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Determining the optimal insulation thickness is useful for designing zero-emission buildings (ZEB) to minimize the environmental impacts. The energy required to heat buildings in cold climates is relatively high. Substantial reductions in the total energy usage of a building can be achieved by reducing the U-value of the external surfaces. Increasing the insulation thickness reduces the operational CO2 emissions, although simultaneously increases the embodied CO2 emissions from materials. To mitigate climate change, Norway and Denmark are trending towards stricter regulations to limit energy use in buildings. However, these countries have no current regulations in the building codes for limit embodied CO2 emissions from materials. This study analyzes the influence of the energy emission factor and future climate change (scenarios?) on the optimal insulation thickness. We used three independent models for case studies in Greenland and Norway. The differences between the case studies highlight the influence of model parameter choices, such as indoor climate, energy emission factor and material emissions, whereas the similarities may be used to analyze the problem from a broader perspective. The results show that optimal insulation thickness calculations are most valuable for case studies in which the energy emission factor is low. Considering energy emission factors above 25–30 g CO2eq/kWh, operational emissions dominated the calculation results in all case studies.

The Greenlandic building sector is under pressure due to ever-changing building trends and a building shortage. Regrettably, there have only been made small efforts to investigate the performance of the existing buildings, and few resources have been dedicated to learning from previous attempts. Consequently, the available information and research are insufficient to ensure the construction of robust and well-functioning buildings. This knowledge gap motivated the ABC project, which had the goal of collecting and sharing information about optimal building practices in Greenland. As a part of the ABC project, this study aimed to determine which building practice is the most suitable for Greenlandic conditions. To this end, several real-time experiments were created, including a test pavilion in Nuuk consisting of five different wall constructions oriented towards north and south. This article presents the measured data from this pavilion. The performance of each construction type was compared with each other and to simulations performed in the hygrothermal analysis software Delphin. Furthermore, the robustness of the facades was tested by performing simulations with weather data for different towns in Greenland, including quantification of mould growth risk using the Viitanen model. It was found that the facades were unevenly affected by orientation. Nevertheless, none of the constructions could be labelled unsuitable for the Arctic climate as the assessments revealed no risk of mould growth. Additionally, reanalysis weather data from ERA5 was found to be suitable for performing hygrothermal simulations. It was also found that Nuuk is a favourable location for future test facilities.

Increased insulation reduces the energy needed during operations, but this may be less than the energy required for the extra insulation material. If so, there must be an optimal insulation thickness. This paper describes the development of a tool to determine the optimal insulation thickness, including what parameters are decisive, and presents some results along with a discussion of the success criteria and limitations. To make these considerations manageable for regular practitioners, only the transmission heat loss through walls is calculated. Although the tool is universal, Greenland is used as an example, because of its extreme climatic conditions. The tool includes climate change, 10 locations and 8 insulation materials. It focuses on greenhouse gas emissions, considers oil and district heating as heating sources, and evaluates four different climate change scenarios expressed in terms of heating degree days. The system is sensitive to insulation materials with high CO2 emissions and heating sources with high emission factors. This is also the case where climate change has the highest impact on the insulation thickness. Using the basic criterion, emitting a minimum of CO2-eq, the Insulation Thickness Optimizer (ITO), generally identifies higher insulation thicknesses as optimal than are currently seen in practice and in most building regulations.

