Reflective Insulation Research Articles

The effect of the use of radiant barriers in building roofs on summer comfort conditions – A case study

A brief analysis on radiant barriers applied in building roofs, included in a wider study, is presented. A case study which involves experimental measurements carried out in a single-family house, located in a mild climate, specifically in the North of Portugal, where radiant barriers were applied and monitored is described.A computer program (CAPSOL) was also used to carry out a sensitivity analysis and to verify if the results pointed to conclusions similar to those of the experimental measurements.In the experimental part of this work, which took place in the summer periods of two consecutive years, two different roofs were monitored in the same house. Values of temperature, relative humidity, solar irradiance, heat fluxes among other parameters were measured. This article presents some of the collected data.In the numerical simulation, the comparison between the situation of the inclusion of a radiant barrier underneath the roof tiles and over the attic floor slab is presented and compared with another situation without this barrier.In general, it was concluded from this brief analysis that the application of a radiant barrier in the roof of a building proves to be advantageous, especially in what regards the attenuation of the maximum temperatures reached at the roof attic, thus mitigating the risk of overheating.

Thermal resistance of selected thermal reflective insulations

The increasingly stringent requirements of thermal engineering standards lead to ever greater thicknesses of thermal insulating layers in the structures, which makes the insulation of the manufacturer to improve material parameters. Thermally reflective insulation currently occupies only a small volume of products in the building industry, but their use in buildings where a large temperature gradient is created for thermal insulation offers many advantages. The pressure on the thermal insulation efficiency is increasing, so that their thickness is as small as possible.

Experimental investigation of the influence of temperature on thermal conductivity of multilayer reflective thermal insulation

The apparent thermal conductivity of several insulation materials was measured over a range of temperatures. A newly developed multilayer reflective insulation system called Mirrorpanel was tested against existing products. Mirrorpanel samples were prepared using layers of aluminum foil (emissivity of 0.11) and coated paper (emissivity of 0.52) separated by air spaces of approximately 5 mm, with fiberboard structural spacers. Steady-state heat flux was measured in the laboratory for 500 mm × 500 mm samples including several Mirrorpanel configurations as well as expanded polystyrene and polyisocyanurate foam insulations. The mean temperature ranged between 0 °C and 35 °C with a temperature difference across the sample of 10 °C. For all insulation materials, the apparent thermal conductivity increased linearly with temperature above 5 °C, and the slope was steeper for the Mirrorpanel samples than the foam insulations. The apparent thermal conductivity of the Mirrorpanel made from aluminum foil was greater than that of polyisocyanurate but less than that of expanded polystyrene. The significant difference of thermal conductivity of lower and higher emissivity reflecting layers highlighted the importance of this parameter in thermal insulation. The steep temperature dependence of the Mirrorpanel should be considered during design of the building envelope for summer and winter conditions.

Evaluation of the thermal performance of insulation sheets in fiberglass security booths

In light-weight buildings under subtropical climatic conditions, it is recommended the use of roof materials that minimize heat gains in summer while avoiding heat losses in winter. A low-cost option for ensuring thermal insulation with radiant barriers and reflective elements is based on the use of open Tetra Pak® packages. The aim of the study was to evaluate the thermal performance of three kinds of insulation strategies, resistive insulation, reflective insulation and radiant barriers: 50 mm Expanded Polystyrene (EPS), double-sided foil insulation and Tetra Pak® sheets, used under the roof of fiberglass security booths. Comparisons of indoor air and surface temperatures were carried out during transitional periods: spring-summer and fall-winter. Tetra Pak® sheets with an upward-facing (acting as reflective insulation) or downward-facing (functioning as radiant barrier) aluminized side or with double-sided aluminum coating showed a reduction in the roof's inner surface temperature, comparable to commercial insulating sheets, though with lesser effect on indoor temperatures. For the spring-summer transitional period, results for double-coated Tetra Pak® sheets were superior to those of commercially available double-sided foil insulation.

