Dr Adam Hardy

Variations of eclipse arrival times have recently been detected in several post-common envelope binaries consisting of a white dwarf and a main-sequence companion star. The generally favored explanation for these timing variations is the gravitational pull of one or more circumbinary substellar objects periodically moving the center of mass of the host binary. Using the new extreme-AO instrument SPHERE, we image the prototype eclipsing post-common envelope binary V471 Tau in search of the brown dwarf that is believed to be responsible for variations in its eclipse arrival times. We report that an unprecedented contrast of δmH = 12.1 at a separation of 260 mas was achieved, but resulted in a non-detection. This implies that there is no brown dwarf present in the system unless it is 3 mag fainter than predicted by evolutionary track models, and provides damaging evidence against the circumbinary interpretation of eclipse timing variations. In the case of V471 Tau, a more consistent explanation is offered with the Applegate mechanism, in which these variations are prescribed to changes in the quadrupole moment within the main-sequence star.

We present ALMA (Cycle 0) band 6 and band 3 observations of the transition disk Sz 91. The disk inclination and position angle are determined to be i = 9.°5 ± 3.°5°and PA = 18.°2 ± 3.°5 and the dusty and gaseous disk are detected up to ∼220 and ∼400 AU from the star, respectively. Most importantly, our continuum observations indicate that the cavity size in the millimeter-sized dust distribution must be ∼97 AU in radius, the largest cavity observed around a T Tauri star. Our data clearly confirm the presence of (2-1) well inside the dust cavity. Based on these observational constraints we developed a disk model that simultaneously accounts for the and continuum observations (i.e., gaseous and dusty disk). According to our model, most of the millimeter emission comes from a ring located between 97 and 140 AU. We also find that the dust cavity is divided into an innermost region largely depleted of dust particles ranging from the dust sublimation radius up to 85 AU, and a second, moderately dust-depleted region, extending from 85 to 97 AU. The extremely large size of the dust cavity, the presence of gas and small dust particles within the cavity, and the accretion rate of Sz 91 are consistent with the formation of multiple (giant) planets.

Context. The evolution of a circumstellar disk from its gas-rich protoplanetary stage to its gas-poor debris stage is not understood well. It is apparent that disk clearing progresses from the inside-out on a short time scale and models of photoevaporation are frequently used to explain this. However, the photoevaporation rates predicted by recent models differ by up to two orders of magnitude, resulting in uncertain time scales for the final stages of disk clearing. Aims. Photoevaporation theories predict that the final stages of disk-clearing progress in objects that have ceased accretion but still posses considerable material at radii far from the star. Weak-line T Tauri stars (WTTS) with infrared emission in excess of what is expected from the stellar photosphere are likely in this configuration. We aim to provide observational constraints on theories of disk-clearing by measuring the dust masses and CO content of a sample of young (1.8-26.3 Myr) WTTS. Methods. We used ALMA Band 6 to obtain continuum and

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Abstract

Models of planet formation and disc evolution predict a variety of observables in the dust structure of protoplanetary discs. Here, we present Atacama Large Millimeter/submillimeter Array (ALMA) Band-6 and Band-7 observations of the transition disc Sz 91 showing that the continuum emission at 870 μm, which is dominated by emission from large dust grains, is localized in an optically thin narrow ring. We find that most of the emission (∼95 per cent) is concentrated in a ring located at 110 au from the central star that is only about 44 au wide. In contrast, the 12CO (2–1) emission peaks closer to the star and is detected up to ∼488 au from the star. The concentration of large grains in a ring-like structure while the gas disc extends much further in and further out is in qualitative agreement with predictions of hydrodynamical models of planet–disc interactions including radial drift and gas drag.

