Long term measurements and HAM modelling of an interior insulation solution for an office building in cold climate

Excessive mould damage was detected in an office building in Northern Europe and thus a renovation need was established. This paper studies a renovation solution using measurements and heat, air & moisture (HAM) modelling. Polyurethane (PUR) foam was used to fill the air gap in masonry while capillary active calcium silicate (CaSi) insulation was used on the interior surface at thermal bridges. During renovation works temperature and relative humidity (t&RH) and heat flux sensors were installed throughout the wall. Nearly 3 years of measurements are presented. Average thermal transmittance (U) of the wall was reduced around 3 times. While the climate was probably not critical during the monitoring, the measured values stayed within hygrothermally safe limits. The paper also compares the measurement data to 2D HAM modelling and discusses the discrepancies. Calibrated models were used to model the wall using real 42-year weather data and give a more thorough assessment of the hygrothermal performance. Although the original wall stayed fairly moist, no performance limits were exceeded and the interior surface became safer in terms of mould risk

Impact of ETICS on Corrosion Propagation of Concrete Facade

AbstractThe durability of reinforced concrete facades is an important field of research as the majority of dwellings in Northern and Eastern Europe were constructed 30–50 years ago. Recent condition assessments of the façades have indicated damage related to carbonation induced corrosion. Moreover, the problem might escalate since the future climate scenarios predict a significant increase of CO2 in ambient air being a driving force for carbonation.Assessment of residual service life of concrete facades is a complex phenomenon with a high level of uncertainty. A validated method used in this study combines dynamic hygrothermal simulation tool Delphin and existing corrosion models. Corrosion propagation consists of the time needed to concrete cover cracking and further expansion of a crack up to a width of 0.3mm as a limit criterion. Additional exterior thermal insulation (mostly ETICS) is applied to existing dwellings as a renovation scenario in order to decrease the heat loss, improve thermal comfort and prevent the degradation mechanism e.g. carbonation induced corrosion. Hence, reinforcement corrosion before and after installing ETICS with mineral wool, EPS or PIR has to be evaluated. Impact of boundary conditions, e.g. wind-driven rain in addition to material properties, and built-in moisture was included.The results indicate that corrosion propagation after carbonation has reached the reinforcement, is three to six years depending on the ratio of concrete cover depth against the reinforcement diameter. While applying ETICS, corrosion accelerates for a short period of time up to one year. Temperature inside the wall rises above +10°C throughout the year, meaning no more freeze-thaw damage. Corrosion of reinforcement in carbonated concrete after applying ETICS is so slow, that no cracking will develop. Drying out moisture or vapour diffusion from indoor air is not able to propagate corrosion of reinforcement in carbonated concrete

Generative reverse-modelling approach to hygrothermal material characterization

Reliable hygrothermal modelling depends on the quality of material characterization, especially so when higher moisture contents are concerned. Previous research has shown that adding additional material tests (e.g. capillary condensation redistribution (CCR) test) to the experimental dataset brings improvements to the modelling accuracy, but also adds to the workload of characterization process. This paper discusses a generative optimization workflow to increase the speed of the characterization and quality of the result. The proposed workflow incorporates optimization tool GenOpt and hygrothermal modelling software IBK Delphin to search for best fit of the water vapour and liquid conductivity curves of interior insulation materials based on modelling the CCR, drying and wet cup tests. Finally, models using material data from the proposed workflow and from the software database are compared to measurement results from two studies on interior thermal insulation. The results suggest that the generative optimization shows promise on the grounds of reducing tedious work analysing material tests. Also, a wider experimental dataset is shown to be useful when characterizing the vapour and liquid conductivity functions in over-hygroscopic region

Capillary condensation experiment for inverse modelling of porous building materials