Reflective insulations for hot-humid climates

Reflective insulations for hot-humid climates

To the determination of heat exchange conditions near the inner surface of walls with reflective thermal insulation from aluminium foil

Materials with a low coefficient of surface radiation intensively reflect the radiant component of the heat flux and reduce heat losses through the building envelope. When designing building structures with reflective thermal insulation it is necessary to evaluate the efficiency of its application. However, at present there are no methods for calculating the value of thermal losses through external walls in the presence of reflective thermal insulation on internal surface of the wall, as well as there are no data on the values of heat transfer coefficients at the inner surface of building envelope with reflective thermal insulation. In this regard, in the climatic chambers of NIISF RAABS, complex thermal engineering studies were carried out. For this a cellular concrete wall 2,8 x1,2 m was put up into the chamber with reflective thermal insulation on the inner surface and without it. The obtained results of experimental studies, presented in the work, allowed obtaining numerical values of heat transfer coefficients at the inner surface of walls with reflective thermal insulation, and use the obtained data in further calculations.

Application of Poensgen apparatus for determining the thermal conductivity of reflective insulations

Multilayer reflective insulations are a combination of several or a dozen low emission screens compressed together, separated by layers of bubble foil or polyethylene foam. This paper presents the results of experimental investigation of thermal conductivity of multilayer reflective insulations. The measurements were made with Poensgens LaserComp FOX 314 apparatus. Five samples of reflective insulation and one sample of foamed polystyrene have been tested. The difficulties of determining the replacement thermal resistance for the discussed materials have been presented. Information about the apparatus used, theory of the measurement method, procedure of the experiment and method of sample preparation were presented. The study was performed for four different temperature pairs representing the real thermal conditions in Poland throughout the year. On the basis of the obtained measurement results the average thermal conductivity and average thermal resistance of the tested materials were determined. The relation between the obtained thermal conductivity and thermal resistance depending on the temperature was discussed.

Insulation systems for buildings and structures based on expanded polyethylene

Insulation systems for buildings and structures imply the use of efficient thermal insulation products based on mineral wool, expanded polystyrene, expanded polyurethane, etc. For a long time, products from non-cross-linked expanded polyethylene were used as insulation for pipelines, reflective insulation, protection against air infiltration, etc. Modern technologies and engineering solutions allowed widening the field of application of non-cross-linked expanded polyethylene (NXLPE) as a construction insulation material. In particular, we can consider a complex of insulation systems for walls, floors and a pitched roof, which allows to form a fully insulating shell of a low-rise building, e.g. a cottage. The novelty of the patented technology Tepofol® and that of the material concerned in comparison with the known solutions is the development of a rolled material based on NXLPE (20 to 150 mm thick) with a lock joint, as well as the technology of seamless connection of individual heat-insulating cloths. The rolls of NXLPE are mechanically fixed to the frame and connected with the lock. One of the advantages of expanded polyethylene, which only few insulating materials possess, is the possibility of forming seamless insulating shells. The article considers a number of insulation systems based on the use of products from expanded polyethylene. In particular, these are the systems of insulation of the walls of frame buildings, the insulation of floors, as well as the insulation of logistics facilities and hangars.

Energy and Economic Analysis for Greenhouse Envelope Design

Abstract. The energy consumption of a building is significantly impacted by its envelope design, particularly for greenhouses where coverings typically provide high heat and daylight transmission. Energy and life cycle cost (LCC) analysis were used to identify the most cost-effective cladding design for a greenhouse located in Ottawa, Ontario, Canada (45.4° N) that employs supplemental lighting. The base case envelope design uses single glazing, whereas the two alternative designs consist of replacing the glass with twin-wall polycarbonate and adding foil-faced rigid insulation (permanent or movable) on the interior surface of the glass. All the alternative envelope designs increased electricity consumption for lighting and decreased heating energy use except when permanent or movable insulation was applied to the north wall and in the case of permanent insulation on the north wall plus polycarbonate on the east wall. This demonstrates how the use of reflective opaque insulation on the north wall can be beneficial for redirecting light onto the crops to achieve simultaneous reductions in electricity and heating energy costs. A maximum reduction in LCC of 5.5% (net savings of approximately $130,000) was achieved when permanent insulation was applied to the north and east walls plus polycarbonate on the west wall. This alternative envelope design increased electricity consumption for horticultural lighting by 4.3%, reduced heating energy use by 15.6%, and caused greenhouse gas emissions related to energy consumption to decrease by 14.7%. This analysis demonstrates how energy and economic analysis can be employed to determine the most suitable envelope design based on local climate and economic conditions. Keywords: Artificial lighting, Consistent daily light integral, Energy modeling, Envelope design, Greenhouse, Life cycle cost analysis, Light emitting diode, Local agriculture.