A central hypothesis in the theory of cataclysmic variable (CV) evolution is the need to explain the observed lack of accreting systems in the ≃2-3 h orbital period range, known as the period gap. The standard model, disrupted magnetic braking (DMB), reproduces the gap by postulating that CVs transform into inconspicuous detached white dwarf (WD) plus main sequence systems, which no longer resemble CVs. However, observational evidence for this standard model is currently indirect and thus this scenario has attracted some criticism throughout the last decades. Here, we perform a simple but exceptionally strong test of the existence of detached CVs (dCVs). If the theory is correct, dCVs should produce a peak in the orbital period distribution of detached close binaries consisting of a WD and an M4-M6 secondary star. We measured six new periods which brings the sample of such binaries with known periods below 10 h to 52 systems. An increase of systems in the ≃2-3 h orbital period range is observed. Comparing this result with binary population models, we find that the observed peak cannot be reproduced by post-common envelope binaries (PCEBs) alone and that the existence of dCVs is needed to reproduce the observations. Also, the WD mass distribution in the gap shows evidence of two populations in this period range, i.e. PCEBs and more massive dCVs, which is not observed at longer periods.We therefore conclude that CVs are indeed crossing the gap as detached systems, which provides strong support for the DMB theory.

Context. The large cavities observed in the dust and gas distributions of transition disks may be explained by planet-disk interactions. At ∼ 145 pc, 2MASS J16042165-2130284 (J1604) is a 5-12 Myr old transitional disk with different gap sizes in the mm- and μm-sized dust distributions (outer edges at ∼ 79 and at ∼ 63 au, respectively). Its

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It is thought that planetary mass companions may form through gravitational disk instabilities or core accretion. Identifying such objects in the process of formation would provide the most direct test for the competing formation theories. One of the most promising candidates for a planetary mass object still in formation is the third object in the FW Tau system. We present here ALMA cycle 1 observations confirming the recently published 1.3 mm detection of a dust disk around this third object and present for the first time a clear detection of a single peak

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Eclipse timing variations observed from the post-common-envelope binary (PCEB) NN Ser offer strong evidence in favour of circumbinary planets existing around PCEBs. If real, these planets may be accompanied by a disc of dust. We here present the ALMA detection of flux at 1.3 mm from NN Ser, which is likely due to thermal emission from a dust disc of mass ~0.8 ± 0.2 M⊙. We performed simulations of the history of NN Ser to determine possible origins of this dust, and conclude that the most likely origin is, in fact, common-envelope material which was not expelled from the system and instead formed a circumbinary disc. These discs have been predicted by theory but previously remained undetected. While the presence of this dust does not prove the existence of planets around NN Ser, it adds credibility to the possibility of planets forming from common-envelope material in a 'second-generation' scenario.

Context.DZ Cha is a weak-lined T Tauri star (WTTS) surrounded by a bright protoplanetary disc with evidence of inner disc clearing. Its narrow Hαline and infrared spectral energy distribution suggest that DZ Cha may be a photoevaporating disc.

Aims.We aim to analyse the DZ Cha star + disc system to identify the mechanism driving the evolution of this object.

Methods.We have analysed three epochs of high resolution optical spectroscopy, photometry from the UV up to the sub-mm regime, infrared spectroscopy, andJ-band imaging polarimetry observations of DZ Cha.

Results.Combining our analysis with previous studies we find no signatures of accretion in the Hαline profile in nine epochs covering a time baseline of ~20 yr. The optical spectra are dominated by chromospheric emission lines, but they also show emission from the forbidden lines [SII] 4068 and [OI] 6300Å that indicate a disc outflow. The polarized images reveal a dust depleted cavity of ~7 au in radius and two spiral-like features, and we derive a disc dust mass limit ofMdust< 3MEarthfrom the sub-mm photometry. No stellar (M⋆> 80MJup) companions are detected down to 0.̋07 (~8 au, projected).

Conclusions.The negligible accretion rate, small cavity, and forbidden line emission strongly suggests that DZ Cha is currently at the initial stages of disc clearing by photoevaporation. At this point the inner disc has drained and the inner wall of the truncated outer disc is directly exposed to the stellar radiation. We argue that other mechanisms like planet formation or binarity cannot explain the observed properties of DZ Cha. The scarcity of objects like this one is in line with the dispersal timescale (≲105yr) predicted by this theory. DZ Cha is therefore an ideal target to study the initial stages of photoevaporation.

