No abstract

Salt damage can affect the service life of numerous building structures, both historical and contemporary, in a significant way. In this review, various damage mechanisms to porous building materials induced by salt action are analyzed. The importance of pretreatment investigations is discussed as well; in combination with the knowledge of salt and moisture transport mechanisms they can give useful indications regarding treatment options. The methods of salt damage treatment are assessed then, including both passive techniques based on environmental control, reduction of water transport, or conversion to less soluble salts and active procedures resulting in the removal of salts from deterioration zones. It is concluded that cellulose can still be considered as the favorite material presently used in desalination poultices but hydrophilic mineral wool can serve as its prospective alternative in future applications. Another important cause of building pathologies is the rising damp and, in this phenomenon, it is particularly severe considering the presence of salts in water. The treatment of rising damp in historic building walls is a very complex procedure and at Laboratory of Building Physics (LFC-FEUP) a wall base hygroregulated ventilation system was developed and patented.

In many European countries, energy poverty is measured on the basis of real energy bills, as theoretical energy costs are hard to calculate. The UK is an exception—the data inputs for the Low Income-High Cost (LIHC) indicator are based on reasonable energy costs, these data are collected through specially designed surveys, often an intensive and costly procedure. Approaches which calculate energy needs are valid when energy bill data are unreliable or where households restrict consumption. In this analysis, energy poverty levels are evaluated for Greece, the municipality of Évora (Portugal), and the Basque Country (Spain): energy bills are modeled based on building energy performance data and other energy uses, and adjusted according to socio-demographic variables. To this end, equivalization weights are calculated using socio-economic data from the aforementioned southern European countries/regions. Data are analyzed to compare measurements with actual versus modeled bills using the Ten-Percent Rule (TPR) and Hidden Energy Poverty (HEP) against twice the median (2M) indicator, enhancing the identification of households with low energy consumption. In conclusion, theoretical energy needs can be combined with socio-demographic data instead of actual energy bills to measure energy poverty in a simplified way, avoiding the problem of targeting households that under consume.

The stability of tubular metal supported SOFC has been studied as a function of current load, thermal cycles and interconnect-sealing concepts. Long term testing under applied current at 800ºC have been performed over 1000 hours on standard cells. Thermal cycles have been proven intensely (250 cycles) during over 700 hours. Major cause for degradation has been identified in terms of the anode interconnect-sealing design, which involves specific handling and machining of tubes and generation of initial submicron cracks. Cell microstructure seems stable after 1000 hours testing at 300 mA/cm2 and 800ºC.

Tubular metal supported SOFC technology has successfully been developed over the past years with the aim at domestic CHP systems below 3 kWe. The basic cell structure consists of a metal porous support, a protective barrier layer, an anode and an electrolyte cofired at 1350ºC. Cathode and contacting layers are subsequently sintered at lower temperatures. Latest achievements include average cell performances of 400 mW/cm2 at 0.7 V and 800ºC, over 350 thermal cycles and more than 1500 hours of steady operation. Several stack concepts are currently being tested and BoP components such as fuel processing, power electronics and control system developed in parallel to achieve a successful micro-CHP proof of concept by the end of 2010.

Thermal properties of mineral wool based materials appear to be of high importance because the most widespread practice is using them as thermal insulation boards. Their thermal conductivity is easily found, i.e. data sheets from producers, often including specific heat capacity, but usually only characteristic values for dry state. Exposure to outside climate or any other environment containing moisture can negatively affect the thermal insulation properties of the mineral wool. This is why the presence of water inside the mineral wool is undesirable for the majority of applications; so, they are often provided with hydrophobic substances, whereas hydrophilic additives are seldom used. However, the later combination has good potential for some applications (i.e. desalination of masonries and green roofs). In those cases, mineral wool will work with a certain moisture content, which will change the thermal properties it had in the dry state. On this account, moisture dependent thermal properties (thermal conductivity and specific heat capacity) of hydrophilic mineral wool (HMW) are studied in a wide range of moisture content using impulse technique. The experimentally determined thermal conductivity data are analysed using a several homogenization formulas based on the effective media theory. In terms of homogenization, a porous material is considered as a mixture of two or three phases: solid (basalt fibres) and gaseous (air) phase for the dry state, adding the liquid phase (water) when moisten. The homogenization techniques are first applied to calculate the thermal conductivity of the solid matrix. Then, it dependence on moisture content is evaluated using some mixing formulas. To verify the obtained results, Wiener's and Hashin-Shtrikman's bounds are used. As a summary, the application of homogenization techniques can successfully estimate measured data for a highly inhomogeneous fibrous material (i.e. mineral wool), even consuming less time.

Hydrophilic mineral wool (HMW) is considered as a possible alternative to the commonly used cellulose in desalination of historical masonry. HMW also allows water and salt solutions transport along the hydrophilic fibres, which is the necessary condition for its possible application for desalination measures, but contrary to cellulose it is inorganic material, which reduces maintenance of the poultice. On this account, the hygric transport and storage properties of newly developed HMW is determined in the paper. In order to get detailed information on HMW performance, its thermal properties are measured as well. For its basic characterization, bulk density, matrix density, saturation moisture and salt content, and apparent total open porosity are accessed. The results are in good agreement with those published in literature for similar types of HMW. The process of drying of three different types of sandstone, as typical materials frequently used in historical buildings, using HMW board is monitored to analyse the practical applicability of the proposed desalination treatment. The obtained results show that HMW slows the drying process. However, the final level of drying is the same as without the HMW, which indicates the possible applicability of studied HMW for desalination purposes.

Salts and water are assumed to damage historical masonries. Therefore, many conservation treatments have been developed by research teams for the consolidation and protection of porous building materials affected by salt attack. Among them, different methods for obtaining effective desalination of historical masonry were proposed, having smaller or bigger disadvantages. Cellulose is the favourite material added to poultices used in desalination, and hydrophilic mineral wool (HMW) is considered as a possible alternative. Thanks to its hydrophilic additive, HMW allows water transport along the fibres, but contrary to cellulose it is an inorganic material, which reduces the maintenance of the poultice. In this paper, behaviour of the hydrophilic additive in relation to the wetting-drying cycles is studied. Basic characterization of the HMW is performed. Water and chloride absorption coefficients are measured using a standard free water uptake experiment. Additionally, moisture profiles are accessed using gravimetric method, and the moisture diffusivity as a function of moisture content is calculated using an inverse analysis procedure. The measurements are performed on samples pretreated several times in water and 1M NaCl water solution. Finally, FTIR and chromatographic analyses of HMW leached in water were performed to verify the assumed leachability of the hydrophilic additive. The measured water and NaCl water solution transport parameters confirm that HMW can be used in building materials desalination; the observed drop in the water absorption coefficient is explained using the FTIR results.