It is often assumed that reduced heat flux to a ventilated attic reduces the temperatureand thereby increases the relative humidity. Consequently, the importance of having atight air and vapour barrier in the ceiling becomes more important with increased insu-lation. Therefore, in Denmark, the recommendation is to have a tight vapour barrierwhen re-insulating ceilings against cold ventilated attics to a total of 150-mm insulationmaterial. The recommendation is independent of the insulation material’s hygroscopicproperties or the indoor moisture level. The aim of this project was to test the rele-vance of the recommendation through testing in a full-scale test building (7322 m) witha series of six different ceilings with or without a vapour barrier and variation in theinsulation material comprising insulation thickness and its hygroscopic properties. Theexamination was performed with a controlled indoor climate after an European humid-ity classes 1–3 and a natural outdoor climate. The study showed very little differencesin temperature and relative humidity in the cold ventilated attics, while the humidityclass of the indoor climate significantly affects the absolute moisture content in the attic.However, the climate in the attic did not cause mould growth in the test sections, evenfor humidity class 3. Consequently, in the test building the thickness or hygroscopic1Danish Building Research Institute, Aalborg University Copenhagen, Copenhagen, Denmark2Department of Mathematical Sciences, Aalborg University, Aalborg, DenmarkCorresponding author:Thor Hansen, Danish Building Research Institute, Aalborg University Copenhagen, A.C. Meyers Vænge 15,2450 Copenhagen, Denmark.Email: thh@sbi.aau.dkproperties of the insulation material did not have a significant effect on the moisturelevel in attics and did not determine whether a vapour barrier should be installed. In thisstudy with the given climate, a vapour barrier is unnecessary in well-ventilated attics ifthe ceiling is airtight. It is often assumed that reduced heat flux to a ventilated attic reduces the temperatureand thereby increases the relative humidity. Consequently, the importance of having atight air and vapour barrier in the ceiling becomes more important with increased insu-lation. Therefore, in Denmark, the recommendation is to have a tight vapour barrierwhen re-insulating ceilings against cold ventilated attics to a total of 150-mm insulationmaterial. The recommendation is independent of the insulation material’s hygroscopicproperties or the indoor moisture level. The aim of this project was to test the rele-vance of the recommendation through testing in a full-scale test building (7322 m) witha series of six different ceilings with or without a vapour barrier and variation in theinsulation material comprising insulation thickness and its hygroscopic properties. Theexamination was performed with a controlled indoor climate after an European humid-ity classes 1–3 and a natural outdoor climate. The study showed very little differencesin temperature and relative humidity in the cold ventilated attics, while the humidityclass of the indoor climate significantly affects the absolute moisture content in the attic.However, the climate in the attic did not cause mould growth in the test sections, evenfor humidity class 3. Consequently, in the test building the thickness or hygroscopic1Danish Building Research Institute, Aalborg University Copenhagen, Copenhagen, Denmark2Department of Mathematical Sciences, Aalborg University, Aalborg, DenmarkCorresponding author:Thor Hansen, Danish Building Research Institute, Aalborg University Copenhagen, A.C. Meyers Vænge 15,2450 Copenhagen, Denmark.Email: thh@sbi.aau.dkproperties of the insulation material did not have a significant effect on the moisturelevel in attics and did not determine whether a vapour barrier should be installed. In thisstudy with the given climate, a vapour barrier is unnecessary in well-ventilated attics ifthe ceiling is airtight.

The study investigated the hygrothermal performance and risk of fungal growth in a phenolic foam system with a closed cell structure and a diffusion-open and capillary active lime-cork based insulating plaster, for internal retrofitting purposes. The setup comprised two 40-feet (12.2 m) insulated reefer container with controlled indoor climate, reconfigured with 24 holes (1 × 2 m each) containing solid masonry walls with embedded wooden elements on the interior side.Focus was on the conditions in the masonry/insulation interface and embedded wooden elements, and the performance of the two systems were compared to three diffusion-open insulation systems and one diffusion-tight. The effect of exterior hydrophobisation was also investigated. Relative humidity and temperature were measured in several locations in the test walls over 2½ years, and the risk of fungal growth was evaluated by on-site measurements and the VTT mould-growth model.The findings indicate that internally insulated walls with bare brick exterior surfaces performed poorly with high risk of fungal growth. The effect of exterior hydrophobisation was found to vary with the orientation and the installed insulation system, with a generally positive effect on walls facing south-west but limited effect for north-east.Furthermore, the more diffusion-tight insulation systems were found to perform better in combination with exterior hydrophobisation than the highly diffusion-open systems. The lime-cork insulating plaster showed high relative humidity and risk of moisture-induced problems. The on-site fungal tests showed no growth in the masonry/insulation interface inside the two insulation systems, probably due to high initial pH-value. The study investigated the hygrothermal performance and risk of fungal growth in a phenolic foam system with a closed cell structure and a diffusion-open and capillary active lime-cork based insulating plaster, for internal retrofitting purposes. The setup comprised two 40-feet (12.2 m) insulated reefer container with controlled indoor climate, reconfigured with 24 holes (1 × 2 m each) containing solid masonry walls with embedded wooden elements on the interior side. Focus was on the conditions in the masonry/insulation interface and embedded wooden elements, and the performance of the two systems were compared to three diffusion-open insulation systems and one diffusion-tight. The effect of exterior hydrophobisation was also investigated. Relative humidity and temperature were measured in several locations in the test walls over 2½ years, and the risk of fungal growth was evaluated by on-site measurements and the VTT mould-growth model. The findings indicate that internally insulated walls with bare brick exterior surfaces performed poorly with high risk of fungal growth. The effect of exterior hydrophobisation was found to vary with the orientation and the installed insulation system, with a generally positive effect on walls facing south-west but limited effect for north-east. Furthermore, the more diffusion-tight insulation systems were found to perform better in combination with exterior hydrophobisation than the highly diffusion-open systems. The lime-cork insulating plaster showed high relative humidity and risk of moisture-induced problems. The on-site fungal tests showed no growth in the masonry/insulation interface inside the two insulation systems, probably due to high initial pH-value.