About a dozen substellar companions orbiting young stellar objects or pre-main sequence stars at several hundred au have been identified in the last decade. These objects are interesting both due to the uncertainties surrounding their formation, and because their large separation from the host star offers the potential to study the atmospheres of young giant planets and brown dwarfs. Here, we present X-shooter spectroscopy of SR 12 C, a ~2Myr young brown dwarf orbiting SR 12 at an orbital separation of 1083 au. We determine the spectral type, gravity, and effective temperature via comparison with models and observational templates of young brown dwarfs. In addition, we detect and characterize accretion using several accretion tracers. We find SR 12C to be a brown dwarf of spectral type L0 ± 1, log g = 4 ± 0.5, an effective temperature of 2600 ± 100 K. Our spectra provide clear evidence for accretion at a rate of ~10

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In the original paper (Santamaría-Miranda et al. 2018), the line fluxes were incorrect which affects several quantities given in the paper, most importantly the mass accretion rates. For example, for Paschen β the correct values are log(LPaβ / L☉) = −7.16 ± 2.25L☉ and Lacc = (− 8.59 ± 2.90) × 10−

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This study investigates whether short-term, single-location indoor environmental monitoring can support the assessment of condensation-related damp risk in residential buildings. Focusing on nine homes previously confirmed to have condensation damp, the research uses data collected over a 24-h period through smart thermostats that record temperature, relative humidity, and external weather conditions. The study first examines whether sensor data can indicate condensation risk through comparisons with dew point and humidity thresholds. It then analyses whether such data evaluate of the relationship between indoor conditions and outdoor climate using polynomial regression. Findings highlight significant variability in indoor environments between houses and weak correlations between internal and external humidity, suggesting a potential role of internal moisture sources. The results also point to limitations in the ability of single-point monitoring to capture localised condensation-prone areas such as cold surfaces or poorly ventilated zones. This raises important considerations for the diagnostic value of simplified monitoring strategies in damp risk management. While single-sensor approaches may offer initial insights into general indoor climate conditions, they are insufficient to fully characterise the complex, localised dynamics that contribute to condensation.

Excess dampness and mould can lead to poor indoor air quality, building damage, and negative health impacts for occupants. This study investigates several Energy Performance Certificate (EPC) variables such as efficiency rating, building type, and wall types and their relationships to damp issues. An EPC gives a property an energy efficiency rating from A (most efficient) to G (least efficient) and is valid for 10 years. 859 homes in England's housing stock were analysed, and a significant relationship was found between wall types and damp levels. The result of this study will help in the management of damp issues and the prediction of risky homes

Damp in residential buildings poses risks to indoor air quality, occupant health, and structural integrity, and affects up to 27% of homes in the England. This study develops a predictive model for damp risk, using 2,073 inspection records from a housing association across 125 local authorities. Homes were labelled as damp (1,630) or non-damp (443), with data supplemented by national Energy Performance Certificate (EPC) records, incorporating building characteristics and energy efficiency indicators. To evaluate model performance, both a balanced dataset (869 homes, 426 damp, 443 non-damp) and a larger imbalanced dataset (2,073 homes) were used. Seven machine learning algorithms were deployed, with the best-performing model achieving 0.636 accuracy on balanced data and 0.793 on imbalanced data. SHAP (SHapley Additive exPlanations) analysis identified heating cost, energy consumption, and wall energy efficiency as the strongest predictors of damp. Statistical tests and causal analysis were applied to interpret SHAP results, offering insights into potential damp risk and mitigations. The findings suggest that machine learning can support early identification of homes likely to develop damp, helping housing managers prioritise interventions before damp issues escalate.

