Interior Thermal Insulation Systems Research Articles

Multi-scale thermal, energetic and economic analysis of composite insulating materials made of silica aerogel in a fibrous inorganic mat

Composite materials made of silica aerogel in a fibrous inorganic mat, hereafter called “aerogel blankets”, represent promising insulating materials that can overcome the low mechanical resistance of monolithic aerogels, while preserving their very low thermal conductivity. Firstly, this paper details an experimentally validated mathematical model to predict the aerogel blankets’ effective thermal conductivity, as a function of the blankets' density, fiber volume fraction, and temperature. Secondly, an experimental test building retrofitted internally with a layer of needle glass fiber (NGF) aerogel blanket is monitored, and its thermal behavior is compared to the baseline case before the retrofit. The retrofitted wall U-value is derived from experimental data series using stationary and transient parametric methods. Then, a validated whole building Energy Plus numerical model is used to predict the annual energy consumption of a detached single-family house retrofitted with an NGF aerogel blanket, in the climates of Brussels (Belgium), Nice (France), and Stockholm (Sweden). Lastly, a 1-D COMSOL multiphysics model evaluates the economic profitability of installing the blanket as an interior thermal insulation system. Results show that the aerogel blankets have an effective thermal conductivity of about 0.0165 W.m−1.K−1. The designed mathematical model can reliably predict the gaseous conduction in the blanket, but deviations from the experimental measurements appear when considering the radiative and solid conduction components. The blanket's effective thermal conductivity increases with fiber volume fraction and temperature while its dependency curve to density is concave, with a minimum for densities of around 140 kg.m−3. Retrofitting a wall with 2.5 cm of NGF aerogel blanket as an internal insulation system almost doubles the thermal resistance of the experimental wall and decreases the heating load by more than 40 % in all tested climates. Internal thermal insulation with aerogel blankets is more profitable than conventional insulation materials, in places of high floor area price, because it can preserve the indoor living space.

Interior thermal insulation systems based on wood fiberboards: experimental analysis and computational assessment of hygrothermal and energy performance in the Central European climate

Two interior thermal insulation systems based on wood fiberboards are analyzed. The first system is composed of soft and hard fiberboards, the second one utilizes a capillary active fiberboard with incorporated water vapor retarder. The hygrothermal and energy performance of the systems in the climatic conditions of Central Europe is assessed using a combination of experimental and computational methods. A laboratory critical experiment is performed at first. The measured temperature and moisture profiles are then used for the validation of computational model of coupled heat and moisture transport, which is applied for hygrothermal and energy simulations. After the successful validation procedure, the model is used for the annual assessments. The energy assessment of the two-layer system shows excellent results from the point of view of energy savings (79 % improvement) but its hygrothermal assessment reveals possible shortages related to excessive hygric straining of the wall on the exterior side. The capillary active insulation system with water vapor retarder, which is able to keep moisture in the envelope within the hygroscopic range, exhibits only slightly worse energy performance (66 % improvement) but much better hygric performance than the two-layer system.

Computational Prediction of Susceptibility to Biofilms Growth: Two-Dimensional Analysis of Critical Construction Details

Retrofitting of historical and traditional buildings is an effective thermal protection measure. The presence of thermal insulation in the composition of building envelopes might, however, bring some shortages due to a decrease of exterior surface temperatures or possible water vapor condensation. These shortages can improve living conditions for various microorganisms on the exterior surfaces, especially in the case of interior thermal insulation systems that are typical with thermal bridges and thus supply the surface with heat to a greater extent. This paper, therefore, aims at the investigation of hygrothermal conditions in selected critical construction details and evaluates the results from the point of view of potential biofilms growth. Two-dimensional modeling of coupled heat and moisture is applied and the hygrothermal patterns are evaluated based on an adjusted isopleth growth model. The results showed that the duration of favorable conditions for biofilms growth is relatively low, accounting for less than 180 h in the worst-case scenario. It means the exterior surfaces of historical buildings provided with interior thermal insulation systems are not threatened by biofilms growth. Anyway, other negative aspects have been revealed that should be treated individually. Possible wood decay or increased hygrothermal straining are the typical examples in that respect.

