Today let’s discuss some of the key considerations when applying spray foam insulation.
First and foremost, the application of spray polyurethane foam insulation is temperature sensitive. And there are multiple temperature parameters that will affect the application and quality of the spray applied material; these include ambient temperate, substrate temperature and chemical temperature. Before the actual application begins, make sure to verify that the ambient air and substrate conditions meet the parameters recommended by the SPF manufacturer. The manufacturer’s technical data sheet and application guidelines will provide guidance for the various temperature parameters.
Additionally, most of what we discuss is high-pressure SPF, which is applied with equipment that can create tremendous pressure. Once again, different formulations from different manufacturers will have varying recommended application pressures depending on the type of project and the desired outcome. And manufacturers, particularly with open cell foam, may recommend mixing, recirculation and possibly heating of the polyol material to prepare it for application. Make sure to follow the manufacturer’s application guidelines closely.
When it comes time to pull the trigger and spray foam into a cavity, on a wall or in or on a roof, there are several application techniques that are typically used. This article is not intended to be all encompassing, but here are a few of the commonly used methods, which includes picture framing a cavity, filling a cavity from stud to stud with a fan pattern and feathering/fanning foam onto a flat surface, like a wall with no studs or a roof.
Picture Framing a Cavity
The picture framing technique is similar to the coloring method of outlining that we all learned as children, first outline the edges and then fill in the middle. You start with the outside edges of the key area and in a cavity that is where the studs meet the sheathing. The first step is to spray apply liquid material around the perimeter of the cavity in such a way that it adheres and seals to both the stud and a portion of the back sheathing. Once you have completed the “picture frame” of the cavity, now you fill in the middle of the cavity with foam. During this step some applicators with use a z-technique, which is a side to side sweeping motion, and others will start at the bottom and spray straight up the middle to fill in the cavity.
Fan Pattern
The fan pattern technique can be very fast when mastered. It is intended to apply liquid material directly to the sheathing and back edge of the studs with a simple motion from bottom to top. A cavity can be filled with one or two passes in this manner but the speed of the applicators moving arm is critical to control the thickness of each pass.
Feathering/Fanning
The feathering or fanning technique is most commonly used with closed cell foam, for example medium density spray foam applied to the exterior of a concrete wall or high density foam applied to a roof. The intent to create as smooth of a finished surface as possible by “feathering” the continuous, back and forth passes together to create a seamless, monolithic application. A key rule of thumb for this type of application is to follow the wet line and overlap continuous passes by 60-80%.
Next, Thickness is a critical factor in every application of spray foam insulation because the thickness has an impact on the insulation’s physical properties, including R-value, air barrier performance and vapor permeance qualities. However, possibly even more important for the SPF contractor and applicator, the applied thickness of spray foam insulation will have a direct effect on the quality of the finished product.
All SPF materials are created by a series of timed chemical reactions, some of which create heat and others that are temperature dependent. You probably understand that as more liquid material is applied in a single-pass, the final thickness will be greater. There is also another correlation, the more liquid material applied in a single pass the more heat that is created by the reacting materials.
Guide your production teams with these techniques and help them improve their skills.