Damp in residential buildings presents significant challenges to housing quality, occupant health, and energy efficiency. This thesis adopts a mixed-methods approach, integrating qualitative (content and thematic analysis) and quantitative (Analytic Hierarchy Process (AHP), machine learning, and statistical analysis) methods to provide insights that could enhance damp management in English housing. To achieve this, the study uses real-world data from housing association inspection reports, surveyor comments, photographic evidence, a damp specialist questionnaire survey, and the Energy Performance Certificate (EPC) database. The research first examines current damp management practices, revealing a reactive approach that relies heavily on visual inspections and inconsistent diagnostic methods. Analysis of survey responses from damp specialists reveals differing views on the frequency of use, accessibility, and effectiveness of both diagnostic methods and remedial measures for damp. Findings also expose a gap between theoretical best practices and real-world damp management. AHP is used to investigate decision-making in damp diagnostics and remedial measures by providing a structured framework that reduces subjective bias. It integrates multiple criteria, such as cost, effectiveness, feasibility, and expertise availability, to support more informed and systematic decision-making. Results show some advanced diagnostic tools and remedial measures were deprioritised due to cost, feasibility constraints, or lack of specialist expertise. Machine learning clustering is applied to 1,655 damp homes, identifying three distinct damp home profiles based on building characteristics and energy efficiency. A defect analysis highlights condensation as the most prevalent issue, primarily affecting bathrooms, bedrooms, and kitchens. Finally, a predictive machine learning model is developed to predict damp risk in over 35,000 homes. Random Forest performed best, with SHAP (SHapley Additive exPlanations) analysis identifying heating cost, energy consumption, wall efficiency, and construction age as key predictors. A Shiny app prototype demonstrates the feasibility of single-property damp risk assessment, though generalisability remains a challenge.

Energy Performance Certificates (EPCs) are the adopted method by which the UK government tracks the progress of its domestic energy efficiency policies. Over 15 million EPCs have been lodged, representing a valuable resource for research into the UK building stock. However, the EPC record has a reputation of containing multiple errors. In this work, we identify many such errors and quantify how common they are. We find that 27% of EPCs in the open EPC record display at least one flag to suggests it is incorrect and estimate the true error rate of the EPC record to be between 36 and 62%. Many of these errors are caused by EPC assessors disagreeing on building parameters such as floor type, wall type and built form. Additionally, flats and maisonettes appear to cause more issues than other property types. This may be due to difficulties in assessing their location in the building and the nature of the surrounding space. We also suggest potential new methods of quality assurance which rely on machine learning and which could allow such errors to be avoided in the future.

Improved building fabric performance is essential for the decarbonisation of buildings. Evaluating fabric performance is often predicted; but inaccuracies are present within commonly used prediction methodologies. Accurate measurement of building fabric is therefore advantageous when identifying the improvement made through retrofit. The QUB/e method is a practical and effective method of measuring the whole building performance in low-to-medium thermal mass properties. In this paper, a property of high thermal mass was studied for the first time with the QUB/e method. The results identify challenges in undertaking QUB/e measurements in the application of high thermal mass including the impact of stored solar heat contributions resulting in a wider dispersion of measurements. In the case presented; a significant prediction gap is identified when comparing the predicted and measured results. The implications of the prediction gap observed include a change in the regulatory EPC band of the property. Additionally, using performance measurements would avoid overestimations of the reported decarbonisation and annual cost saving benefits of future retrofit works to improve the property at 2.3 Tonnes of equivalent CO2 emissions and £570 respectively.

To construct buildings of the future that are both energy-efficient and moisture-resilient, it is critical to have an in-depth understanding of the varying characteristics of brick properties. This study sampled eight brick-cores taken from solid walled homes across the UK, to investigate the impact of thermal conductivity and hygrothermal parameters on U-values and moisture accumulation. Modelled U-values of uninsulated solid walls, in this sample, ranged between 1.6 and 2.6 W/m2K, with 6 of 8 the homes having surface condensation risks. There was even greater variability found in the moisture content in inner brickwork when simulated in WUFI, between 0.1 to 5.8 %, indicating some bricks are at significantly higher risk of moisture accumulation.

