Home Retrofits Research Articles

Retrofitting homes in Ontario entails significant embodied emissions: new policies needed

ABSTRACT Emissions reduction policies and programs should consider both the operational emissions reduction from single family home retrofits and the embodied emissions of the retrofit materials. This is because it can take 0.9–10.1 years before the emissions savings from building envelope upgrades in a gas-heated home equal the embodied emissions from the materials used. The wide range reflects the range of embodied emissions for different insulation and window replacement options. Heat pumps also have significant embodied emissions from their manufacture and from refrigerant leaks, but it takes less than two and a half years of operations in Ontario to offset the emissions investment relative to heating with a gas furnace. We recommend that Canada accelerate the phase out of insulation materials with high embodied emissions and increase incentives for window replacements. Programs and policies should also consider the age of the home and the potential energy savings when recommending building envelope improvements to maximize the total emission reduction potential. Finally, heat pumps should be promoted in all homes where low carbon electricity is available because this is the simplest and most effective way to reduce carbon emissions, especially when embodied emissions are considered.

Retrofit assessment: Getting it right from the start

The UK has some of the oldest buildings in Europe. They are also some of the worst performing in terms of energy performance. In tandem with these issues the UK has committed to making a substantial reduction in CO2 emissions. UK homes are currently responsible for almost 20 per cent of CO2 emissions. This leaves little option other than to make considerable progress with the retrofitting of homes to improve their energy performance. This is a technical process, however, and can introduce risks to building and their occupants. Examples exist of homes being retrofitted with disastrous consequences. Some of these issues can be due to the lack of thorough examination of a home before it undergoes a retrofit. This paper proposes a method that provides a detailed pre-retrofit assessment of a home, to fall in line with PAS 2035, a standard that provides guidance around publicly funded retrofit in the UK.

A whole life carbon analysis of the Irish residential sector - past, present and future

The residential sector is targeted for emission reduction in the climate action plans of many countries. These plans typically focus on reducing the operational energy of the residential sector only, with little focus on the embodied emissions of its construction. To fully decabonise the residential sector both operational and embodied carbon emissions would need to be eliminated.This paper presents whole life carbon quantification of the Irish residential sector, which aggregates the carbon emitted in operating the national housing stock, as well as the carbon emitted year on year in building and maintaining it. A detailed methodology is presented for both baselining, and forecasting, the emissions due to the residential sector. Operational emissions from space heating, hot water provision and electricity usage in the home are amalgamated. Embodied emissions, which are distributed across almost all categories of the national carbon inventory, are also estimated. The whole life carbon emissions of the residential sector account for approximately 25% of the total GHG emissions reported in the national carbon inventories.Modelled forecasts to 2030 are presented for national plans that aim to reduce emissions through retrofit and electricity decarbonisation, but will result in increased embodied emissions through planned housing development. The current Climate Action Plan for reduction of residential sector operational carbon fall short of achieving sectoral target reductions. Additional measures will be required if the sector is to meet its proportional share and sectoral emission ceiling. Even if these are achieved, gains that might accrue from home retrofit and electricity decarbonisation will be negated by the growth in embodied emissions deriving from housing development outlined in government plans, when the sector is considered from a whole life carbon perspective.Forecasts for operational emissions including business as usual and national sectoral targeted reduction scenarios of 40% are outlined. A range of scenarios are then presented to achieve emission reduction across the whole of the residential sector in line with the national 51% reduction targets. These will require; strategic targeting of the worst performing homes for retrofit first, complete decarbonisation of electricity, reduction in the size of future homes, as well as a major reduction in the embodied carbon of building materials used for residential construction. Activation, and renovation, of existing and vacant properties could accelerate the number of homes available while offsetting the need for extensive new construction.

