Solid Wall Dwellings Research Articles

Aesthetic appealing wall insulation: A novel approach for uptake of solid wall insulation in the UK

Solid wall dwellings in the UK are in urgent need for energy retrofit to support achieving the UK net-zero strategies in the building sector and reduce fuel poverty. Several barriers are a cause of uncertainty for householders about Solid Wall 1nsulation (SWI) and slow down the progress. This paper aims to examine people's perceptions of possible inclusion of aesthetics elements in Internal Wall Insulation (IWI), providing a suitable solution to promote wall insulation intake and attractiveness. To achieve this aim, first, the current literature is critically reviewed and analysed to highlight the gap between energy studies and design/aesthetic features of SWI retrofit. Then, an online survey is conducted, and the collected data are analysed. The results show that the aesthetic factor is very important for participants with more than 90% agreement. This level of agreement is as high as other well-known critical factors in renovation such as cost and energy saving. Also, aesthetic integration in IWI can surpasses negative concerns such as the retrofit cost or losing internal space. Furthermore, over 2/3rd of participants are in agreement with a suggested business model for delivering both aesthetic and energy improvement in combined retrofit plans by established approved organizations. It is concluded that aesthetic inclusion is the priority and an encouraging factor in the internal renovation to reduce the barriers and increase success. Finally, the findings from this research pointed to how the retrofit industry, policymakers, and designers should evolve to achieve the benefits of aesthetics in SWI.

Measuring and modelling retrofit fabric performance in solid wall conjoined dwellings

There remains a significant number of occupied and uninsulated solid wall dwellings in the UK. Deep retrofit is often required for these buildings to become energy efficient but it is difficult to determine how these buildings will respond to retrofit without a detailed understanding of their fabric thermal performance Greater certainty can however be achieved by combining theoretical models and practical field tests, prior to the design of retrofit programmes. This type of approach can then be used to inform and optimize the design of retrofit interventions. This paper presents results from a series of in situ fabric performance tests undertaken on two no-fines concrete, conjoined dwellings pre- and post-retrofit and demonstrates how empirical data can be used to inform and calibrate the thermal performance of dynamic simulation models (DSMs). This is a particularly pragmatic calibration method as it eliminates the need for actual weather data, which is expensive and prohibitive to collect and collate. The DSM inputs and outputs were compared with those obtained from Standard Assessment Procedure (SAP) calculations. The results illustrate how the fabric performance of no-fines concrete can vary between similar house types within the same development. This research also validates the effectiveness of the calibration methodology that uses the whole house Heat Transfer Coefficient (HTC) as the qualifying metric. Furthermore, results also emphasize the importance of appropriately characterizing the physical properties of existing buildings before designing retrofit strategies. This paper contributes to the growing knowledge base concerned with the energy performance gap. In this instance, SAP predicts higher absolute savings then measured in situ which is problematic when assessing the financial viability of retrofits.

Measuring and mitigating overheating risk in solid wall dwellings retrofitted with internal wall insulation

Upgrading the thermal insulation of UK houses to improve wintertime energy efficiency raises concerns about potential summertime overheating risk. To address these concerns, experiments were conducted in a pair of thermally matched, solid walled houses, located in the UK. One of the pair was retrofitted with internal wall insulation, while the other remained uninsulated; both houses were monitored for four weeks during the summer of 2015. Operative temperatures in the living room and main bedroom were observed to be higher in the internally insulated house in comparison to the uninsulated house. The houses were again monitored for a further three weeks with a simple overheating mitigation strategy applied consisting of night ventilation and shading using internal blinds. The data were normalised for variations in external weather conditions using a linear regression model, with the exponentially-weighted outdoor running mean air temperature as the predictor variable of indoor operative temperature. The results showed that the mitigation strategy was effective at reducing the internal temperature in the internally insulated house to a level similar to that observed in the uninsulated house. The marginal increase in overheating risk should not be considered a barrier to the uptake of IWI in this type of house and location, at this time. Shading devices and secure noise attenuating vents for existing dwellings may be needed as part of a package of refurbishment in the future. It could become a requirement within the Building Regulations [1] to reduce overheating risk when retrofitting existing homes.

