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Abstract In the course of the European Project Energy Efficiency and Risk Management in public buildings (EnRiMa), a mathematical model has been needed, predicting the room air temperatures based on the physical properties of the thermal zone and weather forecasts. Existing models based on physical building properties and weather forecasts did not deliver acceptable results. Based on the hypothesis that the missing thermal mass in the existing models is the main reason for the unacceptable results, a model based on physical properties and weather forecast, including the storage mass of a building has been developed. Based on this developed model and real data from a test site, Campus Pinkafeld of the University of Applied Science Burgenland, Austria, the model has been verified and validated. With the new developed model it is possible to predict the occurring room air temperature for a whole day with a maximum deviation of approximately ±1 K, which increases the precision compared to other models.

Historic buildings built before 1945 make up a significant part of the building stock in the European Union. They also contribute to the greenhouse gas emissions due to high energy consumption. However, policy makers and building owners are facing “building energy efficiency-heritage value” dilemma when, on the one hand it is important to preserve a building’s heritage value and on the other hand, energy consumption should be reduced significantly. Internal insulation is one of the energy efficiency measures that can be applied. However, this is one of the most challenging and complex energy efficiency measures due to changes in boundary conditions and hygrothermal behaviour of the wall, especially in cold climate. We aimed to study the thermal behaviour of two internal insulation materials applied to historic masonry building in a cold climate. We carried out long term in-situ measurements of heat flux and temperature for internal insulation with aerogel and vacuum insulation panels (VIP) in the case study building in the historic quarter of Riga, Latvia. The original walls are made of 51 cm thick calcium silicate bricks. They were poorly maintained and heavily damaged by moisture before energy efficiency renovation. After renovation the external surface of walls was painted with self-cleaning, water repellent hydrophobic facade paint. The energy efficiency renovation also included insulation of floor and roof, change of windows, new ventilation and air heat pump installation. The analysis of the thermal behaviour show that the masonry part of the wall is exposed to freezing risk for a significant number of days during the winter. Calcium silicate bricks are very sensitive to freeze-thaw damage therefore we carried out computer simulation for the assessment of hygrothermal behaviour. Results show that the calcium silicate masonry part of the internally insulated wall in cold climate leads to exposure to freeze-thaw damage if the moisture content of the brick is higher than the capillary saturation. This process strongly depends on unfavourable outdoor conditions for wall types with and without water repellent hydrophobic paint.

Abstract Home energy management systems (HEMS), providing energy feedback and smart features through in-home displays, have the potential to support more sustainable household decisions concerning energy consumption. However, recent findings from European smart metering trials have reduced the optimism, suggesting only modest savings from energy feedback. In this paper, we investigate the potential of HEMS to foster reductions in energy use, focusing on a population segment of particular relevance; high-income and highly educated households, considered as early adopters of smart grid technologies. Covering 154 households participating in a field trial in a sustainable city district in Stockholm, Sweden during one year, this study draws on the analyses of smart meter electricity and hot tap water data and in-depth interviews to provide an increased understanding of how feedback and features are perceived, used, and acted upon, and resulting effects on awareness, behavior, and consumption. Our results show that impact on energy consumption varies widely across individual households, suggesting that households respond to energy feedback highly individually. Although HEMS may lead to increased awareness of energy consumption, as well as increased home comfort, several obstacles for energy consumption behavioral change are identified. Drawing from these findings, we suggest policy implications and key issues for future research.

Abstract Heat pump (HP) units coupled to thermal storage offer flexibility in operation and hence the possibility to shift electric load. This can be used to increase PV self-consumption or optimise operation under variable electricity prices. A key question is if new sizing procedures for heat pumps, electric boilers and thermal storages are needed when heat pumps operate in a more dynamic environment, or if sizing is still determined by the thermal demand and thus sizing procedures are already well known. This is answered using structural optimisation based on mixed integer linear programming. The optimal system size of a HP, an electric back-up heater and thermal storage are calculated for 37 scenarios to investigate the impact of on-site PV, variable electricity price, space heat demand and domestic hot water demand. The results are compared to today's established sizing procedures for Germany. Results show that the thermal load profile has the strongest influence on system sizing. In most of the scenarios investigated, the established sizing procedures are sufficient. Only large PV sizes, or highly fluctuating electricity prices, create a need for lager storage. However, allowing the storage to be overheated by 10 K, the need for a larger storage only occurs in the extreme scenarios.

Abstract The assessment of local and short-term thermal discomfort in buildings has been widely investigated, and different metrics are available in the literature to predict the likelihood of dissatisfied people. These metrics are named right-here and right-now discomfort indexes and constitute the basis for evaluating long-term thermal comfort conditions in buildings. Well-known examples are the Predicted Percentage of Dissatisfied (PPD) part of the Fanger comfort model included in the ISO standard 7730 and the Overheating risk index (NaOR), built upon the EN adaptive thermal comfort model. This study proposes a new index for use with the ASHRAE adaptive thermal comfort model to fill a gap in the literature and standard. It is called the ASHRAE Likelihood of Dissatisfaction (ALD) and is obtained from a logistic regression of the right-here and right-now thermal comfort field data contained in the 1990s ASHRAE RP-884 database. The recent release of another, more extensive database of thermal comfort field studies, the ASHRAE Global Thermal Comfort Database II, provides an opportunity to validate ALD with an independent dataset and assess its generalisability. The successful external validation of ALD and its agreement with NaOR give support to the reliability of the novel right-here and right-now index and open to the possibility to use it for assessing short-term thermal comfort conditions in buildings, calculating long-term thermal comfort indices based on the ASHRAE adaptive model, optimising both the design of new buildings and renovations and for assessing the operational thermal comfort performance of existing buildings.

Abstract Cool roofs represent an acknowledged passive cooling technique aimed at reducing the amount of solar radiation absorbed by buildings and producing indoor overheating, particularly, in summer conditions. Cool roofs owe their unique behavior to improved thermo-optic performances which, however, have been shown to deteriorate when exposed to intense atmospheric weathering. In this context, the authors produced a shape stabilized composite with improved heat storage performance, by adding 15, 25, or 35 weight percentage of non-encapsulated phase change materials (PCMs) to the original blend of a liquid waterproof-polyurethane-based cool membrane. The behavior of such composite material, when exposed to accelerated temperature, humidity, and UV radiation cycles by means of standardized long-term weathering tests (QUV test), is investigated. The final aim of the study is to clarify if the PCM inclusion could help the membrane to better behave during the course of the time, because of thermal stress reduction. In order to do so, controlled atmospheric forcing and surface temperature continuous monitoring are used to investigate the degradation of the membrane produced by the imposed weathering stress. Results show that the introduction of 25% PCM in weight optimizes the superficial finishing characteristics of the prototype, allowing to maintain a more stable thermo-optic behavior, reducing both the thermal-induced degradation and the leakage phenomenon.