stock

To predict the heat pump readiness of Cornwall’s housing stock, we used stochastic Passive House Planning Package (PHPP ) modelling – which accounts for variability and uncertainty – and calculated 5,000 versions of each building typology with a range of parameters that affect the peak heat load.

We adapted the PHPP calculation to adopt key elements of the MCS heat pump sizing methodology, such as the external and internal design temperatures, airtightness and ventilation assumptions. Parameters were varied for different levels of fabric performance, shading, orientation and form (detached, semi-detached or mid-terrace). This enabled us to predict heat pump readiness more effectively, by understanding best- and worst-case scenarios for typical building types. The results of the PHPP modelling indicated similar ranges of heat loss to industry heating load tools from organisations such as Panasonic and Heat Geek, for different age properties.

Combining this with Energy Performance Certificate data on floor area and age, we were able to determine that 70-80% of homes are expected to be heat pump ready. Some upgrades to the electricity supplies may be necessary, while upgrades to heat emitters and fabric may be desirable. (See Figure 2).

What about costs?

Ensuring good efficiency is the foundation of achieving low operational costs and is an effective approach for all homes. The Electrification of Heat Demonstration Project reported an average efficiency of 290% across around 740 homes with heat pumps. However, the best installers are routinely delivering efficiencies of 340% on their systems, while mature markets in Europe are doing even better.

Dynamic tariffs and solar

While efficiency is important, a heat pump’s superpower is that it can use dynamic electricity tariffs and solar. Unlike gas, wholesale electricity prices vary constantly throughout the day, as demand and the generation mix change.

Use of tariffs that take advantage of this can result in cost reductions of 45% compared with a gas boiler. The addition of solar generation further reduces costs and, where sufficient space is available, can completely eliminate energy bills on an annual basis.

With suitable financing, a large proportion of net zero retrofits can be cash positive for residents on a monthly basis, as reductions to energy bills exceed loan repayments.

What about Grid capacity? This comes up a lot when heat pumps are discussed, but our experience is that, in many cases, electric vehicle charging will draw far more electricity than heat pumps, which means that supply upgrades are often required anyway.

Cornwall’s DNO, National Grid Electricity Distribution, explained to us that it is actively planning for the rollout of heat pumps.

National Grid’s Distribution Future Energy Scenarios are regional versions of its national Future Energy Scenarios. Its two most ambitious heat pump deployment pathways align well with the pathway we calculated for Cornwall based on the CCC’s Sixth Carbon Budget, which provides reassurance that the Grid will be ready.

Building a workforce to decarbonise homes

We see training of adequate numbers of heat pump installers as the foundation of this transition. Our modelling indicates that around 500 installers will be required by 2030, increasing to around 800 by the mid-2030s before levelling out at around 900.

When someone’s boiler fails, they are far more likely to switch to a heat pump if their heating engineer recommends it, as they are a trusted source of information. However, a heating engineer is only going to recommend a heat pump if they understand and can install it, so training heat pump installers becomes a key step to increasing awareness.

Training in good-quality fabric and ventilation measures is also a key part of the strategy, with a focus on a long-term ‘whole house’ approach, where upgrades are carried out in line with the building’s natural life-cycle.

The decarbonisation challenge is significant, but also provides a great opportunity to create permanent reductions in the cost of heating and reskill the workforce.

Commercially available technologies such as heat pumps, fabric upgrades, ventilation, and solar are scalable and ready to deliver. Dissemination of knowledge through sustained training to a consistently high standard will be key to delivering the transition effectively, and must be accelerated. l

References:

1. The requirement for new homes is to achieve a space heating demand of less than 30kWh·m^–² per year, a total energy use of less than 40kWh·m^–² per year, with a net zero energy balance on site achieved through the use of solar photovoltaics
2. Electrification of Heat Demonstration Trials

About the authors
Chris Worboys is a senior sustainability consultant, Naomi Grint a Passivhaus certifier and Kate Millen a sustainability engineer at Etude

The post Kilowatts to Kernow: Decarbonising Cornish housing appeared first on CIBSE Journal.

The heat pump is one in a series of steps taken by Greenpeace UK to cut the energy used servicing the 1920s former printworks that it calls home.

Its decarbonisation journey started in 2010, with a commitment to reduce the office’s CO₂ emissions by 42% in 10 years. This undertaking resulted in the installation of photovoltaic panels on the roof of the office building and on Greenpeace’s adjacent warehouse and upgrades to the lighting systems, along with presence detection to improve control. The organisation also migrated its IT systems to the cloud to benefit from its improved efficiency.

In addition, the organisation undertook thermal imaging surveys of the building envelope. This led to the installation of additional draught-proofing, replacement of the external doors, and the renewal of some of the building’s glazing. A new building management system (BMS) was also installed to optimise operation of the building’s gas-fired heating and hot-water systems.

Despite the Covid pandemic, the organisation succeeded in meeting its initial 42% carbon-reduction target, albeit nine months later than planned. ‘The interventions did make a big dent in our carbon emissions,’ says Andrew Hatton, Greenpeace UK’s resource and technology director.

Having succeeded in stage one of its plan, which Hatton describes as tackling ‘the low-hanging fruit’, Greenpeace UK set about determining the next step in its carbon-reduction journey. ‘It was evident from crunching the numbers that the number one thing we could do, by quite a large margin from a CO₂ reduction perspective, was to come off gas,’ Hatton says.

The organisation duly set about modelling the building to see if ditching its gas boilers was feasible. It worked with a third party and its own in-house energy analyst to model the building to understand its energy demands. Alongside the digital model, data from the BMS, installed a few years earlier, proved invaluable in showing the rate at which the brick-built building heats up and cools down.

Occupancy numbers were also factored into the modelling. This proved to be a tricky exercise in the midst of the pandemic. ‘Before Covid, we might have 180 to 200 people in the building, 30 of whom would be cyclists using the showers, but post-Covid – with hybrid working – we were not sure what the new working pattern would be,’ Hatton explains.

Greenpeace UK’s headquarters in London was the site of an old printworks

A ‘new normal’ of 60% occupancy was assumed to be a realistic scenario – a guesstimate that has subsequently been shown to be fairly realistic, with actual occupancy numbers fluctuating around this figure.

The modelling did prove that it was feasible to replace the building’s two commercial gas boilers with one or more electric heat pumps. ‘We needed a total heating capacity of about 80kW, so we set about exploring heat pump options and looking at where we could locate the unit, given the constraints of our site,’ says Hatton, who adds that he realises this particular solution was not the only way of doing things.

