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Foam plastic thermal insulations have substantially replaced traditional insulations in low sloped roofing systems in North America. Foam plastic thermal insulations used in low sloped roofs are low density (typically 16–48 kg/m3) materials with low permeability to air and water vapour. In many roofs these materials have been directly substituted for traditional (wood and glass fibre) insulations without due attention to the different material characteristics. Moist air movement within roofs,condensation protection (air and vapour barriers),steel deck corrosion,roof membrane blistering and roof traffic damage are discussed. This paper discusses protection of foam plastic thermal insulations in roofing systems, why the protection is needed,and what consequences result if these materials are not protected. Case studies demonstrate the importance of condensation protection in reducing corrosion of galvanized steel in roofs containing closed cell phenolic foam roof insulation in Canada.

The results indicated that commonly used foam plastic roof msula tions will be damaged if exposed to foot traffic, and that their protection with fi brous overlay boards as recommended by roofing contractor associations [1,2] con tinues to be good roofing practice. The results also indicated that finished roof surfaces will be damaged if exposed to frequent roof traffic and that surface protec tion of the membrane is good roofing practice.

As industry began to evaluate CFC-replacements, it became apparent that foam performance characterizations have been based primarily on empirical evidence collected over a long period of gradualimprovements. Much of the existing wealth of knowledge was simply not applicable to new systems. The development of new products with CFC replacements requires understanding how formulation variables(polyol, isocyanate, blowing agent, catalyst) and manufacturing conditions affect foam properties, how conditions in use affect foam performance and how the process of sample selection and testing may be used to provide feedback to design improved foams., Also presented at the World Congress : Polyurethane '93

When sprayed polyurethane foams are fabricated under field conditions, they usually form a continuous layer that controls the flow of heat, air and moisture through the building component they cover. However, the replacement of blowing agents such as chlorofluorocarbons (CFCs) with partially halogenated hydrochlorofluorocarbons (HCFCs), which have thermal insulating performance inherently lower than that of CFCs, has raised the question of the long-term thermal performance of such foams.

Methodology for the evaluation of long-term thermal performance of cellular plastics is being developed under a collaboration of North American foam industry with the National Research Council of Canada. The mechanism of this collaboration includes a joint research project between the Society of Plastics Industryand the NRC Canada. To evaluate long-term thermal performance (LTTP) of cellular plastics the agingprocess must be accelerated. This can be done either by means of elevated temperature or by the use of thin layers of the foam. The first approach changes the permeability and solubility coefficients of different gases to such a degree that predicting the foam performance under field conditions is difficult.

Thin specimens of cellular plastic insulations are used in thermal resistance and gas diffusion property measurements. It is known that several cells on the surfaces of the test specimens are destroyed during specimen preparation. Hence the effective thickness of the test specimen differs from the geometrical thickness and proper corrections are to be made for the thickness of the destroyed surface layers before other properties are calculated. This note presents an apparatus, its operating principles and an experimental procedure to determine the thickness of destroyed surface layers of cellular plastic insulation test specimens.

One of the techniques used to determine aging of gas-filled cellular plastics (GFCP) is to correlate the thermal resistance of thin material layers with that of full thickness boards. Either models of aging or scaling factors may be used for this purpose. This paper discusses the concept of scaling factors relating aging of thin and thick layers of GFCP, and points out their limitations.

Moisture gains of three closed cell and one open cell foam plastic insulation were studied in the laboratory. The purpose of the study was to investigate the relationship between rates of moisture gain and temperature-moisture environment under laboratory conditions.

The thermal properties of polyurethane foams vary during service life depending on environmental conditions, the manner in which they are enclosed in the building partition, or if covered with facing membranes during their production. The effect of facing materials on thermal performance of the composites range from a slight improvement of dimensional stability to a substantial reduction in the rate of loss of thermal resistance. Faced polyurethanes should be tested as composite materials, using a method that simulates performance conditions as closely as possible. Such a test method should include determination of cell gas composition as a measure of the aging process. Determination of cell gas composition after a period of exposure to different service conditions would allow an approximate correlation of laboratory results with in situ performance. The paper gives background information on effects of environmental factors and aging simulations on thermal resistance of polyurethanes and provides a starting point for discussion of the testing method., Symposium on Thermal Insulation Performance: 22 October 1978, Tampa, FL. USA

The moisture accumulation in a number of sprayed-in-place polyurethane (PUR), extruded polystyrene (XEPS), and phenolic foam insulations under a temperature gradient has been measured. The temperature dependence of the water vapor permeance of the XEPSs and the phenolics has also been determined. Field measurements on the accumulation of moisture in sprayed-in-place PUR in a wood frame wall of a test building exposed to an Ottawa winter has shown no significant moisture accumulated in the foam when the sheathing on the cold side of the insulation was permeable to the transmitted moisture., Polyurethanes 88 : Proc. SPI 31st Annual Technical/ Marketing Conference: 18 October 1988, Philadelphia, Pennsylvania, USA

