Does Expanding Foam Damage Wires?

Expanding foam and electrical cables don’t always go well together. This can be an issue, as a product like Tytex expanding foam is ideal for insulating hard to reach areas. However, it’s an issue that can be resolved with a little planning and preparation.

Here at Adkwik we’ve been supplying the construction industry with expanding foam insulation for many years. We offer good quality products backed up by reliable and efficient service, which is why our customers stay with us. So read on to discover how to use expanding foam safely in areas with electrical cables.

The problem with expanding foam and electrical cables

Expanding foam is perfect for insulating between joists in a tight roof space. The problem is, these spaces often have electrical cables running through them. And ironically, it’s the efficiency of expanding foam that creates the issue.

The electrical wires used in construction are already insulated within a PVC sheath. The flow of electrical current causes the wires to heat up, but with air around them this isn’t a problem. However, expanding foam would effectively ‘double insulate’ the wires, preventing the heat from escaping.

This could result in the wires getting too hot and melting. That in turn could cause a power failure, or even worse, a fire.

Larger cable

So how do we make expanding foam and electrical cables compatible, and ensure that wires don’t overheat? One option is to use larger cable. Electrical wire size is based on the thickness needed to carry electrical current safely. To reduce costs, cable is typically manufactured to the smallest acceptable size.

Using larger cable will reduce the amount of heat that’s generated when electrical current passes through the wire. This makes it safer to use alongside expanding foam insulation.

Using conduit

Passing electrical wires through conduits is another way of minimising risk. Placing cables in conduits is commonly recommended, as it helps to protect them from damage. When insulating with expanding foam, it also leaves space for air to circulate around them, reducing the risk of overheating.

The type of conduit used can be metal or plastic, rigid or flexible. The easiest and most cost-effective to install is flexible metal conduit. However, a rigid metal conduit provides the best protection against damage.

Threading electrical cable through conduit can be a time-consuming task, but pre-wired flexible metal conduit is available. Non-metallic tubing supplied in rolls can also be used.

Avoiding wires

A third option when insulating with expanding foam is to leave a channel for the cable to run through. To make this easier, it’s recommended that cables are fixed in place using appropriate staples. You can create a channel by leaving a gap of around three inches on each side of the wiring. However, the actual spray area will need to be wider than this to allow for the foam expanding.