‘We could have spent hundreds of thousands of pounds on greater thermal insulation for the envelope so we could put in a lower-output heat pump, but the solution we opted for was the most appropriate and sensible at the time.’

Although keen to replace its ageing gas boilers, the NGO was equally keen to avoid a major retrofit of its existing low pressure hot water radiator heating system, given the additional costs and disruption this would cause.

Most radiators on the system were low-level, double-panel units, which, Hatton says, had been ‘performing well’ with the gas boiler system, which operated with a flow temperature of around 80^oC. Knowing that a heat pump would run more efficiently at a lower flow temperature, Greenpeace UK experimented with running the existing gas boilers at a lower system temperature during the winter, to understand the impact on the office spaces and to garner occupant feedback. ‘Thermal comfort of staff was our top priority, because we didn’t want them saying “great, you’ve reduced emissions from the building but now my office is too cold for me to work”.’

The exercise proved that the existing radiator system could be used, albeit with a slightly reduced flow temperature of 65^oC, which Hatton says is still high, compared to most ASHP systems’.

Greenpeace UK was also concerned about the choice of refrigerant for the heat pump. Its policy team had been involved in campaigns to raise awareness of the global warming potential of refrigerants, so the organisation was keen to be seen to walk the talk.

‘It was a steep learning curve,’ recalls Hatton. ‘We started to look seriously at R290 [propane], which is a natural non F-gas refrigerant and has a low global warming potential [GWP 3] compared with fluorocarbon-based refrigerants.’

The challenge of using propane as a refrigerant

Greenpeace UK’s headquarters in London was the site of an old printworks

The heat pump contains 9.6kg of R290, which is about 50% more propane than is contained in the gas cylinder used by most domestic gas barbecues and patio heaters.

The heat pump installation has to comply with the Dangerous Substances and Explosive Atmospheres Regulations (DSEAR), the rules that apply to all refrigerant installations, albeit with a higher level of diligence because of this being an A3-class refrigerant.

Broadbent says the Palladium unit doesn’t present an ATEX (explosive atmospheres) risk during operation because it has built-in leak detection, automatic shut-off and, importantly, forced airflow. In addition, before the unit is enabled to start, integrated fans draw air through it to ensure a high-volume flow through the compressor housing, to effectively purge the unit.

The unit will only operate once it senses an air-pressure differential. In addition to meeting DSEAR demands, a 1.5m Zone 2 area is required around the heat pump, to prevent any uncontrolled access and remove any flammability risk.

DSEAR is, effectively, a risk-assessment process. In the case of A3 refrigerants, it is particularly important in ensuring that issues of non-compliance do not emerge at the end of the job. Broadbent says it is good advice to have a DSEAR review carried out at the start of the design stages, to pick up on any obvious issues before the unit position is finalised.

At the same time as it was researching refrigerants, the organisation was talking to the London Borough of Islington’s planning department, to discuss potential placement of the heat pump. ‘It became clear that noise from the unit was something we were going to have to consider seriously, given our location in a moderately built-up residential neighbourhood,’ Hatton explains.

‘We ended up in a situation where we knew we needed a low-noise unit; we knew we needed a natural refrigerant with a low GWP; and we knew we needed an air source heat pump, or heat pumps, that would deliver 80kW.’

It was at this point that Greenpeace UK approached Pure Thermal.

‘We’d just launched our Palladium range of air source heat pumps, which were a nailed on fit for the site because they are R290 units with ultra-low noise operation,’ recalls Garry Broadbent, Pure Thermal’s operations director. ‘It’s not always practical to use R290, because it has a maximum output temperature of 70^oC, but it was perfectly suited to this application, which runs at a maximum of 65^oC.’

Peace garden

The heat pump was to be located externally, in a courtyard area of the garden behind the office building. A Palladium 120.4 model, optimised for R290, was selected. Manufactured by Italian propane specialists Enerblue, it has a seasonal coefficient of performance of 3.58 and is capable of delivering up to 80kW of heat at an outside air temperature of -5^oC.

The unit is also ultra-quiet, with a sound power level of 73dBA. This is the standard specification, without any secondary acoustic measures, which is very relevant where a challenging location such as this is considered.

The unit features twin refrigeration circuits, with each circuit served by two scroll-compressors to provide operational resilience. Having four compressors also ensures efficient load management, by enabling the unit to progressively bring each compressor online only when load demands. Importantly, its twin circuit configuration enables one refrigeration circuit to remain in operation while the other is operating in defrost mode, removing ice from the unit’s coils. This means that the flow temperature remains neutral through the defrost cycle without reducing in temperature, as would be the case without this unique Enerblue defrost feature. In a further eco-friendly touch, the defrost melt-water is collected and used to irrigate the Greenpeace garden, rather than being dumped down the drain.

To maximise its operational efficiency, the heat pump is load compensated. This ensures it operates at the lowest system temperature possible to deliver the required space heating for the building.

The system will run at 65^oC when it is -5^oC outside, but it will decrease to 50^oC when the outside temperature is, say, 8^oC. The BMS dictates the system temperature that the heat pump needs to deliver; if space temperature is not being maintained, the BMS will signal to increase or lower the system temperature.

Of course, the big challenge in retrofitting an electric heat pump to a system previously served by gas boilers is in raising the output temperature to a point where it is able to heat the building’s domestic hot water (DHW). Broadbent notes that heat pumps should provide hot water on an ‘accumulated, rather than instantaneous’ basis, to minimise the specified heat pump capacity.

To accumulate hot water, the Greenpeace UK system incorporates two insulated 2,000-litre hot-water storage vessels, which the heat pump maintains at a temperature of between 55^oC and 60^oC. ‘The rationale for this application is for the hot-water tanks to recharge after the cyclists have had their morning showers and demand drops significantly,’ Broadbent explains.

When the hot-water tanks need heat, valves switch to divert the system flow and the heat pump will switch from the load-compensated space heating temperature to DHW heating mode, and increase the system temperature to 65^oC so that the hot-water tanks can then accumulate heat.

As soon as the thermal stores are up to temperature, the heat pump will return to heating mode and drop the system temperature again. ‘To increase system operational efficiency, the system is load compensated with prioritised hot-water production,’ says Broadbent. ‘For 95% of the time, it has the ability to run at a lower temperature than is required to heat the hot water, which means that the temperature of the double-panel rads will be well below 65^oC a lot of the time.’

The hot-water tanks were installed, along with the heat pump, by contractor VWG Mechanical. The retrofit took approximately six months to complete, including the heat pump lead time, with the heat pump commissioned in August 2024.