Hygrothermal simulations are of major importance for critical problems in building physics, such as the application of internal insulation in heritage buildings. These simulations require numerous material parameters that are challenging to determine. We present measurements of typical internal insulation materials, calcium-silicate and autoclaved aerated concrete, which we expose to a warm, humid climate on one side and a cold temperature on the other side. We measure the moisture gain over time and determine the moisture profile at experiment end. In an inverse modelling approach, the measurements are used to identify material parameters, in particular vapour conductivity and capillary conductivity as a function of moisture content. We found the measurements of crucial importance for the accurate determination of these parameters. When the parameters rely only on isothermal measurements such as the drying experiment, the model fails to predict the capillary condensation process. We demonstrate this on a dataset from another study with interior insulation subjected to changing boundary conditions. The model calibrated with capillary condensation data reliably reconstructs measurements while the drying-calibrated model drastically underestimates the moisture content

Thermal bridge effect of vertical diagonal tie connectors in precast concrete sandwich panels: an experimental and computational study

The purpose of this work was to quantify the thermal bridge effect of vertical diagonal tie connectors in precast concrete sandwich panels (PCSPs). Special interest was in cases where the use of rigid insulation (e.g. PIR) would leave air gaps between insulation boards and diagonal ties, thus intensifying the thermal bridge. A climate chamber experiment using 5 different joint types was performed to gather reference data for CFD model validation. In the experiment, natural convection was observed in joints where no additional insulation was used, i.e. in air cavities. Significantly larger heat fluxes were measured in these cavities compared to insulated joints. The thermal bridging effect was evaluated for a typical PCSP (thermal transmittance without thermal bridges U = 0.11 W/(m²·K)) using CFD software taking into account 3D heat conduction and convection. Simulation results indicate that diagonal ties without adjacent air cavities increased the average thermal transmittance (U-value) of the envelope by 8%, diagonal ties with a 6 mm air cavity – 19...33% and diagonal ties with a 10 mm air cavity – 45...56%. In conclusion, it was found that the joints in insulation caused by diagonal ties affect the overall thermal performance of the building envelope significantly when efforts are not made to fill the air cavities around the connectors

Hygrothermal Performance of Thick PCM Mortar behind PV Panels in Energy-Activated ETICS Facades

The concept of integrating PV panels into traditional ETICS facades has been developing for several years. Problems concerning the options for passively controlling the temperatures of PV panels with PCM and directing excess moisture out of the wall via diffusion channels have been previously studied theoretically. During this study, real wall-scale experiments were conducted to test the thermal and hygrothermal performance of the wall system in an extreme climatic environment, as well as in a real outdoor environment in Tallinn, Estonia. Finally, a simulation model was calibrated according to the measured data. It was found that in case of test walls with diffusion channels, it was possible to keep the moisture content of PCM mortar under 0.11 m3/m3. Excess water drained out via channels leading to the external environment. Without diffusion channels, the moisture content rose as high as 0.18 m3/m3. Both the experiments and hygrothermal modelling showed that the high moisture content of PCM mortar, caused by water leakage, dropped to 0.08 m3/m3 over 10 solar cycles as moisture escaped via the diffusion channels. PCM mortar with a moisture content of 0.08 m3/m3 endured extreme rain and freeze-thaw cycles without visual damage, and PV panels retained their electrical production capabilities

PCSP's Diagonal Tie Connectors Thermal Bridges Impact on Energy Performance and Operational Cost : Case Study of a High-Rise Residential Building in Estonia

| openaire: EC/H2020/856602/EU//FINEST TWINSThis study analyses the effect of air circulation around diagonal tie connectors in precast sandwich panels on heating energy demand, energy performance value and heating costs of a sample residential building. Dynamic simulations were performed using 4 different climatic boundary conditions: Estonian test reference year, Estonian 48-year weather dataset as well as data from Eastern Germany and Northern Finland. The results show that the effect of the thermal bridge is most noticeable in total room heating energy demand (increase of 10.3%), while the influence on energy performance value was 1.1%. The relative increase of total room heating energy demand was similar (7.0-10.3%) in all studied climatic regions.Peer reviewe