Hydrophobization lessens the water absorption by facade materials and is thus presumed to reduce moisture problems in internally insulated facades. However, to do this it should retain the water repellency performance throughout aging. The aim of this study is to evaluate the impact of aging on the durability of the hydrophobic treatment on bricks and mortars. The resulting absorption coefficient, after 635 repeating artificial aging cycles of alternating UV radiation (102 min) and water exposure (18 min) reveals that the hydrophobic layer maintains its water repellency performance both in brick and mortar. The samples were treated with two different water repellent agents in different concentrations and tested for capillary water uptake. Additionally, the findings show that cycles of weathering could contribute positively to further reduction of the absorption coefficient of hydrophobized brick and mortar samples. Subsequently, Karsten tube tests on samples from artificial aging illustrate the same water repellency performance as mock-up walls exposed to ambient conditions, six years after being hydrophobized. Contact angle measurements before and after artificial aging reveal that the beading effect declines through aging. However, the beading effect seems to be just a surface effect affected by UV-light. Moreover, after aging, hydrophobized brick and mortar samples, tested by visual inspection, maintain their appearance while untreated samples show signs of efflorescence. In total, these findings indicate that the water uptake of hydrophobized brick or mortar remains very low after aging including water spraying and UV light. Hydrophobization lessens the water absorption by facade materials and is thus presumed to reduce moisture problems in internally insulated facades. However, to do this it should retain the water repellency performance throughout aging. The aim of this study is to evaluate the impact of aging on the durability of the hydrophobic treatment on bricks and mortars. The resulting absorption coefficient, after 635 repeating artificial aging cycles of alternating UV radiation (102 min) and water exposure (18 min) reveals that the hydrophobic layer maintains its water repellency performance both in brick and mortar. The samples were treated with two different water repellent agents in different concentrations and tested for capillary water uptake. Additionally, the findings show that cycles of weathering could contribute positively to further reduction of the absorption coefficient of hydrophobized brick and mortar samples. Subsequently, Karsten tube tests on samples from artificial aging illustrate the same water repellency performance as mock-up walls exposed to ambient conditions, six years after being hydrophobized. Contact angle measurements before and after artificial aging reveal that the beading effect declines through aging. However, the beading effect seems to be just a surface effect affected by UV-light. Moreover, after aging, hydrophobized brick and mortar samples, tested by visual inspection, maintain their appearance while untreated samples show signs of efflorescence. In total, these findings indicate that the water uptake of hydrophobized brick or mortar remains very low after aging including water spraying and UV light.

This project investigated fungal growth conditions in artificially contaminated interfaces between solid masonry and adhesive mortar for internal insulation. The project comprised several laboratory experiments: test of three fungal decontamination methods; investigation of development of fungal growth in solid masonry walls fitted with five internal insulation systems; and investigation of volatile organic compounds (VOC) diffusion through materials and whole insulation systems. One aim was to examine whether the alkaline environment (pH > 9) in the adhesive mortars could prevent fungal growth despite the water activity (aw) in the interface exceeds the level (aw > 0.75) commonly considered critical for fungal growth. The findings indicate that do-it-yourself decontamination solutions were inadequate for removal of fungal growth, while professional solutions were successful. However, the choice of decontamination method was of minor importance in the case of application of internal insulation with high pH adhesive mortar, as the high pH adhesive mortars were found to inactivate existing growth and prevented spore germination during the experimental period. The three tested VOCs were capable of diffusing through most of the examined products and could potentially affect the indoor air quality.

Most buildings in Greenland are built within the last 70 years. Within this relatively short period, the building styles have often changed; from small wooden houses in the 50ties to also encompass more industrialised buildings in the 70ties, and later more diverse technics. This paper describes the major tendencies in building construction of today. Apart from an extreme climate, one of the challenges in Greenland is the lack of building materials; almost everything has to be imported. Greenland is an island-operated community, with no interlinking road grid between towns and settlements. Therefore, everything must be transported by ship or plane. Furthermore, severe mould growth is a big problem. Consequently, three building strategies are currently prevailing. 1) In-situ concrete gables and partitioning walls, and facades with wooden studs. 2) Focus on non-organic material and therefore concrete structures with exterior insulation. 3) Strategies focussing on the process e.g. mainly using prefabricated elements. The paper describes the pro and cons for the different strategies seen in a Greenlandic context. The harsh climate makes Greenland a good test site for assessing new building designs. Furthermore, assessment of sustainability might be very different in Greenland from countries where resources and transportation is very different.

