Occupant behavior has an important impact on building energy consumption, and the accuracy of an occupant behavior model directly affects the reliability of energy consumption simulation results. Ultra-low energy buildings are crucial to achieving building energy conservation and carbon dioxide reduction in China. In order to effectively promote the development of ultra-low energy buildings in Hot Summer and Cold Winter Climate Zones. where most residents adopt a “part-time, part-space” pattern of intermittent energy use behavior, and to solve the problem of poor indoor thermal environments and the high incremental cost of ultra-low energy, the study described in this paper takes Changsha as an example to carry out a multi-objective optimization study on ultra-low energy housing using a probabilistic behavioral model. On the basis of a probability model representing the residents’ actual behavior in Changsha, the optimization objective indicators, key variables and the technology benchmarks for ultra-low energy building were determined, then multi-objective optimization was carried out for a range of energy efficient technologies to obtain the Pareto optimal solutions. The results showed that the set of optimal solutions could reduce energy demand by 50.2 to 60.2% and reduce indoor thermal discomfort time by 3.52–11.09% compared with those of a reference base case, which just meets the requirements of the current design standard for energy efficient domestic buildings. An optimum solution for energy savings and indoor thermal comfort, along with economic costs, was identified, which can assist in decision-making by providing different preferences and provide useful reference for the design of ultra-low energy buildings in Hot Summer and Cold Winter Climate regions.

This paper presents the results for the operating energy performance of the smart operation for a low carbon energy region (SOLCER) house. The house design is based on a ‘systems’ approach, which integrates the building technologies for electrical and thermal energy systems, together with the architectural design. It is based on the concept of ‘energy positive’ buildings, utilising renewable energy systems which form part of the building envelope construction. The paper describes how the building energy model HTB2, with a range of additional ‘plugins’, has been used to simulate specific elements of the design and the overall energy performance of the house. Measurement data have been used in combination with the energy simulation results to evaluate the performance of the building together with its systems, and identifying the energy performance of individual components of the building. The study has indicated that an energy-positive performance can be achieved through an integrative systems approach. The analysis has indicated that the house, under normal occupancy, needs to import about 26% of its energy from the grid, but over the year its potential export to import ratio can reach 1.3:1. The paper discusses the performance gap between design and operation. It also considers the contribution of a transpired solar air collector (TSC) to space heating. The results have been used to gain a detailed understanding of energy-positive performance.

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.

European governments have set ambitious retrofitting targets driven by the commitment to reduce the greenhouse gas emissions by at least 80% by 2050. The United Kingdom has the oldest housing stock in Europe, with over 2/3 of dwellings built before 1976, when building regulations started to include energy efficiency. This raises concerns over carbon emissions, health, comfort and running costs, and government’s set targets and initiatives for significant improvements. Deep retrofitting by using innovative technologies with respect to aesthetics has considerable and measurable benefits, while it can be a costly and challenging process. This study examines a combination of measures undertaken in a pre-1919 dwelling in south Wales, including reduction of energy demand and the application of renewable energy supply and energy storage. A whole house performance and a systems breakdown evaluation is presented comparing the pre and post intervention status. Both monitoring and modelling tools where used, and the performance gap is also discussed. An annual reduction of 34% in space heating and 78% in electricity import was monitored with an additional electricity export of 3217kWh. This represents a total annual cost saving of £1115, at 2019 UK gas and electricity prices. The total cost of the retrofit was £55K.

This paper presents the design of a monitoring protocol to support retrofit strategies and drive the evaluation of a low carbon house. Monitoring is used during pre-intervention stage to facilitate the decision-making process, as well as in the post-intervention to evaluate the performance of the building and systems. The first phase refers to monitoring as a diagnostic tool with a view to reduce the uncertainty of suggested low carbon solutions by providing real measurements and evidence on building conditions, comfort, systems and occupants behaviour and interactions. The second phase utilises monitoring as an evaluation tool to quantify benefits and challenges of the retrofitting by providing information and analysis on the supply and demand reduction, the difference in comfort and the effectiveness of each intervention. The study explains the protocol development and discuss different monitoring depths and requirements based on the performance indicators required. A typical pre-1919 Welsh end-terraced dwelling is used as a case study to demonstrate the two phases of the proposed protocol. The protocol was developed as part of the Low Carbon Built Environment (LCBE) project at Cardiff University and it was tested in various building types and research-led retrofit packages.