Photovoltaic panels have been fitted to the roof of Greenpeace UK’s headquarters and an adjacent warehouse

Hatton says that, now the system is operational, Greenpeace UK is monitoring and managing it carefully to ensure the system runs as optimally as possible, but it is still ‘too new’ to report any carbon savings. ‘We did some initial modelling based on desktop research, which showed that the carbon savings should be substantial,’ he adds.

While the carbon savings are potentially significant, will the switch from gas to electric heat come at a cost premium? ‘Unfortunately, at the moment, the answer to that question is yes,’ Hatton says, although he expects that to change in the years ahead when gas and electricity costs become more balanced.

‘The heat pump will cost broadly about the same to run – maybe a tiny bit more – than the gas boilers; we’re not saving money at the moment, but I would expect that to change over the next five years.’

As Greenpeace UK becomes familiar with its new heat pump, Hatton says it might focus operation of the unit to those times when the Grid has the lowest carbon intensity. ‘At the moment, we are not doing anything around that because we’re not experienced – and because of the tariffs we are on currently.’

Now that the unit is up and running in the Greenpeace UK garden, it is much quieter than Hatton had expected. Perhaps more unexpectedly, he describes the grey box ‘as having a certain charm’ and says that his colleagues want it to be seen. ‘It’s doing such a noble job, we are going to leave it on display for all to see.’

The post From gas to green: heat pump installation at Greenpeace appeared first on CIBSE Journal.

The properties of MTR Corporation Limited (MTR) encompass 16 shopping malls, four office buildings, and more than 110,000 residential units across 57 property estates. To explore the potential of cutting carbon and greenhouse gas emissions from its estate, MTR implemented two pilot projects.

The first involved the use of a cloud-based data analytics software platform to optimise the central chiller plant at Two International Finance Centre (Two ifc), a commercial development in Hong Kong’s Central District. The second looked at developing an integrated AI solution to enhance energy efficiency and customer experience at the Elements MTR Mall in West Kowloon. Both initiatives resulted in significant annual energy savings and improved building performance.

Big-data analysis at Two ifc

Built in 2003, Two ifc is a skyscraper and integrated commercial development on the waterfront of Hong Kong’s Central District. Rising to a height of 415 metres, it is the second-highest structure in Hong Kong and boasts a total floor space of about two million square feet.

The pilot project involved integrating a cloud-based, big-data analytics software platform to optimise chiller plant. (Big data is described as large and diverse datasets that cannot be processed easily using traditional data-processing techniques). The initial key performance indicator (KPI) was a minimum 5% annual energy saving at the central chiller plant.

The Two ifc chilled-water system encompassed a seawater plant, circulation pumps, and chilled-water and seawater distribution networks, with a total installed plant capacity of approximately 9,800 tonnes
of refrigeration (TR). 

The cloud-based software platform securely collects and analyses data from ultrasonic temperature and water flow transducers, energy meters, and existing building management and energy management systems (BMS/EMS).

Real-time data is analysed to generate actionable insights aimed at enhancing energy efficiency. The platform has a secure connection to offsite storage provided by the software service provider. It incorporates fault detection and diagnostics (FDD) software that analyses hard-wired and virtual data points using time-series data. This allows for effective comparison, diagnosis, evaluation and reporting of the chilled-water system’s performance.

The project team prepares monthly reports to review data analysis, insights and energy savings, allowing for continuous adjustments to the system settings. A key strategy involves optimising the operational sequence of 10 seawater-cooled chillers based on their coefficient of performance (COP), ensuring that the most efficient chiller operates first.

In terms of energy reduction, the project team maintains rigorous measurement and verification standards to comply with international and local regulations.

AI measures at the Two ifc commercial development cut energy use by 9% in 2023

Historical operation data from the BMS serves as a control set for comparison before and after implementing the cloud-based platform. The system continually records trend logs and monitors performance against the energy-saving opportunities, allowing for timely adjustments to optimise energy savings.

Elements MTR Mall

Opened in 2007, the Elements MTR Mall has a retail area exceeding one million square feet and accommodates more than 120 stores.

Elements undertook a proof-of-concept project aimed at developing an integrated AI solution to enhance energy efficiency and improve customer experience. The initial KPI was a minimum 3% annual energy saving at the central chiller plant.

Like Two ifc, the chilled-water system at Elements included a seawater plant, seawater and chilled-water circulation pumps, and chilled-water and seawater distribution networks. It had a total installed plant capacity of around 7,000TR.

The development of an air conditioning and mechanical ventilation optimisation model uses advanced machine learning techniques to address the dynamic characteristics of HVAC systems and fluctuating environmental conditions.

Supervised learning, where algorithms learn patterns and relationships between inputs and outputs, plays a crucial role in understanding complex, non-linear correlations.

Additionally, self-adaptive reinforcement learning, which involves dynamically adjusting the learning process based on feedback, means the system optimises equipment performance based on real-time energy usage and COP.

This continuous learning process enhances the model’s accuracy over time, driving energy efficiency. The AI model forecasts cooling load every 30 minutes, using historical data, weather forecasts, and solar radiation.

Big-data analytics cut annual energy use by 9% at the Elements MTR shopping mall

Insights from the model guide equipment combinations and chilled-water setpoints, allowing chiller plants to proactively manage cooling demand fluctuations and optimise energy usage. The model is improved through iterative testing and operator feedback.

Real-time data collection is vital for optimising the system based on actual demand patterns. Integrated people-counting techniques use CCTV to analyse foot traffic in different mall zones, which identifies peak usage periods.

This data informs energy-saving strategies, such as adjusting air handling unit supply temperatures while maintaining thermal comfort. More than 45 indoor air quality (IAQ) sensors monitor parameters such as CO₂ levels, temperature and humidity, enabling the AI to refine recommendations for fresh air optimisation. Compliance with local and international air quality standards, including the Reset Air Standard for airborne viral transmission, is maintained, with studies indicating excellent IAQ ratings, even during peak periods.

A data quality (DQ) assessment framework was developed to enhance AI model training. This framework identifies DQ issues and provides recommendations for the BMS. Following the assessment, a digital infrastructure upgrade plan was implemented to improve sensor accuracy and data completeness, which are essential for effective energy management analysis.

The optimisation model includes a visualisation platform that recommends optimal chiller configurations based on historical performance. A daily recommendation dashboard and a rule engine for real-time anomaly detection enhance predictive maintenance capabilities.