S-01-3: SMART WELLNESS HOUSING AND BLOOD PRESSURE CONTROL

Objective: Mortality due to cardiovascular diseases (CVDs) rises sharply in winter, a phenomenon known as excess winter mortality. It is partially explained by cold exposure induced hypertension. Nevertheless, existing countermeasures for the prevention of hypertension and CVDs place emphasis only on improving lifestyle habits. Improving life environment has attracted attention recently because people spend 60–70% of their time at home. Therefore, we aimed to quantitatively evaluate the relationship between housing thermal environment and blood pressure (BP) in a real-world setting. Design and method: We conducted a nationwide prospective intervention study named the Smart Wellness Housing survey in Japan, as a nonrandomized controlled trial. The intervention was the thermal insulation retrofitting of homes. Participants were recruited by construction companies throughout all 47 prefectures of Japan. Home BP and indoor temperature were measured for 2 weeks before and after the intervention in winter (November-March) of FY 2014 to 2019. Results: Cross-sectional analyses before intervention involving about 2900 participants (1840 households) showed that systolic blood pressure (SBP) in the morning had significantly higher sensitivity to changes in indoor temperature (8.2 mmHg increase/10°C decrease) than that in the evening (6.5 mmHg increase/10°C decrease) in participants aged 57 years (mean age in this survey). Interaction terms between age/women and indoor temperature were significant, indicating that SBP in older residents and women was vulnerable to indoor temperature change. The association between BP variability and indoor temperature instability was also analyzed using the morning-evening (ME) difference as an index of diurnal variability and the standard deviation (SD) of 2-week data as an index of day-by-day variability. The analyses showed that the ME difference in indoor temperature was closely correlated with the ME difference in SBP (0.85 mmHg/°C). The SD of indoor temperature was also associated with the SD of SBP (0.61 mmHg/°C). In the comparison of before and after intervention, insulation retrofitting significantly reduced morning SBP by 3.1 mmHg. In addition, there was heterogeneity in the effect of insulation retrofitting on morning SBP in hypertensive patients compared with normotensive occupants (-7.7 versus -2.2 mmHg). Conclusions: Hypertension might be not only lifestyle diseases but also life-environment diseases. Residents should keep the indoor temperature high to reduce BP level and keep it stable to reduce BP variability through strategies such as installing high thermal insulation. We expect that these results will be useful to prevent excess winter mortality due to CVDs.

Decarbonising suburbia: Homeowners’ perspectives on home retrofits and travel mode shift in Perth, Scotland

Abstract Suburban neighbourhoods pose challenges to decarbonisation, due to high car-dependency and relatively large and energy inefficient homes. Home ownership dominates suburbia, thus putting responsibility on households to adopt measures to decarbonise their domestic lives and transportation. This paper examines household perspectives on the feasibility of such measures. We ran a survey and focus groups in Perth (Scotland) during the energy crisis. Whilst we found high levels of concern about climate change, energy costs, and growing engagement with cleaner technologies (e.g. heat pumps), most residents felt decarbonisation options were limited. Barriers like technologies’ up-front costs, worsened with the cost of living crisis. Participants had low familiarity with sharing economy approaches like car clubs. Despite high (non-electric) bike ownership and prevalence of storage space (garages), cycling was more perceived as a leisure activity than a regular transport mode. There were shared views that the state should take a stronger role in coordinating and implementing systemic changes required for energy transition, including measures affecting residents directly, like reducing car traffic into the city centre. We conclude that despite the economic privilege of high home and car ownership in suburbia, few felt financially able to decarbonise and most seem locked into high-carbon suburban lifestyles.

Multiobjective Optimization for Hurricane Retrofit to Improve Coastal Community Structural and Socioeconomic Resilience

With recent hurricanes causing devastating economic losses, structural damages, and societal impacts on coastal communities, residential building hurricane mitigation measures have gained increasing attention. However, retrofits are often costly and therefore beget inherent tradeoffs. In particular, the balancing of the postdisaster losses against upfront mitigation costs remains a constant challenge for community resilience planning. Existing mitigation optimization frameworks on the community scale have primarily focused on seismic hazards and typically have weak integration of the structural damages with the socioeconomic impacts. In the present study, finite element modeling of the residential buildings is applied to better incorporate the structural damages under combined wind and wave loadings. A multiobjective linear constrained optimization framework for improved residential building hurricane retrofit is developed to balance the structural damages, home displacements, morbidities, net direct economic losses, and initial mitigation expenditures under hurricane threats. For the present analysis, the mitigation actions of building elevation and improved construction practices are simulated. The framework is tested in a case study for an existing coastal community under 50-, 100- and 500-year hurricane events considering community-specific socioeconomic factors. The generalized pattern search algorithm is selected to determine the Pareto-optimal solutions. The results indicate large potential reductions in social, structural, and economic losses under optimized mitigation, but tradeoffs exist if the mitigation technique is found to be cost-ineffective, such as in the case of the improved construction practices. The findings highlight the importance of informed decision-making and home retrofits in improving community resilience.

