EU countries have committed to taking national measures to reduce the average energy use of residential buildings by 16% by 2030 and 20–22% by 2035. Each country has decided how to achieve this and which buildings to focus on. However, certain categories of residential buildings, including historical buildings but also second homes, may be exempt from these obligations. In Sweden, second homes constitute a substantial part of the housing stock and contribute to energy use for heating and hot water of 2.79 TWh, of which 2.16 TWh is electricity. Even if the owners of second homes are not obliged to take energy efficiency measures, quite simple and inexpensive measures may contribute to substantial energy savings. In this study, simulations of energy use in 862 second homes heated with direct electric heating were carried out for five energy efficiency measures (additional attic insulation, new windows, air-to air heat pump and decreasing the temperature during absence to 10 and 5 °C). With the assumption that the 862 second homes are representative of the entire stock of electric-heated second homes in Sweden, the energy saving potential was estimated to be 1.17 TWh per year if all homes install heat pumps and 0.99 TWh and 1.30 TWh per year if all lower the temperature to 10 °C or 5 °C when the house is not used. 

Identifying potential moisture damage is crucial for maintenance practices and assurance of well-being of oc cupants. However, due to limited information availability and standardization, assessing damage prevalence on the building stock scale remains understudied. By combining investigation records and building databases, this study leverages data analytic techniques and machine learning modeling to characterize damage pathology and predict its occurrence in Swedish buildings. The interrelationships between damage-specific attributes and their associations with building parameters of several damage types were analyzed using feature selection, forming the basis for developing predictive models. Results show that multilabel classifiers outperform binary classifiers for every damage type, with lead tree ensemble models achieving minimum average AUCPR and F2 of 0.85 for microbial growth, 0.87 for deformation, 0.91 for odor, and 0.95 for water leakage. The identified patterns were interpreted and verified against descriptive statistics. The binary relevance models estimate that one-third of school buildings, 20 % of commercial and office buildings, and 15 % of residential dwellings in regional building stock contain moisture damage. These findings advance the quantification of moisture damage by providing new knowledge and approaches for appraising moisture damage likelihood at aggregated and individual building levels, thereby aiding in moisture safety evaluations and preventive maintenance efforts

Moisture damages lead to significant costs and impact indoor environments negatively. Identifying their occurrence patterns is crucial for the implementation of preventive or mitigative measures, though it remains highly challenging due to the complex interplay of multidimensional variables. This study aims to identify primary moisture damage profiles in Swedish buildings and evaluate their prevalence. Using data-driven analytical and visualization techniques, 2,100 complex moisture-related damage records between 2014 and 2020 with information on building parameters and damage specifics from Sweden were examined in multivariate analysis. The association analysis reveals varied relationships among factors related to damage, with damage types distributed proportionally across damaged components, causing components, sources, building phase, and responsible actors. The presence patterns of damage differ significantly by building types, yet they are generally reported more frequently in buildings built during the 1960–1980 and 2000–2020. Prevalent moisture damages in Swedish buildings include microbial growth and deformation at the building envelopes and roof, odor in indoor environments caused by wind-driven rain, and indoor or outdoor humidity. Additionally, these damages appear more often in buildings constructed with non-ventilated crawlspaces, wood, concrete, brick structures, façade, exterior walls, and non-ventilated cold attics. The characterized moisture damage patterns and estimated frequency enhance the understanding of their occurrence and associating factors.

The escalating utilisation of second homes has led to an extension in heating periods and, to a certain degree, renovations to elevate the standard, resulting in augmented energy and resource consumption. A comprehensive survey was conducted in Sweden, examining user patterns across different seasons, heating systems, and implemented energy efficiency measures. The results indicate that second homes are occupied for extended periods during the summer season and intermittently throughout the year. Over half of the second homes are heated even when unoccupied, with 12% maintaining a temperature above 16 °C. The predominant heating method is direct electricity (32.2%), followed by heat pumps (29.5%) and stoves (17.5%). A variety of renovations are undertaken, primarily to enhance the standard and technical performance, but also to implement energy efficiency measures such as window replacement, additional insulation, or heat pump installation. Based on the reported user and heating patterns, and the energy renovations carried out, the potential energy savings with different energy renovation strategies were estimated for the Swedish second home stock. The results show that though lowering the temperature when a second home is unoccupied emerges as the most efficient measure, both in terms of cost-effectiveness and climate impact, it needs to be complemented with intermittent heating or dehumidification to ensure that the relative humidity is below critical levels, to avoid the risk of damages caused by, for example, mould growth. Installing a heat pump is the second most energy- and cost-effective measure and has the advantage that the indoor temperature can be maintained at rather high levels. 

