During the last decade, the use of timber (especially massive timber) has increased worldwide, mainly driven by anticipated environmental benefits. However, there is debate on how to handle the susceptibility against microbial growth for wooden constructions, especially during the construction phase. Sometimes full weather protection is used to avoid exposing the wooden material to outdoor conditions, but oftentimes the structures are fully exposed to precipitation. In an earlier study, one construction site using a full weather protection was studied, and the results showed promising results on the improved hygrothermal conditions and reduced risk of mould growth. Moreover, the site contractor also indicated improved work environment and productivity, however, this was not included in that study. This present study aims to investigate the effects of using full weather protection during construction in seven different construction projects to follow-up and broaden the earlier single project study. The studied aspects include the hygrothermal conditions, potential of mould growth, and influence on the work environment. Temperature and relative humidity were measured and analysed. Samples of cross-laminated timber (CLT) were analysed using a microscope, and the results are compared to theoretical mould growth potential. This is measured both inside the weather protection and outside at the seven construction projects. Furthermore, a work environment questionnaire is distributed to workers at the sites to collect the perceived work environment using a full weather protection. The results of the study partly confirm the conclusions from the earlier study, i.e., reducing the risk of mould growth and causing a slightly warmer and dryer conditions than outside. In addition, the results indicate an improved work environment. The majority of the interviewees wishes a weather protection in their next project regarding the work environment.

Preventing mould growth on building materials during construction requires understanding the conditions under which mould can grow. This study conducted an inventory of literature published in the field of moisture, wooden material, and mould growth, selected, documented and categorised relevant literature, and summarised the state of current research. The study is part of a bigger project working to produce a handbook for the moisture-proof production of wooden buildings. The criterium for selecting literature was whether it could provide information on the conditions under which mould growth can occur on wood and wood-based materials during the production stage. This information mainly covers limit values for humidity and temperature, how long these limit values can be exceeded without mould growth, and whether there are differences between different wood materials and between different wood-based products. Both laboratory tests and field studies are included in the material. Most published laboratory studies have been performed under high relative humidity (RH), very favourable to mould growth. Often in these conditions, mould growth begins within one week on all wooden material. Mould growth at lower, less favourable humidity conditions is less studied. However, there are indications that the lowest RH at which mould can grow varies between different qualities of wood. The laboratory studies use different methodologies, and it is not easy to compare results and make general conclusions to achieve the purpose of this study. For example, only discolouring growth is studied, resulting in misleading interpretations, as there may be extensive growth on a material without being visible to the naked eye. Outdoor field studies were evaluated first after several months. The results are difficult to apply to the construction of buildings, as these are not exposed for such long periods without weather protection. Additionally, the field studies only considered the development of discolouring growth. The report also summarises several studies performed at RISE using the same methodology. Some are yet unpublished. More information about the relationship between moisture, temperature, wood material, etc. can be obtained by additional analysis of the results from these studies.

Mould growth results from a complex interaction between environmental factors, material properties, and mould fungi characteristics. These interactions must be considered during the design, construction and maintenance of a building to prevent growth. Mould prediction models aim to predict whether mould will grow on a specific material in a part of building with a known, or simulated, relative humidity and temperature. They are often used in the design phase. Several models are available. There is limited research on the performance of the models in real buildings. This study aimed to evaluate six different models, using data from five building parts. The predictions on whether mould growth was expected or not were compared to actual mould growth observations on five building materials. The study was performed as a round-robin. Most models underestimated the possibility for mould when humidity and temperature varied a lot by time. The outcome also depended on the end-user, who needs to make assumptions and parameter values choices on, for example, material susceptibility for mould growth. Therefore, using the same climate data, mould growth prediction may differ depending on who makes the prediction. One model, MOGLI model, where input data comes from laboratory tests and no such assumptions must be made, predicted correct in most cases. One conclusion of the study is that when predictions are made in practice, the results must be used cautiously. More knowledge is needed to understand, and more accurately model, the relationships between the moisture and temperature variations in buildings and the risk for mould growth. 