Municipal governance and energy retrofitting of owner-occupied homes in the Netherlands

The building sector is responsible for more than one-third of global greenhouse gas (GHG) emissions. The Netherlands has set an ambitious target to reduce GHG emissions by 95% by 2050 compared to the 1990 baseline. Several factors, such as low retrofitting rates, lead to uncertainties in achieving these targets. In the residential sector, the energy retrofit rate of the owner-occupied homes is low. Homeowners encounter different types of barriers when deciding to make energy retrofits. The purpose of this study is to explore the policy implications of the main identified influencing factors and consequently the potential mismatch between current policy and the homeowners’ actual needs. We used semi-structured interviews and focus group meetings with experts from the largest cities in the Netherlands as the data collection methods. We identified the discrepancy between current policy and the actual needs of homeowners as follows: (a) less attention to the right message and the right messenger: policymakers cannot motivate the households using the word sustainability. Policymakers can convince homeowners to make energy retrofits through the improvement in quality of life, the expected cost savings, and the integration of energy retrofits into the maintenance of the home (message effect). Moreover, the trustworthiness and familiarity of the energy ambassador with the households are the main characteristics of these ambassadors (messenger effect). (b) the lack of integrated financial, informational and technical support: the main identified transaction cost barriers (non-monetary costs) are difficulties to inspire homeowners to carry out energy retrofits, lack of knowledge on how to start the energy retrofits, many steps in carrying out energy retrofits of old houses. More importantly, there is a lack of an active and accessible party in the market to reduce the financial, technical and informational barriers.

Deep multimodal learning for residential building energy prediction

The residential sector has become the second-largest energy consumer since 1987 in the UK. Approximately 24 million existing dwellings in England made up over 32% of the overall energy consumption in 2020. A robust understanding of existing buildings’ energy performance is therefore critical in guiding proper home retrofit measures to accelerate towards meeting the UK’s climate targets. A substantial number of predictions at a city scale rely on available data, e.g., Energy Performance Certificates (EPCs) and GIS products, to develop statistical and machine learning models to estimate energy consumption. However, issues with existing data are not negligible. This work adopted the idea of deep multimodal learning to study the potential for using Google Street View (GSV) images as an additional input for residential building energy prediction. 20,031 GSV images of 5,933 residential buildings in central Barnsley, UK, have been selected for a case study. All images were pre-processed using a state-of-the-art object detection algorithm to minimise the noise caused by other elements that may appear nearby. Building specifications that cannot be easily determined by the appearance are extracted from existing EPC information as text-based inputs for prediction. A multimodal model was designed to jointly take images and texts as inputs. These inputs are first propagated through a convolutional neural network and multi-layer perceptron, respectively, before being combined into a connected network for final energy prediction. The multi-input model was trained and tested on the case study area and predicted an annual energy consumption with a mean absolute difference of 0.01kWh/m2 per annum on average compared with what is recorded in the EPC. The difference between the predicted results and the EPC may also provide some hints on the bias the certificates potentially contain.

A grey-box modelling methodology to express home heat-energy usage as statistical distributions — case studies in urban Ireland

