Spray Foam and Sprinkler Pipes


There seems to be a surge of stories about spray foam being incompatible with CPVC sprinkler pipe.  There have been numerous reports and studies done on it.

Bressler Insulation offers this observation on the matter.  Bressler Insulation has not provided any testing and this observation is based on our personal experience and is presented without guarantee.

CPVC pipe is Chlorinated Poly Vinyl Chloride and is a common product used in fire sprinkler pipes.  There have been reported cases of the CPVC pipe failing when used in conjunction with spray foam.  The failure of the pipe has been stated to either to be caused by Environmental Stress Cracking (ESC) or by being exposed to elevated temperatures from the foam application.    Additional problems can arise from the use of low temperature glues for the fittings or by the movement of insufficiently blocked pipe.

It has been suggested that the vegetable oil or phosphate esters in foam can cause ESC.  CPVC is typically not compatible with certain vegetable oils.  Most foam manufactures have formulated their product so this is not an issue.  Phosphate esters in fully cured foam have been tested and not found to be an issue. 

               While fully cured foam appears to not to have an impact on Environmental Stress Cracking, it is possible that foam, which applied off ratio and not cured, could have a long term effect on ESC.

The most common and well-known cause of CPVC and spray foam failure is from excessive heat build during the foam application.   This has been well documented although the exact temperature at which there is a system failure remains unknown.

Every brand of foam has its own exclusive formula and the temperature at which it reacts vary.  However the basic chemistry remains the same for all of them.

Spray foam is exothermic, creating heat during its chemical reaction.  The thicker the foam is applied the hotter the reaction becomes.   Foam that is applied way too thick can have the ability to self ignite.  Foam sprayed thicker than suggested can char, where it turns brown or black, but does not self ignite.  Charred foam loses its physical and insulative properties and it is unknown if this affects the ESC on the pipe

Normal closed cell foam applied in around a 2” thick pass will have a temperature of around 200 degrees.  The self-ignition temperature of foam is around 800 degrees.  Somewhere in between is the temperature of charred foam. 

Installing thicker layers of foam are often advertised by the manufactures as a cheaper way to install the foam with less labor, as the foam will not char at those thicknesses.  However this does increase the temperate of the foam considerably.

               As most CPVC piping is rated to around 200 degrees, the application of thicker passes of foam can become a heat issue, compromising the pipe and causing bursting.

Adhesives used in the joints can also add to complications.  Low temperature rated adhesives can be compromised when exposed to heat.

Pipe movement is another major concern.  Pipe that is not blocked about every 4 feet will move with the foam application putting stress on the connecting joints.

Many 10’s of thousands successful foam/sprinkler pipe applications have been made.  These applications have a common bond.

*Sprinkler pipes are installed as close to the interior surface as possible reducing the need for large foam build up around them.

*Roofs sprayed from above require baffling over the pipes to reduce freezing.

*The foam around the pipes is applied in thinner lifts.

*The pipes are properly blocked about every 4 feet.

*Higher temperature adhesives are used.

*The foam is on ratio and properly applied.

There are a variety of sprinkler pipe materials that are used.  Some are dry charged, some have a glycol system, some are water charged.  Some roof systems are foamed down onto requiring the sprinkler trade to baffle their piping.  Sprinkler located in unheated attics may need to be addressed.  Piping that is ran in the middle of joists will require the sprinkler trade to install baffling to prevent freezing.

               We are always happy to do an onsite walk through of the project with the sprinkler trade before work begins to ensure that the project gets done in the owner’s best interest.