Exterior Thermal Insulation Research Articles

Effectiveness of vertical barriers in preventing lateral flame spread over exposed EPS insulation wall

Insulation panels made of organic, combustible materials are frequently used in the exterior thermal insulation systems (ETIS) for buildings. Such combustible insulation panels have been involved in several catastrophic building fires in recent years in China. One potential strategy to mitigate this fire hazard is to limit fire spread over the ETIS. The present work evaluates the effectiveness of vertical fire barriers in inhibiting fire spread over exposed insulation walls made of expanded polystyrene (EPS) panels. Reduced-scale experiments were carried out indoors using EPS panels with or without two vertical barriers made of non-combustible mineral wool, the fire started at the bottom center of the middle panel. The interval and width of the barriers were varied systematically, while the temperature distribution on the wall, the radiation heat flux from the fire, and the infra-red (IR) images were recorded. To demonstrate the validity of the concept, an outdoor, full-scale experiment was carried out using a 7-floor building. Our reduced-scale experiments showed that the installation of two vertical fire barriers successfully stopped the lateral flame spread, decreasing the peak temperatures of the two side panels by about 300°C for all barrier configurations tested. When barrier width was fixed at 5cm, an increase of the barrier interval from 30 to 90cm led to increases in the peak temperatures, radiation heat flux, and the maximum rate of upward flame spread. By contrast, when barrier interval was fixed at 90cm, an increase of the barrier width from 2 to 5cm had little influence on the combustion dynamics of the middle panel but the peak temperature on the side panels dropped, consistent with the smaller heat transferred with wider fire barriers. In the regions of the side panels next to the barriers, pyrolysis and deformation could be observed with barrier widths of 2 and 3cm, but not 5cm. Finally, our outdoor, full-scale experiment demonstrated that a 30cm wide vertical barrier made of air-filled cement successfully stopped the lateral flame spread over exposed EPS wall. The study highlights the effectiveness of vertical fire barriers in preventing the lateral flame spread over the exposed EPS insulation wall and provides another option for enhancing the fire safety of the combustible insulation systems.

Experimental study of the out of plane behavior of masonry infill walls with exterior insulation systems

The objective of this study is to evaluate the out of plane behavior of a masonry infill wall provided with an exterior thermal insulation system. For this purpose there were constructed two 1:1 scale specimens of masonry infill walls in order to compare a simple wall with one having already applied an exterior thermal insulation system composed by a polystyrene insulation and a protection layer of plaster and a glass fiber mesh. The load was applied through a horizontal force, acting at the mid height of the wall. Both specimens were tested in displacement control, using alternate force with 3 cycles per loading step. As it was expected, an increased stiffness and out of plane resistance was observed for the wall provided with the insulation system. Various observations were noticed related to the technology and overall behavior of the infill masonry wall.

Impact of ETICS on Corrosion Propagation of Concrete Facade

The 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.