Home energy retrofit has recurred in public policy throughout recent decades. However, the savings in energy usage attributable to home retrofit have remained difficult to accurately predict. Occupants cause prediction inaccuracies by varying different factors, especially heating setpoints temperatures and heating patterns. Acting together, such occupant factors result in distributions — not single values — of heat-energy usage, even among similar homes. Datasets of heat-energy distributions can be found by building performance simulation using modern grey-box models. This study presents a methodology to simulate grey-box models of home heating through ranges of heating setpoints and patterns. An entire process to calibrate, validate and simulate at a large scale is described, and then demonstrated using case studies. Grey-box models, written in Modelica language, can conveniently simulate through large ranges of occupant factors. The case studies exploited this advantage of grey-box models to simulate empirical data on occupant factors. (For instance, empirical data found that home heating setpoints shifted before and after home energy retrofit.) In doing so, the datasets of simulation results enabled the exploration of home heat-energy usage with the normal and Weibull statistical distributions. Additionally, the heat-energy distributions of case-study homes were statistically tested, first for retrofit savings, second for equality to each other and third for equality to an official heat-energy estimate. Results demonstrate that home heat-energy usage, at a large scale, is best expressed as a Weibull distribution not normality. After home energy retrofit, heat-energy usage displays less variation (in general), less skewness, and thus becomes closer to normality. Occupant factors were found to vary home heat-energy usage into distinct distributions, even within similar homes. Therefore, in most case-study homes, heat-energy usage did not equal an official estimate. Finally, shallow retrofit of a modern home in Ireland fails to save heat-energy usage by most occupants.

Homeowner Preference for Household-level Flood Mitigation in US: Analysis of a Discrete Choice Experiment

AbstractThe Federal Emergency Management Agency (FEMA) offers a portfolio of flood risk mitigation options for high-risk homeowners, hoping to reduce flood damages. Buyout (home acquisition) and home retrofit (e.g., home elevation) are candidates available to homeowners. FEMA has recently amended and increased its buyout efforts. This study examines homeowners’ stated preference for buyout and home elevation contracts using survey data. Results indicate multiple factors influence the decision to participate in home acquisition and elevation programs. Importantly, we find that preferences vary with the timing (whether the contract is offered before or after a damage event) of the contract offered.

Preparing for Wildfire: Home Retrofits and Household Preparation

Preparing for Wildfire: Home Retrofits and Household Preparation

Decarbonising existing homes in Wales: a participatory behavioural systems mapping approach.

To reduce carbon emissions, urgent change is needed to high-carbon human behaviours including home energy use. Previous policy failures point to insufficient integration of systemic and behavioural approaches which are too often seen as alternative and incompatible approaches to bring about change. A novel behavioural systems mapping approach was used to inform national policy recommendations for energy-saving retrofit of homes in Wales. Three participatory workshops were held with the independent Welsh residential decarbonisation advisory group ('the Advisory Group') to: (1) map relationships between actors, behaviours and influences on behaviour within the home retrofit system; (2) provide training in the Behaviour Change Wheel (BCW) framework and (3) use these to develop policy recommendations for interventions. Recommendations were analysed using the capability, opportunity and motivation (COM-B) model of behaviour to assess whether they addressed these factors. Two behavioural systems maps (BSMs) were produced, representing privately rented and owner-occupied housing tenures. The main causal pathways and feedback loops in each map are described. Necessary interventions to achieve national-scale retrofit included: government-led investment, campaigns and awareness-building, financial-sector funding mechanisms, enforcement of regulations and creating more streamlined and trusted supply chain services. Of 27 final policy recommendations, six addressed capability, 24 opportunity and 12 motivation. Participatory behavioural systems mapping can be used in conjunction with behaviour change frameworks to develop policy recommendations that address the behavioural determinants of complex environmental problems in a systemic way. Research is underway to refine and extend the approach through application to other sustainability challenges and methods of constructing systems maps.

Man caves, granny flats and alternative living spaces: Low carbon home retrofit and implications for policymaking

This paper presents new insights into low carbon home retrofit by highlighting home improvement practices to spaces beyond the main dwelling. We use social practice theories and draw on empirical research with householders in Australia focused on practices of homemaking in man caves, garages and granny flats to trace negotiations and relations between spaces, practices and the governance of retrofit. In doing so, we understand the adaptation of what are often considered ‘outside’ or ‘uninhabitable’ spaces as alternative lived spaces, or alternative retrofit spaces. The paper argues that studying the textures, or socio-spatial-material relationships of these alternative retrofit spaces helps understand how unexpected trajectories of future energy use are established. The research problematises policy making and related interventions that treat material dwelling upgrades in binary ways, such as ‘outside/inside’ and/or ‘habitable/uninhabitable’. Retrofit governance is shown to extend across various scales such as urban planning and consumption of small appliances, across space and time, and shaped by traditional values and inclusiveness in the community. The research highlights the informal homemaking practices that mean retrofit governance traverses both formal and informal aspects. Retrofit and urban policies may need to take these aspects into account in terms of regulations and strategies, but also as they relate to larger social change interventions focused on understandings, experiences and end goals.

