Research from North Lanarkshire Council has sought to quantify the performance of 19 net zero homes built within a program of 150 new council properties, gathering data from an array of environmental sensors installed within the homes. The homes were built were built with fabric efficiency measures and technologies beyond standard new-build requirements, including triple glazing, additional insulation, photovoltaic panels, battery storage, and heat pumps.
The report served a dual purpose, aiming to reveal how the net zero homes performed on a day-to-day basis, and as well as the efficiency of data recorded in understanding differences between housing types, identifying patterns in indoor environmental conditions and energy use, and interpreting these findings considering household routines and behaviours.
Methodology
The research required a mixed-methods approach combining quantitative monitoring data with qualitative and survey based behavioural evidence. The project drew on four main categories of data:
Monitored/environmental data: indoor environmental data, relating primarily to conditions such as temperature and co2, alongside energy and property data where possible.
Economic data: relating to construction cost information for the Net Zero homes.
Contextual/property data: relating to dwelling type, housing cohort, heating system, and basic property characteristics.
Behavioural data: relating to occupier experiences, heating and ventilation practices, comfort, satisfaction, and everyday household routines.
The report does concede some shortcomings in the data gathered and the analysis that was carried out. One of the report’s goals of understanding household heat demand through gathered sensor data was less able to be implemented as the research intended, which led to a gap in behavioral data to enable a thorough analysis of heat demand.
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Rather than producing robust heat-demand index as originally intended, the monitored data was instead used to examine patterns in environmental conditions, to compare relative performance across cohorts where possible, and to assess the practical strengths and limitations of the available monitoring approach.
Available data to understand space and water heating demands was also limited, as well as gas consumption data also having difficulties. The lack of complete overall data limited the original scope of the report, but the research undertaken was still able to give some insight into the into the in-use performance of dwellings.
Key findings
Overall, the study indicated effective housing improvement programmes need to address both the physical performance of homes and the circumstances and practices of households. Effective improvement programs should combine fabric and system upgrades with financial support, household advice and follow-up guidance where necessary in order to achieve reliable improvements in comfort, affordability, and energy performance across the housing stock.
Building fabric was found to be crucial when it comes to resident experience and outcomes. Households in well-insulated homes were able to benefit from comfortable stable temperatures with consistent, relatively low heating output, even when compared with homes with more net zero technology. The findings highlight the need for technology such as heat pumps to be used in conjunction with well-insulated homes, rather than as a bolt-on technology. The report listed the importance of a fabric-first approach as the first in it’s list of operational recommendations.
Net zero homes were generally found to have performed positively, with residents reporting higher levels of thermal comfort, while sensor data showed stable indoor temperatures alongside relatively low energy use. Net zero and standard new-build homes were found to record the highest satisfaction levels, typically recording a comfort score of 8-10 out of 10. Existing and older housing stock reported much more variation, including the lowest comfort scores of the study.
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Affordability was also found to have a strong influence on resident behaviour. Cool and warm homes rarely have the same underlying cause, and a combination of behavioural sensor data is needed to find a comprehensive view of a home and how it performs. The distinction requires thorough research and cross-referenced data to establish, but without it landlords risk a one-dimensional view of both how homes are performing and the lives of the residents living in them. The behavioural research also found considerable use of coping strategies such as additional clothing, blankets and hot-water bottles, although these practices varied substantially between households.
Recommendations
The final conclusion of the report showed the benefits of monitored and contextual data when used in tandem, monitored data can give the what and contextual data the why. The report advocated for a more strategic, large scale research effort with a similar methodology, gathering statistical data from a larger housing stock and using case studies within the broader group to provide detailed monitoring and evaluation to identify causality.
A number of operational recommendations came from the research, including prioritizing a fabric-first approach for existing homes, identifying and supporting homes found to be rationing heat, and addressing hot water and appliance efficiency alongside space heating.
A number of wider policy implications were also identified. The first is the importance of environmental and energy monitoring, which gives valuable insight into the practicalities and everyday effects of policy initiatives and resultant changes in standards and regulations. There is also a profound gap between projected levels of performance in the design stage and in everyday use. Policy targets and objectives can only be reached by homes that can function in an everyday environment rather than an idealised one, and research should seek to understand and quantify the practicalities of performance mapped before homes are lived in. Regulation and standards should be driven by in-use, rather and expected performance. Consideration should be given to elements of control, usability and information as critical drivers for performance.
Although the report faced difficulty with gathering data to the detail intended, it is also adamant of the benefits provided by both net zero improvement and environmental sensors in providing evidence for their performance. The North Lanarkshire case study suggests that high-quality building fabric, heat pumps, solar PV and battery storage can produce homes with good thermal comfort and relatively low energy use. But it also demonstrates that technology alone is not the answer. Poor building fabric can undermine low-carbon heating, household circumstances can drive energy consumption, and residents need appropriate information and support to operate new systems effectively.