The performance of building fabric is a critical component in the complex problem of heat decarbonisation. However, a growing body of evidence has shown that there is often a difference between the measured performance of building fabric and its predicted or design performance. This phenomenon is known as the performance gap. Awareness of the performance gap has popularised the concept of measuring fabric performance. This can be characterised by the U-values of individual fabric elements or the HTC (Heat Transfer Coefficient) that describes the whole house fabric performance. HTC measurements are commonly used to evaluate any performance gap. The current standardised method for HTC measurement, coheating, is extremely disruptive as it is required that a home is empty for 15 days or more for steady state conditions to be maintained within the property. As such, coheating can be considered unsuitable for uses outside of research. The QUB method is a dynamic method of HTC and U-value measurement that is completed within a single night. Owing to its short duration the QUB method could potentially be used in mainstream applications such as new build housing and retrofit where a coheating test would not be feasible. This research aims to improve and demonstrate the accuracy (closeness to true value) and precision (dispersion of repeat measurements) of the QUB method. This will identify where the method can be deployed to give informative measurements and its limitations. A method consisting of six field-based case studies was deployed in which repeated QUB measurements were completed and compared to reference HTC and U-value values to determine the accuracy and precision of the measurements. This revealed that variations in test conditions were impacting the dispersion of results and negatively affecting accuracy and precision. These included variability of the temperature ratios in unconditioned spaces, transient thermal mass effects introduced by solar radiation and changes in external temperature, and wind conditions impacting heat transfer. Where observed, this impact is linked to select building characteristics. Consequently, houses with minimal areas of indirect heat loss, insulated building fabric and not of a characteristically high thermal mass often resulted in highest levels of accuracy and precision in QUB measurements. From the results of the case studies, indicative values of accuracy and precision for the QUB HTC measurements were derived based on the building characteristics of the test homes. For homes with characteristics associated with high accuracy and precision the following levels of accuracy and precision are expected: root mean squared error (RMSE) ≤ 15 %, mean bias error (MBE) ≤ |13| %, relative range ≤ 19 % and standard deviation ≤ 7 %. For homes with characteristics associated with low accuracy and precision the equivalent metrics are RMSE ≤ 34 %, MBE ≤ |34| %, relative range ≤ 55 % and standard deviation ≤ 16 %. These values can be used by those conducting QUB HTC measurements to determine the suitability for an application and to provide context on the measurement result. The level of accuracy seen in the QUB U-value measurements was notably lower than that seen in existing work. The reasons for this could not be determined. A novel approach for adjusting HTC measurements for indirect heat loss through unconditioned spaces was proposed. This was done through use of additional temperature and heat flux density measurements and was shown to improve the accuracy and precision of measurements in all applicable instances. However, this practice may, in turn, affect the suitable use cases for the measurement. Future work should consider how these adjustments are communicated in the most understandable way. This study has demonstrated the accuracy and precision of the QUB test in a discrete number of real-world case studies. Whilst limitations of the QUB test are highlighted, its potential to give informative evaluations of building fabric performance are evident. Future work should conduct multiple QUB tests over a duration of close to one year to better understand the impact of changing test conditions. Additionally, the measurements completed in this study could be combined with data from other projects to enable an evaluation of accuracy and precision against a wider range of building characteristics. This will further the understanding gained from this study and give findings that can be generalised across the building stock.

© 2018 Elsevier Ltd Keeping homes at a comfortable temperature and reducing household fuel bills are priorities for many governments. In the UK, several interventions have been implemented to achieve these objectives. This paper investigates one such policy lever - the Energy Price Cap - to understand if it has been designed and implemented efficiently and equitably. The price cap was introduced for customers on prepayment meters to combat increased levels of fuel poverty and a lack of competition in this group. However, the price cap was based on several assumptions of how energy is used. In this work, we assess how well the price cap accounts for real energy use using smart meter data. Households on economy 7 (EC7) tariffs were found to spend more than those on standard rate tariffs, as EC7 customers use more electricity during peak hours than assumed in government calculations. Additionally, many of the EC7 customers in this sample still use a considerable amount of gas, suggesting the EC7 heating product is either not sufficient, or is not being utilised in a cost-effective manner. Revisions to the input assumptions in government models for EC7 customers would therefore be beneficial in future price cap levels.

Measuring the performance of building fabric is increasingly important as stakeholders wish to compare as-built performance with design expectations. When measuring whole house performance (Heat Transfer Coefficient) heat losses through the floor in slab-on-ground type constructions are intractable and introduce uncertainty into measurements. As such efforts are often made to isolate them from measurements. The QUB method is a practical method of measuring whole house building performance. Previous work has shown floor losses can successfully be isolated from measurement through use of heat flux measurements and additional calculation steps. To further test this isolation procedure, three QUB tests were performed on a slab-on-ground Passivhaus dwelling. Whilst the whole house performance measurements agree with the design performance (all results within 11% of the design) the floor losses measured appear unrealistically high. The conditions of the tests, conducted in late summer and in a highly insulated property, are likely causing the heat flux measurements to capture heat being stored in the floor construction rather than heat being lost from the property. Follow up measurements in more preferable conditions are planned which will assist in determining the cause of these observations.

