Building Services Engineering Research & Technology

This paper presents the energy and environmental performance of whole house energy systems implemented in six 1970s bungalows in South Wales, owned by Swansea Council. The objective was to reduce energy demand and carbon emissions, maximise renewable supply whilst ensuring a comfortable and affordable home for the residents. The whole house energy system for each home involved the installation of a combination of passive and active low carbon solutions. Detailed monitoring was carried out for a year before and for more than 2 years after the work, annual figures have been validated and normalised for weather. Analysis of monitored data confirms that Standard Assessment Performance ratings improved from 12 to 95. The average annual energy consumption across the six bungalows was reduced from 16,117 to 4560 kWh. 2418 kWh was provided by the PV panels and battery, with 1963 kWh of excess electricity that could be sold back to the grid. Real-life average Ground Source Heat Pump CoP was monitored at 3.3. Embodied carbon for retrofitting each house is estimated at 22,980 KgCO2e +/−20%, approximately 5-years carbon payback. Indoor conditions have been improved with internal temperature and relative humidity achieving standards with residents reporting levels of improved comfort satisfaction.

Practical Application: A whole house energy system demonstrates the benefits of a holistic, fabric and systems retrofit approach. The work informs how gathering data using appropriate methods assists modelling predictions and decisions throughout the retrofit stages. The study demonstrates extensive monitoring as a vital tool to evaluate the performance of the individual components and the whole system within the home, as used by the residents. Performance evaluation is critical in identifying issues, allowing resolutions to be made both immediately on-site as well for longer term, follow on retrofit programmes. Real-life performance evaluation and visualisation methods are transferable across global building industry.

Proactive strategies for data-driven operational schedules based on monitored occupancy patters can enable energy demand reduction and optimal resource utilisation. A replicable framework that enables strategic closure of specific thermal zones is introduced and design and operational considerations are discussed. The potential of the framework is illustrated through a case study building, where up to 6% annual energy savings were estimated, highlighting the effectiveness of zone closures. Further findings indicated that total energy savings from the simultaneous closure of multiple zones were marginally larger compared to savings from closing off zones individually, depending on zone capacity and use. Therefore, balanced considerations should take place prior to selecting which zones to close off, also taking into account user acceptability, capacity of systems and controls as well as the internal layout of the building. The research enhances the understanding of the relationship between occupancy and energy demand, while offering recommendations for more energy efficient and sustainable building design and operations that require minimal capital cost.

Practical Application: This paper provides design and operational considerations based on a robust and replicable framework for energy savings by optimising operational building schedules based on monitored occupancy patterns. This allows a proactive implementation of data-driven strategies that maximise resource utilisation, such as closure of specific zones during periods of low occupancy, without requiring any physical intervention. The findings on a case study building demonstrate that annual energy savings can be achieved, underscoring the potential for substantial cost reductions and improved energy efficiency. Applications can also extend to optimising energy demand for energy flexibility.

Energy Performance Certificates (EPC) are used across Europe to communicate the energy performance of buildings to a range of different end users. However, as new approaches are introduced and guided at the European level via the Energy Performance Buildings Directive (EPBD), the ability of assessment methodologies and assessors to accommodate these new forms is likely to differ due to the significantly different frameworks in each country. The Horizon-funded crossCert project investigates this by identifying how EPC methodologies differ across countries, highlighting the implications of these differences on the performance gap and what that means for future innovations. Results indicate that methodologies vary considerably regarding general approaches, from highly standardised to highly tailored and assessor qualifications. This paper will look at such differences and investigate how these differences can affect future efforts towards improving EPCs.

Practical application: With the recent recast of the Energy Performance of Buildings Directive (EPBD) emphasising the need for future innovations of EPCs across Europe and encouraging next-generation EPCs, it is important to study country-specific calculation methodologies. In particular, the lack of harmonisation in different approaches can make top-down innovations difficult to implement and raise questions about how an individual country can or should respond to those guidelines. This paper explores the variations in different aspects of EPC assessment methodologies across 10 European countries and how these differences impact the EPC performance gap and future metrics.

