Urve Kallavus

The Influence of Indoor Climate Control on Risk for Damages in Naturally Ventilated Historic Churches in Cold Climate

ABSTRACT This article analyzes the indoor climate that creates risk of damages in naturally ventilated churches in the cold climate of Estonia. Indoor temperature and humidity were measured over a one-year period and the results were analyzed on the basis of damage functions: mold growth, risk of cracking and fracturing of wooden objects, and delamination of the gesso layer of panel paintings. In unheated churches, one of the most dominant problems was very high relative humidity throughout the year, creating a high risk for mold and algae growth. Churches may need background heating to avoid freezing during a long cold winter that causes low surface temperatures of massive walls during the spring–summer period. It was found that mold risk was significantly lower in heated churches than in unheated or intermittently heated churches. The risk of mold growth was not decreased by the use of intermittent heating. In heated churches, overheating (room temperature >+10ºC) causes a RH below 50% during cold periods, and the favorable period for irreversible response of panel paintings was significantly longer, so there is a higher risk that the gesso may crack or delaminate. From the point of view of the cracking and fracturing of wood, indoor climate conditions are in the safe range for most of the year.

Simulated Influence of Indoor Climate and Ventilation on Schoolwork Performance in Estonian Manor Schools

Abstract Indoor temperature and humidity conditions as well as CO2 and airborne mould concentrations were measured in four manor schools in the Estonian cold climate. Based on these measurements, the influence of the indoor climate on the performance of schoolwork was assessed. The indoor environmental quality in manor schools turned out to be quite poor due to the inadequate performance of ventilation and heating systems. Intermittent stove heating was found to secure the minimum temperature in general but in winter thermal comfort was not always guaranteed. In addition, temporary overheating resulting in a significant temperature rise in the morning was intended to maintain room temperatures until the afternoon. Overheating in the summer period was not a problem in these schools. Ventilation airflow and indoor air quality were significantly lower in classrooms equipped with natural ventilation, resulting in higher CO2 and airborne mould concentrations and higher humidity loads for the building envelope. Original natural passive stack ventilation and window airing were not suitable solutions for providing the required indoor environmental conditions in cold climate conditions due to the type and efficiency of ventilation, inadequate duct size and air speed in ducts. Using previously published models, the level of schoolwork performance was estimated to be lower (75%…95%) in classrooms with natural ventilation and stove-heating. Air change was significantly higher in classrooms with mechanical exhaust ventilation; however, according to current standards for classrooms, the airflow was too low with both ventilation systems. Occupation density influences the indoor air quality significantly. To fulfil the requirements of indoor climate, pupil density in classrooms must be 2–3 times lower than the current requirement. In order to maintain schools in old manors in a cold climate, special attention should be paid to ensuring indoor environmental conditions. In addition to heritage values, other values, such as schoolwork performance and energy efficiency, should also be used as parameters in the improvement of indoor conditions and building service systems in old manor schools.

CdTe Films on Mo/Glass Substrates: Preparation and Properties

Short-bandgap group II-VI compound cadmium telluride is widely used for the infrared optics, radiation detectors, and solar cells where p-type CdTe is needed. p-type conductivity of CdTe is mainly caused by the chlorine-based A-centers, and in part, by the less stable copperoxygen complexes. As a rule, CdTe films are recrystallized by the help of a cadmium chloride flux that saturates CdTe with chlorine. In chlorine-saturated CdTe A-centers are converted to isoelectronic complexes that cause resistivity increasement of CdTe up to 9 orders of magnitude. Excess copper and oxygen or group I elements as sodium also deteriorate the p-type conductivity of CdTe like excess chlorine. p-type conductivity of CdTe can be restored e.g. by the vacuum annealing which removes excess chlorine from the film. Unfortunately, treatment that betters ptype conductivity of the CdTe film degrades the junction of the superstrate configuration cells. In this work we investigate possibilities to prepare p-type CdTe films on the molybdenum coated glass substrates. Samples were prepared by the vacuum evaporation and dynamic recrystallization of 6N purity CdTe on the top of Mo-coated glass substrates. Then samples were recrystallized with cadmium chloride flux under tellurium vapour pressure. Results of the test studies on the structure and electronic parameters of samples are presented and discussed.