Results

The innovative pilot project enabled Two ifc to achieve a total energy saving of more than 2.3 million kWh of electricity over two years (January 2022 to December 2023), translating to a total reduction of more than 1,500 tonnes of CO₂e. The energy savings percentages stood at approximately 11% in 2022 and 9% in 2023.

Meanwhile, at Elements, the AI optimisation system delivered an annual energy saving of approximately 9% during the period August 2023 to July 2024, amounting to more than 1.3 million kWh of electricity saved and a CO₂e reduction of more than 715 tonnes.

The projects have already been recognised by the industry. They have garnered four building awards that acknowledge the project teams’ exceptional accomplishments in designing and operating energy-efficient structures.

About the author

Ethan Poon is the assistant chief project and maintenance manager at MTR Corporation

The post Smart thinking: AI-driven energy savings appeared first on CIBSE Journal.

To help the UK safely lift restrictions on large gatherings, the government initiated the Events Research Programme (ERP). One key area of focus was identifying risks associated with event venues, particularly focusing on ventilation in high-traffic areas, to better understand how indoor air quality (IAQ) might influence the spread of airborne viruses such as SARS-CoV-2.

The results of the study were presented at the CIBSE Technical Symposium in Cardiff earlier this year.

A significant portion focused on monitoring air quality in food and drink concession stands because they often experience transient, yet high occupancy. CO₂ monitoring was used to assess ventilation performance, as elevated CO₂ levels serve as a proxy for poor ventilation and potentially higher concentrations of exhaled breath.

The study used non-dispersive infrared CO₂ sensors capable of measuring concentrations up to 5,000ppm with an accuracy of 30ppm. Loggers were installed at breathing height (1.6m to 2.3m) to provide high-resolution data.

Ventilation was monitored at 10 venues in England, covering 179 spaces over 90 events. These venues included a range of indoor spaces, from seating areas and concourses to toilets, restaurants, private boxes, and food and drink concession stands.

The research team recorded CO₂, temperature and relative humidity levels, noting times of high occupancy and verifying this data with CCTV footage. The research was observational, with the team present during most events but refraining from intervening in venue management.

CIBSE Guide A recommends a provision of 10 l/s per person of outdoor air in spaces like concession stands, but post-occupancy evaluations are rare. To assess whether ventilation strategies are adequate during peak occupancy, CO₂ levels were closely monitored in concession stands at Royal Ascot, Wembley Stadium, and the O2 Arena.

At Royal Ascot, a single bar was monitored over five events with an 18% occupancy (12,600 attendees). Similarly, 16 bars and kiosks were monitored at Wembley Stadium during Euro 2020 football matches, with occupancies ranging from 3% to full capacity (90,000). Lastly, four bars were observed at the O2 Arena during a music awards ceremony with 18% occupancy (3,532).

Air-quality classification bands were developed to rapidly assess ventilation effectiveness and the associated risk of airborne virus transmission. The bands, ranging from A to G, classified spaces based on average and maximum CO₂ concentrations, with ‘A’ indicating good ventilation and ‘F’ or ‘G’ suggesting ventilation improvements were needed.

Results showed that 86% of kiosks had good ventilation when considering the average CO₂ levels at the event, which included high and low-occupancy periods. However, at maximum CO₂ levels during peak occupancy, only 45% of kiosks maintained good ventilation, while 12% were in F and G bands, indicating ventilation could not cope.

One outcome was the influence of event management and structure on ventilation performance. For example, the O2 Arena and Royal Ascot had more frequent breaks, which allowed for a more even distribution of people in concession stands, resulting in relatively flat CO₂ levels. However, Wembley, where fans are not permitted to take drinks into the seating areas, saw significant spikes in CO₂ before the match and during half-time, reflecting higher concentrations of people.

Here, the research also showed that ventilation strategies differed across levels. Level 1 and 2 concourses, which are naturally ventilated, maintained CO₂ concentrations below 1,500ppm even at full capacity. But level 5, with natural and mechanical ventilation, experienced higher concentrations at occupancies above 72%, suggesting ventilation was insufficient for peak demand.

This has important implications for event management and building design. Ensuring sufficient ventilation in high-occupancy areas is critical. Organisers and venue designers should consider the layout and structure of events when planning ventilation strategies. It’s vital that solutions can adapt to occupancy levels and event structures.

About the author
Filipa Adzic, is a research associate in fluid mechanics at UCL

The post Working with fans: monitoring air quality at concession stands appeared first on CIBSE Journal.

This ambitious project will see the dilapidated General Market building, which dates back to the Victorian era, and the domed Poultry Market building, built in the 1960s, both being brought back into use with the addition of contemporary interventions, to create exciting and flexible exhibition spaces.

The servicing and sustainability strategy for these two historic buildings that will form the heart of the world’s greatest museum has been developed by Arup. Working with lead architect Stanton Williams, together with Asif Khan and conservation architect Julian Harrap, the engineer has devised a building services solution sympathetic to the heritage buildings without compromising visitor comfort.

Operational performance of building services will be further enhanced by a smart building strategy where every item of plant and equipment is data-enabled to optimise the running of the museum and minimise its carbon emissions.

Fundamental to developing an energy efficient services solution was the thermal performance of the buildings’ historic façades. At the project’s outset, the teams worked to enhance the thermal performance of the existing envelope by adding insulation and double glazing where possible. Fritting was also applied to some glazing elements to help control solar gains.

Beneath this historic envelope will be the museum’s permanent gallery spaces and temporary exhibition spaces, alongside extensive storage, research and education areas.

Arup’s servicing strategy has been to work with the fabric of the buildings to help deliver the environment needed for the various spaces with the minimum amount of energy.

‘We were fortunate with these buildings because their former purpose was to keep products fresh while allowing traders access; this overlaps with the museum’s requirement to preserve artefacts and provide entry for visitors,’ says Vasilis Maroulas, associate director at Arup and lead mechanical engineer on the project.

Central to this approach is the distribution of the various spaces and galleries. Arup developed a solution based on positioning galleries and spaces where environmental conditions were most critical at the core of the buildings. The temporary galleries, to host loaned exhibitions, is the space with the tightest environmental conditions: it’s on the ground floor at the centre of the Poultry Market, sandwiched between the basement art storage and the multifunctional space on the first floor. ‘It is effectively a box within a box, completely protected from solar gains,’ explains Maroulas.

The HVAC system used to serve the temporary galleries is an all-air centralised ventilation system with high-level supply and extract to provide mixed and uniform conditions within the entire volume of the galleries.