Assessing the quality of retrofits in solid wall dwellings

PurposeThe purpose of this paper is to provide a detailed appraisal of the quality of domestic retrofits.Design/methodology/approachThis paper presents the results of technical surveys on 51 retrofits undertaken before, during and after the retrofits.FindingsFailures are observed to be endemic and characterised into five themes: 72 per cent showed moisture issues pre-retrofit, 68 per cent had moisture risks post-retrofit, 62 per cent did not adopt a whole house approach, 16 per cent showed inadequate quality assurance protocols and 64 per cent showed evidence of insufficient design detailing. Each theme is further subcategorised with a view to identifying implications for future policy.Research limitations/implicationsThe findings suggest the 10 per cent Ofgem retrofit failure rates predictions are an underestimate and so there may be a need for additional investigations to understand the trend across the UK.Practical implicationsRecommendations to reduce the failure rates may include making changes to the current inspection regime, widening understanding among installers; providing standard repeatable designs for repeated features; and empowering occupants to trigger inspections.Social implicationsThe sample is representative of a substantial proportion of the homes in the UK suggesting that retrofit quality may in many instances be below the required standards.Originality/valueRisks of moisture issues and underperformance in domestic retrofit are a concern for government industry and households. This research shows that many installation failures are the result of not implementing existing guidelines and a change to the enforcement of standards may be needed to enact a fundamental change in installer practice and process control.

Solar Energy Gain and Space-Heating Energy Supply Analyses for Solid-Wall Dwelling Retrofitted with the Experimentally Achievable U-value of Novel Triple Vacuum Glazing

A considerable effort is devoted to devising retrofit solutions for reducing space-heating energy in the domestic sector. Existing UK solid-wall dwellings, which have both heritage values and historic fabric, are being improved but yet they tend to have meagre thermal performance, partly, due to the heat-loss through glazings. This paper takes comparative analyses approach to envisage space-heating supply required in order to maintain thermal comfort temperatures and attainable solar energy gains to households with the retrofit of an experimentally achievable thermal performance of the fabricated sample of triple vacuum glazing to a UK solid-wall dwelling. 3D dynamic thermal models (timely regimes of heating, occupancy, ventilation and internal heat gains) of an externally-insulated solid-wall detached dwelling with a range of existing glazing types along with triple vacuum glazings are modelled. A dramatic decrease of space-heating load and moderate increase of solar gains are resulted with the dwelling of newly achievable triple vacuum glazings (having centre-of-pane U-value of 0.33 Wm-2K-1) compared to conventional glazing types. The space-heating annual cost of single glazed dwellings was minimised to 15.31% (≈USD 90.7) with the retrofit of triple-vacuum glazings. An influence of total heat-loss through the fabric of solid-wall dwelling was analysed with steady-state calculations which indicates a fall of 10.23% with triple vacuum glazings compared to single glazings.

Modelling insulated coving's potential to reducing thermal bridging and moisture risk in solid wall dwellings retrofitted with external wall insulation

Mould growth and surface condensation are problems for many dwellings, and the retrofitting of insulation can increase the risk of these occurring. This is especially the case for historical solid wall properties receiving external wall insulation (EWI), which often have architectural details at the roof eaves that cause discontinuities in the insulation and so can result in excessive thermal bridging. This paper presents the results of an investigation into retrofitted solid wall properties where modelling is used to investigate the problem and effectiveness of insulated coving products which are designed to reducing thermal bridging. Thermal modelling is undertaken to establish the optimum design to reduce risk. The insulated coving was found to be effective in reducing thermal bridging in all the scenarios investigated and to reduce moisture risks occurring in some solid walls situations.