In situ measurement can enable accurate evaluation of a building’s as-built performance. However, when measuring whole house performance, party walls introduce measurement uncertainty. Subsequently, it is common to “adjust” measurements to isolate heat transfer through party walls. This study explores the behaviour and impact of party walls in QUB and coheating measurements of a semi-detached house, presenting empirical evidence on the validity of these measurements where a party wall is present. Two different party wall heat transfer behaviours were observed through heat flux density measurements. Thermal charging is apparent in QUB tests and the initial stages of coheating. After 48 h of coheating, the party wall has become heat saturated and exhibits stable heat transfer. Consequently, using heat flux density measurements to isolate party wall heat transfer in QUB tests, where thermal saturation has not been achieved, can result in misleading inferences. The coheating and QUB measurements without party wall adjustment are in close agreement, irrespective of differing heating patterns in the neighbouring property. The generalisation of these findings is problematic since they describe the impact of the case study-specific built form and the test conditions. Future work to explore the impact of built form and test conditions is needed.

Environmental conditions in buildings are linked to the physical and mental wellbeing of occupants. Thus, it follows that the internal environment affects human performance and user experience during sport and activity. There are several indices that are used to evaluate occupant thermal comfort, the Predicted Mean Vote (PMV) index being the metric most commonly used. PMV is designed to evaluate comfort for sedentary occupants with low metabolic rates; however, PMV has also been used to evaluate comfort for individuals engaged in high metabolic rate activities, such as those common in sport facilities. This paper investigates the implication of using PMV to evaluate thermal comfort in sport facilities using empirical data recorded over 24 months in a multi-purpose sports hall in the North of England. Data are used to develop and propose methodological modifications to improve the standard PMV model prediction to account for occupants having higher metabolic rates. The paper evaluates the use of metabolic rate data from different sources including the Compendium of Physical Activities and quantifies the impact that the metabolic weighting approach has on predicted comfort. Finally, a novel method is proposed to modify PMV for use where occupants have high metabolic rates. Despite the improvements made, the findings suggest that even a modified PMV may not be able to accurately evaluate the thermal comfort of people engaged in non-sedentary activity, recommending that use of the PMV index is restricted to activities with metabolic rates <2 MET.

Improving the energy efficiency of the UK housing stock is important both to meet carbon emission reduction targets and to reduce fuel poverty. For this reason, domestic properties are frequently retrofitted with energy saving measures. This study looks at how the energy consumption, thermal properties and internal temperature of 14 dwellings change as a result of a solid wall insulation (SWI) retrofit. A decrease in heat transfer coefficient of 11+6−7% was calculated for 2 dwellings, which is slightly lower than the previously modelled value of 18%. However, many houses displayed evidence that the full benefit of SWI was not being realised as, for example, energy savings were offset with increases in internal temperature. Future retrofit schemes should therefore consider supplementing the changes in fabric with increased guidance for the occupant.

Occupants affect energy consumption in buildings by contributing internal heat gains, increasing internal carbon dioxide levels and adapting their behaviour. Estimated occupancy schedules are used in building energy models for regulatory compliance purposes and when empirical data are not available. Metadata, such as personal location data, is now collected and visualised on a global scale and can be used to create more realistic occupancy schedules for non-domestic facilities, such as large retail outlets. This paper describes a protocol for extracting and using freely available metadata to create occupancy schedules that are used as inputs for dynamic simulation models. A sample set of twenty supermarket building models are used to demonstrate the impact metadata schedules have when compared with models using the estimated schedules from regulatory compliance. Metadata can be used to create bespoke occupancy profiles for specific buildings, groups of buildings and building archetypes. This method could also help reduce the gap between predicted and actual performance. In the example models, those using the regulatory compliance schedules underestimated heating demand by approximately 10% and overestimated cooling demand by over 50% when compared to models using the metadata schedules. Although this work focuses on UK facilities, this methodology has scope for global application.

