Heat and Moisture Modelling of Vacuum Insulated Retrofits with Experimental Validation

Vacuum insulation panels (VIPs) offer 8-10 times the thermal resistance of fiberglass insulation and would fit the need for a low conductivity exterior insulation. A composite insulation panel using VIPs encased in rigid foam was developed, built, and tested. Two different sizes of VIPs were used for that stage of the project, and after monitoring and evaluation, they showed contrasting results. A simulation study was performed to find the optimal VIP solution that maximized the effective thermal conductivity and minimized the mould growth potential. In total, 5 wall assemblies with VIPs used as the exterior insulation were simulated using WUFI and WUFI2D. The simulations showed that the humidity levels at the inside face of the OSB inboard of the VIPs decreased when 200 mm by 300 mm VIPs were used, but they did not reach the thermal performance thresholds of R5.28 m2K/W. The hygrothermal analysis showed that under similar conditions, a VIP insulated wall assembly would have a lower relative humidity at the sheathing surface compared to EPS and XPS. The one-and two-dimensional simulations were compared and found that WUFI Pro was capable to evaluate a VIP-insulated wall assembly.

A climate-based moisture index approach for hygrothermal analysis in Australia

In Australia, one-third of new constructions are affected by condensation and about 50% of buildings suffer from mould risk, mainly due to inappropriate design and management strategies. Despite the potential structural damage and serious health hazards, there is a lack of preventive moisture management strategies at the legislative level. The first hygrothermal management provisions were adopted in the National Construction Code only in 2019, with very general indications that correlate the breathability of the membranes with the climate zone. However, the building code identifies only eight zones for the entire Australia, which were originally developed for thermal analysis and energy efficiency provisions. The result is a coarse climate grid that clusters locations with highly variable humidity conditions. This paper undertakes a semi-empirical approach to identify whether the current climate zones are suitable for hygrothermal purposes. This research represents the first step towards an Australian-specific moisture risks management framework, and it advances the discussion about the suitability of the current hygrothermal design and construction policy and practices. The outcomes reveal the highly variable moisture indices obtained for the different representative cities, affirming the inappropriate use of existing climate zone clustering for hygrothermal assessment purposes.

Preliminary investigation on the transient hygrothermal analysis of a CLT-based retrofit solution for exterior walls

This paper investigates the transient hygrothermal performance of an innovative energy and seismic renovation solution for reinforced concrete (RC) framed buildings, based on the addition of Cross-Laminated Timber (CLT) panels to the outer walls, in combination with wood-based insulation. This solution is being developed in the framework of a four-year EU-funded project called e-SAFE. The investigation relies on numerical simulations in DELPHIN 6.1, by considering combined heat and mass transfer (HAMT) due to water vapour diffusion and capillary transport. The proposed solution is tested in three different climates in Italy, to verify whether the CLT layer and the outer waterproof vapour-open membrane, inserted to protect the wood-based insulation from rain, still allow the effective drying of the vapour accumulated in liquid form in the walls, while also preventing mould formation. The results show that the increased thermal resistance of the wall assembly significantly reduces the total water content, although moderate risks of mould growth in the wooden materials may occur in coldest climates.

Hygrothermal Analysis of CLT-Based Retrofit Strategy of Existing Wall Assemblies According to EN 13788 Standard

In the framework of the ongoing EU-funded innovation project called e-SAFE (energy and Seismic Affordable rEnovation solutions), several solutions for the energy and seismic deep renovation of reinforced-concrete (RC) framed buildings in the EU countries are going to be developed and demonstrated. One of these solutions makes use of cross laminated timber (CLT) panels connected to the existing RC frame through specifically designed dampers to increase the seismic and energy performances of the existing envelope. This paper aims to preliminary assess the hygrothermal performance of such CLT panels when applied to various typical wall structures under different climate conditions in Italy through numerical simulations carried out according to the EN 13788 Standard and considering various indoor vapor production classes. Results show that the most problematic existing wall structures are uninsulated concrete walls, for which a risk of surface condensation and mold growth is predicted in all climate zones because of their low thermal resistance (U-value of 3.55 W·m-2·K-1), followed by uninsulated solid brick walls (U-value of 1.81 W·m-2·K-1). The application of CLT panels is found to not only significantly improve the thermal behaviour of the walls, but also to eliminate any surface and interstitial condensation issues in all climate zones.