Retrofit solutions for solid wall dwellings in England: The impact of uncertainty upon the energy performance gap

This study seeks to evaluate the impact of uncertainty in the pre-retrofit thermal performance of solid walls of English dwellings on post-retrofit energy use. Five dwelling archetypes, broadly representative of English solid wall properties, were modelled pre- and post-retrofit, under different wall insulation scenarios, using dynamic thermal simulation. Findings indicate that whilst solid wall insulation could result in a significant reduction of space heating demand, uncertainties in the pre-retrofit solid wall U-value could lead to a gap between the anticipated and actual energy performance. Specifically, results show that if the current U-value assumption of 2.1 W/m2K is indeed an overestimation of the in-situ U-value of solid walls, then the anticipated carbon savings could be significantly reduced by up to 65%. Practical application: The performance gap observed in this study revealed that the actual carbon savings arising from the retrofit of solid wall properties could be significantly lower than predicted. This will not only affect UK Government carbon reduction targets but it can also result in a lack of confidence amongst stakeholders who may consequently doubt the effectiveness of energy retrofit measures, thus reducing their uptake. Uncertainties regarding solid wall U-values may necessitate the re-examination of the carbon targets set for the retrofit of solid wall dwellings and the exploration of alternative ways to further reduce their carbon emissions, e.g. by specifying higher insulation thicknesses.

Estimating the impact of reveals on the transmission heat transfer coefficient of internally insulated solid wall dwellings

Internal wall insulation as a retrofit measure could help to reduce energy use and greenhouse gas emissions in many of the 6 million solid wall buildings in the UK. However during retrofit, junctions that are hard to deal with are often left uninsulated, increasing heat loss and surface mould growth risk at thermal bridges. Furthermore the effect of junctions, insulated or uninsulated is not properly taken into account in commonly used assessments of heat loss.This paper presents a study on the impact of the junctions around openings, also called reveals, on the transmission heat transfer coefficient of internally insulated dwellings and a discussion on potential areas of improvement of common assessment tools for retrofit.Findings showed that reveals account for the majority of the transmission heat transfer coefficient at junctions, that thicker wall insulation is not necessarily advantageous from a heat loss perspective, and that the transmission heat transfer coefficient at junctions per unit area of exposed elements was often higher than the reference value used in the UK.

Analysing the potential of retrofitting ultra-low heat loss triple vacuum glazed windows to an existing UK solid wall dwelling

Heat loss through the windows of solid wall dwellings is one of the factors contributing to high energy consumption for space heating ensuing in preventable carbon emissions. This research forms a part of novel contribution in vacuum glazing science presenting the refurbishment technology of an experimentally achievable thermal performance of triple vacuum glazing to existing UK solid wall dwelling by investigating the space-heating load, solar energy gain and window to wall area ratios. Three-dimensional dynamic thermal models, considering realistic heating and occupancy regimes, of an externally insulated solid wall dwelling with single glazed, double glazed air filled, double glazed argon gas filled, triple glazed air filled and triple vacuum glazed windows were developed. Predictions for the simulated dwelling when replacing single glazed windows with triple vacuum glazed windows indicate space-heating energy saving of 14.58% (871.1 kWh) for the winter months (Dec, Jan and Feb); predicted annual energy savings are 15.31% (1863.5 kWh). The predicted reduction in the solar energy gains for the triple vacuum glazing was 75.3 kWh in the winter months. The effects on solar energy gain are analysed and the potential to increase window-to-wall area ratios (WWR’s) examined. For a simulated room with triple vacuum glazed windows increasing the WWR’s from 5% to 59% led to a reduction in the predicted required space-heating; whilst for a room with single glazed, double air filled, double argon gas filled and triple air filled windows the predicted required space-heating increased with increasing WWR. It was shown that retrofitting existing solid wall dwelling with triple vacuum glazed windows could be a robust retrofit solution in improving building energy efficiency. This research also implicates a need of the cost-effective development of triple vacuum glazing at the manufacturing level, which would then be more beneficial to consumers in terms of energy and cost savings.