Fire Spread Caused by Combustible Facades in Japan

With regard to fire safety for exterior walls of a building, fire-resistance performance is considered, according to the current building standard law of Japan. And it was revealed that the fire safety is not specifically regulated from the viewpoint of reaction-to-fire performance, such as fire propagation caused by combustible materials or products which are installed on the exterior side of fire-resistant load-bearing walls. Actual fire issues in the world have shown that massive facade fire could occur at the exterior side of building wall even when the wall itself is fire-resistant. In previous studies of the authors, a test method of facade fire was tentatively proposed for evaluating the vertical fire propagation over an external wall within the same building. Furthermore, especially at the high-density residential areas in Japan, fire spreading would occur mostly from window to window between adjacent buildings, while walls are not burning by facade fire. But in case of combustible facades, such as insulating materials, combustible coating, or even sandwich panel are installed on the wall surface, once they are ignited, facade fire would occur and accelerate both the fire propagation in the same building and the fire spreading to the adjacent building. In this paper, results of fire tests on combustible facades are discussed from the viewpoints of both vertical fire spread along facades and fire spread between adjacent buildings assuming the densely populated residential area in Japan. The tentative criteria were determined based on the time to reach 500°C and duration time exceeding 500°C on facade surface for vertical fire spread along facade. As for intensively burned cases, at 2500 mm height from upper edge of the opening, specimens of exterior thermal insulation system with 200-mm thick expanded polystyrene (EPS), aluminum composite panel with polyethylene core and wooden facade without fire-retardant treatment continued exceeding 500°C for 3.1 min, 5.7 min, and 3.6 min, respectively, that were longer duration compared with specimens of resin painting (approximately 1 min). On the other hand, the another tentative criteria were determined for horizontal fire spread to an adjacent building based on the duration time exceeding the calibration test’s peak incident heat flux on opposite surface 2000 mm from facade surface for horizontal fire spread to an adjacent building. At 500 mm height from upper edge of the opening, specimens of exterior thermal insulation system with high-density 100-mm thick EPS and wooden facade without fire-retardant treatment continued exceeding the peak incident heat flux of calibration test for 13.1 min and 13.6 min, respectively, while one specimen of resin painting and aluminum composite panel with polyethylene core continued for shorter duration of 4.2 min and 5.8 min, respectively, even though they showed relatively high peak facade surface temperatures.

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.

The Effectiveness of Horizontal Barriers in Preventing Fire Spread on Vertical Insulation Panels Made of Polystyrene Foams

Expanded polystyrene (EPS) and extruded polystyrene (XPS) foams are both excellent exterior thermal insulation materials for buildings. However, their flammability also induces high fire hazard. Current regulation in China requires horizontal fire barriers with a minimum height of 30 cm when polystyrene foams are used as the external insulation. The present work evaluates the effectiveness of such barriers in inhibiting fire growth in insulation walls. The walls were made of B2 grade EPS and XPS foams without protective coatings but with mineral wool as horizontal barriers. Altogether six combinations of fire positions and barrier positions were tested for both EPS and XPS. The heat release rate (HRR) of the fire and the temperature distribution on the wall were recorded and analyzed. The results indicate that, without a barrier, fire starting at the middle of the wall generated higher peak HRR than that starting at the bottom, which was in turn higher than that starting at the top. When the insulation panel below the barrier was 1 m high, the upward fire spread from the bottom could be stopped by 40-cm, but not 30-cm, barriers. However, when the insulation panel below the barrier was 2 m high, even the 40-cm barriers failed. Lastly, the downward fire spread from above could not be stopped by 40-cm barrier due to dripping of burning plastics. The study highlights the limitations of horizontal fire barriers in preventing the vertical fire spread over exposed B2 grade polystyrene insulation and establishes protocols for further investigations.

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.

Biocides in urban wastewater treatment plant influent at dry and wet weather: Concentrations, mass flows and possible sources

In recent years, exterior thermal insulation systems became more and more important leading to an increasing amount of houses equipped with biocide-containing organic façade coatings or fungicide treated wood. It is known that these biocides, e.g. terbutryn, carbendazim, and diuron, as well as wood preservatives as propiconazole, leach out of the material through contact with wind driven rain. Hence, they are present in combined sewage during rain events in concentrations up to several hundred ng L−1.The present study focused on the occurrence of these biocides in five wastewater treatment plants in Denmark and Sweden during dry and wet weather. It was discovered, that biocides are detectable not only during wet weather but also during dry weather when leaching from façade coatings can be excluded as source. In most cases, the concentrations during dry weather were in the same range as during wet weather (up to 100 ng L−1); however, for propiconazole noteworthy high concentrations were detected in one catchment (4.5 μg L−1). Time resolved sampling (12 × 2 h) enabled assessments about possible sources. The highest mass loads during wet weather were detected when the rain was heaviest (e.g. up to 116 mg h−1 carbendazim or 73 mg h−1 mecoprop) supporting the hypothesis that the biocides were washed off by wind driven rain. Contrary, the biocide emissions during dry weather were rather related to household activities than with emissions from buildings, i.e., emissions were highest during morning and evening hours (up to 50 mg h−1). Emissions during night were significantly lower than during daytime. Only for propiconazole a different emission behaviour during dry weather was observed: the mass load peaked in the late afternoon (3 g h−1) and declined slowly afterwards. Most likely this emission was caused by a point source, possibly from inappropriate cleaning of spray equipment for agriculture or gardening.