Previously, only solutions with long-term experience were used in the building sector and it was sufficient to describe, e.g. in the building regulations, how they should be constructed. However, the innovation rate has gradually increased, encouraged by industrialization and by building regulations becoming more functional based. As a result, the required performance is often described for the whole building or for a building component, but not at product level. Furthermore, CE marking makes it possible to market and sell a product in any country within the European Union if only one or a few properties are declared, and these may even not be the most relevant ones for a specific application in a technical solution. A CE mark is therefore neither a quality mark nor an approval of the product for a specific application, although clients and consultants often believe this is the case. It is therefore a major challenge for the building sector to determine if a new building product is suitable in a specific technical solution (wall, roof, etc.). The paper identifies a gap between performance-based requirements for a technical solution and specific requirements to properties of building products. Two cases (flat roofs with no slope, MgO-containing boards used as wind barriers) show the possible economic consequences of not closing this gap; the technical solution failed, as one of the products was not suitable for Danish weather conditions. The first case initiated the formation of the Danish Building Defects Fund in 1986, the second one from 2015 shows that the gap still exits, 30 years later. The cases show how difficult it can be even for professionals to understand different certifications, especially when a product seems to be well suited for a specific use. Based on the cases, the paper presents a systematic approach that guides users through important issues relating to requirements for a moisture-safe building envelope. Previously, only solutions with long-term experience were used in the building sector and it was sufficient to describe, e.g. in the building regulations, how they should be constructed. However, the innovation rate has gradually increased, encouraged by industrialization and by building regulations becoming more functional based. As a result, the required performance is often described for the whole building or for a building component, but not at product level. Furthermore, CE marking makes it possible to market and sell a product in any country within the European Union if only one or a few properties are declared, and these may even not be the most relevant ones for a specific application in a technical solution. A CE mark is therefore neither a quality mark nor an approval of the product for a specific application, although clients and consultants often believe this is the case. It is therefore a major challenge for the building sector to determine if a new building product is suitable in a specific technical solution (wall, roof, etc.). The paper identifies a gap between performance-based requirements for a technical solution and specific requirements to properties of building products. Two cases (flat roofs with no slope, MgO-containing boards used as wind barriers) show the possible economic consequences of not closing this gap; the technical solution failed, as one of the products was not suitable for Danish weather conditions. The first case initiated the formation of the Danish Building Defects Fund in 1986, the second one from 2015 shows that the gap still exits, 30 years later. The cases show how difficult it can be even for professionals to understand different certifications, especially when a product seems to be well suited for a specific use. Based on the cases, the paper presents a systematic approach that guides users through important issues relating to requirements for a moisture-safe building envelope.

This article describes testing of peel and shear resistance and airtightness of joints of air and vapour barrier systems before and after artificial aging. The testing of peel and shear resistance was based on standardised methods while the test of airtightness was a method invented for this project. The results show that while peel and shear strength increased with aging, the airtightness was significantly reduced. As these two results seem to contradict each other, the methods are discussed, especially whether the standardised tests are too far from the conditions on site or joints should be tested on other materials as well. Furthermore, weaknesses in the airtightness method is also pointed out. This article describes testing of peel and shear resistance and airtightness of joints of air and vapour barrier systems before and after artificial aging. The testing of peel and shear resistance was based on standardised methods while the test of airtightness was a method invented for this project. The results show that while peel and shear strength increased with aging, the airtightness was significantly reduced. As these two results seem to contradict each other, the methods are discussed, especially whether the standardised tests are too far from the conditions on site or joints should be tested on other materials as well. Furthermore, weaknesses in the airtightness method is also pointed out.

The study investigated the hygrothermal performance and risk of mould growth in two thermal insulation systems for internal retrofitting purposes; a phenolic foam system with a closed cell structure, and a capillary active diffusion-open lime-cork based insulating plaster. The setup consisted of a 40-feet (12.2 m) insulated reefer container with controlled indoor climate, reconfigured with several holes (1x2 m each) containing solid masonry walls with embedded wooden elements on the interior side and different interior insulation systems, with and without exterior hydrophobisation. Focus was on the conditions in the interface between wall and insulation system, and in the embedded wooden elements. Relative humidity and temperature were measured in several locations in the test walls over two years, and the mould risk was evaluated by measurements and the VTT mould growth model. Findings for the interior phenolic foam system indicated that exposed walls experienced high relative humidity and high risk of moisture-induced problems. Exterior hydrophobisation had a positive effect on the moisture balance for the southwest oriented wall with phenolic foam. The lime-cork based insulating plaster showed high relative humidity and risk of moisture-induced problems, with and without hydrophobisation.