For the remainder of the spaces, Maroulas says Arup has adopted ‘an adaptive comfort approach’ to the servicing. ‘Credit to the museum, it accepted a much wider temperature and humidity band for most spaces than is the norm in the arts and culture world, which helped us immensely,’ says Maroulas.

Beneath the temporary galleries, the former basement cold stores are currently being transformed into a store to house part of the museum’s seven-million-strong collection. The store includes a publicly accessible space, where visitors will be able to glimpse the collection. This area is served by a mechanical ventilation system with air conditioning from high level supply and extract terminals. ‘This is a low air volume air conditioning system, with minimal operational energy, because this is a collection store and the lights will be off for most of the time,’ Maroulas explains.

This is also the only space in the buildings that has a water mist fire suppression system. This is a bespoke installation that goes beyond the manufacturers and code recommendations and has been proven by extensive mock up fire tests in Norway to confirm the efficacy of the system in those bespoke storage arrangements.

The space above the temporary galleries is open to the building’s dramatic, domed reinforced concrete roof – once the largest single-span concrete roof in Europe. This space will  be for a wide variety of uses, from exhibitions to evening events, lectures, receptions and so on.

Here, Arup is looking to exploit the thermal mass in the roof combined with a natural ventilation solution. Maroulas says: ‘We have adopted the simple strategy of opening the lunettes windows at high level to help create air movement during the day.’

In winter, the space is heated by an underfloor system using pipes concealed in the new floor slab. This is designed to keep the space at a temperate 18^oC t0 20^oC during occupied hours. On hot summer days, the exposed thermal mass of the giant domed roof will be supplemented by cooling the floor slab. ‘Rather than introduce a cooling system, we decided to run cool water through the underfloor pipes to activate the floor’s thermal mass to take out the temperature peaks,’ explains Maroulas.

Average temperature on a section running east-west through the Museum of London during mid-season event mode

The museum’s main entrance is off the canopied West Poultry Avenue, the covered street that runs between the two buildings. The entrance channels visitors on to the ground floor of the General Market building. This floor is intended to be the museum’s sociable space, complete with restaurant, bookshop and galleries, which are all open to the glazed roof with its central dome. This space, too, is naturally ventilated throughout the year, supplemented with underfloor heating.

An additional challenge is that the large, naturally ventilated spaces in the General Market ground floor had to be able to host evening events, including formal dinners. For these events, air is brought into the space through attenuated low-level openings to keep external/outside noise to a minimum while rooftop exhaust fans will assist air movement through the space.

Beneath the bustle of the ground-floor entrance is the space for the permanent galleries. These contain the majority of the museum’s exhibits housed within the high brick-vaulted basement and the previous Salt Store spaces, parts of which were only discovered once restoration was under way. In these subterranean galleries, the museum’s curators accept temperatures of between 16^oC-24^oC.

Two different methods are used to supply conditioned air to the 30m-wide, labyrinthine space. For the entrance area, which is open to the floor above, a high-level mixing system supplied from either side, is used to provide a buffer at the entrance to the galleries. Beyond this, the rear two-thirds of the space is supplied with air from an extensive network of floor trenches, using a displacement system. ‘Our mechanical engineers had to work with the exhibition design team and our CFD building physicists to develop physical mock-ups to reach a compromise solution that would allow sufficient air movement to create uniform conditions within that space,’ explains Maroulas.

In Victorian times, goods and livestock deliveries arrived by rail to this level. The tracks are now used for Thameslink trains, which themselves will become a moving exhibit, viewed through a window in the basement wall.

Heating and cooling for both buildings is being provided by E.ON’s Farringdon energy centre – see ‘Greening the City’, April 2022 CIBSE Journal. Maroulas says there was a debate about whether to connect to the energy centre in line with the GLA’s priorities or whether to use air source heat pumps to provide an all-electric fossil-fuel free system from the outset.

In the end a decision was made to connect to the energy centre because E.ON are in the process of decarbonising the energy centre, which will help decarbonise the heating and cooling networks.

This ambitious project had originally targeted Breeam Excellent: it is currently on target to achieve Breeam Outstanding.

What’s more, Maroulas says by being lean with the design and using passive techniques, the current estimate is that the museum’s energy consumption will be 70% lower than that of a baseline building representing the proposed end use. This calculation includes the existing building fabric and assumes the building services systems is compliant with the latest Part L minimum requirements.

The General Market building is due to open in 2026, and the Poultry Market building two years later.

Already, there is a presumption that the scheme might actually achieve the targeted levels of energy consumption predicted using CIBSE TM54 as it has the added benefit of smart-enabled  building services.

When it opens, it is expected the building can be tuned to get the energy use down to the predicted figure, and the smart data means it will be much easier to know what to tweak to get energy to those levels.

Working on the London Museum

Arup engineer Joseph Halliday charts his career progression at the London Museum, which he has worked on since 2018

I began working on the Smithfield market conversion project at early design stages back in 2018 and over the years have witnessed the project’s evolution from initial concepts to construction, with my role expanding alongside it. This experience has been instrumental in honing my skills and understanding of complex design processes, setting a strong foundation for my ongoing professional development.

Working on the conversion of a historic food market into a museum in the heart of London has been an exhilarating challenge as a design engineer. The project, which represents the City of London’s largest singular investment, demands a meticulous approach to every detail.

Unlike typical construction projects, no area within this transformation is standard or straightforward. Each section of the market presents unique architectural and structural intricacies that require innovative mechanical, electrical, and plumbing (MEP) solutions. From preserving the original character of the market to integrating modern museum functionalities, the design process involves a delicate balance of respecting the building’s heritage while embracing its future.

 The journey of converting the Smithfield market into a museum has paralleled my own professional growth in remarkable ways. Starting as a draftsman, I was initially involved in the detailed drawings and plans for the project. As I pursued my university degree, I gained deeper insights into engineering principles, which allowed me to transition into a more integral engineering role within the company.

Achieving my Incorporated Engineer (IEng) status was a significant milestone, reflecting my growing expertise and commitment to the field. Now, as I work towards my Chartered Engineer (CEng) qualification, I find myself taking on more complex challenges within the project, contributing to innovative solutions and leading design efforts and inspecting the application of those on site. This project has not only transformed a historic part of London but has also been a catalyst for my personal and professional development, shaping me into a more skilled and confident engineer.

The post The museum of tomorrow: The London Museum transformation appeared first on CIBSE Journal.

Modern methods of construction and digital design have played a pivotal role in the scheme from the outset, with 70% of the stadium’s mechanical, electrical and plumbing (MEP) services – and much of its superstructure – delivered to site as prefabricated and modular assemblies.