From Audits to Projects: Evaluating New York State Policy to Encourage Home Retrofit Projects

This research explores socio-spatial characteristics of home retrofit projects in New York State and their association with the state’s free home energy audit program. Prior work by the authors found that zip codes with more elder individuals and higher levels of education are more likely to undertake an energy audit; it was also found that higher incomes may be negatively correlated with audit decisions. Less understood is the follow-up decision after an audit to undertake a retrofit. From a policy and climate perspective, the actionable retrofit decision is far more impactful than the informational audit, making it an important area of further research. This work examines this understudied area using a combination of datasets, including census data, American Community Survey (ACS) data, and retrofits data provided by the New York State Energy Research and Development Authority (NYSERDA). Findings indicate that many of the same socioeconomic characteristics that predict audits are influential in retrofit projects as well (age, education, higher home values). A strong statistical relationship was found between audits per capita and subsequent retrofit projects, which is to be expected, as NYSERDA requires audits of residents desiring efficiency retrofits. However, this also indicates that the role of the audit in information transfers may be highly influential in encouraging home energy efficiency projects. This finding underscores the policy importance of offering low- or no-cost energy audit incentives to encourage greater participation in home retrofit programs.

Energy transition process and community engagement on geographic islands: The case of Culatra Island (Ria Formosa, Portugal)

Islands have the potential to be precursors in the transition to clean energy, by adopting new technologies and applying innovative solutions that can serve as showcases at an international level. This paper is a contribution towards understating the importance of community engagement on energy transition processes. It covers multiple aspects of a green transition process, including technical, environmental, social, and economic issues. Starting by a participatory diagnosis process, the community of a small island located in Portugal (Culatra Island, Algarve), was challenged to lead the transition process and define different pillars of energy transition. The process brought together local authorities, academia, citizens and companies. Using practical examples, it is shown how the community is succeeding in tailoring new technological solutions for a green transition, according with the specific needs of the island, as expressed by the islanders themselves, including batteries, electric vehicles, retrofitting of homes, or heat pumps, which, when combined, could lay the foundations for the creation of a Renewable Energy Community and leverage socioeconomic benefits.

Racial inequity in household energy efficiency and carbon emissions in the United States: An emissions paradox

Residential energy use represents roughly 17% of annual greenhouse gas emissions in the United States (U.S.). Studies show that legacy housing policies and financial lending practices have negatively impacted housing quality and home ownership in non-Caucasian and immigrant communities. Both factors are key determinants of household energy use. But to date there has been no national scale analysis of how race and ethnicity affect household energy use and related carbon emissions. In this paper, we estimate energy use and emissions of 60 million household to clarify how energy efficiency and carbon emissions vary by race, ethnicity, and home ownership. We find that per capita emissions are higher in Caucasian neighborhoods than in African-American neighborhoods, even though the former live in more energy-efficient homes (low energy use intensity). This emissions paradox is explained by differences in building age, rates of home ownership, and floor area in these communities. In African-American neighborhoods, homes are older, home ownership is lower (reducing the likelihood of energy retrofits), and there is less floor area per person compared to Caucasian neighborhoods. Statistical models suggest that historical housing policies, particularly “redlining”, partially explain these differences. We suggest three policies to address this emissions paradox: Government financing of home retrofits, particularly in rental units; Increased access to photovoltaics in disadvantaged communities; and Disincentivizes for high energy consumption and emissions. Addressing this emissions paradox provides an opportunity for an equitable decarbonization of the U.S. housing sector.

Split incentives and endogenous inattention in home retrofits uptake: a story of selection on unobservables?