A circular economy (CE) represents the key alternative to the linear ‘take-make-consume-dispose’ economic model, that still predominates in the construction sector. This study investigates how policies support CE-focused businesses in the construction sector in the Nordics. A literature review, the creation of a database, a review of Nordic actors with a CE focus, and targeted interviews with actors across the value chain of the construction sector in Denmark, Finland, Norway, and Sweden enabled us to benchmark the CE policy landscape and assess how CE policies at different levels support CE business models in the construction sector. The results show that the construction sector is well represented in the CE policy frameworks and that many business opportunities are created when national and local policies are put into practice. The implementation of policies is mainly done via three key concepts, i.e., planning, requirements for sustainable constructions, and requirements for public procurement. It can be concluded that policies are drivers for the implementation of a CE and support CE business models in the Nordics. © 2021 by the authors. 

Studies investigating microbial diversity in buildings have been performed mainly through the study of dust collected from e. g. floors and door frames and on moisture damaged building materials. A great diversity of mould fungi has been found and the fungus flora is dominated by the genera Aspergillus and Penicillium. The building materials targeted in this specific study were sampled on the back of ceramic tiles from bathroom walls and floors. Furthermore, two different analyses were used to investigate to which degree this specific environment was supportive of microbial growth. Microbial findings were detected in 48 % of the specimens from the spots exposed to liquid water in the bathrooms. To our knowledge, the microbial occurrence in this type of environment has not previously been investigated.. © The Authors.

Mould growth in buildings is a complex process, affected by moisture and temperature, the properties of the building material as well as characteristics of the mould fungi. The complexity poses challenges when assessing the risk of mould growth in buildings. Mathematical models are often used to predict whether mould will grow in a part of building with expected RH and temperature conditions. The models can be described as static or dynamic. In a previous round-robin study, comparing results from models with observations from field studies, the outcome of the dynamic models evaluated depended on the user of the model. Also, the models often underestimated the risk of mould growth. A better agreement was found for static models, especially for the PJ-model. It is a part of a standardised technical specification (SIS-TS 41:2014) and has not previously been described as a model. The critical moisture level (RHcrit), determined by tests according to the method, is used as input. Thus, the subjectivity in the predictions is reduced. RHcrit is the lowest moisture level at which mould can grow and is temperature-dependent. The PJ-model provides an equation to estimate RHcrit at typical temperatures in buildings. If RH in a building section exceeds the limit values at the current temperature, growth is predicted. This paper describes the PJ-model version 1.0, some of the extensive work performed during the development and validation of the model and the ongoing work to refine the model to include considering transient conditions and measurement uncertainties. © The Authors

The susceptibility for mould growth varies among different building materials. One way to describe the susceptibility is the lowest RH at which mould can grow on a specific material, the critical moisture level (RHcrit). Determining RHcrit for materials provide the basis for material choice in designs where moisture and temperature conditions are known. In this study, RHcrit of 21different products were determined according to SIS-TS 41:2014/SPMet 4927. This test method is developed based on the results of a variety of laboratory studies and validated by field studies. Test specimens were inoculated with a suspension containing spores from six different mould fungi and were then incubated in moisture chambers at four levels of RH at 22 °C. After 12 weeks specimens were analysed for mould growth. RHcrit was determined based on the lowest RH at which mould grew on the specimens. RHcrit varied among different products, even between product belonging to a similar group of material, for example, calcium silicate boards or gypsum boards. The results show, and confirm, previous findings that it is not possible to estimate RHcrit for a specific product based on material group. Instead, each product must be tested. © The Authors

Plasterboard is a common building material used in several parts of a building. In the case of retrofitting and demolition a part of the waste consists of components combined with the plasterboards, for example, frame work timber.

In the case of new construction and retrofitting, construction waste is produced from clean plasterboard boards, either as cut off pieces or as unused whole boards. This waste can be used as raw material to produce new plasterboards. Manufacturers want to use gypsum from wasted boards to decrease the use of primary gypsum from mining and the quality requirements are relatively easy to achieve.