Thermal and hygric properties of biomaterials suitable for interior thermal insulation systems in historical and traditional buildings

Historical and traditional buildings account for 10–40% of the building stock in various countries and regions. Retrofitting of their building envelopes aimed at the improvement of thermal performance is often feasible using interior thermal insulation systems only. The effectiveness of systems without vapor barrier depends on the application of modern insulation materials with enhanced water transport properties contributing to fast liquid moisture redistribution and mitigating the risks related to water vapor condensation. In this paper, thermal and hygric properties of several biomaterials potentially applicable as thermal insulation boards on the interior side of historical building envelopes are investigated. The obtained experimental data include all transport and storage parameters necessary for appropriate hygrothermal- and energy-related assessment of buildings provided with interior thermal insulation systems using advanced computer simulation tools. Wood fiberboard, flax fibers, hemp fibers, jute fibers, and sheep wool are found to have, at the same time, low thermal conductivity (∼0.05 W m−1 K−1) and high moisture diffusivity (1.1 × 10−6 – 1.2 × 10−5 m2 s−1) which can classify them as good candidates for the use in interior thermal insulation systems without water vapor barrier. They exhibit convenient water vapor diffusion parameters and hygroscopic properties as well, which favors their use on the interior side. The natural origin presents another benefit. In a comparison with conventional materials (calcium silicate, hydrophilic mineral wool) having similar thermal and hygric properties, they bring more harmony to the process of retrofitting historical building envelopes.

Influence of hydrophobation and deliberate thermal bridge on hygrothermal conditions of internally insulated historic solid masonry walls with built-in wood

A large share of the Danish building stock contains historic multi-storey buildings. A considerable energy saving potential exists, achievable through thermal insulation of the façades. Previous research has elucidated problems regarding poor hygrothermal conditions when interior thermal insulation is applied to the façade, but examples exist with positive results.Eight 1 × 2 m solid masonry test walls with wooden members were installed in an insulated container. The hygrothermal implication of applying 100 mm AAC as interior thermal insulation system was investigated with variations including use of hydrophobation and substitution of insulating material with a deliberate thermal bridge.Relative humidity and temperature were monitored in the walls over 2 years in 10 measurement points. The amount of wind driven rain was monitored with rain gauges and calculated from climate station data. The indoor excess of humidity by volume corresponded to the highest indoor climate class for dwellings.Damage models indicated risk of mould growth in the insulation/masonry interface, and risk of wooden decay in the wall plate for the reference and insulated case. Hydrophobation of the exterior surface in tempered cold climate reduced the overall relative humidity, although it increased during winter due to a reduced dry-out potential towards the outside.

Computational simulation of hygrothermal processes in historical building envelopes provided with interior thermal insulation

Interior thermal insulation systems are an integral part of retrofitting works, especially when historical buildings are taken into account. In this paper, three different insulation materials (mineral wool, calcium silicate, and sheep wool) were investigated in order to assess their suitability for the application in historical buildings. First, the basic physical, hygric and thermal properties of those materials were measured in laboratory conditions and then a series of computational simulations was carried out. Finally, based on the simulation results, the hygrothermal response was analyzed and several conclusions were drawn. The presented results proved all materials suitable for application in interior thermal insulation systems but some differences in the hygrothermal response of individual materials were observed.

Determination of material parameters of thermal insulation boards for the application on interior side of historical walls

At the reconstruction works on historical buildings, considerable financial means are spent. Therefore, it is desirable to assess the durability of applied materials in the particular conditions of a specific building. This cannot be done effectively without the knowledge of their hygric and thermal properties which can be used as input parameters of computational models. In this paper, hygric and thermal properties of several types of materials which can be used as interior thermal insulation layers in reconstructions of historical buildings on Czech territory, among them calcium silicate, hydrophilic mineral wool, and sheep wool, are investigated. Experimental results show that all analyzed materials can be considered as suitable for interior thermal insulation systems of historical building envelopes, in general. Their hygrothermal performance in specific applications should though be verified using computational simulations, taking into account the complex character of some historical construction systems.

