Moisture Performance Criteria for UK Dwellings

The new ventilation regulations in England and Wales have introduced performance criteria for the control of mould. The UK Government\'s Building Regulations Research Programme has funded University College London (UCL) to investigate the extent to which these are the most appropriate criteria for thecontrol of mould in UK dwellings. This paper reports on the plans for this study which involve both field and laboratory related work. Some initial early work has already been undertaken and the paper summarises the progress to date. This initial work is based on analysis of data from a national study of England\'s Home Energy Efficiency scheme (Warm Front). Surveys were undertaken of dwellings and households participating in the scheme in five urban areas. Half-hourly living room and main bedroom temperatures and relative humidity measurements were recorded for two to four weeks (in the heating season) in approximately 1600 dwellings. This data is being analysed to investigate the typical relativehumidities that exist in UK dwellings and also any relationship that exists between these levels and the mould growth that was recorded

Decision-Making Processes of Residents in Preservation, Thermal Comfort, and Energy Efficiency in Heritage Buildings: A Pilot Study in Mexico City

With building construction representing one of the largest sectors responsible for the use of natural resources, retrofitting existing heritage buildings becomes a necessity, albeit a challenging one. The emergence of specific guidance on retrofitting heritage buildings has unveiled more than never the need to understand how residents negotiate, thermal comfort, energy efficiency, and heritage conservation decisions. The paper reports the complexity of the decision-making process of residents of heritage buildings in the Historic Centre of Mexico City regarding energy efficiency, intending to improve thermal comfort and reduce energy consumption while preserving heritage values. The study involved in-depth semi-structured interviews with users of heritage buildings that were thematically analysed, complemented by the monitoring of internal environmental conditions and system dynamics analysis. The results show that although the residents perceived the buildings’ temperature as poor, passive thermal comfort actions (e.g., wearing more clothes and closing windows) were preferred against invasive retrofitting solutions for thermal comfort due to residents’ resistance to a potential loss in the buildings’ values and the high cost of changes. The degree of change necessary for maintenance, renovation, and actions for improving the thermal comfort of a heritage building is related to values and to their preservation for future generations. The users’ changes were limited to small-scale interventions in floors and ceilings while avoiding touching what they consider essential to preserve and protect (i.e., social and cultural values). Integrating the user into the decision-making process would enhance the long-term continuity and sustainability of retrofitting policies and guidelines, thus avoiding losing heritage-built stock

Retrofitting traditional buildings: a risk-management framework integrating energy and moisture

Traditional buildings constitute a large proportion of the building stock in many countries worldwide; around 40% of the UK’s housing stock was built before 1940 and was primarily made with solid masonry walls. Only 11% of UK solid-walled dwellings had insulation installed, suggesting the high potential of the low-carbon retrofit of traditional buildings. However, there is evidence of the occurrence of unintended consequences, often associated with excess moisture. A method is presented for moisture risk management that includes the development of a process and a framework. These tools are then integrated into a novel framework for the combined energy and moisture performance retrofit of traditional buildings. An example of the framework’s practical application is provided, with a focus on retrofit measures for solid-wall insulation. The proposed systematic approach demonstrates the interconnected nature of energy and moisture. It harmonises the principles needed to support organisations in the delivery of robust retrofit of traditional buildings through the integration of pre-retrofit building assessment and post-retrofit monitoring in the process. The risk-management process and framework presented can be valuable tools to support designers in providing robust and scalable retrofit measures and strategies.   'Practice relevance' An integrated energy and moisture risk-management process is presented to support designers in the retrofit of traditional buildings. This is accompanied by a framework that explains the steps required for moisture risk management at the various stages of the retrofit process. This systematic approach harmonises the principles needed to support organisations in delivering robust low-carbon retrofits and integrates pre- and post-retrofit building assessment in the process. While previous work has addressed energy and moisture management separately, this integrates the two aspects into a framework for risk management. An example illustrates the relevant modes and methods of assessment and monitoring in support of risk management. When combined with practical guidelines and training, the risk-management process and framework can be valuable tools to provide robust and scalable retrofit measures and strategies. The framework was developed within the context of the UK construction industry; it can be adapted to other contexts

Design factors affecting the passive release of tracer gas for ventilation measurements

The ventilation rate is an important parameter for assessing indoor air quality and energy efficiency. In occupied buildings, ventilation measurements utilising passive methods are preferable to active methods due to their simplicity and less intrusive nature. The perfluorocarbon tracer method can be used to measure long-term ventilation rates for this purpose. This method requires the passive release of a tracer gas which is often a liquid chemical diffusing out of a vial. The tracer gas emission rate is a key parameter of the vial design as if it is too low, the sampler will not be able to detect the tracer gas. If the emission rate is too high, the sampler can become saturated. Both scenarios will lead to inaccurate ventilation results. There is wide variability in vial design but little information about the relative impact of each design factor. Thus, the aim of this study was to compare the emission rate of a common tracer gas, perfluoromethylcyclohexane, using different vials designs i.e. capping styles, septa materials, and fill levels. Samples were kept in an incubator and gravimetric analysis was carried out using a semi-microbalance (resolution: 0.01 mg). The results demonstrate that the emission rate is significantly affected by capping style but not by fill level

COVID-19 & informal settlements: is ‘Stay Home’ safe?

The disproportional burden of coronavirus (COVID-19) and vulnerability to containment measures in informal settlements have been recognised; however, the role of poor housing conditions in propagating these remains neglected. Poor housing conditions makes it difficult to effectively implement social distancing measures. With increased time spent in cramped, dark and uncomfortable indoor environments, water and sanitation outside the home, and no outdoor space, higher exposure to existing health hazards and high levels of stress, with women and children being most vulnerable, are anticipated. Through this commentary paper, we reflect on these interconnections and recommend immediate measures and the long-term need for adequate housing for health and well-being

Participatory Action Research as a Framework for Transdisciplinary Collaboration: A Pilot Study on Healthy, Sustainable, Low-Income Housing in Delhi, India.

