Resource Use and Circular Economy

The entire building is a testbed in testing circular economy design principles. Without defined circular economy industry standards or accreditations to work towards, it was necessary for the client and design team to set their own standards and goals based on the GLA’s 6 core principles of Building in Layers, Designing out Waste, Building for Disassembly, Building for Longevity, Building for Adaptability and Use of Re-Used materials.Ìý

Key circularity approaches included a layered construction strategy allowing each part – whether structural, service-related, or internal – to have a different expected lifespan and enable easy separation for maintenance, upgrades, or future reuse without damaging the surrounding fabric.ÌýÌý

Reused materials were prioritised, including reused steel, raised access flooring and parts of the external landscaping. Internal finishes have been chosen and assembled with a focus on Circular Economy. Cradle-to-Cradle carpet tiles feature in the main office floors. Engineered cork flooring, made from off-cuts from the wine cork industry, features in the central circulation spaces.Ìý

Materials were selected to enable disassembly and onward re​use​​​, helping to lower the building’s carbon footprint throughout its lifecycle. To support with this a modular frame was used to enable flexibility and future proofing. Bolted connections were used on the entire frame, cladding was mechanically fixed, flooring was fixed with non-adhesive substrate and window details enable easy removal.ÌýÌý

Further, design for longevity has also been considered, through a flexible layout and the use of durable materials. This includes Accoya cladding with a 50 year warranty and a durable Kalzip roof. Connection details are also robust, with a concrete slab to protect the timber structure.ÌýÌý

The construction approach also minimised waste, through the use of prefabricated wall and roof systems. There is also an operational waste management plan in place.ÌýÌý

Operational Energy Performance

The energy use intensity of the building is 39.44 kWh/m2/yr, which exceeds LETI and RIBA 2030 target requirement of 55kWh/m2/yr. It is also EPC A+.ÌýÌý

To achieve this, key measures include taking a fabric-first approach for thermal efficiency. Prefabricated timber framed SIP wall panels were used, highly insulated with recycled glasswool and lined with airtight OSB. This approached ensures quality to the thermal envelope seeking to minimise the performance gap. The U-values of the walls are 0.15 W/m2K and the roof was 1.12 W/m2K and all windows are triple glazed.Ìý

This approach of thinking beyond the standards provides a building which is net positive for operational energy in the summer months and already meets LETI 2030 standards.Ìý

Renewable Energy

Renewable energy is supplied by rooftop solar panels which powers an air source heat pump, providing all of the building’s energy in the summer.Ìý

Embodied Carbon

Although a whole-building WLC assessment ·É²¹²õ²Ô’t done in accordance with RICS, individual savings were calculated based on specific measures. A Ìýwas used in the substructure saving 18.9 tonnes of CO2. A primary timber glulam frame was also used, allowing long spans to ensure the future flexibility of the internal spaces, without the high embodied carbon of steel or concrete.ÌýÌý

Reused material choices also contribute significantly to carbon savings, including ​​savings of 19.9 tonnes of CO2 from reused steel, 21 and 0.9 tonnes ​of​ CO2 from reused raised access floors. ​​Additionally, the use of biogenic materials allows the building to store approximately 94.5 tonnes of CO2.ÌýÌý

Further, the building was also a testbed for the use ´¡»å²¹±è³Ù²¹±¹²¹³Ù±ð’s Breathaboard, a natural compostable alternative to gypsum plasterboard.ÌýÌý

Social Value

The design not only prioritises the clients but ​employees and visitors ​as well ​​by incorporating features that support comfort, focus, and connection. Elements such as dedicated tech-free areas, quiet zones for focused work, and the inclusion of greenery both inside and outside the building are all designed to support and enhance user wellbeing. Shared spaces such as reception, corridors, and breakout areas were intentionally arranged to foster interaction and a sense of community. Accessibility and inclusivity were built into every aspect of the layout, with thoughtful details such as​ÌýÌýÌýÌý ​ the internal staircase and mezzanine designed to aid navigation, particularly for those with cognitive or spatial challenges. A mix of outdoor settings, including dining terraces and contemplative areas by an ecological pond and a memorial tree honouring founder Alan Jacobi, further enhances the user experience, offering places for relaxation, reflection, and connection to nature.Ìý

