Urban Heat Island: Summer Outdoor Climate Measurement Within the University Campus and City

Work of researchers from various areas is focused on problematics of urban heat islands. Its importance is rising with the global climate change. The difference of the air temperatures within the area can be also caused by the measurement error. Usual error is not the accuracy of the sensor, but the radiation shield or location of the weather station. In this case, averaged difference can be up to 80 %. Difference of temperatures between the weather stations within the analyzed area can vary from 0.2 up to 6 °C. Difference depends usual on the size of the city and the location influenced by the surrounding geomorphology. In this paper three different radiation shields are compared which influenced the measurement and analyzed are also the results from four different weather stations, two of them are within the University of Zilina campus. One of them is placed on the roof, which is a usual location for the solar radiation measurement; the second one is placed on the grass land at the end of the campus. Other two stations belong to the national weather institute. Comparison is made for two very hot days of August 2020. Averaged difference was 0.3 °C for the whole month and 0.5 °C for selected days.

Spatiotemporal variation of the indoor mycobiome in daycare centers

Background Children spend considerable time in daycare centers in parts of the world and are exposed to the indoor micro- and mycobiomes of these facilities. The level of exposure to microorganisms varies within and between buildings, depending on occupancy, climate, and season. In order to evaluate indoor air quality, and the effect of usage and seasonality, we investigated the spatiotemporal variation in the indoor mycobiomes of two daycare centers. We collected dust samples from different rooms throughout a year and analyzed their mycobiomes using DNA metabarcoding. Results The fungal community composition in rooms with limited occupancy (auxiliary rooms) was similar to the outdoor samples, and clearly different from the rooms with higher occupancy (main rooms). The main rooms had higher abundance of Ascomycota, while the auxiliary rooms contained comparably more Basidiomycota. We observed a strong seasonal pattern in the mycobiome composition, mainly structured by the outdoor climate. Most markedly, basidiomycetes of the orders Agaricales and Polyporales, mainly reflecting typical outdoor fungi, were more abundant during summer and fall. In contrast, ascomycetes of the orders Saccharomycetales and Capnodiales were dominant during winter and spring. Conclusions Our findings provide clear evidences that the indoor mycobiomes in daycare centers are structured by occupancy as well as outdoor seasonality. We conclude that the temporal variability should be accounted for in indoor mycobiome studies and in the evaluation of indoor air quality of buildings.

Application of physical theory of cavity in the construction of double skin facades

The article deals with the issue of double skin transparent facades as a new technological-operational system of transparent exterior walls. Especially of high-rise buildings, which with its operating modes ingeniously uses a renewable source of solar energy to reduce the energy needs of the building. The basic precondition for the correct function of the double skin facade is its functional aerodynamics in any climatic conditions of the outdoor climate. In the critical state of windlessness, the aerodynamic quantification of a double skin facade is the total aerodynamic resistance of the cavity, which consists of the aerodynamic frictional resistances along the length of the air flow line and local aerodynamic resistances of the cavity. The article analyses the functional aerodynamics on two frequented types of double skin facades with a narrow type and corridor type cavity. At the end it confronts functional aerodynamics with the results of their temperature, aerodynamic and energy regime obtained from in-situ experiments.

A large field study of relationship between indoor and outdoor climate in residential buildings

High-quality data on indoor climate and energy collected in buildings is required to deepen our understanding of building performance. The aim of this work was to investigate the relationship between the indoor and outdoor climate in Danish residential buildings. Field data was collected in 45 apartments from April 2019 to November 2020. Internet of things (IoT) devices were installed to record the temperature, relative humidity and CO2 concentration in the central corridor of each apartment. High CO2 concentration (above 1,000ppm) and overheating were observed in the apartments. The changeover between the heating mode and the free running mode occurred between 11.1 to 13.6°C of outdoor air temperature. The temperature setpoints of the heating systems were around 20.6-22.3°C, which could be useful values to feed building simulations in order to achieve more realistic predictions of indoor climate and energy. The results of this study improve our understanding of indoor environmental quality in residential buildings at a national level.

Influences on the drying behavior of a concrete ceiling below a cold attic

The article describes the current state of a project examining the influences on the moisture distribution in cold attics above concrete ceilings of residential buildings. Considerable research has been done on moisture damages in cold attics, especially in Scandinavia and North America, focussing on spaces above wooden ceilings. The project (ongoing until Sept 2021) underlying the article deals with cold attics above concrete ceilings resting on masonry walls, a frequent variant in Austria. Research was triggered by a regional Austrian building industry association to shed light onto recent detrimental moisture accumulation in the wooden wall plate (= bearing for the rafters along the eaves) and in the two EPS insulation layers on top of the ceiling. Suspected reasons for the moisture problems and for the local moisture distribution are 1) a too small diffusion resistance of the vapour retarder covering the ceiling, 2) insufficient (natural) attic ventilation and 3) convection, e. g. in the gap between the polystyrene blocks. In order to rank these potential causes by influence and also to find a practical solution a two stage experimental approach was chosen: 1) A handy small scale replica (order of dimension: 1m) of the situation was exposed to the according indoor and outdoor climate in a climate chamber. Different vapour retarders on top of the ceiling were chosen. 2) A larger 1:1 replica has been erected as well but not yet delivered monitoring data. In parallel, a hygrothermic model taking convection into account was established and simulations carried out. The project will deliver a contribution to the Austrian standard on moisture safety 8110-2 on how to judge the moisture safety of joints via simulation.