A recently Danish study reported that no vapour barrier is needed in ceilings, if the attic is well ventilated and the ceiling towards the dwelling is airtight. Based on that study, new investigations were initiated with focus on the hygrothermal behaviour in ventilated attics with different air change rates. A test house with three sets of four different ceiling constructions – all airtight – was used in this study. The ventilation rate was reduced in two of the sets with approx. 35 % and 50 %, respectively. Air change rates were measured with tracer gas. Furthermore, temperature and relative humidity was measured every hour. Measurements in similar ceilings with mineral wool or cellulose-based insulation material show that hygroscopic properties of the insulation have very limited effect on relative humidity. Furthermore, only at low ventilation rate the effect of a vapour barrier could be measured with minor impact. Based on the short-measured period the calculations of the risk of mould growth showed no risk. The results indicate that even when the ventilation is reduced by 50 %, the ventilated attic still performs well if the ceiling is highly airtight. However, the importance of vapour barriers becomes more important at lower air change rates.

Buildings are more vulnerable to faults in design and construction, when exposed to the extreme Greenlandic climate, however, most new materials and designs have not been tested for Arctic conditions. Thus even minor errors can result in failures like mould growth, discomfort, and unnecessary heat loss. Rekognizing the source of the error can be difficult, yet valuable. But how can it be identified whether the error lies in the design or quality of workmanship? This paper describes a case study from Nuuk, Greenland, where a new mineral wool insulation system was implemented. Residents were complaining about draft and cold areas. An investigation revealed that inaccurate use of the system caused several problems. Simulations of the exterior wall performance were conducted and compared to measurements. This paper discusses whether these measurements and simulations support the identified issues, and therefore if this kind of general surveillance of exterior walls can be used to determine the total performance of an exterior wall. The paper concludes that the collected data can support the issues of the complaints, and that the fundamental reasons for the problems are the design, the precision of the casted concrete and the lack of a wind barrier protecting the insulation.

This study investigated the hygrothermal performance of five insulation systems for internal retrofitting purposes. Focus was on the hygrothermal performance near partition brick walls compared to the middle of the wall. The setup comprised two insulated reefer containers with controlled indoor climate, reconfigured with several holes containing solid masonry walls with interior embedded wooden elements, an internal brick partition wall and different internal insulation systems, with and without exterior hydrophobisation. Relative humidity and temperature were measured over five years in the masonry/insulation interface and near the interior surface, in the centre of the test field and near the partition wall. In addition, calibrated numerical simulations were performed for further investigation of the thermal bridge effect. Findings for the masonry/insulation interface showed higher temperatures and lower relative humidity near the partition wall in comparison with the central part of the wall. Near the interior surface, measurements showed only minor differences between the two locations. The relative effect of the thermal bridge was smaller in the case of a high driving rain load on the exterior surfaces. The numerical simulations showed that the hygrothermal conditions were affected further away from the partition wall than what could be measured in the experimental setup.

DTU has established a single-family three-level test house in Nuuk, Greenland. The main idea of the house was to have a relatively small heated area but a split building envelope, where a ventilated space behind the rain screen in some areas could be used as a sunroom. This paper describes the process of transforming the architectural ideas to a test building. Main issues have been how to design the rain screen and how to ventilate the space behind the rain screen.

According to ISO 13788 internal moisture supply in dwellings can be described by humidity classes defined by outdoor temperature, occupancy and ventilation. Hygrothermal measurements in 500 Danish single-family houses were made to investigate if building style and geographical location are important as well. Further it was investigated whether snapshot measurements in materials could replace logging of relative humidity and temperature. Building type has only a limited effect on the moisture supply. Geographical location has an effect; however variations are not systematic. It is not possible by means of two-pin or capacitive moisture meter measurements to estimate indoor relative humidity.

Predictions of long term hygrothermal performance can be assessed by dynamic hygrothermal simulations, in which material parameters are crucial input. Material parameters for especially historic materials are often unknown; therefore, there is a need to determine important parameters, and simple ways for estimation of these. A case study of a brick wall was used to create and validate a hygrothermal simulation model; a parameter study with five different parameters was performed on this model to determine decisive parameters. Furthermore, a clustering technique has been proposed to estimate decisive parameters through simple testing of interrelated parameters that are easier to determine.

