Combining insights from HAM-simulations with case-specific knowledge

Heritage buildings often require renovation to obtain better energy performance. Because their exterior walls are preserved, these buildings need to be insulated from the inside. However, interior retrofits drastically change the hygrothermal behaviour of a wall, which is why installing interior insulation is by no means risk-free. By performing Heat-, Air- and Moisture (HAM) simulations on the wall assembly, the moisture-related risks can be analysed. Although HAM tools such as Delphin and WUFI are commercially available, they are rarely used in practice to perform hygrothermal assessment on facades. How can we ensure that the insights and knowledge gained from using these tools are translated to and applied in the building industry

A long-term monitoring study on the thermal comfort and durability of a straw bale Passivhaus cottage

The built environment sector accounts for 40% of the UK's total carbon footprint; bio-based construction materials can play an important role in reducing the whole-life carbon of a new build. Straw bale construction is one of the most promising bio-based methods of construction, due to its availability and material properties. Among the declared benefits of straw bale construction are the internal regulation of heat and moisture and the ability of the fabric to dry out. This paper presents a long-term monitoring study aimed at understanding the indoor temperature and moisture balance of a straw bale cottage built in the UK to a near Passivhaus level. The study lasted 6 years, monitoring the temperature and relative humidity of the indoor and outdoor environments, and in ten locations within the straw bale walls. The analysis has shown that the indoor environment achieved thermal comfort throughout the monitoring period, even when the building was used intermittently. Also, an analysis of surface temperatures and a mould growth risk analysis identified very limited mould growth risk within the building fabric. This paper shows the potential of straw bale low-energy construction in providing thermal comfort and a durable building fabric while minimising the whole-life carbon of buildings

Towards a new method to estimate liquid redistribution coefficients in small fragments of mortar

Inappropriate replacement mortars in historic buildings often lead to irreparable damage to historic masonry; the influence of the mortar on drying dynamics is crucial to these risks. The chemical and compositional analysis of historic mortar is widely practised for the purposes of formulation of replacement mortars but the compatibility, hygrothermal behaviour and moisture safety mainly depend on the physical properties. The chemistry and composition alone do not give a complete understanding of these functional properties, so physical measurements are necessary. However, it is often the case that only small fragments are available from existing walls due to the thickness of mortar joints, friability of the material and conservation constraints on removing material. While some physical properties lend themselves to measurement with small specimens (pore size distribution, sorption curves), liquid transport is harder to measure accurately for small (<25mm) irregular specimens. A new approach was proposed, combining several established techniques, allowing liquid redistribution to be estimated in such specimens. Specimens were subjected to drying experiments, without the usual constraints to approximate 1D flux (sealing the sides and bottom of a strictly prismatic specimen). The experiment was duplicated in 3D hygrothermal simulation, in which the liquid transport properties were adjusted until the simulation results closely approximated the experimental results. The method was demonstrated on cast cylinders of control materials, and will be developed to cover smaller, irregular pieces in subsequent work

Investigating the role of calibration of hygrothermal simulations in the low carbon retrofit of solid walls

Solid masonry buildings account for around 20% of the UK building stock. As a traditional building material in the UK, stone could enhance the architectural style of buildings and last for thousands of years. However, historic buildings inevitably face the issue of diminished performance over hundreds or thousands of years. For these historic buildings whose appearance is protected, internal wall insulation (IWI) is a possible solution for protecting the façade while saving energy, improving indoor thermal comfort, and reducing carbon emissions. Of concern is that IWI could alter the drying capacity of the structure, thereby increasing moisture accumulation and causing durability issues such as freeze-thaw damage and mould growth. Hygrothermal simulations is one of the most commonly used methods to compare the performance and feasibility of different IWI assemblies. However, an inadequate assessment could lead to the specification of inappropriate IWI, prompting an incorrect choice of retrofit strategy. This study investigates the role of calibration in the assessment of moisture risks and durability of a solid masonry wall. The calibration of a hygrothermal model was performed using in-situ monitoring data; the model can be used for the comparison of IWI systems. According to the results, the selection of material properties had the highest impact in the calibration