Embodied Carbon

Embodied carbon has been modelled following BS EN 15978 and RICS Professional Standard on whole life carbon modelling, version 2. Building fabric elements have been assessed, with material quantities derived from the BIM model and provided by the structural engineer. MEP systems have been assessed following the CIBSE TM65 methodology for embodied carbon, providing a robust estimate of the carbon emitted by the production of the systems and refrigerant leakage. The project targeted RIBA 2030 and LETI limits for embodied carbon, pioneering this approach during the design phase in 2019. Through the extensive use of timber for the structure, the upfront carbon is currently calculated to be 3,328 tCO2e or 413 kgCO2e/m^2 (following the RICS v2 methodology). Focusing on the upfront carbon, Old Paradise Street achieves the LETI 2020 design target, and the equivalent RIBA 2030 as-built target (using the LETI ratings for comparison). Due to this, the whole life cycle embodied carbon for the building is determined to be 491 kgCO2e/m^2. Additionally, the timber structure locks away 1,884 tCO2e, representing a significant storage of carbon.

The embodied carbon was largely reduced due to the use of mass timber, and this lighter construction method also reduced the concrete requirements for the sub-structure.

Concrete was used in the core of the building for fire reasons, utilising 60% cement replacement in the form of GGBS, significantly reducing carbon emissions.

Resource Use and Circular Economy

The frame has been designed to be fully demountable to enable the building elements to be directly reused in future buildings. This includes creating alternative solutions for fire protection on the floors, moving away from permanent screeds to panel systems, and using custom connection details that needed to be tested for compliance with fire requirements.

Operational energy performance

The key sustainability target for Pall Mall was that it is net zero in operation with low energy consumption. The aim was for all electricity supplied to the building to be derived from renewable sources, and intelligent building management technology will also be incorporated throughout to ensure energy use is optimised.

A switch from gas heating to hybrid variable refrigerant flow (HVRF), with an air source heat pump (ASHP) serving domestic hot water and air handling unit (AHU) coils will dramatically reduce the overall carbon emissions and set the building on a trajectory for zero carbon as the grid emissions reduce. Note that achieving the ‘Paris Proof Targets’ as set out in UKGBC guidance was not possible due to the existing nature of the building and the listed status, as certain elements of the fabric were required to remain, however, a 74% EUI reduction is predicted. A focus on air tightness and façade replacement, within the constraints of the listed building status provided a significant energy consumption improvement.

Resource use and circular economy

The fit-out uses circular economy approaches by utilising recycled and reclaimed furniture and materials for timber partitions and reclaimed raised access floors. Through retaining the existing structure, Bruntwood has avoided the need to rebuild which is estimated to have resulted in approximately 7,900 tonnes of additional carbon emitted – equivalent to around 16,000 flights from London to New York.

Climate change adaptation

The new façade and glazing system has been designed to limit the solar gain to the building and thus limit the energy required to cool it. At the same time, it will allow the building to respond to increasing external temperatures over time.

Health, well-being and social value

The site contained an existing external area of public realm that was under-utilised and a target for anti-social behaviour, therefore the space was redesigned to create a vibrant amenity area and linked to the retail space within the building.

Climate change mitigation

The carbon assessments achieved the below figures at stage 4 design:

• Upfront Carbon (A1 A5) – 393 kg CO2e/m2,
• Embodied Carbon ( A1-A5, B1–B5, C1-C4) 840 kg CO2e/m2
• Operational Energy – 99.8 kWh/m2 per annum

This was based on most of the structure and façade being retained, with window replacements and the addition of an upper floor. The most impactful measures included; switching from gas boilers to ASHP, improving the efficiency of the AHUs (Air Handling Units), implementing demand-led ventilation, and refining the fabric performance.

As part of the Design for Performance process, it was necessary to model ‘off-axis scenarios’. These are iterations of the energy model that consider potential variations from the baseline design, such as future increased summer temperatures, failure or mis-operation of key systems, changes to occupancy, or increased air permeability.