Imperfect information in rental sector and housing-induced returns heterogeneity among occupiers are typically estimated with cross-sectional single-equation models. This approach leads to the estimation of conspicuous wedges in insulation investment propensity between tenants vs owner–occupiers (≥20 percentage points) and low-return vs high-return dwellings households (0.10–0.20pp) in the UK. I analyse their sensitivity to assumptions on unobservables à la Oster (2019) and Cinelli and Hazlett (2020). According to the former’s parametrization, under equally strong observables and unobservables, the effect of split incentives on loft/wall insulation investment can be up to 40%/26% lower, while the effect of housing choices is unaltered. The latter’s strategy suggests that an equal selection scenario would reduce by at least 60% the split incentives estimates, whereas non-random housing would just cause the estimates to drop by less than one third. Hence, I quantify a certain degree of selection on research conclusions and offer some convenient tools to integrate in the assessment of the sources of under-retrofitting with cross-sectional data.

Indoor air quality impacts of residential mechanical ventilation system retrofits in existing homes in Chicago, IL

Mechanical ventilation systems are used in residences to introduce ventilation air and dilute indoor-generated pollutants. A variety of ventilation system types can be used in home retrofits, influencing indoor air quality (IAQ) in different ways. Here we describe the Breathe Easy Project, a >2-year longitudinal, pseudo-randomized, crossover study designed to assess IAQ and adult asthma outcomes before and after installing residential mechanical ventilation systems in 40 existing homes in Chicago, IL. Each home received one of three types of ventilation systems: continuous exhaust-only, intermittent powered central-fan-integrated-supply (CFIS), or continuous balanced system with an energy recovery ventilator (ERV). Homes with central heating and/or cooling systems also received MERV 10 filter replacements. Approximately weeklong field measurements were conducted at each home on a quarterly basis throughout the study to monitor environmental conditions, ventilation operation, and indoor and outdoor pollutants, including size-resolved particles (0.3–10 μm), ozone (O3), nitrogen dioxide (NO2), carbon dioxide (CO2), carbon monoxide (CO), and indoor formaldehyde (HCHO). Mean reductions in indoor/outdoor (I/O) ratios across all systems after the intervention were approximately 12% (p = 0.001), 10% (p = 0.008), 42% (p < 0.001), 39% (p = 0.002), and 33% (p = 0.007), for CO2, NO2, and estimated PM1, PM2.5, and PM10, respectively. There was a reduction in I/O ratios for all measured constituents with each type of system, on average, but with varying magnitude and levels of statistical significance. The magnitudes of mean differences in I/O pollutant concentrations ratios were generally largest for most pollutants in the homes that received continuous balanced with ERV and smallest in the homes that received intermittent CFIS systems, with apparent benefits to providing ventilation continuously rather than intermittently. All ventilation system types maintained similar indoor temperatures during pre- and post-intervention periods.

Does information encourage or discourage tenants to accept energy retrofitting of homes?

We study whether providing information about the consequences of residential energy retrofitting encourages public housing tenants to agree with retrofitting, and how this differs by type of information offered. We run a choice experiment in which tenants select between retrofitting packages that differ on the renewable technology used, the energy bill savings, the corresponding rent increase and the CO2 reduction. Two subsamples of participants get additional information on the financial respectively comfort-related consequences of retrofitting. We find that an average tenant is willing to agree with retrofitting when energy bill savings are 30% higher than the rent increase. Information on comfort-related consequences of renovations makes people more likely to choose for retrofitting. On the contrary, information on financial consequences reduces the support for retrofitting.

Barriers to domestic retrofit quality: Are failures in retrofit standards a failure of retrofit standards?

Thermal retrofits of homes are central to the UK's fuel poverty and net zero carbon policies but there are concerns about poor quality installation and so new standards are to be introduced (PAS2035). We have explored retrofit installers' perceptions of the barriers to installing internal wall insulation (IWI) and of current regulations and standards for retrofits. We conducted four focus groups with retrofit installers. Thematic analysis identified three themes. (1) IWI is viewed as impractical in situations other than new builds, extensions and conversions as it is too time-consuming and expensive. (2) Installing IWI is perceived as an unskilled job with no need for training or referring to standards during installation. (3) Because standards lack credibility, installers can be sceptical of potential problems caused by on-site installation adaptations, for example thermal bridging. Our results show that retrofit standards have not improved retrofit quality. Awareness and credibility of standards is low, and new standards (PAS2035) will introduce additional costs which may reduce the pool of installers willing to engage in the retrofit market. Policies need to address installer training, professional identity and social practices, and reduce barriers to change in order to increase success.