Correct Angle of Spray

The spray gun should be held perpendicular to the surface of the substrate. Maintain as close to a 90 degree angle as possible when spraying. A different angle may cause elongation of the cells and negatively affect physical or thermal properties.

Consistent Distance

12 to 18 inches is a good distance to maintain between the substrate and tip of the mixing chamber. Spraying closer to the substrate may result in a more inconsistent pattern. Spraying further away may allow for a smoother finish, but more heat is lost in the mix as it travels further in the air. This can lead to lower yield. For the most consistent results, maintain a consistent distance from the substrate throughout the day's application. This will allow for more accurate monitoring of temps and pressures.

Spray Pattern

Round pattern mixing chambers are the most common. They produce a conical shape out of the tip, resulting in a round pattern applied to the substrate. Flat tips produce a fan shape out of the tip, resulting in an elongated pattern applied to the substrate.  Flat tips are allowed but typically have issues with plugging quickly after application. With a clean flat pattern tip, it is possible to spray an entire wall cavity with a single up/down pass. The below application methods are performed with round pattern mixing chambers.

Side to Side

Most common and considered by many as the easiest method. It can be trickier to keep foam off the face of the studs due to the repeated side to side motion. Special attention and practice are also needed to ensure even thickness in the wall cavity. With poor technique, the foam may form a concave or convex shape with shallow areas near the center or edges.

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Up and Down

The up and down method can help reduce the chance of overspray on the face of the studs, due to the single pass up each side of the stud. When mastered, this method can produce a very even pattern in the cavity. It is more often used in closed cell applications, or on wide open substrates. This is a great technique when trying to achieve a more visually appealing finish. With longer up and down motions, this method can result in more fatigue than the side to side method.

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Picture Frame

The picture frame method combines techniques from both of the previous methods. It is usually found to improve performance in cold weather because it allows the material to "bite" on the studs. This method can also be beneficial in elevated moisture scenarios. The initial flash coat around the perimeter can quickly heat the substrate and help with adhesion.

Waste in the spray foam process can occur in several ways:‍

Temperature

Heat aids in the chemical reaction of foam and is your friend when trying to maximize yield and minimize waste. Keeping your equipment and hose at the proper temperature, along with a warmer substrate, will all increase yield and reduce waste. Be certain to follow the temperature guidelines, as excess heat can also cause issues like shrinkage and clogging in the mixing chamber. See Foam Reaction for more details.

Mixing

Like heat, mixing the resin (B-side) chemical also aids in foam yield. Mixing before spraying is very important to get the most out of your chemicals. See Mixing Resin for more details.

Spray Technique

Practice and experience pulling the trigger will allow you to hone your technique and reduce the amount of wasted foam chemicals. This may seem obvious, but can go overlooked. When you have excess foam build-up against the stud sides, or overspray on the face of the studs, this is all unnecessary foam that is wasteful and requires more labor to clean. Aim for a consistent pattern and try not to apply foam where unnecessary. This will make the job look great and help with consistency of yield, thus reducing waste.

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Pro Tip

Follow the sun to reduce waste from heat loss. As we know, heat aids in the chemical reaction of foam. This includes the temperature of the substrate and the ambient temperatures within the spray environment. The eastern side of a building will heat earlier in the day, while the western side of the building will remain warmer later in the day. Use this to your advantage by starting on the eastern side of the building in the morning and following the sun throughout the day.

Overspray is a mist of spray foam that goes beyond the intended area and may be carried by the wind traveling some distance. The mass of the foam is too small to generate enough heat to completely react and cure until it hits a surface, allowing it to travel and attach itself to undesirable substrates.

Proactive Approach

Determine in advance the overspray risk posed by the job. Having a plan in place to address overspray incidents in the event that an issue arises is a good practice. Identify and protect surfaces that could be affected (windows, doors, equipment, or building exterior and automobiles) in advance of the spray application. When in doubt about covering a surface, it is a best practice to cover it.

Overspray is a reality, however the severity and frequency can be mitigated through prevention and engineering controls. This can occur in both commercial and residential applications.

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Interior / Residential Considerations

• Open soffits are a frequent area where overspray can occur. Always stuff or block soffits and make sure no outside light is coming through. Failure to block the entire opening might allow foam to travel outside and attach to windows, wooden porches, or other finished products.
• All personal property and finished products should be removed from the application location and all possible overspray pathways. When this is not possible, all items should be thoroughly prepped, covered with plastic, and monitored through the project duration.
• Also consider the hose route into your spray area. When working in existing homes, it is important to protect the finishes where your hose is being pulled into the attic. Cardboard can be used to protect window ledges and wall corners, along with plastic to protect the floor.

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Exterior / Commercial Considerations

• Spray foam application should never occur at wind speeds greater than 15 mph. Spraying during these conditions greatly increases the risk of overspray damage.
• If a vehicle has come into contact with overspray, a proactive approach is generally the best. Located the driver, determine the severity, and document all possible vehicles in the area.
• Attempting to remove overspray can potentially damage the substrate further. UV degradation will aid in overspray removal, however, convincing a vehicle owner to leave the overspray mist alone is not the easiest task.

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Pro Tip

Use "flags" and "targets" to monitor wind conditions and overspray risk throughout the day. This simple proactive approach can save you thousands of dollars in damage. Consider this for exterior applications, along with interior applications where window and door openings remain open during install. A wind tunnel can occur on the interior of a building, carrying overspray outside.

• Flags made of caution tape can be attached to equipment, building structures, and on scrap wood stakes in the ground. The key is to place multiple flags around the job site, allowing you to monitor wind from different angles. Visibility is key, so make certain these flags can be seen by the sprayer and/or helpers. When the flags are blowing, take the necessary precautions, or stop spraying.
• Targets can be made out of scrap pieces of cardboard or plywood. Paint with black spray paint and place at locations around the job site where spray foam is being applied. The black paint allows for easy visibility of overspray droplets. Multiple targets at varying distances from the spray location can allow you to measure how far overspray is traveling. If overspray is seen on the targets, take the necessary precautions, or stop spraying.