Thermal and hygric assessment of an inside-insulated brick wall: 2D critical experiment and computational analysis

A combined experimental-computational approach is used for the analysis of hygrothermal performance of a brick wall provided with interior thermal insulation system. A 2D laboratory experiment is performed to determine temperature and moisture fields in a characteristic segment of the envelope over a sufficiently long period including cold winter months. Then, a computational model of moisture and heat transport is developed, using an integral two-phase balance equation capable of distinguishing between the particular phases of water and an enthalpy-based heat balance equation. A 2D computational representation of the experiment is used for model calibration and identification of unknown parameters, resulting in a very good agreement of experimental and calculated fields, with R2 between 0.9687 and 0.9888. The calibrated model is subsequently used for a long-term hygrothermal assessment of the studied detail to demonstrate the functionality of the interior thermal insulation system, as well as the applicability of the developed model.

Properties of a Sandwich Thermal Insulation Composite with Silica Aerogel

Properties of a new type of sandwich composite based on magnesium board, silica aerogel thermal insulation layer, and water vapour barrier are experimentally analysed in the paper. For the basic characterization of the studied material, bulk density, matrix density, and total open porosity are measured. Among the thermal properties, thermal conductivity, thermal diffusivity, and volumetric heat capacity are accessed. Water vapour transmission properties are determined using the dry-cup and wet-cup arrangements of the cup method. In order to describe the liquid moisture transport, water absorption coefficient and apparent moisture diffusivity are calculated based on the data obtained from the free water intake experiment based on the sorptivity concept. Ability of the tested material to accumulate water vapour is described by the sorption and desorption isotherms measured using a dynamic vapour sorption device. Mechanical resistivity of the tested composite is characterized by its compressive and flexural strength. Additionally, in order to get information on material performance at high temperature exposure, simultaneous TG and DSC analysis is done. The obtained data gives clear evidence on sandwich performance and proved its applicability in interior thermal insulation systems.

Heat and Water Vapor Transport Properties of Sandwich Composite with Aerogel Insulation

Several thermal insulation systems were developed for improvement of thermal performance of buildings. Exterior thermal insulation systems represent usually natural solution of the problem of low thermal resistance of building envelopes. However, in some cases, there is necessary to realize interior thermal insulation systems, what brings number of possible problems. Their common disadvantage is a limitation of interior space due to the thickness of thermal insulation layer and a possible condensation of water vapor which permeates the thermal insulation system. On this account, new sandwich composite with silica aerogel originally designed for application in interior thermal insulation systems is studied in the paper. Thermal properties are measured by two transient methods using devices ISOMET 2114 and RTB. The water vapor transport parameters are determined on the basis of dry cup and wet cup methods. The obtained data gives information on thermal and water vapor transport properties of the particular layers of sandwich composite and predetermines its behavior at real climatic exposure of building.

Moisture dependent thermal properties of hydrophilic mineral wool: application of the effective media theory

