The UK has one of the least energy-efficient housing stocks in Europe. By 2030, the emissions from UK homes need to fall by at least 24% from 1990 levels to meet the UK’s ambitious goal, which is reaching net-zero emissions. The originality of this paper is to apply the building typology approach to predict energy savings of the UK housing stock under a step-by-step energy retrofit scenario, targeting the Passive House Standard for refurbishments of existing buildings, namely the EnerPHit “Quality-Approved Energy Retrofit with Passive House Components.” The typologies consist of twenty reference buildings, representative of five construction ages and four building sizes. The energy balance of the UK residential buildings was created and validated against statistical data. A building stock retrofit plan specifying the order in which to apply energy efficiency measures was elaborated, and energy savings were calculated. The predicted total energy demand for the UK residential building stock for the year 2022 is 37.7 MTOE, and the carbon emissions estimation is 65.33 MtCO₂e. The energy-saving potential is 87%, and carbon reductions are about 76%, considering all the steps of renovation applied. It has been demonstrated that the step that provides the biggest savings across the housing stock is the one that involves replacing windows, draught-proofing, and installing mechanical ventilation with heat recovery.

Energy retrofit tools are considered by many countries as one of the strongest incentives to encourage homeowners to invest in energy renovation. These tools help homeowners to get an initial overview of suitable retrofit measures. Although a large number of energy retrofit tools have been developed to inspire and educate homeowners, energy renovation by individual homeowners is still lagging and the impact of current tools is insufficient as awareness and information issues remain one of main obstacles that hinder the uptake of energy retrofitting schemes. This research extends the current knowledge by analysing the characteristics of 19 tools from 10 different countries. The selected tools were analysed in terms of energy calculation methods, features, generation and range of retrofit measures, evaluation criteria, and indications on financial support. The review indicates that: (1) most toolkits use empirical data-driven methods, pre-simulated databases, and normative calculation methods; (2) few tools generate long-term integrated renovation packages; (3) technological, social, and aesthetic aspects are rarely taken into consideration; (4) the generation of funding options varies between the existing tools; (5) most toolkits do not suggest specific retrofit solutions adapted to traditional buildings; and (6) preferences of homeowners in terms of evaluation criteria are often neglected.

Many retrofit projects went wrong in the UK principally because of the application of inappropriate retrofit solutions, which resulted in damp issues, with some leaving houses in worse conditions than pre-retrofit. Various online tools were developed to inform homeowners about the benefits of retrofitting. Prior to this study, little was known about users’ evaluation of these tools and the effects of calculator use. Furthermore, no retrofit tool aims to raise the awareness of homeowners about moisture risks in a retrofit project. The originality of this study is to develop and evaluate an online moisture-safe retrofit decision-making tool for homeowners. The adopted methodology consisted of two phases. Phase one aimed to develop the tool. In phase two, semi-structured interviews were conducted to evaluate the tool. The results indicate that the tool has been well received by homeowners. The tool significantly increased participants’ awareness of moisture risks related to a retrofit project. Most participants considered the tool an eye-opener, while few of them found it scary. However, the tool did not result in an increased willingness to invest in energy efficiency measures. The discouragement was related to high investment costs and long payback periods of some retrofit measures. Based on our findings, we formulate a set of design recommendations to improve the proposed tool and help retrofit calculators, in general, overcome challenges.

The UK government has legal binding objectives under the “climate change act 2008” to accomplish net-zero carbon emissions by the year 2050. The government has implemented a variety of measures across many different sectors of the UK economy that are accountable for the emissions. The aim of this research was to evaluate and compare some existing renewable energy technologies. It discusses the advantages and disadvantages of installing these technologies into homes across the UK and the impact it has on the “net-zero housing” scheme. A series of results were produced using the SAP rating, deploying an existing dwelling located in Bradford, UK, fitted with a gas boiler and comparing the results to those obtained for an air source heat pump (ASHP) and a mechanical ventilation with heat recovery system (MVHR). The three systems were analysed in terms of cost-effectiveness, carbon footprint and energy savings. The study found that the installation of a gas boiler costs less than that of the other systems, whilst ASHPs involve high upfront costs. However, the latter showed higher energy savings, with an efficiency of 4.0 compared to 0.75 and 0.95 for the gas boiler and MVHR, respectively. The SAP rating showed that the ASHP had a carbon footprint of 2396.3 kg/year for the studied flat of 65.72 m², whilst carbon footprints of 3406.92 CO₂ kg/year and 7143.45 kg/year were determined for the gas boiler and the MVHR system, respectively. The study concluded that ASHPs work better than the other systems for most of the existing UK housing, unless a whole building fabric improvement is considered, in which case, some other renewable options could be a choice.