Field evaluation of reflective insulation in south east Asia

AbstractThe objective of this research was to obtain thermal performance data for reflective insulations in a South East Asia environment. Thermal resistance data (RSI, m2 ⋅ K/W) for reflective insulations are well established from 1-D steady-state tests, but thermal data for reflective insulation in structures like those found in South East Asia are scarce. Data for reflective insulations in South East Asia will add to the worldwide database for this type of energy-conserving material. RSI were obtained from heat flux and temperature data of three identical structures in the same location. One unit did not have insulation above the ceiling, while the second and third units were insulated with reflective insulation with emittance less than 0.05. RSI for the uninsulated test unit varied from 0.37 to 0.40 m2 ⋅ K/W. RSI for a single-sheet reflective insulation (woven foil) varied from 2.15 to 2.26 m2 ⋅ K/W, while bubble-foil insulation varied from 2.69 to 3.09 m2 ⋅ K/W. The range of RSI values resulted from differences in the spacing between the reflective insulation and the roof. In addition, the reflective insulation below the roof lowered attic temperatures by as much as 9.7° C. Reductions in ceiling heat flux of 80 to 90% relative to the uninsulated structure, due to the reflective insulation, were observed.

The Dispersion Process based on Organic-inorganic Composite Technology and its Application in Thermal Reflective Insulation Coatings

With the photochemical activity of titanium dioxide, the surface polymer encapsulation is conducted to titanium dioxide under ultraviolet light initiation. It studies the influence of light source type, light exposure time and rate of charge on the product structure; the dispersion oftitanium dioxide was compared before and after modification by using light absorption method; the modified titanium dioxide was prepared into thermal reflective insulation coating, and the difference of thermal barrier effect among uncoated, rock wool board and thermal reflective insulation coating was contrasted by self-made equipment.

Cylindrical cryogenic calorimeter testing of six types of multilayer insulation systems

Extensive cryogenic thermal testing of more than 100 different multilayer insulation (MLI) specimens was performed over the last 20 years for the research and development of evacuated reflective thermal insulation systems. From this data library, 26 MLI systems plus several vacuum-only systems are selected for analysis and comparison. The test apparatus, methods, and results enabled the adoption of two new technical consensus standards under ASTM International. Materials tested include reflectors of aluminum foil or double-aluminized Mylar and spacers of fiberglass paper, polyester netting, silk netting, polyester fabric, or discrete polymer standoffs. The six types of MLI systems tested are listed as follows: Mylar/Paper, Foil/Paper, Mylar/Net, Mylar/Blanket, Mylar/Fabric, Mylar/Discrete. Also tested are vacuum-only systems with different cold surface materials/finishes including stainless steel, black, copper, and aluminum. Testing was performed between the boundary temperatures of 78 K and 293 K (and up to 350 K) using a thermally guarded one-meter-long cylindrical calorimeter (Cryostat-100) for absolute heat flow measurement. Cold vacuum pressures include the full range from 1 × 10−6 torr to 760 torr with nitrogen as the residual gas. System variations include number of layers from one to 80 layers, layer densities from 0.5 to 5 layers per millimeter, and installation techniques such layer-by-layer, blankets (multi-layer assemblies), sub-blankets, seaming, butt-joining, spiral wrapping, and roll-wrapping. Experimental thermal performance data for the different MLI systems are presented in terms of heat flux and effective thermal conductivity. Benchmark cryogenic-vacuum thermal performance curves for MLI are given for comparison with different insulation approaches for storage and transfer equipment, cryostats, launch vehicles, spacecraft, or science instruments.