The modelled operational energy performance of the building – which was completed in line with NABERS Design for Performance standards – was sufficient to achieve a NABERS 5* rating at the design stage, including the necessary margin.

Health, well-being and social value

Targeting £70 – £111million in social value over the lifecycle of the development through:

• Jobs: promoting local skills and employment
• Growth: supporting growth of responsible regional business
• Social: healthier, safer, and more resilient communities

Resource use and circular economy

To minimise the embodied carbon impact, the structure was maintained and, instead, the building underwent an exterior refurbishment with solar PV and solar shading installed.

Operational energy performance

The core plant and all heating and ventilation equipment were replaced. Alongside this, technologically integrated variable air flow valves were included which enabled automated air quality management on a localised basis. The lighting was upgraded to new, highly-efficient LED systems.

To support the ongoing running of the building, a new building management system (BMS) was installed, integrating a smart building server, sensors, access and visitor management systems. Furthermore, a building app Coalhouse.life was introduced to facilitate interaction between the smart technology, building amenity and the building occupants.

Health, well-being and social value

Had the required level of investment not been committed, the asset was at risk of becoming a stranded asset, but it now makes a strong and positive impact on the users and the streetscape along a key route through Cardiff city centre, thereby contributing to broader social value.

Resource use and circular economy

To establish the best retrofit strategy the team undertook a whole life carbon options appraisals considering a number of scenarios from a light retrofit to a complete demolition and rebuild. This analysis shaped the project brief, ultimately resulting in the deep retrofit and repositioning of the asset as opposed to more whole life carbon intensive outcomes.

A deep retrofit enables the building to take a major step toward net zero carbon in operation whilst retaining the existing frame & foundations, making significant savings in embodied carbon emissions as a result. The whole life carbon options appraisal was an effective tool is providing comparative data and creating meaningful discussions on the benefits of frame retention.

Operational energy performance

Operational energy performance savings have been identified via NABERS Design for Performance modelling and EPC modelling to define a performance-based design that will also deliver an high-performing Regulatory outcome. The building is targeting a NABERS UK 5-star rating & EPC A.

Notable energy & carbon savings have been enabled via:

• Early engagement and provision of comparative whole life carbon data at an early stage.
• Retention of the existing frame and foundations.
• Optimising core location and arrangement, riser provision and naturally lit office arrangement.
• An optimised façade design balancing daylight, thermal performance and solar control
• Systems control and build automation eliminating unnecessary energy consumption in the first instance
• Good management practices and the provision of systems that enable insight and interrogation of building performance.

From a cost perspective, the major refurbishment of Havelock came in toward the top end of the benchmark range for re-purposing/refurbishment schemes in Manchester in late 2021. This is reflective of the level of ambition and extent of the works. Notwithstanding this, it is estimated that the contract sum was approximately 25-35% less than the equivalent cost for a new build Grade A office in Manchester (late 2021).

Operational energy performance

The building will be fully electrified, and no fossil fuel use is proposed: it will be mechanically ventilated with heat recovery in place to reduce energy demand. The heating and cooling demands of the building will be met by highly-efficient modular Variable Refrigerant Flow (VRF) systems installed in accordance with BCO guidance for zoning.

A 57% reduction in EUI is anticipated to be achieved through a deep retrofit of the building. This is, in part, due to a proportion of the existing fabric being removed and replaced with a new system which will increase the air tightness and thermal performance of the building. The retained façade will also be insulated, and the glazing replaced to ensure the thermal performance is improved.

Resource use and circular economy

Through careful planning, 75% of the existing structure (by volume) will be retained and only 25% will be demolished to make way for a new extension structure. The existing structure comprises 55% of the overall proposed building structure volume.

Health, well-being and social value

An important driver for the retrofit project is improving the quality of the space to attract new tenants and improve user well-being. Roof terraces with extensive planting are proposed on levels 5-9, providing valuable amenity outdoor space for the building users, promoting their wellbeing and connection with nature. The scheme will also include two plant enclosures at roof level which will be covered in full height green walls.