To meet the UK’s 2050 net zero carbon targets, Whole Life Carbon Assessment (WLCA) is used to calculate the lifetime carbon emissions of building projects. This paper aims to compare different estate regeneration scenarios for meeting the interim 2030 benchmarks for the 2050 target. The research consists of a case study employing co-design and WLCA experiments, and impact evaluation surveys. The results of the WLCA demonstrate the lower operational impacts of fossil-fuel-free scenarios, and lower embodied and overall carbon emissions of retrofitting scenarios. To make an informed decision towards the future of the estates, different regeneration scenarios need to be studied, and the stakeholders should understand the carbon emissions of different materials and systems. The findings of this study can be used to compare regeneration schemes of other building types.

Practical application: This study underscores the critical role of early-stage design decisions and engaging with the communities in minimising the carbon footprint of building projects and making informed decisions. The study reinforces the potential superiority of retrofitting over new builds, which serves as a clear call for the inclusion of retrofit options in the analysis of diverse regeneration and redevelopment scenarios. The study’s outcomes also highlight the pivotal role of stakeholder engagement in comprehending the Global Warming Potential (GWP) of materials and systems, influencing the participatory development and evaluation of regeneration scenarios. This approach is paramount to devising strategies that align with net zero ambitions, thereby ensuring environmentally and socially responsible estate regeneration.

This study reviews Soft Landings (SL) implementations, focusing on its role in achieving Low and Net Zero Emission (LZE) buildings and reducing the energy performance gap. With buildings contributing significantly to global carbon emissions, it is crucial to understand the effect of integrating approaches like SL for meeting Net Zero goals. Notably, this research identified that the extended 3-year aftercare phase of SL does not always lead to reduced operational carbon emissions. While SL promotes collaboration and structured delivery, its overall impact on consistently achieving LZE buildings remains unclear, largely due to insufficient in-use performance data. The paper advocates for integrating SL with other performance-based methods, emphasising the need for enhanced industry collaboration and data sharing to augment the understanding and effectiveness of SL in delivering LZE buildings.

Practical Application: This paper offers a thorough analysis of the Soft Landings (SL) framework in achieving Low and Net Zero Emission (LZE) buildings. It examines barriers at each project lifecycle stage and evaluates SL’s effectiveness through case studies, revealing inconsistencies in reducing operational emissions. The findings emphasise integrating SL with performance-based initiatives and enhancing industry collaboration and data sharing. Built environment professionals can leverage these insights to improve project delivery, optimise building performance, and achieve LZE goals more effectively.

The domestic sector made up 16% of UK’s total greenhouse gas emissions in 2021. The build-to-rent market is experiencing a rapid expansion, but the energy performance and distinctiveness of this building sector are still generally undiscovered. Therefore, 423 build-to-rent flats from three build-to-rent developments in England were evaluated with top-down approach. Energy use intensities of flats were compared against domestic energy benchmarks and design targets. Possible determinants of energy consumption in build-to-rent flats, including EPC rating, number of bedrooms, air permeability, glazing area and glazing orientation were investigated through correlation analyses. Research discovers discrepancy between actual energy performance of the studied flats and design targets supporting UK’s 2050 net zero target. In this case study, number of bedrooms is identified as the most noticeable factor influencing energy consumption. Results of this study provide an introductory insight of the build-to-rent sector and serve as a starting point to encourage further exploration.

Practical application: This paper specifically focuses on build-to-rent buildings within the domestic sector. Energy use situations of build-to-rent flats in the UK were investigated with actual measured data provided by a build-to-rent developer. Results demonstrate the discrepancy between energy use in the build-to-rent flats being studied and existing domestic benchmarks. This paper provides insights to researchers, building developers and policymakers regarding the energy performance of this upsurging build-to-rent building sector and its associated influencing factors. It also contributes ideas on the importance of data sharing and development of energy benchmarking of the build-to-rent sector.

