Can a Junction Box Be Covered by Insulation?

Electrical boxes are not just ugly to look at, they also pose a threat to those around; especially children. Covering these boxes is permissible in the National Electrical Code with wooden boxes, so long as they are accessible; i.e., the box can be opened. However, NEC only talks about this if the box is located outside your house.

What if the box is located in your attic or the basement? Old houses have these boxes in the basement, while some designs call for the same to be in the attic. What then? Can a junction box be covered by insulation?

The answer to this isn’t present in the NEC, but other code check books that state that conduit or other insulation enclosures can be installed in a way that the electrical box is accessible without having to remove any part of the structure, or excavate any ground around it. However, that’s not all. In this article, we will dive into the numerous intricacies of covering a junction box by insulation.

Can a Junction Box Be Covered By Insulation; The Code

All NEC says about covering junction boxes is that it should be accessible. If we want to answer the question on whether we can cover it with insulation or not, let us first consider Article 314.29 of NEC (2014):

314.29 Boxes, Conduit Bodies, and Handhole Enclosures Need to Be Accessible. Any box, conduit, or handhole enclosures installed on top of junction boxes or have wiring contained within must be accessible without removing any part of the building or structure, without handling any underground circuits, or without excavating sidewalks, paving, earth, or other substance that established the finished grade.

Article 314.29, NEC 2014.

To translate the excerpt above, this suggests that no matter what you install, it needs to be accessible without you having to remove any part of the building or your house’s structure, dig around it or mess with any underground circuits to reach it.

But what about insulation? Does it fall under the category of your house’s (or building’s) structure? For that, let’s consider what the Electrical Inspections of Existing Dwellings suggests. The book we mentioned is what home inspectors use when they need reference material. According to this book: 

Junction boxes can be covered by insulation in such a manner that it can be removed without damaging it to access the box. Foamed-in-place insulation isn’t removable and therefore not permissible.”

Electrical Inspections Of Existing Dwellings

This shows that if you’re going to cover a junction box with insulation, make sure it remains accessible.

Accessible; What Does It Mean?

Can a junction box be covered by insulation?
A junction box with various wiring being terminated inside.

The codes mentioned above, both suggest that the junction box must be accessible if you’re going to cover it by insulation. But what does accessible mean? According to the NEC, accessible means:

“Accessible in terms of insulation around junction boxes mean anything that can be removed, unwound, or exposed without having to damage the building, structure, or the finish around the object. Furthermore, the box must not be permanently enclosed directly or indirectly due to the insulation.”

NEC

This suggests that you must be able to remove the insulation around the junction box without damaging the insulation itself or the junction box, for that matter. This is the reason foamed-in-place insulation isn’t allowed near junction boxes. These insulations harden up and in order for electricians (or you) to reach the junction box, you will have to break or tear the insulation up.

In our personal opinion we would suggest that before you cover the junction box with insulation, you should considering installing access panels in the ceiling that open directly to these concealed boxes. You can cover those access panels with insulation, thus remain on the safe side. Just remember to mark the box’s location.

Not covering junction boxes at all isn’t recommended, either, so if you’re going to do it, why not take a route that is safer for you, inspection- and otherwise?

What If I Don’t Cover a Junction Box by Insulation?

The lack of insulation around your junction box can lead to several problems; particularly rust on the contacts. This is because your junction box is then exposed to the elements such as cold air and moisture; even if it’s in the attic.

Your junction box is going to run hot and therefore warm the air around it. When the cold attic air comes into contact with the warm air, it will lead to condensation on your junction box and thus introduce moisture into the system. Best case scenario; you will need to replace the contacts or do maintenance work on them more often. Worst case; fire.  

Best Insulation to Cover Junction Box

A simple Google search on the internet will show that foamed-in-place insulation is quick and easy to install, but as we mentioned above, it isn’t permissible since the box isn’t accessible anymore. So, which insulation to use?

The best insulation to use around your junction box, in our opinion, is the fiberglass insulation:

Insulation in a Wall
Insulation under a wall.

There is no ambiguity with regards to this insulation, either; it’s allowed. This insulation inhibits air exchange and therefore doesn’t introduce moisture inside; thus protecting the junction box.

Furthermore, it is fire resistant and is known to smother fires because of its glass content. We recommend avoiding fiberglass insulation that has batts backed with paper or foil. Batts made out of paper or foil can burn easily.

Summing up, you can cover a junction box by insulation, so long as you do it in such a manner that it is accessible. Here, accessible means that you can read the contacts and do regular maintenance or repair without having to tear the insulation or anything else around the box.

About Charlie D Paige

Charlie is a massive DIY fan, with dozens of DIY projects under his belt - ranging from tiling to electrics, and concrete pads to walls. Charlie loves tinkering, seeing how things works, the outdoors and playing with power tools... so is it any wonder that he's completed so many DIY jobs over the years?

Charlie loves spreading his hard-won DIY experience with the world via this blog.