It has been quite a task: ‘There are 53,000 elements, of which nearly 40,000 are mechanical, electrical and plumbing services, so we’ve had to think modular from day one,’ says Ian Siddy, associate mechanical engineer at Buro Happold, the project’s engineers.

The move to a new home has been a long time coming. Everton has been at its current Goodison Park site since 1892; the club was one of 12 to participate in the first football league season in 1888. Unable to upgrade its existing stadium because of constraints imposed by its location, the club secured a new site in Liverpool’s Northern Docks area in 2017. In 2019, US architect Dan Meis was appointed to develop a concept for the club’s new home. Its design draws on the brick-warehouse typology of neighbouring buildings, including the Tobacco Warehouse and the Titanic Hotel, with four brick-clad stands surrounding the pitch. Unusually, these are topped by giant picture windows that bring views of Liverpool and Merseyside into the steeply raked seating bowl. The stadium is crowned with a distinctive curved barrel roof.

Working with Everton, Dan Meis  and technical architect BDP Pattern, Buro Happold helped refine the stadium’s design. In 2020, Laing O’Rourke (LOR) was appointed as design and build contractor under a pre-construction service agreement (PCSA). The PCSA shifted the project focus from design development to design optimisation, to enable the stadium to be split into components and modules for manufacture offsite, under LOR’s design for manufacture and assembly (DfMA) process.

The stadium’s design draws on the brick-warehouse typology of neighbouring buildings in the Northern Docks area of Liverpool

‘DfMA is a design approach that focuses on the ease of manufacture and efficiency of assembly; by optimising the design of a product, it is possible to manufacture and assemble it more efficiently, more quickly, more safely, and at a lower cost,’ explains Siddy.

LOR’s DfMA philosophy is 70:60:30, which means delivering 70% of a build using offsite production, making things 60% more efficient, and saving 30% on programme. A major benefit is that a lot of work that would traditionally be done on site is taken offsite. This ensures better build quality and greater control of wastage, making the process more environmentally friendly. DfMA reduces time on site. Manufactured modules and components are simply craned into position, because every service interface will already have been positioned digitally before module manufacture can begin.

Buro Happold and BDP Pattern were contracted to LOR to ensure the design was DfMA-ready. ‘By reducing the workforce on site, DfMA helps create a more efficient and safer site,’ says John Edwards, project technical leader at LOR. LOR created a federated BIM model of the stadium, which allows models from all disciplines’ designs to be combined in a single place in which to coordinate all objects to the construction programme. This model was linked to detailed construction programme information, to enable a dynamic digital twin to be created to help plan exactly how the stadium’s construction would be executed.

In addition to identifying potential risks or clashes in the build programme, the 4D model allowed the LOR team to identify efficiency opportunities that might not have been realised with more conventional programming methods.

Rather than attempt to modify its MEP designs to make them suitable for modularisation and offsite assembly, Buro Happold took the bold decision to start again. Working with LOR and Crown House Technologies (CHT), LOR’s MEP contracting arm, Buro Happold set about embedding offsite principles into its MEP design from the outset 

The stands are topped by giant picture windows and the stadium is crowned with a distinctive curved barrel roof

‘We knew the elements that needed to be incorporated. Crown House Technologies gave us guidance, explained how it wanted the systems set out, defined the space needed for access, and explained the capabilities of its manufacturing processes,’ explains Siddy.

The location of primary service routes for the mechanical, electrical, public health and containment systems was defined at the start. Regular workshops enabled Buro Happold to draw on CHT’s expertise to establish these routes, taking into account practical constraints for modularisation, including weights, transportation, access requirements, and spacing of systems.

The adoption of a modular servicing solution also set constraints for the stadium architecture, including ceiling heights, and the location of access points and risers. The West Stand, for example, contains 35 large, prefabricated modules for the primary runs.

These 10-tonne modules are floor mounted and create a ground level corridor with a integrated service walkway above. They enable ducts, pipes and cables to be safely accessed and maintained. ‘That was the beauty of the PCSA; the earlier we are involved with the client and their consultant team, the more value we can give to a client around the design solutions,’ says LOR’s Edwards.

With the primary routes established, it was important to maintain and monitor the quality of the digital models by reporting and recording clashes and coordination issues early, so they could be resolved before impacting the programme. ‘When we handed over the stage-four model to Crown House, very little changed in developing it into a stage-five model that could be built,’ says Andrew Waugh, associate director at Buro Happold.

In keeping with Everton’s aspiration for the stadium to be built with sustainability to the fore, building services systems are designed to provide flexibility of operation. The stadium will host around 20-30 matches a season, so there are more than 300 days a year without match-day revenue. On these days, the stadium will host events and conferences, to generate additional income – so the building services have been zoned to allow individual systems to run in isolation, with everything else effectively turned off. ‘If a system doesn’t need to run, then let’s not run it,’ says LOR’s Edwards.

The conditioned spaces are typically hospitality areas. Each area is served by dedicated, decentralised fresh air handling units (AHUs) with integrated reversible air source heat pump, sized to provide cooling and heating based on the occupancy profile of each space.

A plant skid manufactured in Laing O’Rourke’s factory

The use of integrated heat pumps helps minimise the size of the centralised heating and cooling plant and the length of pipe runs. ‘Using dedicated heat pump units is really efficient in terms of operational energy, and really good in terms of embodied carbon, because we don’t need huge centralised systems,’ says Buro Happold’s Siddy. ‘Simply by changing the AHU to one incorporating a heat pump, which is practically no bigger, there are huge benefits.’

Water usage, too, has been minimised through the use of low-flow fittings. These help minimise peak domestic hot-water loads, which occur just before kick-off. Buro Happold used its extensive stadium design experience to shed loads and improve security of supply with the addition of buffer vessels. Even so, at 3.2MW of a total 4.5MW heating load, hot-water heating is by far the largest primary heat demand. The inclusion of buffer vessels, however, helps overcome the peak and has enabled the gas boilers to be sized below peak demand. ‘This leads to more efficiency in terms of equipment, cost and everything else,’ Siddy says.

Water usage for pitch irrigation has been minimised through the addition of rainwater harvesting from the stadium roof.

As with water consumption, power, cooling and heating load profiles also vary considerably between match and non-match days. ‘Match days have short-term peak loads half an hour before kick-off and at half-time, which far exceed anything else,’ explains Siddy.

To come up with realistic power demands for the stadium, Buro Happold used its experience and benchmarking data from recently completed stadiums, including Arsenal’s Emirates Stadium, the Tottenham Hotspur Stadium, and the transformation of the London Olympic Stadium into West Ham’s new home.