Forecasting retrofit performance often relies on building energy models, which can be inaccurate due to differences between predicted and actual performance. This introduces uncertainty to energy and carbon savings estimates. Research suggests that heat loss measurements improve model accuracy and provide more robust evaluations of retrofit effectiveness. Several whole-house heat loss measurement methods have undergone field trials for validation. However, the assessment of these measurements is limited to the specific field trial test conditions. Simulated measurements in a virtual environment could complement field trials by exploring conditions unattainable in real-world settings, increasing confidence in the measurements. This study replicated dynamic whole-house heat loss measurements from field trials in a calibrated energy model using local weather data. Differences of 7% (pre-retrofit) and 26% (post-retrofit) were observed between simulations and field trial results. The differences could be associated with the modelled heat dynamics not reflecting the true thermal behaviour of the house recorded in the field trials with a particular focus on thermal bridging heat loss. This study has shown that for simulations to be used in validating measurements, further work is needed to determine if the dynamic thermal behaviour of buildings can be replicated in simulations.

Retrofitting solid walled homes is one of the greatest challenges for the UK in achieving its net zero ambitions. Solid walled homes have unique features, that require special consideration. They are among the least efficient in the UK, and their occupants are more likely to be in fuel poverty. They are also at elevated risk of surface condensation, excessive cold in winter and overheating in summer. Retrofitting these homes is a cornerstone of UK policy to tackle fuel poverty and to facilitate the delivery of decarbonised electrified heat into homes. However, installing solid wall insulation is costly and poses more risks of unintended consequences than any other retrofit. Previous projects investigating solid wall insulation have identified major failures when retrofits are installed in a ‘piecemeal’ way i.e., they did not consider how the retrofit measure affects risks of damp, inadequate ventilation, and overheating in homes. This led to the adoption of the whole house approach in new technical standards for retrofit installers (PAS 20351) to ensure that all risks of retrofit measures were always considered, even if only one measure was being installed at a time. Industry is beginning to adapt to these standards, but more research is needed to explore the benefits of adopting the whole house approach, and more guidance is needed to support retrofits in solid walled homes. Insights from this project explain how solid walled homes can be retrofitted more safely and effectively.

The DEEP case study retrofits provide compelling evidence on how a whole house approach to retrofit can reduce heat loss, surface condensation risk and overheating risks in solid walled homes. From the data collected, specific guidance is produced outlining how to install retrofits in solid walled homes more safely and effectively. Recommendations are provided on how to make measurements and modelling predictions of the technical performance of retrofits more accurate. The findings can inform evidence-led decisions at multiple levels to ensure retrofits in solid walled homes are safe and effective.

17BG was one of fifteen case study homes retrofitted in the DEEP project. The case studies were used to identify the performance of, and risks associated with, retrofitting solid walled homes. The data from the case studies was also used to evaluate the accuracy of modelled predictions around retrofit performance and risk.

56TR is one of fifteen homes being retrofitted in the DEEP project. The case studies are being used to identify the performance of, and risks associated with, retrofitting solid walled homes as well as to evaluate the accuracy of retrofit models.

01BA is one of fourteen case study homes retrofitted in the DEEP project. The case studies identify the performance of, and risks associated with, retrofitting solid walled homes. A retrofit was undertaken in stages, reflecting a piecemeal approach to retrofit, followed by undertaking activities that would be required for a whole house approach as a final stage. The data from the case studies is also being used to evaluate modelled predictions of retrofit performance and risk.

55AD and 57AD, are a pair of identical semi-detached homes, and are two of fourteen DEEP case study homes in which the comparison between a whole house and piecemeal approach to retrofit was evaluated.

00CS is one of fifteen case study homes retrofitted in the DEEP project. The case studies were used to identify the performance of, and risks associated with, retrofitting solid walled homes. The data from the case studies was used to evaluate the accuracy of modelled predictions around retrofit performance and risk.

04KG is one of fourteen case study homes being retrofitted in the DEEP project. The case studies are being used to understand the performance of, and risks associated with, retrofitting solid walled homes. The data from the case studies is also being used to evaluate modelled predictions of retrofit performance and risk.