Thermal properties of mineral wool based materials appear to be of particular importance for their practical applications because the majority of them is used in the form of thermal insulation boards. Every catalogue list of any material producer of mineral wool contains thermal conductivity, sometimes also specific heat capacity, but they give only single characteristic values for dry state of material mostly. Exposure to outside climate or any other environment containing moisture can negatively affect the thermal insulation properties of mineral wool. Nevertheless, the mineral wool materials due to their climatic loading and their environmental exposure contain moisture that can negatively affect their thermal insulation properties. Because the presence of water in mineral wool material is undesirable for the majority of applications, many products are provided with hydrophobic substances. Hydrophilic additives are seldom used in mineral wool products. However, this kind of materials has a good potential for application for instance in interior thermal insulation systems, masonry desalination, green roofs, etc. For these materials, certain moisture content must be estimated and thus their thermal properties will be different than for the dry state. On this account, moisture dependent thermal properties of hydrophilic mineral wool (HMW) are studied in a wide range of moisture content using a pulse technique. The experimentally determined thermal conductivity data is analysed using 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. In case of dry state, material consists from solid and gaseous phase. When moistened, liquid phase is also present. Mineral wool consists of the solid phase represented by basalt fibers, the liquid phase by water and the gaseous phase by air. At first, the homogenization techniques are applied for the calculation of solid matrix thermal conductivity. Subsequently, the thermal conductivity dependence on moisture content is evaluated by means of several mixing formulas. To verify the obtained results, Wiener’s and Hashin-Shtrikman’s bounds are used. The results show that the application of homogenization techniques can provide useful estimates of measured data and can be successfully used for much less time consuming thermal conductivity evaluation even for the highly inhomogeneous fibrous material such as mineral wool. The data on thermal properties can find use in building practice, especially in the design of thermal insulation building envelopes. DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7334

Hygrothermal performance of exterior walls covered with aerogel-based insulating rendering

In this study, we present a recently patented insulating rendering based on silica-aerogels. It is mainly developed for exterior thermal insulation applications. In addition to new buildings, it can be used for retrofitting existing ones since it has a high insulation performance and its application is easy, compatible with the traditional masonry facades, and using the well-known ordinary techniques. The objectives are to examine the hygrothermal performance of walls with this rendering and to compare different thermal insulation configurations. The methodology followed is developing a numerical model, then conducting an experimental set-up on a test-cell having the rendering on its south wall to validate the numerical model under real weather conditions. Different exterior wall structures are examined: no insulation, exterior insulation using this rendering, interior insulation, and interior and exterior insulation. Six assessment criteria are used: assembly water content, drying rate, mold growth, condensation risk, ASHRAE-160 criterion, and heat losses. Results show that interior thermal insulation systems can cause several moisture problems: inability to dry out over the years, condensation risk, etc. Adding the aerogel-based rendering on the exterior surface of the un-insulated or the already internally insulated walls reduces significantly or even removes the moisture risks. Also, it reduces significantly the wall heat losses.

Moisture Transport Properties of Hydrophilic Mineral Wool

Mineral wool materials are widely used for thermal insulation of buildings due to their low thermal conductivity and high fire resistivity. On this account, they are popular materials for passive fire protection of buildings. Thermal insulation boards are usually provided with hydrophobic admixtures that ensure their functional properties even in the contact with moisture. In this paper we focused on investigation of hygric transport properties of hydrophilic mineral wool materials that could find application in interior thermal insulation systems as well as in desalination and drying of salt laden materials and building structures. The obtained results give evidence of the effect of fiber orientation on studied material properties and reveal that fiber orientation perpendicular to board surface is a perspective way of materials development.

Computer aided design of interior thermal insulation system suitable for autoclaved aerated concrete structures

The idea of using interior thermal insulation systems for autoclaved aerated concrete (AAC) structures is introduced. In the computer aided design, the hygric properties of the thermal insulation layer and the connecting layer between the AAC block and the thermal insulation board are investigated. The computational analysis shows that the moisture diffusivity, κ, of the thermal insulation layer should be very high (≈1 × 10−6 m2/s), its water vapor diffusion resistance factor, μ, very low (≈3–5), and hygroscopic moisture content, whyg, moderate (≈0.01 m3/m3). This combination of properties can potentially be met by modifications of some not commonly used thermal insulation materials, such as are hydrophilic mineral wool or calcium silicate. On the other hand, the hygric properties of the connecting layer are not found very restrictive. Common lime–cement or lime–pozzolan mortars can meet the required criteria of κ ≈ 1 × 10−9 m2/s–1 × 10−8 m2/s, μ ≈ 10–20, and whyg ≈ 0.05 m3/m3. The application of an interior thermal insulation system with the properties given above for an AAC envelope can reduce the hygrothermal straining of exterior plaster, which is typical for the exterior thermal insulation systems, in a very significant way, thus increase the service life of the whole envelope.