The stadium’s riverside location exposes it to strong winds, so materials and systems have to be able to withstand the harsh conditions

Electrical resilience

The total electrical load for the new stadium’s match and broadcast needs, and for catering, totalled 18MW. However, Buro Happold used its benchmarked data to anticipate how the stadium would actually be used and was able to apply a 60% diversity figure to the total electrical load, which brought it down to a more realistic 7.6MW. ‘The load we requested from Scottish Power Energy Networks is about 43% of the connected load; even then, we have spare capacity built into that,’ says Waugh.

Load diversity was also applied to the main electrical infrastructure, to ensure that it too was not oversized. This enabled smaller cables to be installed, to reduce costs and save on embodied carbon. In addition to diversity, electrical resilience is critical for the safety of the stadium’s 52,888 spectators. If a mains power failure should occur, all life-safety systems will continue to operate, as will the giant screens and all field-of-play lights, to enable the match to be completed with spectators remaining in their seats. ‘Match continuation for a Premier League club is huge; the show must go on,’ says Waugh.

Integrated reversible ASHP heat pump unit

The site electrical supply benefits from two primary 33kV district network operator connections from independent electrical grids, either of which is capable of supporting the full electrical load. In addition, there are three 500 kW battery sets and one 600kW battery set, capable of delivering 9.3MWh of battery storage capacity.

‘If there was a mains failure, that would give us about three hours of continued operation, with some non-essential stadium services restricted, so that a game could easily be completed,’ says Waugh.

Life-safety systems – including public address, voice alarm and emergency lighting – have local, independent uninterruptible power supply systems for enhanced levels of resilience.

Construction of the stadium began in summer 2021 and fit-out is nearing completion. Everton aim to start playing there in 2025 – then we will see whether their new home inspires the Toffees to live up to their Nil satis nisi optimum motto.

The post Home advantage: Everton Football Club’s new stadium appeared first on CIBSE Journal.

To meet this ambitious target, the plan is to do away with diesel generators and to connect all the Paris Olympic sites to the electric grid (London 2012 reportedly burned four million litres of diesel to power its venues).

Of the two million pieces of sporting equipment that will be used, three-quarters will be rented or provided by sports federations. More than 75% of the electronic equipment, such as computer screens, will also be rented, as will many of the venue tents. In addition, 25% of the ingredients for the meals served to spectators and athletes will be sourced locally.

The most sustainable element of the Games, however, is what the organisers are not doing: building new venues. Instead, many of the city’s existing venues are being repurposed, including the Stade de France – built for the 1998 Football World Cup – which is being transformed into the main arena.

The one major exception to this reuse edict is the new, purpose-built Aquatics Centre – but even this incorporates a timber structure and uses recycled materials in its fit-out. Most importantly, after hosting the Olympics, the centre will be transformed into a multi-sports facility for the local Seine-Saint-Denis community for the next 50 years.

The Aquatics Centre has been constructed under a design, build, finance, maintain and operate contract by Bouygues Bâtiment Ile de France consortium, working with architects VenhoevenCS and Ateliers 2/3/4, along with MEP engineers INEX. The building’s form has been kept deliberately compact to minimise construction costs, the quantity of materials needed and the energy required for the legacy phase of its operation.

A section view of the Aquatic Centre’s sustainability features

Its thin, curved roof is the venue’s most distinctive feature. This is highest above the diving tower and the raked spectator stands that flank the pool north and south. From here it swoops down towards the swimming pool and the lower, less-imposing community-facing west façade.

According to Cécilia Gross, partner-director at Dutch architect VenhoevenCS, the roof’s hollowed out, concave shape reduces the volume of the hall compared with designing a box. ‘We are not talking a little reduction – we are talking about halving the volume and thus helping minimise the energy required to condition the air filling the arena,’ she says.

The roof is supported on a lean catenary structure of 91, individually curved, timber glulam beams, which are just 500mm deep and 200mm wide, and span the 89m width of the building. The beam’s slender profile helps minimise the void between beams, which co-architect Laure Mériaud, a partner at Paris-based Ateliers 2/3/4, describes as ‘wasted space that would require energy to heat’.

Lateral stability of the timber structure is provided by a timber deck. There is no ceiling, so the timber beams and deck are visible from the pool hall, as is the cabling, lighting and small air conditioning ducts. The larger, main distribution ductwork is located on top of the roof, so as not to detract from the structural form.

Timber louvres provide solar shading for glass elevations

The roof incorporates 5,000m² of photovoltaic panels. These provide up to 20% of the centre’s electrical demand. Rainwater is also harvested by the roof and stored in a subterranean tank for use in irrigating the surrounding planting.

Timber louvres form a slatted enclosure surrounding the building, which offers solar shading for the centre’s fully glazed east and west elevations, and creates a sheltered colonnade for pedestrians. Gross says daylight from these glazed elevations brings ‘magic’ to the building, although the glass will be covered for the Olympics, to give the TV crews complete control of the lighting.

The reinforced, low carbon concrete pool is also designed to minimise the volume of water required. Rather than construct multiple pools for the diving, swimming, water polo and artistic swimming competitions, there is just one, 71m-long pool. This incorporates two movable walls to allow it to be configured into a 50m swimming and 20m diving pool, or a 33m pool to host water polo or artistic swimming and a diving pool. 

The depth of the pool varies, too; it is at its deepest for the diving, but slopes up towards the west, where the swimming and other events will take place. Sculpting the floor means it contains 25% less water, which does not need to be kept warm or treated over the lifetime of the building. In addition to movable walls, the pool has a movable floor to further increase its versatility when operating in legacy mode.

The Paris 2024 Aquatics Centre is a fitting showcase for one of the Games’ premier events. Ultimately, however, it is the people of Saint-Denis and other neighbourhoods who will benefit from its transformation after the Games into a multifunction sports facility. The huge bank of 2,500 temporary seats (made from recycled bottle caps) on the north side of the building will disappear, to be replaced by padel tennis courts and pitches for team sports, along with a fitness and bouldering area.

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It is a setup that can consume a lot of energy during the construction, adding to the contractor’s running costs and increasing carbon embodied in the building.

Now, at contractor Sisk’s residential development for Quintan at Wembley Park, an innovative, containerised heat pump-based energy module is being trialled as a more energy efficient solution to supplying heating and cooling to the site’s welfare facilities. The energy module, designed and built by Solaris Energy, has been up and running since January this year, and it has already helped reduce Sisk’s site energy bill by around £10,000 a month.