To tackle global challenges, research collaborations need to integrate multiple disciplinary perspectives and connect with local practices to find solutions that are sustainable and impactful. This paper discusses how participatory action research (PAR) is used as a framework for transdisciplinary collaboration to integrate different disciplines and identify healthy and sustainable housing solutions appropriate for local development practices and policy. By analyzing a transdisciplinary research collaboration investigating housing interventions for low-income settlements in Delhi, reflections and recommendations are provided for other projects wishing to use a similar methodology. It is found that the PAR framework has successfully guided the integration of contrasting methods and improved the impact of research outcomes, resulting in the emergence of new shared practices. However, it proves to be challenging and requires heightened communication and engagement to achieve understanding between all disciplines and practices. It is recommended that focus is given to developing relationships and effective communication channels and that time should be preallocated for reflection. The work provides insights for integrating academic disciplines, the community, and relevant stakeholders in the cocreation of evidence that is paramount to formulate effective solutions to global challenges

Parametric study on the hygrothermal performance of timber frame walls with external airtightness membranes in a temperate maritime climate

In recent years, external airtightness membranes have become an option for timber frame wall systems, as they allow high levels of air- and wind-tightness with an easy installation and provide rainwater protection during construction. This opens up the option of removing the internal air and vapour control layer. However, the hygrothermal risks associated to this option could be higher than in conventional construction, because vapour transfer can occur from the indoor environment into the timber frame wall not just via diffusion but also advection. This can lead to moisture accumulation and mould growth risk within the wall structure. This paper presents a parametric study that aims at identifying the moisture risk when external airtightness membranes are installed on a timber frame wall in a temperate maritime climate. The parametric study considered the two-dimensional heat, air and moisture transfer within a timber frame wall. Parameters having higher influence on moisture risk were identified and should be considered when designing robust wall systems

Assessing the Relationship between Measurement Length and Accuracy within Steady State Co-Heating Tests

Evidence of a fabric performance gap has underlined the need for measurements of in situ building performance. Steady state co-heating tests have been used since the 1980s to measure whole building heat transfer coefficients, but are often cited as impractical due to their 2–4 week test duration and limited testing season. Despite this, the required conditions for testing and test duration have never been fully assessed. Analysis of field tests show that in 12 of 16 cases, a heat loss estimate to within 10% of the result achieved across a full test period can be achieved within just 72 h. These results are supported by simulated tests upon a wider range of dwellings and across wider environmental conditions. However, systematic errors may still exist, even in cases of convergence and cases with significant uncertainties may never converge. Simulated examples of traditional dwellings and those built in line with current building regulation limits may be tested for more than half the year. However, even when simulated with reduced uncertainties, dwellings with low heat loss and high solar gains, such Passivhaus dwellings and apartments, could be successfully tested for just 22% and 12% of a year respectively, demonstrating the limitations of the co-heating method in assessing such dwellings

Understanding current retrofit practices to prevent the unintended consequences affecting IEQ and health

The climate crisis demands an urgent societal shift, and the UK government has responded with a strong policy targeting energy retrofit to improve the energy performance of homes to achieve the net zero target by 2050. However, research has shown that standard retrofit measures have resulted in undesirable unintended consequences. Incorrect interventions such as using incompatible materials can affect the equilibrium of the building, increasing the risk of surface and interstitial condensation due to excessive humidity levels. Mould growth may develop under high levels of humidity, damaging the building fabric but also posing a risk to the occupants; it has been linked to asthma exacerbation and other respiratory infections. Therefore, what is needed is a well-integrated retrofit approach that not only reduces energy use but protects the building and the health and well-being of its occupants. This paper discusses the retrofit practices, the main challenges that retrofit practitioners face in the UK, and which guidance and tools they work with through the lens of the impact on occupants. A deeper understanding of the current practices is needed if those unintended consequences are to be avoided. For instance, replacing a 'fabric-first' mindset with a 'people-first' approach that considers more factors like the causes of thermal discomfort, and the gains to be made from passive and adaptive comfort approaches, could contribute to deliverer energy and carbon savings and increased building's indoor environment quality and usability justified

Climate Resilience of Internally-Insulated Historic Masonry Assemblies: Comparison of Moisture Risk under Current and Future Climate Scenarios

The conservation of cultural heritage built of historical brick masonry alongside meeting targets in energy reduction will most likely require widespread installation of internal wall insulation (IWI). In London, traditional buildings (pre-1919) make up 40% of the existing stock and insulating from the interior is a likely retrofit solution for solid brick walls. Adding insulation may introduce a higher risk to moisture accumulation and consequences such as mould growth and material decay. To investigate resilience to future moisture loads, three interior insulation assemblies (conforming to two U-value guidelines) were simulated in DELPHIN under reference, near-future (2040), and far-future climate (2080) scenarios. Calcium silicate, phenolic foam, and wood fibre assemblies were simulated. The reference year climate file was compiled from observed data and future files developed using the UK Climate Projections 2018 (UKCP18). Assemblies were evaluated for moisture accumulation, mould growth risk, and freeze-thaw (FT) risk. Results show low-to-medium risks in 2040 and high risks in 2080, assemblies of higher absorptivity and thinner insulation comparatively performing best. The calcium silicate assembly fared best for moisture performance; however, all assemblies will be subject to high moisture risk levels in the far future and responsible retrofits must take this and alternative design solutions into account