Hygrothermal Analysis of a Museum Storage Room for Metal Cultural Artifacts: Quantification of Factors Influencing High Humidity

Several methods for appropriate control of the hygrothermal environment in museums to prevent the deterioration of cultural artifacts were presented in previous studies. However, few detailed hygrothermal simulation models have been used considering the hygrothermal performance of building components and airflow through gaps. Furthermore, hygrothermal properties of a type of storage facility with buffer spaces prevailing in Japan have not been quantitatively evaluated. The objectives of this study were to develop a detailed numerical model of a museum storage room with buffer spaces exhibiting high humidity during summer and to quantitatively evaluate the potential factors causing it; the inflow of humid outdoor air and indirect cooling caused by the air-conditioning system of a surrounding room. We analyzed the simulated temperature and humidity for various cases in which each influencing factor was suppressed. The humidity was reduced when the exhaust fan for the surrounding rooms was stopped or the windows were made airtight, but it hardly changed when the cooling ducts and the reinforced concrete beams were insulated. Thus, the high humidity in the room was attributed to the inflow of humid outdoor air accelerated by the ventilation of surrounding rooms. Although indirect cooling had a small impact on high humidity, its impact on energy loss could still be significant.

Hygrothermal Analysis And Prediction Of Long-Term Thermal Performance Of Aerogel-Enhanced Superinsulation Products

Aerogel-enhanced insulating materials provide significantly higher thermal resistance per unit of thickness compared to conventional insulating materials. These superinsulation materials are relatively new in the construction industry, and their thermal properties under different hygric conditions and their durability are still unknown. In this study, the main characteristics of a variety of aerogel-based materials under different climatic conditions were studied. Furthermore, the samples underwent accelerated aging tests, and the impact of aging on the thermal performance of aerogel-based products was investigated. The results showed that the thermal properties of aerogel-based products are affected by moisture content and their thermal resistance degraded under extreme humidity conditions. The analysis of the aging effects showed that aerogel-based products would maintain their superior thermal performance over time. The average increase in the thermal conductivity (compared to the pristine condition) was below 10% after the equivalent of twenty years of aging under various climatic factors.

Hygrothermal Analysis And Prediction Of Long-Term Thermal Performance Of Aerogel-Enhanced Superinsulation Products

Aerogel-enhanced insulating materials provide significantly higher thermal resistance per unit of thickness compared to conventional insulating materials. These superinsulation materials are relatively new in the construction industry, and their thermal properties under different hygric conditions and their durability are still unknown. In this study, the main characteristics of a variety of aerogel-based materials under different climatic conditions were studied. Furthermore, the samples underwent accelerated aging tests, and the impact of aging on the thermal performance of aerogel-based products was investigated. The results showed that the thermal properties of aerogel-based products are affected by moisture content and their thermal resistance degraded under extreme humidity conditions. The analysis of the aging effects showed that aerogel-based products would maintain their superior thermal performance over time. The average increase in the thermal conductivity (compared to the pristine condition) was below 10% after the equivalent of twenty years of aging under various climatic factors.

Validation of wind-driven rain module for HAM-tools

This study is a continuation of previous research carried out to improve the hygrothermal analysis capabilities of the readily available HAM-Tools building simulation software. Previous study intended to improve the program by adding a wind driven rain (WDR) module using the semi-empirical model from ASHRAE 160P. However, further verification of the model was needed. In this study, the WDR module’s verification process was corrected and compared to WUFI simulation. The module was then validated by comparing its results with field measurements. The results indicated that the newly designed HAM-Tools WDR module have good agreement with field measurements. HAM-Tools with added WDR module is then used to study the hygrothermal responses of wood-frame wall with WDR amount calculated using different averaging techniques of high resolution meteorological data. It was concluded that in climates with high rainfall, it is best to use high resolution data (at least 10 minutes) for hygrothermal simulations.

Validation of wind-driven rain module for HAM-tools

This study is a continuation of previous research carried out to improve the hygrothermal analysis capabilities of the readily available HAM-Tools building simulation software. Previous study intended to improve the program by adding a wind driven rain (WDR) module using the semi-empirical model from ASHRAE 160P. However, further verification of the model was needed. In this study, the WDR module’s verification process was corrected and compared to WUFI simulation. The module was then validated by comparing its results with field measurements. The results indicated that the newly designed HAM-Tools WDR module have good agreement with field measurements. HAM-Tools with added WDR module is then used to study the hygrothermal responses of wood-frame wall with WDR amount calculated using different averaging techniques of high resolution meteorological data. It was concluded that in climates with high rainfall, it is best to use high resolution data (at least 10 minutes) for hygrothermal simulations.