Climate change adaptation

Blue roof attenuation will be adopted on the roof terraces, reducing the overall site discharge rate in excess of 60% from the existing flow rate. The river wall is also designed with consideration for rising sea and flood levels. The wall will have the provision for extension, should the need arise in the future.

Water efficiency

A combined rainwater and greywater reclamation system will be provided to capture rainwater from the building’s terraces along with greywater from the showers. This will be treated on-site for reuse to reduce the amount of fresh potable water the building needs. The treated water will be used to irrigate the terraces planting, and for WC flushes.

Biodiversity

Biodiversity is promoted through the wide range of planting proposed, ranging from sedum and wildflower green roof blankets to lush herbaceous planting. Swallow terraces and swift boxes will be integrated within the new façade areas to increase local habitat for these birds. New trees and planting will be added to the site as part of the new public realm design at ground level. The development will achieve an overall Urban Greening Factor of 0.3.

Operational energy performance

Light Retrofit – The overall retrofit strategy was to initially carry out a light retrofit of the office spaces to replace the CatA fit-out with an efficient solution and converting from the existing VAV system to minimum fresh air and fan coil units. This was combined with some significant structural interventions in areas of the building where there is a change of use.

Deep Retrofit – Once the office spaces have been retrofitted, a deep retrofit of the central plant was carried out, replacing gas-fired boilers and air-cooled chillers with air source heat pumps.

Health, well-being and social value

An important driver for the retrofit project was improving the quality of the space to attract new tenants and to increase the lettable area. This was achieved by increasing the perimeter floor-to-ceiling heights by 500mm and undertaking structural interventions to create a better-connected floor plate. Roof terraces were added with the necessary slab strengthening. Mezzanines in double-height spaces were also added and an under-used loading bay and basement car parking were converted into office spaces. Where planning permission was required due to building extension, BREEAM certification was achieved.

Operational energy performance

The software identified inefficiencies such as the plant running times being inconsistent with occupant hours, meaning vacant floors often had air conditioning units running. Flawed air recirculation strategies were also in place that did not fully utilise the available heat recovery/energy conserving functionality, due to ineffective Building Management System (BMS) control.

After the completion of the initial actions to address these issues, the electricity consumption in November/December reduced from a baseline of approximately 4800 kWh/day to 3800kWh/day (-20%), equating to cost savings of more than £100,000. Virtual meters also estimate a reduction of around 25% in gas consumption from boilers. The platform was key in facilitating collaboration between tenants, the landlord and the operations/facilities management (FM) team.

Operational energy performance

The four most significant energy savings that had relatively little impact on the use of the building were – in descending order – ASHPs, HVAC upgrades, lighting improvements, and mixed mode operation. More noticeable changes, such as tenant IT (mostly cloud servers) and behaviour (temperature set points, dress codes and remote working approach) are ones over which the landlord has limited operational control, but which do still have a marked influence.

Demand Control Ventilation: New variable air volume (VAV) terminal units will provide demand-based control of the ventilation system. The VAV units will extend from the reused main riser ductwork and be controlled via CO₂ sensors used to measure the equivalent level of occupancy. This will significantly reduce the amount of ventilation air required during periods of lighter occupation.

Partial Mixed Mode Operation: The existing smoke vents within the perimeter facades will be re-tasked to provide natural ventilation to the office floors. Actuators will be refurbished or replaced as required and interface units provided to allow connection and control to the building management control system. This will allow passive ventilation to the perimeter zones during the shoulder period (spring and autumn). When either too cold or too warm the whole building will revert to sealed operation.

Resource use and circular economy

The ethos is to minimise the embodied carbon associated with the project via the retention and refurbishment of as much of the existing building as feasible, including the façade and centralised MEP. The existing air handling plant and secondary pump sets will be comprehensively refurbished. Pipework and ductwork installations, main electrical infrastructure and distribution are to be retained (following testing).

Health, well-being and social value

Common spaces are to be revitalised, roof terraces updated, with planting and bio-diversity increased. Demand controlled ventilation will lead to improved air quality while also reducing energy consumption.