Façade Tests on Fire Propagation along Combustible Exterior Wall Systems

With regard to fire protection for exterior walls of a building, only fire-resistive performance is considered, according to the current building standard law of Japan. In previous authors' studies, a new test method for evaluation of fire propagation along combustible cladding was proposed using primarily test specimens of facade walls with exterior thermal insulation without vent layers. In this paper, newly made results of facade fire tests also with other specimens of combustible facades, such as sandwich panels, photovoltaic sheets, combustible coating materials, and exterior insulation with vent layer, are discussed.

Experimental Study of the Heat Flux Effect on Combustion Characteristics of Commonly Exterior Thermal Insulation Materials

For the sake of examining the heat flux effect on combustion characteristics of commonly exterior thermal insulation materials, the six kinds of exterior thermal insulation materials were tested by the cone calorimeter in this paper included rock wool, adhesive polystyrene granule, phenolic resin, EPS, XPS and RPU. The experimental results showed that the fire risk of different thermoplastic insulation materials arrange in descending order was XPS>RPU>EPS> adhesive polystyrene granule> phenolic resin> rock wool; with the increase of radiation intensity, the heat release peak rate of PS increased and the ignition time and the peak time reduced, the heat release peak rate and the peak time points showed inverse proportion; the peak HRR value of B2 RPU is 2 times of B1 RPU and the efficiency of fire retardant of B1 RPU increases by 37.53% compared to B2 RPU.

Temperature Comparison of External Thermal Insulation Wall Using Foam Glass under Thermal and Humidity Effect

Experiments are performed aiming at the hot summer and cold winter area climate characteristics. The BWNH-3021 type weather-resistant testing apparatus is used to achieve performances of foam glass exterior thermal insulation walls. Real-time temperatures of each functional layer are tested under hot rain cycle effect. The temperature curves are plotted to make comparisons. When the environment temperature rises about 60°C, the temperatures of primary wall will rise only 8.20°C9.30°C each in 1#2# testing wall. When cold water is suddenly sprayed, the environment temperature will fall about 51°C. Then the temperatures of primary wall will fall only 4.00°C4.20°C each in 1#2# testing wall. It shows the good thermal insulating property of foam glass exterior thermal insulation wall. The environment temperature fluctuation can also be eliminated significantly. Attenuation coefficients of different thermal insulation walls are calculated. The maximum attenuation coefficients are present when temperature is rising. The coefficients of 1#2# testing wall are 15.00 and 4.60 separately. And the delay-times of two walls are 148min133min respectively. Both of the total attenuation coefficient and delay-time of 1# wall are greater than those of 2# wall. It indicates that a thicker layer makes the temperature wave decays more and takes longer time to delay. It proved that a thicker external thermal insulation structural layer contributes to the resistance of temperature fluctuation and thermal stability.

Study on Spread of Fire Overflow on Building Facades with Insulation Materials

Fire overflow on exterior wall with thermal insulation system has been studied by numerical simulation. The spread laws of fire overflow are analyzed through the temperature distribution near the window. The computational results are compared with those of test in the Exterior Insulation Fire Barrier Technical Guidelines (EIFBTG). It has been found that the calculated maximum temperature points is closed to the test on the first floor, the first ceiling, and the points near the above two windows. However, there are differences between two kinds of results above two floors and ceilings, and the points near the first window. It has also shown that when the HHR is 7.5KW, the scope of damage of exterior thermal insulation layer is about 15 square meters near the window. The research would provide reference for fire protection design of exterior wall thermal insulation in the high-rise buildings.

