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Can Romex Touch Insulation? 5 Tips On Using Romex Correctly

A person with a tool belt and gloves carrying wire cables.

Making changes to your house or building an entirely new house can be one of the most stressful things to experience. When Romex wires and boxes have been used throughout the area, it’s important to know whether or not you can safely use the different types of insulation you have.

You can use any insulation with Romex cables, just be sure that they have been pulled properly and terminated in boxes. No wires should be unconnected before putting in the insulation, ensuring that the insulation does not catch on fire due to the open cables.

You will need to know several things before starting to insulate over Romex, ensuring that you can sleep safely at home. Many assume that everything will be fine, only to find themselves having to deal with hidden-away cables behind insulation layers. Insulation is imperative, read more about why you should never skip attic insulation in my article here.

What to Consider When Insulating Around Romex

There are five things that must be considered when using Romex cables and adding insulation to the house (sold on Amazon). Each tip ensures the best possible experience. We always recommend considering these things when making changes to a home or building a new one.

Many people have started to build and renovate their own houses and apartments, so understanding what can and can’t be done is more important than ever. We always recommend understanding what to do before insulating, since it may be necessary to undo everything to connect one wire.

#1: Cable Spacing

It should go without saying to not spread the cables throughout the wall to hang loose and wild. Instead, the Romex cables and boxes should be grouped with only the necessary cables, leaving the bundles to connect to switches and plugs as needed.

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If there are cables hanging loose throughout the wall before adding insulation, it could damage them. We always recommend keeping the cables together and passing them through the right routing holes before adding insulation.

#2: Routing Cables Before Insulating

Something we have only encountered once or twice was someone adding insulation to their house walls before adding all the cables. We recommend routing all the cables throughout the house before doing the final insulation.

Have the cables in place before the insulation, so no damage will be done to the insulation or the Romex cables. The insulation makes it difficult if there is a scheduling issue and the cables aren’t done first.

#3: Leaving Extra Cable Length

If routing the cables on your own or checking over the work being done by the electrician, ensure the cable is not pulled taught. This is a first-time mistake for many installers, causing problems when the house moves and relaxes.

Leaving some cable length in the wall ensures you are never quite at the limit of what can be done with the cables. Many electricians even leave spooled cables inside the wall to ensure they can move plugs and switches around without adding or splicing more cables.

#4: Pressure Applied By Spray Insulation

For spray-on insulation, ensure that the Romex has been fully secured and connected first. Spray-on insulation expands immediately after it has been applied, pushing into nooks and crannies, and molding around everything on the wall.

When spray insulation is expanding it can move the cables around, with the heat from the insulation causing more problems to deal with.

Spray insulation does a wonderful job of controlling the temperature in the house but it is recommended to use truncating instead of just normal Romex.

#5: Heat Caused By Multiple Romex Cables

The next problem is electrical once the insulation (which can be found on Amazon) has been installed, whether:

No matter how thick the insulation is on the Romex cables they will naturally heat up when used, even when they aren’t shorting.

This is why cables should never be grouped together and then completely enclosed; allowing some air to travel along them is the safest choice. Insulating too tightly around cables increases the chance that the Romex melts or that a short circuit causes a fire within the insulation.

Cable wires laid over pink insulation.
Never insulate too tightly around cables

How To Insulate Around Romex

Now that we have the basic suggestions for insulating over Romex, look at how to insulate around Romex. There are several things to consider, especially since the cables are in different sizes and shapes as necessary.

Everyone should be aware of these suggestions, to ensure that the Romex is loose but also tight in all the right places. Don’t assume that putting in Romex cables will be easy and done, with no special requirements or considerations.

#1: Create A Good Space

Be sure that there is space for every Romex cable before putting in the insulation. Just like making space for the beams and support structure, the insulation also should have space for the cables.

This ensures that any shorts or sparks won’t affect the insulation, and leaves space for future cables. It can be a problem when the insulation is so tight around cables that they cannot be pulled through or adjusted once everything is closed up.

#2: Route The Cables Before Insulating

Once it’s known where all the boxes for switches and plugs are within the house, route all the cables before putting in the insulation. This makes room to put in more cable than is strictly needed. Romex recommends having everything ready before installing the insulation.

Many people assume that cables can be rerouted after the insulation has been installed or even routed over the insulation. However, this is not true and usually causes more issues when the insulation has been cut to fit perfectly in the wall only to be recut to make space for cables.

#3: Create A Space For Connections

When building onto the house, usually adding one or two new cables is sufficient. However, when remodeling or building a whole home, the sheer number of cables that need to be connected can be overwhelming.

It’s necessary to create connection boxes for the cables within the walls and create connections with new cables for the rest of the house. The insulation will need to work around the connection boxes, ensuring they are stable and there is room to add more if needed.

#4: Insulation Should Be The Second Last Thing You Do

Insulation is the step that marks the project as nearly complete, so it should wait until right before the drywall goes up. Don’t make the mistake of trying to get the insulation up too soon prior to completion.

As the plans and shape of the project change, it causes issues if the insulation needs to be cut into or have parts removed. We recommend leaving the insulation until the very last moment, to be sure the walls are as ready as possible before closing them completely.

#5: Put Down Extra Cables

Something that we always recommend doing is adding extra cables to the wall before getting the insulation installed throughout the house. Many modern builders put down thin wires that run throughout the house specifically to allow for more cables to be added later.

When using Romex, we recommend adding wires to areas and rooms that are likely to change as you grow into the space. Having some extra cable in the wall will ensure a new plug or switch can be installed in minutes.

A plug being installed in a home.
Extra cable allows for new plugs or switches


Romex can easily handle being covered by insulation, as long as all the proper considerations have been taken. Be sure there is some extra cable in the wall and the insulation does not completely push the cables into a corner.

Remember that Romex is made to work alongside most insulation and can safely be used without issue.

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