Experimental and Computational Analysis of Hygrothermal Performance of an Interior Thermal Insulation System

Experimental and Computational Analysis of Hygrothermal Performance of an Interior Thermal Insulation System

Analysis on Regional Adaptability of Interior Thermal Insulation System in South China

For seeking out suitable means of thermal insulation system of building envelope in south China, this paper has conducted simulation analysis on respective energy consumption of the typical residential template in cold region and south China, when adopt exterior thermal insulation system or interior thermal insulation system. The study has shown that the exterior thermal insulation system is much better than the interior thermal insulation system in energy efficiency in the cold region, but there isn’t obvious difference between them in south China. And from the aspects of the climate’s influence on the insulation quality, the installation’s influence on the building facades and the construction practices, it is proved that the interior thermal insulation system is more suitable than the exterior thermal insulation system in south China.

A concept of capillary active, dynamic insulation integrated with heating, cooling and ventilation, air conditioning system

When a historic facade needs to be preserved or when the seismic considerations favor use of a concrete wall system and fire considerations limit exterior thermal insulation, one needs to use interior thermal insulation systems. Interior thermal insulation systems are less effective than the exterior systems and will not reduce the effect of thermal bridges. Yet they may be successfully used and, in many instances, are recommended as a complement to the exterior insulation. This paper presents one of these cases. It is focused on the most successful applications of capillary active, dynamic interior thermal insulation. This happens when such insulation is integrated with heating, cooling and ventilation, air conditioning (HVAC) system. Starting with a pioneering work of the Technical University in Dresden in development of capillary active interior insulations, we propose a next generation, namely, a bio-fiber thermal insulation. When completing the review, this paper proposes a concept of a joint research project to be undertaken by partners from the US (where improvement of indoor climate in exposed coastal areas is needed), China (indoor climate in non-air conditioned concrete buildings is an issue), and Germany (where the bio-fiber technology has been developed).

Hygrothermal performance study of an innovative interior thermal insulation system

An innovative interior thermal insulation system on the basis of hydrophilic mineral wool which can serve as an alternative solution to the commonly used systems with water vapor barrier is presented in the paper. At first, the process of materials design is described. Then, the hygrothermal performance of the designed insulation system is tested in the difference climate conditions that correspond to the winter climate in Middle Europe. In the experiment, the profiles of temperature, relative humidity and liquid moisture content are monitored. Measured temperature profiles demonstrate the proper thermal insulation function of the system. The hygric function can also be considered very good as no water condensation during the whole testing period of five months appears in the insulation layer. Therefore, the basic requirements for the successful application of the system in building practice are met.

Long-term on-site assessment of hygrothermal performance of interior thermal insulation system without water vapour barrier

On-site assessment of hygric and thermal performance of an interior thermal insulation system on the basis of hydrophilic mineral wool is presented in the paper. The system is applied during the summer period on a brick-built house from the end of 19th century. Hygrothermal testing is done during the time period of 4 years. The reconstructed building envelope exhibits very good hygrothermal performance. The thermal resistance increases approximately two times. Water condensation is never observed inside the envelope during the whole testing period. A comparison with the previous experiment in semi-scale conditions which was performed for similar insulation system constructed during the winter season shows that the precedence should be given to the application of the system in summer period as it is more considerate to the old masonry.

Experimental assessment of hygrothermal performance of an interior thermal insulation system using a laboratory technique simulating on-site conditions

A laboratory technique simulating on-site conditions is used for hygrothermal performance assessment of two building envelopes. Interior thermal insulation system on the basis of hydrophilic mineral wool which is applied on two common load bearing structures is analyzed. Sufficiently large specimens of studied building envelopes are exposed to difference climate conditions very close to reality. Monitoring of moisture and temperature fields in the investigated structures is carried out using laboratory measuring technology. Experimental results give evidence that the hygrothermal performance of both tested building envelopes is satisfactory.