Understanding What Affects The Coverage Rate Of Spray Polyurethane Foam

Understanding What Affects The Coverage Rate Of Spray Polyurethane Foam 

Spray polyurethane foam is a monolithic insulation used in residential and commercial buildings. The product is composed of two parts: isocyanate (Part A) and resin (Part B), which form an insulating foam when they are sprayed. 

Product performances are rated per CAN/ULC-S705.1 standard, while installation performances are rated per CAN/ULC-S705.2. In fact, since the insulating foam is made during installation, medium-density spray polyurethane foam (2 lb) such as SOPRA-SPF 200 and 200 LT must be installed by certified installers. Proper installation of the product is very important to ensure a quality result. 

Several variables influence the coverage rate of spray polyurethane foam, which is not specific to a product but to the technology. Among the most important variables are the following: 

1. The temperature and type of substrate; 

2. The density of the product;

3. The equipment and installation. 

The Temperature and Type of Substrate

The temperature will affect the coverage rate of the product. The colder it is, the lower the coverage rate will be and conversely, the warmer it is, the higher the coverage rate will be. This is explained by the fact that the blowing agent expands more in heat than in cold. Following this same logic, the winter version of a product is expected to obtain a slightly lower coverage rate than the summer version as the product is installed in colder conditions. 

The capacity of the substrate to be affected by the outside temperature will also have an impact on the coverage rate. For example, ambient temperature has a greater impact on metal and concrete than on exterior gypsum panels (e.g. DensGlass Gold® and Securock®) and plywood. The coverage rate will be affected positively if it is hot and negatively if it is cold. 

Also, substrates that do not have a regular surface such as brick or concrete require more material in order to obtain a uniform finish. This could have an impact on the coverage rate since the installation will require more material to fill these irregular surfaces compared to smooth surfaces. 

Finally, the number of coats will also influence the coverage rate. As the subsequent layers are installed on a first layer of spray polyurethane foam at a temperature that is usually warmer than the substrate, this will allow for better performance on subsequent layers. The installer will therefore use more material if they make thinner layers or even a single layer instead of two. 

The Density of the Product

Density will impact the coverage rate and LTTR (long-term thermal resistance) of the installed product. The lower the density, the higher the coverage rate will be. However, the performance of the insulation (LTTR) could be negatively affected if the density is lower than what is found in the technical documentation of the product. It is therefore important during installation to obtain a density that comes as close as possible to what is listed on the technical data sheet in order to ensure that the adequate thermal performance is achieved. To validate the density of the product on the construction site, it is recommended to do a few density tests during the installation. 

The Equipment and Distance Between the Installer and the Substrate 

The equipment and the installer have an impact on the coverage rate of spray polyurethane foam. 

Indeed, a smaller mixing chamber, which is used in order to achieve more precision during installation, will provide higher coverage. Usually, greater precision also means it will take longer to complete the installation. The use of this type of mixing chamber is required for situations where the installer must be more precise, such as in a restricted space. A larger mixing chamber will be less accurate, and therefore will save installation time. However, it will provide less coverage. This type of mixing chamber will be used, for example, to install the product on a large exterior surface where there is not necessarily a need for precision. 

The distance between the installer and the substrate will also influence the coverage rate. The blowing agent included in the product being a very volatile material, the closer the installer is to the surface, the less the blowing agent will have the opportunity to escape into the ambient air. Conversely, the farther the installer is from the surface, the more volatile the blowing agent can be. As this material allows the expansion of the foam, the blowing of the foam and therefore, the covered surface, will be impacted if it escapes into the ambient air. This is even more true on job sites with windy conditions or others that could affect the product between the moment it comes out of the gun and the moment it hits the surface. 

In conclusion, the installation of spray polyurethane foam is not an exact science but rather an art that installers learn to master with experience. You just need to find the right balance in order to obtain a quality result!