The measured study of natural weathering performance of reflective thermal insulation coating in hot-summer and warm-winter region

In order to study the attenuation performance of solar direct reflectance of reflective thermal insulation coating under natural weathering, we conducted a measured study on five coatings with the built natural weathering platform. After the 18-month natural weathering experiments, the color of coating templets turn undertint or black with coating layer pulverized and fallen off, some of the templets starting to crack, fall off and go mouldy. Meanwhile, the reflectance ratio of reflective thermal insulation coating decreased significantly after 3 to 6 months, the degree of attenuation of the five templets is 2% to 28%. After 18 months’ exposure to the blazing sun, the most significant degree of attenuation reached 46%. The solar direct reflectance of coating templet of the same brand remained high as before after natural weathering with an initial high solar direct reflectance

Thermal performance analysis of residential attics containing high performance aerogel-based radiant barriers

This paper is focused on a new, easy to install, extremely light weight, and high R-value radiant barrier that shows promise for attics and wall cavities in residential and light-commercial buildings in cooling-dominated and mixed climates. Roofs and attics are one of the major sources of thermal loads affecting energy performance of residential and commercial buildings in North America. Several novel prototype residential roofs and attics have been constructed in different North American climates. These technologies have demonstrated a significant reduction of the heat transfer penetrating the roof deck and the overall attic-generated thermal load compared to conventional insulation. One of these technologies is radiant barriers. This paper discusses the development, testing, and thermal performance of a novel radiant barrier containing aerogel insulation core. The newly developed aerogel-based radiant barrier is characterized at the system-scale in a controlled laboratory setting and deployed in a side-by-side field test with conventional insulation technology. The experimental data is used to validate numerical models created with the Fraunhofer Attic Thermal Model (FATM). The validated models were then used for thermal performance predictions of similar attic configurations located in 11 different climatic conditions worldwide.

A computational and experimental study of conjugate heat transfer through composite thermal envelopes in post-frame buildings

The thermal performance of eight post-frame thermal envelopes was studied and optimized using a computational fluid dynamics model validated experimentally with a rotatable guarded hot box. In addition to providing thermal performance values for typical wall designs, this study proposed a new wall design that greatly increased thermal performance without sacrificing material efficiency. Study variables included structural geometry, level of insulation, and the presence and placement of radiant barriers. To reduce computational demand, modeling was primarily conducted using an area-weighted average of two-dimensional slices to represent three-dimensional assemblies. After modeling a portion of the assembly in three dimensions and comparing it with its two-dimensional counterpart, this simplification was found to result in less than a 6.7% error. Significant error (up to 57%); however, was determined to be integral to the simplifying assumptions commonly used by building designers, especially in envelopes common to the agricultural industry. This error was estimated to underpredict energy costs for a 2200m2 cold-storage warehouse in Wisconsin by approximately $1700ayear.

Life-cycle cost analysis of roofing technologies in tropical areas

Various technologies have been applied on roofs to reduce the air-conditioning load in buildings during summer or in tropical areas, including cool paint, roof ventilation, mass and reflective insulation. These technologies help to reduce roof temperatures or heat transmission effectively in summer at different economic costs. It is desirable to evaluate the cost effectiveness of different roofing technologies, especially in the tropical climate.This work analyzes the heat gains of concrete-based roofs combined with different roofing technologies, as well as the cost effectiveness of these technologies in the tropical climate of Singapore. The transient roof temperatures and heat transmissions are predicted using Complex Fast Fourier Transform (CFFT) method, and the impacts of roof ventilation on heat gain are predicted using correlations proposed for convective resistance prediction via computational fluid dynamics (CFD) simulation. The daily heat gains of different roof components are hence predicted, and Life-cycle Cost Analysis (LCCA) is performed to evaluate the payback periods of different roofing technologies, including cool paint, expanded polystyrene foam (EPS), radiant barrier (RB), and roof (natural and forced) ventilation. It is concluded that the application of cool paint on unventilated roof shows the shortest payback period, and the combined use of RB and natural ventilation yields the largest energy savings in the long run. Compared with forced ventilated roofs, those passive roof technologies (cool paint, RB, air gap and EPS foam) without electricity requirement are more recommended, due to their cost effectiveness.