In this project it has been found that the major construction companies already handle gypsum from new construction separately. This waste fraction could already be used in the production of new boards. Gypsum from retrofitting is usually assembled with other building materials and require more extensive efforts to achieve necessary purity to be used in the productions of new boards. Today, plasterboard waste is deposited or used to improve soil and/or sludge. In order to increase the recycling of plasterboards new inventory routines of rebuilding and demolition projects need to be elaborated. New tools and methods for dismantling plasterboard need to be development to achieve safe working environment and environmentally and economically sustainable recycling.

Preparation plants producing raw material from plasterboard waste are already in operation. Today the waste mainly is wastage from the production stage. In order to increase the recycling of plasterboards from the construction- and demolition branch new logistic systems need to be developed, for example by creating collection points for gypsum board waste and / or developing new transport vehicles and systems. Prerequisites of changing the system of piece work in the construction industry need to be investigated with the intension to create a more sustainable building industry.

Gipsskivor är ett vanligt byggnadsmaterial som används i flera olika delar av en byggnad. Vid ombyggnation och rivning uppkommer därför rivningsavfall som består av gipsskivor tillsammans med det material som gipsskivor är sammanbyggda med som t.ex. regelvirke. Vid nybyggnation och ombyggnation uppstår byggavfall av rena, oanvända gipsskivor, antingen som kapspill eller som överblivna hela skivor. Dessa kan användas som sekundär råvara för att producera nya gipsskivor. Det finns en efterfrågan på sekundärgips från producenter och kvalitetskraven är relativt enkla att uppnå.

I projektet har det framkommit att de större byggbolagen redan idag hanterar gipsspill från nybyggnation separat och att denna fraktion redan nu skulle kunna användas för nytillverkning av skivor. Gips från rivning och ombyggnation är i regel sammanbyggd med andra byggmaterial och kräver mer resurser i avfallshanteringen för att nå en renhetsgrad så att den kan användas för återvinning till nya gipsskivor. Idag deponeras denna gips eller används till jordförbättring. För att öka återvinningen av denna gips behöver nya rutiner för inventering av ombyggnads– och rivningsprojekt samt utveckling av redskap, som möjliggör att en demontering av gipsskivor blir arbetsmiljömässigt och ekonomiskt hållbar.

Anläggning finns redan för att bereda sekundär gips till råvara för nytillverkning med bibehållen kvalitet. För att öka återvinningsgraden behöver nya logistiksystem utvecklas, t.ex. genom att skapa uppsamlingspunkter för sekundär gips och/eller utveckla nya transportfordon och -system.

Förutsättningar för ett förändrat ackordsystem inom byggbranschen behöver undersökas med syfte att skapa ett system som premierar ett mer hållbart byggande.

In this project we have tested a mould model originally developed by Skanska (the m-model) and a method developed by RISE in Sweden (the GLC-method) on data from both laboratory and field measurements. The laboratory measurements had durations of a few months and were made in climate chambers at RISE; the field measurements were made in 12 buildings during 30 months. In both cases, temperature, relative humidity and mould growth was assessed on six different materials. The results were used to investigate if the m-model or the GLC-method could predict when there was mould growth. Both methods could differentiate between the (dry) cases without mould and the (moist) cases with mould. However, we could not find mould resistance parameters for the tested materials to be used with the m-model. This could be because the m-model cannot predict mould growth well enough, but it can also be because the types of measurements that we have made have relative large uncertainties in relative humidity. Isotheral calorimetry was also investigated as an interesting method to study how drying affects the activity of mould fungi.

Building materials differ in their susceptibility to mould growth. Wood is a material often considered to have a low mould resistance. However, wood is not a homogenous material and different characteristics of the material are expected to have an impact on mould growth. In this paper, it was shown that wood species (pine or spruce), sawing pattern (centre-board or side-board) and surface structure (planed or sawn) affected mould growth. In addition, it was indicated that the susceptibility cannot be described by one single parameter, but also depends on other parameters. It is therefore difficult to estimate the susceptibility of wood in general. These conclusions were drawn from a meta-analysis, using data from five separate, previously performed laboratory studies conducted at 90% relative humidity and 22 °C, and from a laboratory study performed at 95% RH and 22 °C. © 2016 Springer-Verlag Berlin Heidelberg