A committee of manufacturers, applicators, users, and concerned interests was charged with writing a Canadian standard for urea formaldehyde (UF) foamed-in-place thermal insulation. The findings of this committee and of the research that it commissioned are presented herein. The integrity of the material was found to be retained after several years' service, but installation techniques need drastic improvement. Available data suggested that the linear shrinkage of UF foam installed in wall cavities could be expected to stabilize at about 7 percent. The magnitude of the shrinkage, equivalent to 21 percent by volume, was estimated to reduce the effective thermal performance of the material to 60 percent of that which would have been realized had there been no shrinkage., Symposium on Thermal Insulation Performance: 22 October 1978, Tampa, FL, USA

Components of the research program jointly sponsored by the Institute for Research in Construction, National Research Council of Canada, and the Polyurethane Division, Society of the Plastics Industry of Canada, are described. The program is designed to improve the means of evaluating and comparing the value-in-use of various residential thermal insulation materials and systems. To assess value-in-use of insulations such as glass fibre, cellulose, and spray- applied products of which sprayed polyurethane foam is one, the performance of the building envelope as a system, in addition to analysing the materials and components, will be considered. Elements of the program will include: -- thermal and energy performance, -- contribution of the insulation to the air and vapour barrier performance of the envelope system,-- interaction with other building components, -- changes in the material performance with time.

During the service life of gas-filled cellular plastics ( GFCP), air diffuses into the foam cells and the gaseous blowing agent diffuses out, each at a rate that depends on the type of polymer and temperature. This process, which reduces the effectiveness of insulation, is known as aging. This paper presents a model for calculating the thermal resistance of the GFCP slab as a function of time. It incorporates the effect of phase changes (condensation and evaporation) in the gaseous blowing agent and the use of material characteristics (diffusion coefficient) varying in the cross-section of the GFCP slab. The results are compared with measurements., Also published in Improved Thermal Insulation : Problems and Perspectives

Water vapor transport through rigid polyurethane and polyisocyanurate foams was investigated using three test methods--two under isothermal conditions and one in the presence of a thermal gradient. All three methods yielded water vapor transmission coefficients of the materials. It is observed that the magnitude of the coefficients increases rapidly with temperature above 20 deg. C. In one of the isothermal methods called a modified cup method, developed at the Institute for Research in Construction, only the temperature has to be controlled and this is considered a definite advantage over the other method, ASTM Test Methods of Water Vapor Transmission of Materials, (E 96-80) dry cup method, in which both temperature and relative humidity are to be controlled. Further, the modified cup method also allows the determination of moisture accumulated in the test specimen during moisture transport. It was conclusively shown that during isothermal transport processes no moisture accumulates in either the polyurethane or the polyisocyanurate specimens. The accumulation and distribution of moisture in the presence of a thermal gradient was also investigated. Contrary to the isothermal process, the moisture transport in the presence of a thermal gradient acting in the same direction as the vapor pressure gradient results in the accumulation of large quantities of water in the foams. This phenomenon may be partly attributed to the temperature dependence of the water vapor transmission coefficients., Water Vapor Transmission through Building Materials and Systems : Mechanisms and Measurement : Symposium: 10 December 1987, Bal Harbour, FL, USA

Increasing amounts of insulation are used in buildings to conserve energy. In buildings of noncombustible construction, insulation is usually placed in the wall cavity with or without an air space. The use of foamed plastic insulation has been restricted due to its combustibility characteristics when tested by methods adopted for regulatory purposes. A series of tests on foamed plastics and con ventional insulation materials show that these methods do not realistically assess the fire performance of foamed plastic insulation when used in cavity walls.

This paper describes a method for measuring gas diffusion through cellular plastics A specimen is placed in a chamber, which is then scaled and pressur ized with the test gas. The pressure increase causes some gas to enter the specicmen, and this entry results in a reduction of the chamber pressure By following the change in chamber pressure with time an appropriate transport characteristic for the material is determined An application of this method to a core specimen of an extruded polystyrene board is presented.

This report presents a joint project of the Society of the Plastics Industry and the Institute for Research in Construction of the National Research Council of Canada. The objectives of this project were to manufacture two spray polyurethane foams bases on the existing industrial technology but using alternative blowing agents, compare the properties of these foams with those blown with CFC-11 and establish a basis for development of new polyurethane spray foams with alternative blowing agents. The following properties were examined: thermal resistance, dimensional stability, compressive strength, water vapour permeance, blowing agent concentration and effective diffusion characteristics. This study combined advanced industrial and academic research, predicted 25-year thermal performance from 3-4 months testing results and characterized foams with selected thermal, moisture and mechanical properties.