Predicting modeling and analysis of moisture damages in Swedish buildings Moisture damage in buildings poses significant challenges, leading to costly repairs and negative impacts on indoor environments. Understanding the patterns and prevalence of such damage is crucial for implementing effective preventive and mitigative measures. This report synthesizes findings from the comprehensive study on moisture damage in Swedish buildings, highlighting the complex interplay of multidimensional variables that contribute to these issues. Analyzing 2,100 moisture-related damage records from empirical damage investigations from 2014 to 2020, the study employs data-driven analytical techniques to identify primary moisture damage profiles and evaluate their prevalence. Multivariate analyses reveal diverse associations among factors related to moisture damage, with significant variations in damage types across different building components, phases, and actors responsible. The findings indicate that moisture damage is most prevalent in buildings constructed between 1960-1980 and 2000-2020, with common issues including microbial growth, deformation of building envelopes and roofs, odors caused by humidity-related problems and wind-driven rain. Buildings with non-ventilated crawlspaces and non-ventilated attics are particularly susceptible. By characterizing moisture damage patterns and their associated factors, these findings enhance our understanding of moisture damage occurrences and informs strategies for relevant actors to improve their practices on moisture damage prevention along building lifecycles. Furthermore, various predictive modeling techniques and machine learning algorithms were explored to predict the presence of prevalent moisture damage types, including microbial growth, deformation, odor, and water leakage. The binary and multilabel classification models achieve high prediction rates of over 0.9 average AUCPR and F2 scores by training with building-related features in cross-validation and validation. The lead binary relevance models estimate that approximately one-third of school buildings, 20% of commercial and office buildings, and 15% of residential dwellings in the uninvestigated Swedish building stock may contain unreported moisture damage. These findings advance quantitative research on moisture damage, providing new insights and tools for assessing the extent and patterns of in-situ moisture damage, thereby aiding existing moisture safety evaluations, and building maintenance strategies. Specifically, the results can help building owners, insurance companies, and damage investigators predict and address potential moisture damage in buildings. They also support developers, designers, and contractors in making informed decisions about construction solutions, helping to avoid designs with a high risk of damage. By preventing moisture damage in both existing and new buildings, we can significantly reduce costs and the environmental impact of remediation and material replacement, which currently result in substantial expenses and CO2 emissions.

In the context of the circular economy, there is an urgent need for transformation into circular material flows by avoiding waste, reducing extraction of virgin raw materials, and extending product life cycles. Within the construction and real estate industry, the reuse of building materials stands out as a critical strategy for value retention. The objective of this paper is to localise the forefront of the practical implementation of reused materials within the Swedish construction and real estate industry. To achieve this, the current state of reuse practices through the perspective of property companies as clients in decision-making positions was conducted through semi-structured interviews to identify key barriers and enablers associated with reuse. The three most significant barriers that emerged were a lack of measurable economic incentives, the absence of a professional reuse market, and obsolete project management. Conversely, the three most significant enablers were new and improved project management methods, enhancing competence and learning within and beyond organisations, and introduce reuse at an early stage. The results emphasise the need for project management to develop and adopt circular economy principles. This is further understood due to responders highlighting the industry’s linear approach as a major obstacle to circularity together with uncertainties related to product performance, responsibilities and economics characterising reuse efforts. However, an industry in transition is witnessed, e.g. by the emergence of new roles which suggests a continued need for focused research in organisational matters.