Reflective Insulation for Energy Conservation in South East Asia

Thermal resistances have been measured for attic spaces insulated with reflective insulations. Three test units located in Malaysia were instrumented to provide heat flux and temperatures for the calculation of time-average RSI-values (RSI is representing R-value in SI units). The RSI for attics with enclosed reflective air spaces were in the range 2-3 m2·K/W while the uninsulated attics averaged about 0.4 m2·K/W. The RSI-values determined in this project were for heat-flow down, the predominant heat-flow direction for attic spaces in Equatorial regions. The observed thermal resistances due to the installation of the reflective insulation results in an 80-90% annual decrease in the heat transfer across the ceiling. This reduces utility usage for air conditioned units and improved comfort for occupants. The research demonstrates the use of transient data for the determination of thermal insulation performance and usefulness of enclosed reflective air spaces for thermal resistance.

Исследование возможностей применения отражательной теплоизоляции в многослойных сэндвич-панелях с учетом многократного отражения

Исследование возможностей применения отражательной теплоизоляции в многослойных сэндвич-панелях с учетом многократного отражения

Architecture for Refugees, Resilience Shelter Project: A Case Study Using Recycled Skis

In emergency and post-disaster situations one of the hardest issues to deal with regards the means and materials suitable to build temporary and livable shelter. In this prospective, the following work analyze the potentiality (from technological, thermal and structural point of view) of a lightweight shelter skin composed by recycled skis, covered by a textile envelope coupled with thermal reflective multilayer insulation able to provide high-quality thermal comfort. This solution addresses different purposes: recycling high technology material, construction speed, lightness and low embodied energy. As skis are constituted by different layers of high-performances materials, that are also difficult to dismiss, their reuse reduce the CO2 emissions and the amount of wasted material. In collaboration with the University of Grenoble, some laboratory tests have been carried out in order to investigate the mechanical properties of skis and design durable and resistant structure. The morphology of proposed shelter comes from the archetype of the Mongolian Yurt, modelled and adapted to improve energetic performances: a detailed building model has been used to perform dynamic building energy simulation. The structure is composed by 130 pair of skis with different lengths and characterized by a circular basement (6 meters of diameter) divided in 24 concentric sectors that constitute the structural axis, where are located pillars and beams made by coupling different combinations of skis. Externally two orders of circular hoops help to absorb the loads coming from the covering, and between the pillars are placed two bracing elements. At the center of the circumference a steel pillar supports the flat-roof window. A real-scale prototype has been developed in order to verify the assumptions made during the design phases. The shelter is now built and used in a humanitarian mission in Guinea Bissau.

Use of a hot-box facility to evaluate hybrid reflective insulation assemblies

The determination of the thermal performance of hybrid insulation assemblies that include an enclosed reflective airspace and a separate layer of insulation is being done using a hot-box test facility operated in accordance with ASTM C1224, the Standard Specification for Reflective Insulation. The thermal resistance determination of the insulated region requires a hot-box test with known thermal insulation to determine heat flow through the framing. Factors that affect the result for the hybrid insulation assembly will be discussed along with results obtained using the ASTM C1224 protocol. The thermal resistance obtained using the hot-box apparatus will be compared with calculated values obtained from published correlations. The uncertainty in the hybrid insulation assembly and the enclosed reflective airspace due to uncertainty in the thermal resistance of the calibration material are of particular interest.