Dimitrios Kraniotis

Elevated air movement enhances stomatal sensitivity to abscisic acid in leaves developed at high relative air humidity

High relative air humidity (RH ≥ 85%) during growth leads to stomata malfunctioning, resulting in water stress when plants are transferred to conditions of high evaporative demand. In this study, we hypothesized that an elevated air movement (MOV) 24 h per day, during the whole period of leaf development would increase abscisic acid concentration ([ABA]) enhancing stomatal functioning. Pot rose ‘Toril’ was grown at moderate (61%) or high (92%) RH combined with a continuous low (0.08 m s-1) or high (0.92 m s-1) MOV. High MOV reduced stomatal pore length and aperture in plants developed at high RH. Moreover, stomatal function improved when high MOV-treated plants were subjected to leaflet desiccation and ABA feeding. Endogenous concentration of ABA and its metabolites in the leaves was reduced by 35% in high RH, but contrary to our hypothesis this concentration was not significantly affected by high MOV. Interestingly, in detached leaflets grown at high RH, high MOV increased stomatal sensitivity to ABA since the amount of exogenous ABA required to decrease the transpiration rate was significantly reduced. This is the first study to show that high MOV increases stomatal functionality in leaves developed at high RH by reducing the stomatal pore length and aperture and enhancing stomatal sensitivity to ABA rather than increasing leaf [ABA].

Moisture buffering, energy potential, and volatile organic compound emissions of wood exposed to indoor environments

The use of wood in built environments has been increasing during the last decades, and more focus has been set on the influence of wood surfaces on indoor environments on the objective and subjective measures of human well-being. In addition, the moisture buffer capacity of hygroscopic materials, such as wood, has been under investigation in order to quantify the impact of wooden surfaces on energy savings in buildings. The current study presents the results of wood surfaces and indoor air temperatures as well as indoor air relative humidity measured in two solid timber test houses. The findings reveal a substantial effect on wood surface temperature under fluctuating indoor relative humidity due to the latent heat of sorption of water vapors. The results were compared with hygrothermal numerical simulations, showing good agreement and the validated numerical model was used in order to quantify the energy performance in a bathroom when the latent heat of sorption is exploited. The combination of wood with a well-controlled HVAC system in rooms with moisture production shows significant potential for indirect energy savings by adjusting the indoor temperature and exploiting the increase of surface temperature in the hygroscopic structure. Furthermore, the emissions of volatile organic compounds from pine wood were studied in laboratory facilities, with focus on the variations of emissions due to diurnal fluctuations in air humidity. Human participants were exposed in a large test chamber to a concealed source of volatile organic compound emissions in the form of fresh pine wood, while the actual exposure reached air levels of monoterpenes up to 18 mg/m3 during the intervention situation. Perceptions of air quality and mucosal irritation effects were reported in a standard questionnaire during this double-blind test with no irritation effects reported.

Investigating Instantaneous Wind-Driven Infiltration Rates using the CO2 Concentration Decay Method

Abstract Carbon dioxide has already been recognized as a potential tracer gas for estimating the mean air exchange rates of a room or building. The wind direction and mean wind velocity have also been identified as critical factors that affect the air infiltration. In this paper, the indoor CO2 concentration has been logged at three specific points in an office room for seven selected measurement-periods. The decay method was used to estimate the infiltration rates (ac/h). In parallel, an ultrasonic anemometer was used outdoors for monitoring wind characteristics such as the direction angle and the instantaneous velocity components. The results of the calculated ac/h varied from 0.32 h-1 to 0.75 h-1 from measurement to measurement and thus an investigation was carried out from the perspective of unsteady wind conditions. The wind direction angle and the relevant velocity components seem inadequate to entirely explain the differences in ac/h and thus the wind turbulence intensity was calculated and a spectral analysis of the wind measurements was applied. The corresponding power spectra Syy(f) were correlated to the mean ac/h of the room, giving a better understanding of wind-driven infiltration and depicting the role of the wind fluctuation frequency. In addition, a hypothesis of using the indoor spatial distribution of CO2 concentration as an airflow pattern tracer is presented respective to the location of the leakages. Finally, the local CO2 fluctuations are discussed and the respective standard deviations are presented as indicators of leakage detection.

Assessment and monitoring of aesthetic appearance of building biomaterials during the service life

Bio-based building materials offer a wide range of outlooks, from traditional rustic to modern design products. Recent development in the science of materials significantly improves their functional performance. However, when considering the use of bio-materials in outdoor environments, materials will deteriorate due to processes like weathering, oxidation, biodegradation, wear, and decay. Consequentially, biomaterials may lose visual appeal, leading to a perceived need for replacement even if the material is far from reaching functional failure. Visual assessment is the most direct method for evaluation of the aesthetic appearance of materials. However, it possesses a high degree of subjectivity when performed by an untrained person. On the contrary, measurement of surface properties with dedicated sensors provides objective values that might be related to the current state of the material in use. Recent developments in field of optics and electronics opens a new possibility to perform measurements in-situ. Colour-, gloss-, or spectro-photo-meters allow non-destructive measurements without particular sample preparation. Since all of the above techniques provide complementary information, the multi-sensor approach is more frequently suggested for applied research. The material state can be assessed regularly during service life. In this case, such measurement turns into monitoring. The paper illustrates examples of assessment and monitoring of biomaterials’ degradation due to weathering. Direct implementation of various sensors is demonstrated. A proposal for the approach of combining data provided by various sensing techniques with data mining is also presented.