According to ISO 13788, the internal moisture supply in dwellings can be described by humidity classes defined by outdoor temperature, occupancy and ventilation. Hygrothermal measurements in indoor air in 500 Danish single-family houses were made to investigate if this corresponds with reality. The study focuses on the dependency of number and age of occupants, occupants’ time spent in the house, square meters living space, ventilation habits and type of room. Moisture supply depends on the type of room; bathroom, basement and living room have the highest values. None of the other parameters seems to have a significant effect.

Adding insulation material on ceilings against cold ventilated attics is one of the most straightforward tasks of adding insulation. Theoretically, a higher amount of insulation in the attic decreases the temperature and consequently the capability of removing infiltrated indoor humid air. Field measurements of the moisture balance in 20 cold ventilated attics with different amounts of insulation material were analysed. Results show that the amount of insulation material has no decisive effect on temperature in the attic during winter. The moisture level during winter was generally just below the threshold for mould growth.

The transfer of particulate and gaseous pollution from hidden fungi growing on non-visible surfaces within the building envelope to occupied rooms is limited by the separating structure. Yet, growth, even in sealed construction cavities, is known to cause annoying smells and other more adverse health symptoms among the building occupants. This study analyses limitations of air change rate measurements in inaccessible construction cavities as well as analyses of the air exchange between living areas and accessible cavities such as crawl spaces and attics. It was necessary to invent a field study technique to use the tracer gas decay method in small and inaccessible cavities. This technique allowed further investigation on the exposure risk from hidden fungal growth. Assessment of the air transfer between crawl spaces and living areas indicate that the tightness of separating structure has an influence on the exposure risk.

This article presents a project for renovation of a large residential area, where the focus is on moisture-safe internal insulation measures and the energy saving potential. Parts of two three-story houses were renovated with different combinations of capillary active insulation measures, including mechanical ventilation with heat recovery in one house. For two years, energy use for heating was measured, as well as temperature and relative humidity in the internal insulation, indoors, and outside. The insulation was dismantled in two apartments after 2 years, to test for mold growth at the original wall surface. Furthermore, the indoor climate and energy use for heating was measured in nine reference apartments. The inspection and mold measurements after the removal of the insulation material did not show signs of mold growth. Apparently, the used insulation material can be used in these specific cases without risk of mold growth. However, the relative humidity behind the insulation was measured at up to 90% in the first winter and decreased to 70% relative humidity in the next winter. There was good agreement between measured and calculated energy savings for heating; up to 24% savings was documented for the house with more far-reaching measures.

To remove moisture by ventilating constructions is a well-known strategy, used successfully in numerous facades and roofs. However, simulating ventilation is often difficult as convection in this case is in another dimension than what is usually in focus in 1D hygrothermal simulations. There are strategies for simulating ventilation in 1D programs assuming a fixed air change rate (ACH). Unfortunately, ACH in roofs highly depend on wind direction and speed, hence a constant rate is a gross simplification. The article describes a comparative study between simulations with a 1D hygrothermal simulation program (WUFI) and simulations with BSim, a program in which the indoor climate can be simulated in different zones, in this case the ventilated attic. Focus is the effect of ACH in the attic on temperature and relative humidity. Finally, measurements of ACH in attics of ten single-family houses are presented. These measurements show that average ACH measured over more than two weeks differ very much from house to house although the ventilation openings in all houses seemed to be in accordance with current guidelines. Even measurements of the same attic differ considerably from time to time. The paper discusses what implications this should have on simulations.

The present project investigated the hygrothermal performance and risk of mould growth in solid masonry walls fitted with three diffusion-open capillary active interior insulation systems installed in containers with a controlled indoor climate. The project was carried out as a large experimental study in two 40-feet reefer containers reconfigured with 24 holes (1 × 2 m), in which solid masonry walls with embedded wooden elements were installed. The focus of the study was on the conditions in the interface between the masonry and the interior insulation, and in the embedded wooden elements. The effect of exterior hydrophobisation was also investigated. Relative humidity and temperature were measured at several locations in the test walls over a period of four years. The findings indicate that exposed walls with interior insulation and high indoor RH performed poorly in terms of the risk of mould growth. Combined with exterior hydrophobisation against driving rain, the semi diffusion-tight insulation system performed better than the highly diffusion-open systems. Good performance was observed for the semi diffusion-tight polyurethane foam insulation with calcium silicate channels combined with exterior hydrophobisation. The effect of hydrophobisation varied with the orientation. Mould observations found no growth in the interface in most walls, probably because the high alkalinity of the adhesive mortars and scarce nutrition prevented growth. Growth was however found in some walls having low alkalinity and possibly available nutrition. Little correlation was found between on-site and modelled mould growth.