Performance analysis of the MICRO-V (Multifunctional, Integrated, Climate-responsive, Opaque, and Ventilated) façade with different ventilation modes

Climate-responsive facades (CRFs) are a potential solution to respond to transient energy exchanges in buildings to control and enhance the indoor environmental quality (IEQ). In addition to space heating and cooling, adequate ventilation within a thermally comfortable range is critical in new and retrofit constructions, particularly as current high-performance facades maximize airtightness. In this study, an opaque multifunctional CRF (MICRO-V) was investigated to regulate the flow of heat and air into buildings with daily and seasonal responses. This façade is made of phase change materials (PCMs), an adjustable insulation system, and an embedded ventilation unit to provide conditioned fresh air. The effect of different ventilation modes (balanced, only-exhaust, only-supply) on the overall thermal performance of the façade was studied. A CFD simulation study in the context of Toronto, Canada, in the cooling season was performed. The study showed a correlation between increased airspeed and overall heat recovery in the façade, with an average of 75-80% heat recovery between the indoor exhaust air and fresh supply air. The results showed how the façade’s operational modes could be adjusted based on the outdoor climate conditions. MICRO-V is a decentralized façade system with simultaneous air supply and exhaust, the findings showed the interconnected behaviour of the components in the façade and how it can provide conditioned fresh air.

Damage risk analysis of a Timurid heritage located in Iran exposed to outdoor climate change (Ghiassieh school)

The first step to preserving the historical heritage against global warming effects is finding how this phenomenon affects building material degradation. Due to the vulnerability of Iranian heritage to climate change and lack of proper literature, research on climate change’s impact on Timurid heritage buildings in Iran has been determined as the primary research goal. The study is performed by analysing weather data, HAM simulations, and different damage criteria. This paper aims to find an appropriate method to study climate change’s impact on historical buildings. A Timurid historical school is chosen as a case study to better understand the current climate change effects on building components. The analysis shows that the significantly rising air temperature and wind speed, along with reduced rainfall and humidity, causes a notable decrease in building envelope moisture content in addition to an increase in hydrated salt crystallisation cycles during the studied period. These fluctuations may have played a crucial role in the pathologies that can be observed on site, and their continuation and expansion in the future, as the models have predicted, may lead to irreparable damages to the building.

The indoor mycobiome of daycare centers is affected by occupancy and climate

Many children spend considerable time in daycare centers and may here be influenced by indoor microorganisms, including fungi. In this study, we investigate the indoor mycobiome of 125 daycare centers distributed along strong environmental gradients throughout Norway. Dust samples were collected from doorframes outside and inside buildings using a citizen science sampling approach. Fungal communities in the dust samples were analyzed using DNA metabarcoding of the ITS2 region. We observed a marked difference between the outdoor and indoor mycobiomes. The indoor mycobiome included considerably more yeasts and molds compared to the outdoor samples, with Saccharomyces, Mucor, Malassezia and Penicillium among the most dominant fungal genera. Changes in the indoor fungal richness and composition correlated to numerous variables related to both outdoor and indoor conditions; there was a clear geographic structure in the indoor mycobiome composition that mirrored the outdoor climate, ranging from humid areas in western Norway to drier and colder areas in eastern Norway. Moreover, the number of children in the daycare centers, as well as various building features, influenced the indoor mycobiome composition. We conclude that the indoor mycobiome in Norwegian daycare centers is structured by multiple factors and is dominated by yeasts and molds. This study exemplifies how citizen science sampling enables DNA-based analyses of a high number of samples covering wide geographic areas.

Determining Building Natural Ventilation Potential via IoT-Based Air Quality Sensors

Natural ventilation (NV) represents the most energy-efficient way to operate buildings and, in an attempt to reduce the built environment's global carbon footprint, represents a resource, the usage of which has to be maximized. This study demonstrated how a combination of an IoT environmental sensing network implemented locally outdoors and indoors can help to determine the NV potential and actual utilization throughout the year with the consideration of outdoor climate variance, air pollution levels, and window open/closed status. An NV potential index was developed by analyzing indoor and outdoor PM2.5, and outdoor air temperature and air speed throughout the year at different spatial (from room scale to building level and local weather stations) and temporal (instantaneous, season, and annual) scales. The index was applied on a case building located in Berkeley, California, during the period of August 2018 to the end of 2019. Compared to the potential NV availability, the actual window opening time in typical rooms was less than 35%. These results point out that the actual window usage behavior was the key limiting factor in NV potential utilization. Even during periods when climate- and pollution-wise outdoor conditions allowed use of the NV, many occupants kept their windows closed. Keeping windows open or closed was significantly affected by outdoor climate condition and air pollution levels, especially during the wild-fire period.