52NP and 54NP are two of fourteen case study homes retrofitted in the DEEP project. The case studies were used to identify the performance of, and risks associated with, retrofitting solid walled homes. The data from the case studies were also used to evaluate modelled predictions of retrofit performance and risk.

This report describes the common data collection and analysis methods used in the DEEP retrofit case studies. These are generically described to avoid repetition in the individual case study reports.

Thermal and hygrothermal simulations are undertaken to estimate energy performance, condensation risks, the potential for moisture accumulation, and timber rot. These simulations use default book values to estimate the material properties of solid brick walls. This report investigates the variability of brick properties found in solid walled homes in the UK and compares these to the default book values. It also explores how varying material property inputs in models affects thermal performance and moisture risk in solid walled homes.

Surveys and air tests were performed at 160 solid and cavity walled homes in Northern England, which had a mix of insulated and uninsulated walls. Blower door tests and Pulse tests were compared and used to quantify the airtightness of the homes. An evaluation of how building characteristics affected the results was performed, and common leakage pathways were identified. Data was also collected on the condition of the homes, potential barriers to external wall insulation (EWI) retrofit, as well as perceptions of occupants.

19BA is a mid-terraced pre 1900 solid walled home where airtightness improvements and room-in-roof retrofits have been installed. Building performance testing has been undertaken to collect data on the performance and risks of these improvements, and to evaluate the accuracy of modelled predictions on the retrofit performance and risk.

07LT and 09LT are two of fourteen case study homes retrofitted in the DEEP project. The case studies have been used to identify the performance of, and risks associated with, retrofitting solid walled homes. The data have also been used to evaluate the accuracy of the modelled predictions of the retrofit performance and risk.

08OL is one of fourteen case study homes being retrofitted in the DEEP project. The case studies are used to identify the performance of, and risks associated with, retrofitting homes without conventional cavities. The data from the case studies are used to evaluate the accuracy of modelled predictions of retrofit performance and risk.

27BG is one of fourteen solid walled DEEP case study homes. In this home building performance tests were undertaken to investigate the success and risk of retrofitting suspended timber floors and how the results compare to predictions.

Thermal performance is often assumed to be constant over the service life of insulation. The aim of this project was to establish the existing evidence on the impact of retrofit degradation over time, and what it means for insulation performance. This report summarises current understanding, classifying key mechanisms for degradation and makes recommendations for how to address identified knowledge gaps.

The benefits and risks associated with installing internal wall insulation (IWI) and thin internal wall insulation (TIWI) retrofits into solid wall homes are researched and evaluated for BEIS. In order to deliver this, a holistic approach was adopted and the project was split into four main sections, each of which has an accompanying Annex to this summary report: Annex A: Review of existing literature as well as primary investigations using house surveys, householder questionnaires and installer focus groups into the sociotechnical barriers to IWI and TIWI. Annex B: Technical evaluation of the performance of IWI and six novel TIWI retrofits installed in field trial solid wall Test Houses using before and after building performance evaluations. Annex C: Modelling of the impact on annual energy consumption, EPC rating, overheating risk, condensation risk and moisture accumulation made by IWI and TIWI retrofits in a range of UK house archetypes. Annex D: Laboratory testing of test walls using hygrothermal chambers to quantify the change in moisture and thermal performance of solid brick walls when they are insulated with IWI and TIWI to determine how weather

Whole house heat loss or heat transfer coefficient (HTC) measurements are rarely undertaken to validate the performance of retrofits installed in homes. This means policy, certification and householders must rely on predictions made by energy models. Multiple domestic energy models exist, with varying underlying rules and input requirements. This means predictions made by different models may not always agree. However, few studies have compared the predictions from these models with each other, and with measured whole house heat losses for a home before and after a retrofit. This paper compares the HTC of a three bed, semi-detached, solid-walled home measured via the coheating test, with the HTCs predicted by the Reduced Data Standard Assessment Procedure (RdSAP), Building Research Establishment Domestic Energy Model (BREDEM), Dynamic Simulation Modelling (DSM) and the Passive House Planning Package (PHPP). The results show that most predicted HTCs from the models are not similar to the measured HTC, and there is a large variation between the different modelled HTCs. The paper explores why these differences occur and reflects on how to improve the accuracy and consistency of domestic energy models.