The present research project investigates the hygrothermal performance of four insulation systems for internal retrofitting solid masonry walls with embedded wooden wall plate and beam end. The study was carried out through numerical simulations calibrated with 2–4 years of measurements and material data from a large field experimental in the cool, temperate climate of Lyngby, Denmark. The experiment comprised two 40-foot insulated reefer containers reconfigured with 24 1 × 2 m holes, accommodating the solid masonry walls. The calibrated simulation models were used to investigate several untested design variations which included alternative brick and mortar types, masonry and insulation thickness, indoor moisture load and future climate conditions. The findings indicate that a reduction of the indoor moisture load would improve the hygrothermal performance in the interface between wall and insulation, and in the embedded wooden elements. Increased masonry thickness was seen to make the hygrothermal conditions worse due to increased drying time for the built-in moisture, while in the case of low initial moisture content, increased masonry thisckness improved the hygrothermal performance in the interface and embedded wooden elements. Increased insulation thickness also made the hygrothermal conditions worse. Regarding the brick and mortar types, the results showsed increased relative humidity in the critical locations in the case of high cement mortar compared to low cement mortar. The brick type was however found not to impact the relative humidity levels considerably. Robustness against future climate conditions was seen only for two of the four insulation systems, when combined with exterior hydrophobisation.

Existing building stock in Europe accounts for approx. 40% of the total energy consumption. Upgrading the thermal insulation of the existing buildings is an important measure to reduce heat losses through the building envelope. In some cases, increasing the thermal resistance of the construction may compromise the hygrothermal performance of the retrofitted construction. In particular, if vapour barrier is necessary for the good performance and it is practically difficult, if not even impossible, to install a well-sealed air- and vapour tight layer. To investigate the robustness of the hygrothermal performance of ventilated cold attics – with or without a vapour barrier – a monitoring campaign in a full-scale test building was set up. Also role of number of other parameters like moisture buffering capacity of the insulation material and thermal resistance was investigated. This paper presents part of this measuring campaign, which includes conditions both in the attic space and inside the insulation layer. The monitored data covers a period with two winters. The results show that it in temperate climate is practically indifferent for the hygrothermal performance of the monitored, well-ventilated attics with air-tight ceilings whether there is a vapour barrier or not and if the insulation material has moisture buffering capacity or not.

In historic masonry buildings, wood can be embedded in the walls as storey partition beams, or as supportive wall plates. Half-timbered masonry constructions, or wooden frames, e.g. combined with internal insulation, are other examples of wooden elements. Wood decaying fungi can cause serious damage to wood, which may lose mass and strength, ultimately yielding the risk of collapse. In addition, some fungal species may even be hazardous for occupants. All wood decaying fungi depend on favorable moisture and temperature conditions, although the threshold conditions may vary with various fungal species and types, and state of the wood. To predict the risk of occurrence of wood rot, several models have been developed, however most of these are based on a limited number of experiments, or very specific cases. For these reasons, the applicability of the models to other scenarios (fungal species, wood species) may not be appropriate. Furthermore, another failure mode for wood and moisture, is mold growth, which is initiated at lower moisture levels. An indication of risk of mold growth would indicate problems or risks before the initiation of wood rot. Mold growth does not deteriorate the wood, but is usually equally undesired due to health concerns of occupants. For this reason, there might be places where some mold growth would be acceptable, e.g. embedded beam ends if there is no transfer of air from the moldy area to the indoor air. Therefore, risk of rot could be important. The paper investigates models for mass loss due to wood decay and mold growth based on exposure time to favorable hygrothermal conditions. The investigation is based on inspection of wood samples (wall plates) from a full-scale experimental setup of masonry with embedded wood and monitored conditions, to which the prediction models will be applied. Monitored hygrothermal conditions were implemented in mold and wood decay models, and samples were removed from the test setup. The implemented models yielded high mold index and mass loss, whereas neither mold nor decay was observed in the physical samples. Results indicate that the implemented models, in these cases appear to overestimate the risks of mold and rot in the supportive lath behind the insulation.