Diagnosis of Moisture Movements in Massive Dolostone Walls of Medieval Churches

The current study presents one of the dielectric methods, reflection of the microwaves from material, used for diagnosis of moisture content of massive dolostone walls in Estonian medieval churches. Cold and humid climate, porous materials, absence of rainwater pipes, absence of waterproof layers avoiding rising damp leads to moisture damages in massive walls. The problem is relatively complex and cannot be modeled easily due to inhomogeneity and complex shapes of walls. Therefore, main tool for diagnostics is determination of the distribution of moisture in walls and its change over the time by moisture content measurements. The microwave method for determination of moisture content in massive walls is nondestructive and therefore very suitable for the diagnostics of moisture problems in buildings of national heritage importance. Graphically presented results are easily readable even for a nonspecialist and expedite significantly analysis of problem. Measurements of moisture content of walls in medieval churches with different measuring heads during different seasons were carried out over a 10 year period. Seasonal and long period changes of moisture content were analyzed.

Method for Data Collection and Integration into 3D Architectural Model

Rapid development in the field of smartphones over past years has enabled using their multimedia capabilities in virtually reconstructing and visualizing architectural objects by creating 3D-models of such objects. Several authors have tested cell phone cameras accuracy. For example Nokia N93, Sony Ericsson K750i, iPhone placed under test could be successfully used in applications not requiring ultimate precision [Gruen A, Akca D (2009) Evaluation of metric performance of mobile phone cameras. Institute of Geodesy and photogrammetry, ETH, Zurich. doi:10.3929/ethz-a-005749738; Takahashi Y, Chikatsu H (2009) 3D Modelling and visualization of cultural heritage using mobile phone cameras. In: Proceedings of the 3rd ISPRS international workshop 3D-ARCH, Trento]. Rapid technical development in the field of unmanned aerial vehicles (UAV) and lowering of their cost has made them available practically for everyone interested and eased tremendously use of such machines in aerial photography and photogrammetry [Eisenbeiss H (2009) UAV photogrammetry. Ph.D thesis, Dissertation ETH no. 18515, ETH Zurich; Remondino F, Barazzetti L, Nex F, Scaioni M, Sarazzi D (2011) UAV photogrammetry for mapping and 3D . In: Proceedings of the international conference on unmanned aerial vehicle in geomatics (UAV-g), Zurich]. We used Nokia N8 smartphone in our study since it had best optical, computing and communications capabilities at the time of this writing. In present paper we illustrate two ways of using smartphone’s camera in mapping object’s properties. One is a well known method of photogrammetric 3D-modelling. Another is a less used method of photogrammetric positioning [Dillon MJ, Bono RW, Brown D. L (2004) Use of photogrammetry for sensor location and orientation. IMAC-XXII: conference and exposition on structural dynamics, Jacksonville; Mautz R, Tilch S (2011) Survey of optical indoor positioning systems. In: Proceedings of the international conference on indoor positioning and indoor navigation, Guimaraes]. Firstly we demonstrate mapping of moisture content using photogrammetric positioning of sensor. Mechanically rigidly connected moisture probe and phone (together with built-in camera and special software) are linked via a bluetooth adapter enabling thus synchronisation of moisture measurement results to exact location. Individual results are stored directly to accompanying image file used for positioning each measurement. Such approach should eliminate possible human errors common in long and tedious measurements. Secondly a 3D model of a Tallinn Observatory tower is created by traditional means using phones built-in 12 megapixel camera. Low weight of the phone (about 120 g) enabled transporting it to suitable photographing positions onboard an airborne UAV. Described in present paper method is suitable for 3D-mapping of a large variety of physical properties of objects in interest.