Hygrothermal risk assessment tool for brick walls in a changing climate

Due to the heritage value of historical buildings, external facades can often not be modified. Therefore, in heritage buildings interior insulation is often considered when undergoing an energy renovation. However, interior retrofitting drastically changes the hygrothermal behaviour of a wall and can potentially cause moisture-related problems. Besides an interior retrofit, a changing climate might also trigger some of these damage mechanisms as parameters such as temperature and precipitation will change over time. Hygrothermal models can provide relevant insights into the risk of deterioration associated with these damage phenomena. However, these Heat, Air and Moisture (HAM) tools are commercially available but rarely used in the building industry to study deterioration risks. Translating research into practical tools and guidelines is a challenge across the whole field of building renovation. This paper aims to tackle that challenge, by means of creating a hygrothermal risk assessment tool based on 48,384 HAM-simulations for the climate of Brussels, Belgium. Seven different performance criteria are addressed and discussed: freeze-thaw damage, mould growth, wood rot, corrosion, moisture accumulation, salt efflorescence and bio-colonisation. Subsequent to a sensitivity analysis, the study further explains how these results can be translated into practice, providing building practitioners the most suitable insights and recommendations. The development of an interactive web tool to assess hygrothermal risks is demonstrated and its use and benefits are further elaborated

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

Bringing the building envelope into a safer, more integrated, sustainable built environment

Recent issues in construction have demonstrated the complexity of delivering a safe, integrated and sustainable building envelope. An expert community from research, the construction industry and policy was invited to come together for two workshops held in January 2022, to identify the key questions around the delivery of a safer, more integrated and sustainable building envelope. This briefing highlights the challenges currently faced in the built environment and sets out how a truly interdisciplinary building envelope network can address these challenges. UCL BERN, the Building Envelope Research Network, is a UCL cross-faculty research network established to help integrate knowledge of the building envelope into UCL’s research and teaching programmes

How Can Scientific Literature Support Decision-Making in the Renovation of Historic Buildings?:An Evidence-Based Approach for Improving the Performance of Walls

Buildings of heritage significance due to their historical, architectural, or cultural value, here called historic buildings, constitute a large proportion of the building stock in many countries around the world. Improving the performance of such buildings is necessary to lower the carbon emissions of the stock, which generates around 40% of the overall emissions worldwide. In historic buildings, it is estimated that heat loss through external walls contributes significantly to the overall energy consumption, and is associated with poor thermal comfort and indoor air quality. Measures to improve the performance of walls of historic buildings require a balance between energy performance, indoor environmental quality, heritage significance, and technical compatibility. Appropriate wall measures are available, but the correct selection and implementation require an integrated process throughout assessment (planning), design, construction, and use. Despite the available knowledge, decision-makers often have limited access to robust information on tested retrofit measures, hindering the implementation of deep renovation. This paper provides an evidence-based approach on the steps required during assessment, design, and construction, and after retrofitting through a literature review. Moreover, it provides a review of possible measures for wall retrofit within the deep renovation of historic buildings, including their advantages and disadvantages and the required considerations based on context

A multidisciplinary approach to address climate-resilience, conservation and comfort in traditional architecture: The PROT3CT example

Traditional dwellings despite their environmental credentials, due to age, previous damage, and residents unable to afford even the limited maintenance allowed by restrictive legal framework, may offer poor thermal performance, which is expected to be further exacerbated by changing climate. More than 70% of Turkey’s built heritage stock is composed of traditional dwellings, which makes this stock able to create a major impact nationally on the building-related energy use, carbon emissions and population wellbeing. This research aims to develop an evidence-based multidisciplinary methodology for cost-effective retrofit of the traditional dwellings in Turkey, to improve energy performance, satisfy user expectations of comfort, and protect heritage value