Internal insulation is often the only possible solution when improving the thermal performance of solid walls of historic buildings, as many of these have architectural or cultural values. However, as internal insulation is regarded risky from a moisture perspective, guidelines are needed. The paper presents a new set of guidelines that combine written guidelines, a web-based preliminary assessment tool and a website that can be used independently of each other. The website provides simple ways of assessing the building to determine whether internal insulation is feasible in the specific case and what needs to be done before it can be applied. It also describes different failure mechanisms. The website includes links to information (written guidelines), described for different types of users, depending on their level of expertise. The web tool is based on an extensive number of simulations of hygrothermal conditions within a solid wall depending on location, orientation, wall type and thickness, and insulation type and thickness. The web tool determines the risk for mould and algae growth in a probabilistic way and determines heat loss and CO2 emission before and after renovation through 1 m² of the wall. The guidelines, the website and the web tool are developed in RIBuild, a research project funded by the European Commission, running from 2015 to 2020.

This paper presents a pilot project for renovation of a large residential area; focus is on energy consumption and risk of mold growth. The renovation included internal insulation of walls with capillary active insulation material, balanced mechanical ventilation with heat recovery and insulation of floor towards basement. These types of measures are not completely new and have been used in other buildings as well, however the measures may be either risky regarding mold growth or the effect is uncertain with the specific external wall composition.A pilot project including six apartments was performed to test the measures in these specific buildings. Furthermore, six reference apartments were monitored simultaneously. For two years, energy use for heating was measured as well as temperature and relative humidity in the internal insulation, indoors and outside. The insulation was dismantled in two apartments after two years, to test for mold growth at the original wall surface.In extreme cases, the relative humidity in the walls behind the insulation system was up to 90 % RH shortly after installation, and mold growth models predicted growth of mold. However, the relative humidity decreased, typically to 70 % RH in the second winter. The inspection and measurements after the removal of the insulation material did not show signs of mold growth. Apparently, the used insulation material can be used in this specific case without risk of mold growth. Energy savings for heating was measured and calculated to around 25 %. However, the electricity use for ventilation was almost equal to savings from heat recovery. This paper presents a pilot project for renovation of a large residential area; focus is on energy consumption and risk of mold growth. The renovation included internal insulation of walls with capillary active insulation material, balanced mechanical ventilation with heat recovery and insulation of floor towards basement. These types of measures are not completely new and have been used in other buildings as well, however the measures may be either risky regarding mold growth or the effect is uncertain with the specific external wall composition. A pilot project including six apartments was performed to test the measures in these specific buildings. Furthermore, six reference apartments were monitored simultaneously. For two years, energy use for heating was measured as well as temperature and relative humidity in the internal insulation, indoors and outside. The insulation was dismantled in two apartments after two years, to test for mold growth at the original wall surface. In extreme cases, the relative humidity in the walls behind the insulation system was up to 90 % RH shortly after installation, and mold growth models predicted growth of mold. However, the relative humidity decreased, typically to 70 % RH in the second winter. The inspection and measurements after the removal of the insulation material did not show signs of mold growth. Apparently, the used insulation material can be used in this specific case without risk of mold growth. Energy savings for heating was measured and calculated to around 25 %. However, the electricity use for ventilation was almost equal to savings from heat recovery.

SBi-anvisning 267 omhandler generelle krav og anbefalinger til klimaskærmen i nybyggede småhuse i henhold til Bygningsreglement 2015 (BR15). Anvisningen indgår i en serie af SBi-anvisninger om småhuse. Småhuse omfatter fritliggende og sammenbyggede enfamiliehuse med lodret lejlighedsskel i indtil to etager samt eventuelt kælder. Det omfatter også kæde- og rækkehuse samt sommerhuse. Målgruppen for SBi-anvisning 267 er projekterende arkitekter, ingeniører samt udførende og tilsynsførende. Anvisningen kan desuden anvendes af den kommende bygningsejer og som lærebog ved byggetekniske uddannelser.

Several studies have reported poor indoor air quality (IAQ) in day care centers (DCCs), and other studies have shown that children attending them have an increased risk of respiratory and gastrointestinal infections. The aim of this study was to investigate whether there is an association between ventilation in DCCs and sick leave among nursery children. Data on child sick leave within an 11-week period were obtained for 635 children attending 20 DCCs. Ventilation measurements included three proxies of ventilation: air exchange rate (ACR) measured with the decay method, ACR measured by the perfluorocarbon tracer gas (PFT) method, and CO2 concentration measured over a 1-week period. All but two DCCs had balanced mechanical ventilation system, which could explain the low CO2 levels measured. The mean concentration of CO2 was 643 ppm, exceeding 1000 ppm in only one DCC. A statistically significant inverse relationship between the number of sick days and ACR measured with the decay method was found for crude and adjusted analysis, with a 12% decrease in number of sick days per hour increase in ACR measured with the decay method. This study suggests a relationship between sick leave among nursery children and ventilation in DCCs, as measured with the decay method.