What’s more, the energy savings have resulted in 14 tonnes of carbon savings so far this year, which will be reflected in the embodied carbon of the six apartment blocks that Sisk is constructing for Quintain over the next five years.

‘Like all good ideas, this one was formulated in a pub over a cold pint of beer,’ says Daniel Large, director and owner of heat pump specialist Solaris Energy. He had been playing around with the concept of developing a mobile, containerised heat pump system that could be used to deliver energy-efficient, simultaneous heating and cooling. So, when a conversation with the project director turned to ways in which the amount of energy consumed by its site accommodation at Wembley Park could be reduced, Large suggested trialling a heat pump-based solution.

The welfare facility was being planned to accommodate up to 2,000 operatives when the project is at its peak. ‘Sisk sent me details of the proposed facility, which was, in effect, a temporary, four-storey building, complete with offices, meeting rooms, induction rooms, a canteen and kitchen, changing rooms, toilets and showers – it was massive,’ Large says.

Solaris Energy set about developing a heat pump-based solution – capable of meeting all the welfare facility’s heating and cooling demands – that would fit into a standard 6 metre shipping container, to enable it to be relocated at the end of the project.

The heat pump specialist worked with ADR Consulting Engineers to produce a thermal model of the building and its associated heating and cooling loads. It then developed a solution based on two heat pumps (normally used as ground sourced heat pumps) that would deliver up to 160kW of heating and 150kW of cooling.

Part of the distribution system in one of the site offices

‘The water-to-water heat pump captures heat from cooling to reuse it for heating, or to pre-heat domestic hot water [DHW]. It simultaneously provides heating and cooling,’ Large explains. In addition to the heat pumps, the container contains a chilled water buffer tank, a low-temperature hot water (LTHW) buffer tank, and a pre-heat tank for the DHW.

The DHW pre-heat uses heat reclaimed from cooling the facility to heat a 500-litre vessel full of water to a constant 55^oC. The DHW is pre-heated by circulating the system through a coil contained within the tank of heated water. ‘Rather than oversize the system to meet the once-a-day peak demand from the showers, we decided to continue using electric showers and point-of-use water heaters, which we supply with water pre-heated to a temperature of 50^oC,’ says Large. The DHW is then brought up to a supply temperature of 60^oC by the point-of-use devices, to kill off any legionella bacteria, with a thermostatic mixing valve to deliver water at an appropriately safe temperature.

ADR Consulting Engineers’ thermal model showed the meeting rooms would require cooling throughout the year, even in winter, and that – for a large part of the year – the facility would require simultaneous heating and cooling.

‘As soon as there is a cooling demand, rather than rejecting the heat outside, we take the absorbed heat to the heat pump evaporator, where it is turned into high-grade heat by the heat pump before being stored in the LTHW buffer or DHW preheat vessel, or it is used directly for heating if there is a demand,’ Large explains.

‘Heat that would have been wasted is recovered and used in the building, which gives a better system COP [coefficient of performance],’ he adds.

The heat pumps also connect to two dry air coolers installed on top of the container. These reject or absorb heat depending on the system demand. ‘If there is cooling demand and no requirement for heating – and the buffer tanks are up to temperature – we’ll use the dry air cooler to dump surplus heat,’ Large says. ‘Similarly, in mid-winter, when we might not have any cooling, we’ll use the dry air cooler to source energy from the air to generate heat for heating and hot water.’

A particular challenge with using a GSHP coupled with a dry air cooler to provide heat when it is cold outside is that any moisture on the dry air cooler can freeze and frost the heat exchanger. ‘Frost is not something you’d normally consider when using a water source heat pump,’ Large says.

The containerised plant room, with a dry air cooler above, services a fourstorey site accommodation block

Fortunately, the manufacturer was able to adapt its air source heat pump control logic to work with its water source heat pump, so it could run a defrost cycle. ‘This allows us to use the thermal store, or even bring a compressor online, to defrost the heat exchanger if we need to,’ Large explains.

In April 2023, while the accommodation modules were being assembled on site, Large visited the site with ADR Consulting Engineers to establish how best to tie in the containerised heat pump system to the temporary building, and to establish heating and cooling pipework routes.

‘A heat pump is only as good as the system to which it is connected, so we had to develop a low flow temperature solution to ensure we could get the best energy reduction from using heat pumps,’ he explains. ADR Consulting Engineers designed a simple heating circuit, using radiators for the welfare facility’s ground and first-floor site accommodation, and fan coil units (FCUs) to deliver heating and cooling to the second-floor subcontractor office and Sisk’s third- and fourth-floor offices.

The containerised plant room, with a dry air cooler above, services a fourstorey site accommodation block

Along with the mobile energy module, the radiators and FCUs are intended to be reused at the end of the project. Copper is used for the connecting pipework inside the building, which, Large says, will enable it to be recycled in future ‘when the facility is decommissioned’.

The containerised heat pump system and buffer vessels were connected using stainless steel pipework, along with all the system controls, in an off-site process. ‘It is a plug-and-play solution, with everything inside the box,’ Large says.

The container was shipped to site in October, commissioned in November, and powered into use in January.

Heating and cooling has been scheduled to run between set times, with the system turned off out of hours. Weather compensation is also used to maximise system efficiency by varying the system temperature with outside temperature – so, at 0^oC, the heating runs at a temperature of 40^oC, which will increase to 50^oC if the temperature drops to -10^oC. Similarly, the cooling is designed to run at 12^oC when it is 20^oC outside and get progressively colder as outside temperatures increase.

The innovation has been successful. In the short time it has been in operation, its COP has been improving steadily and is currently running at a COP of 4.9, which, Large says, is ‘pretty good for a temporary welfare facility’.

Display showing real-time operational data

Savings in electricity use are equally impressive. On a previous site between 2017 and 2019, when the cost of electricity was £0.13 per kWh, Sisk was spending £25-£30,000 per month on site electricity. On the energy module site, the site electricity bill has dropped 60%, to £15-£20,000 – even though the price of electricity has increased by 77%, to £0.23 per kWh.

Large acknowledges that, if the cost of electricity was to fall, the savings from the heat pump solution would be less impressive compared with an all-electric solution, but the carbon savings would remain the same.

Perhaps more impressively, Large says the figures do not take into account additional infrastructure savings, including a reduction in the size of the site’s leased step-down transformer, which was reduced in capacity from 2MW to 1.5MW, saving an additional £120,000 on set-up and leasing costs to date. ‘If people are truly driven to reduce energy consumption, it can be done. The capital cost can be high, but the savings are not limited to the energy consumption alone.’

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