This paper proposes a methodology for the early-stage selection of climate control systems in building design, focusing primarily on minimising whole life carbon (WLC) emissions. A significant obstacle is the limited availability of comprehensive data on the carbon footprint of Heating, Ventilating and Air Conditioning (HVAC) equipment and materials, along with the challenges or absence of early-stage energy models and detailed HVAC designs. This paper presents and compares the WLC for seven different HVAC systems and designs for an office building. The study demonstrates how HVAC engineers and designers can make informed decisions by selecting HVAC systems, materials, and components in the early stages. It illustrates the outcomes of a typical project design from both WLC and operational energy perspectives. Additionally, the paper provides normalised WLC benchmarks for each system in terms of kgCO₂e per square metre of floor area.

Practical Applications: This study provides practical guidance for HVAC engineers and designers in achieving net-zero building goals by minimising Whole Life Carbon (WLC) across seven climate control systems. The developed benchmarking tool enables early-stage selection of these systems by normalising embodied and operational carbon data per square metre of floor area, facilitating direct comparisons. Insights into the benefits of low-GWP refrigerants and efficient designs support the adoption of sustainable solutions. The integration of operational energy and consideration of decarbonising grids ensure future-proof designs that remain effective under evolving energy conditions. The study offers valuable benchmarks and actionable strategies to support industry decision-making and policy development for reducing the environmental impacts of HVAC systems.

Low-temperature domestic hot water (DHW) systems provide significant carbon reduction benefits, supporting the UK’s 2050 net-zero target. Typically, low water volume applications do not need recirculation and storage when instantaneous heaters are employed, such applications can be more flexible in terms of temperature range and safety requirements. However, commercial applications may have high volumes of hot water and hence, will require high working temperatures to satisfy the recirculation requirements. This study developed a comprehensive toolkit to benchmark the embodied and operational carbon in terms of kgCO₂e/m² for various DHW systems, including equipment, refrigerants, and operational emissions. Analysis of seven DHW designs for an office building revealed that low-temperature systems consistently demonstrate the lowest whole-life carbon (WLC), underscoring the impact of grid decarbonisation and low-GWP refrigerants. The WLC results are normalised per square metre of floor area. Low-temperature systems showed the lowest WLC even with the inclusion of water treatment and chemical dosing systems.

Practical Application: Our contribution aligns with modern building industry practices by promoting the adoption of low-temperature domestic hot water (DHW) systems to reduce carbon emissions. This approach supports the industry’s shift towards sustainable construction and the net-zero carbon target by 2050. We emphasise the benefits of these systems, particularly in reducing whole life carbon (WLC) impacts, which is crucial for environmentally conscious building designs. By demonstrating that low-temperature systems maintain low WLC even with additional components like water treatment, our work provides practical insights for professionals aiming to implement energy-efficient and sustainable heating solutions in commercial buildings.

Retrofitting heat networks will play a major role in improving building performance and facilitating a net zero environment by 2050. A 94-dwelling social housing development based in the UK, was operating a heat network and experiencing significant issues with overheating, resident discomfort, and poor network efficiency. An Automatic Meter Reading (AMR) system was installed to baseline network performance and identify improvement opportunities. The data revealed the network was operating with a 74/66 °C temperature profile, and that the total network losses exceeded 1000 W/dwelling. This paper sets out the detailed methodology and considerations in retrofitting the heat network to enable future connections to low carbon heat sources such as heat pumps or low temperature district heating. Quality assurance was undertaken during the design, install and commissioning stages to facilitate the project’s success and hit key milestones. At present, the operating temperatures have been reduced to a 55/37 °C flow and return temperature, enabling a gas consumption reduction of 38% and network heat loss reduction of over 90%, with heat losses currently at 56 W/dwelling. This data driven approach to retrofitting has simultaneously improved resident comfort, reduced heat costs and enabled a straightforward connection to low carbon heat sources when available.

Practical Application: This paper outlines the interdependencies of typical issues on existing heat networks and the effect of these issues on operational performance, cost, carbon emissions and resident satisfaction. A methodology is given which outlines the importance of maximising heat network performance prior to moving to low carbon heat sources. The results of carrying out this methodology on an existing heat network act as an example to the industry showing that the 100 W/dwelling heat loss target in CIBSE CP1: heat networks code of practice can not only be achieved, but significantly improved upon in existing buildings.