Simulated Fire Testing of a Real Building with EPS Exterior Thermal Insulation Composite Systems (ETICS) Including Rock Wool Fire Barrier

In this paper, a three stories villa was build and furniture was arranged according to the actual usage condition. The scene that building caught fire and flames escaped from the window and spread upward along the facade cladding system was simulated to verify the actual effect of fire barrier. The results showed that the first fire barrier obviously prevented flame dispersing and can raise ETICS fire safe ability.

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 study on fire propagation over combustible exterior facades in Japan

With regard to the fire protection for exterior walls of building, only the fire resistance has been considered, according to the current building law of Japan. In the previous studies of the authors, a new test method for evaluation of fire propagation along combustible cladding was proposed using primarily test specimens of facade walls with exterior thermal insulation without vent layers. In this paper, newly obtained test results are discussed on other specimens of combustible facades such as wood, sandwich panel, photovoltaic sheet mounted on composite panel, combustible coating material, and exterior thermal insulation with vent layer.

A New Type Thermal Insulation Fireproofing Wallboard

Exterior thermal insulation technology has many advantages such as light weight, good thermal insulation effect, and so on. So it is widely used in energy-saving building and existing building energy-saving renovation project all over the word. This article describes material selection, product performance and process characteristics of a new type composite phenolic wallboard which has double functions of thermal insulation and fireproofing.

Exterior thermal insulation systems for AAC building envelopes: Computational analysis aimed at increasing service life

A computational analysis aimed at increasing service life of exterior thermal insulation systems suitable for building envelopes based on autoclaved aerated concrete (AAC) in the climatic conditions of Central Europe is presented. In the first step, a sensitivity analysis of the effect of hygric parameters of materials involved in thermal insulation systems on the hygrothermal performance of AAC envelopes is accomplished, in order to identify appropriate ranges of their values. Computational simulations of temperature and moisture fields in AAC building envelopes are then performed, using proper combinations of properties of exterior layers. The results are evaluated from the point of view of frost resistance of the whole building envelope, and the appropriate values of hygric properties of thermal insulation layer and exterior plaster are identified. Finally, prospective types of materials suitable for the investigated thermal insulation system are proposed.

In search of better energy performance in the Portuguese buildings—The case of the Portuguese regulation

The Energy Performance of Buildings Directive (EPBD) is an important European policy tool to improve energy performance of buildings and has been applied in 27 countries with specific adjustments. The aim of this paper is to analyze the application of the Portuguese energy certification system and regulation to the residential sector using a case type, whilst considering a set of alternative and complementary solutions involving the regulation values for the envelope, interior and exterior thermal insulation, lower air renovation ratio, light colored exterior walls, better glazing system, shading elements and a Trombe Wall. In order to understand the role and the importance of bioclimatic measures in the Portuguese application of the EPBD, a comparison with the Passivhaus Norm applied to warm countries in Europe will be made. Due to the diversity of the Portuguese climate, three different climate regions were considered. Finally, we will discuss what new measures should be added to the Portuguese regulation, so that the proposed recast of the Directive might be transformed into a more effective tool in the search for better energy performance, passive house buildings and sustainable constructions.

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.

Experimental Study on Heat Transfer Coefficient for Foam Glass Exterior Thermal Insulation Wall

The heat transfer coefficients of two foam glass exterior thermal insulation walls were tested by weather-resistant testing instrument and heat flow meter. The experimental values were compared with the theoretical values. The results show that with the temperature differences Δt>20 °C, the testing errors of two walls are smaller than 1% and 3% respectively. In view of thermal performance, testing accuracy and operability, the test program is practicable to meet the testing requirement with a temperature difference greater than 20 °C and without seasonal restrictions. In the zones without heating such as hot summer and cold winter zone, therefore, the weather-resistant testing instrument (i.e. temperature control box) and heat flow meter can be used to test the heat transfer coefficient of a wall.