The growing utilization of second homes has led to extended heating periods and, to some extent, renovations to enhance their standards, resulting in increased energy and resource consumption. This study, conducted in Sweden, investigates user patterns across various seasons, heating systems, and implemented energy renovation measures. Findings reveal that 40% of second homes in winter sport areas are inhabited prolonged periods during the winter, and more than half are used for shorter durations throughout all seasons, surpassing the usage frequency of second homes in general. Additionally, more than half of these second homes are heated to temperatures exceeding 16°C even when unoccupied. The predominant heating method is direct electricity (48%), followed by heat pumps (32%). Renovation activities primarily focus on interior surfaces, kitchens, and bathrooms to elevate standards, with less than 15% implemented energy-efficient measures like heat pump installation, added insulation, new lighting, or control systems. Considering reported user and heating patterns, along with energy renovations undertaken, the study estimates the energy-saving potential associated with various energy renovation strategies. By installing heat pump the energy consumption can be reduced by more than 50% and by lowering the temperature when the house is unoccupied the energy consumption may be reduced by almost 50%. 

PVC flooring accounts for a significant share of PVC use in the construction sector and has great potential for recycling. Nevertheless, the actual recycling rate of PVC flooring spillage in 2018 was less than 20%, according to the national system for the separate collection and recycling of material residues from the installation of PVC floorings, developed by flooring manufacturer Tarkett AB and now used by all manufacturers in the flooring industry. To improve the sorting and recycling process of old PVC flooring it is necessary to identify where the material is located and evaluate its recycling potential. Such information is crucial for demolition waste recycling companies and flooring manufacturers to improve recycling practices for PVC flooring and then use the recycled PVC materials in the new flooring production. The challenge is to find out in which buildings there is PVC flooring and when it was installed which will indicate when it is planned to be dismantled and replaced. Since the PVC flooring manufactures do not keep track on where their products are laid such information is lacking. The best source of information that was made available for the researchers appeared to be the public building owners´ maintenance plans. Therefore, it was decided to focus on the presence of PVC flooring in public preschools as an example. By combining data from maintenance plans with national building registers, the PVC flooring in the Swedish preschools have been forecasted. The project results show an example how limited data sources can be used to predict presence of materials in larger stocks and is therefore expected to contribute to a climate-neutral supply chain with recycled PVC flooring. Based on the results of this study, dialogue, recommendations and guidelines can be developed for the flooring industry, the waste and recycling industry and the Swedish real estate and construction sector.

There is an increased interest in using Cross-laminated timber (CLT) in construction, but many buildings are erected without weather protection, which poses a risk of moisture impact if wood is exposed to precipitation during construction. The construction industry argues that there are no documented critical moisture levels for CLT and no specific test method. In the study, a laboratory test set-up was developed to study mould growth under realistic and controlled climatic conditions after exposure to distilled water and spore suspension. In the experiments, small test specimens of CLT structures were exposed to distilled water for 1 day or 1 week. During the development of the method it was found that exposed for one day and then given the opportunity for open drying did not give rise to mould growth. On the other hand, growth occurred on surfaces that could not dry immediately, for example at connection points. For specimens exposed for one week, mould growth arose regardless of whether the surfaces could dry immediately or not. The conclusions apply primarily to the climates studied. The methodology needs to be further developed, with other scenarios being studied, and calibrated against samples exposed to outdoor air, dust, dirt and rainwater. 

During and post pandemic more people spent time in their second homes, which is expected to have led to higher energy use for heating. The knowledge of energy performance, heating systems, energy renovation and use patterns of second homes is still poor. The aim of the research is therefore to compile available information from building registers but also to empirically investigate user patterns, heating source and the renovation and energy efficiency measures carried out in second homes. A first step is to synthesize existing knowledge and develop a method for a broad mapping in a next step. The methods used are analysing statistics from national building registers and collecting information from owners/users through a pre-survey that is developed and tested. In this paper statistics on Swedish second homes and results from a pre-survey responded by 92 second homes owners/users are reported. From statistics, the energy performance and the main heating source for second homes with an EPC are identified. Despite the limited sample, the results from the pre-survey give an indication of user patterns, energy renovation measures carried out, and also whether the owners care about cultural values. Based on the experience from the pre-survey, a national survey has been initiated in Sweden.