Measured winter and spring-time indoor temperatures in UK homes over the period 1969–2010: A review and synthesis

This paper presents a review and synthesis of average winter and spring-time indoor temperatures in UK homes measured over the period 1969–2010. Analysis of measured temperatures in a sample of solid wall dwellings in the UK, conducted as part of the CALEBRE research project, is included. The review suggests that, for periods when occupation was likely, there has been little or no increase in winter and spring-time average living room temperatures over the last 40 years, with average recorded living room temperatures having been historically lower than the WHO-recommended value of 21°C. Correspondingly, for periods of likely occupation, average bedroom temperatures appear to have increased. Compared with non-domestic buildings, there have been fewer investigations of domestic thermal comfort, either in the UK or elsewhere, and hence the paper also calls for further detailed investigations of domestic indoor temperatures during occupied hours together with thermal comfort evaluations in order to better understand domestic thermal environments. Based on suggestions from the limited range of studies available to date, living room temperatures may need to be maintained within the range 20–22°C for thermal satisfaction, though this requires confirmation through further research. The study also emphasises that improving the energy efficiency of homes should be the primary means to effect any increases in indoor temperatures that are deemed essential. Considerations for future policy are discussed.

Energy‐led retrofitting of solid wall dwellings: technical and user perspectives on airtightness

PurposeMechanical ventilation with heat recovery (MVHR) is increasingly being promoted in the UK as a means of reducing the CO2 emissions from dwellings, and installers report growing activity in the retrofit market. However, the airtightness of a dwelling is a crucially important factor governing the achievement of CO2 reductions, and the purpose of this paper is to understand the technical implications of airtightness levels in an experimental dwelling, purpose built to typical 1930s standards, at the same time as gaining the users’ perspectives on airtightness and ventilation in their homes.Design/methodology/approachIn‐depth interviews were carried out with 20 households to collect information on their retrofit and improvement strategies, attitudes to energy saving and their living practices as they impinge on ventilation. The experimental house was sealed in a series of interventions, leading to successive reductions in the air permeability as measured by a 50 Pa pressurisation test. The behaviour of a whole‐house MVHR system installed in the experimental house, was simulated using IES Virtual Environment, using a range of air permeability values corresponding to those achieved in the retrofit upgrading process.FindingsIn the house considered, air permeability must be reduced below 5 m3/m2h for MVHR to make an overall energy and CO2 saving. However, to achieve this required a level of disruption that, on the basis of the views expressed, would be unlikely to be tolerated by owners of solid wall dwellings.Originality/valueThe paper is the first to combine results from a user‐centred approach to exploring the existing practices of householders with a simulation of the energy and CO2 performance at different levels of airtightness of an experimental house in which MVHR has been installed.

Investigating the potential of overheating in UK dwellings as a consequence of extant climate change

Dynamic simulation is used with defined domestic building variants to investigate internal temperatures of UK dwellings. Factors such as a warming climate and varying internal heat gains are estimated to examine whether UK domestic buildings are likely to be prone to overheating in the future, and therefore require mechanical air conditioning. The study suggests that the ability, or inability, of the occupant to adapt to bedroom temperature is paramount in the understanding of the conditions for overheating. While this is difficult to quantify (and a range of comfort temperatures are proposed), the effect of changing the building construction and geographical location can result in significantly different thermal conditions. As might be expected, the problem appears most noticeable for buildings in the south of the UK and with lightweight constructions. Even with a window-opening schedule applied to such a scenario, the average internal temperature is simulated as being over 28 °C for almost 12% of the year. A different metric, defined as “cooling nights”, suggests that there might be a cooling problem in bedroom areas for approximately a third of the year. In the North of the UK, and also for solid wall dwellings, this problem diminishes significantly.