Can You Run Ethernet Cables Through Vents in Your House?

When looking for possible ways to run a network cable from one part of a home to another I often come across air vents and duct work as a possible solution. Many people stumble onto this exact same opportunity and wonder if they can run their Ethernet cable through vents.

Ductwork can be a viable pathway to get your network cabling from one part of the house to another but there are a few important things that you should consider before trying it in your own home. First filling your air vents with cabling can make them harder to clean and cut down on their efficiency. Second, a special type of Ethernet cable, called plenum, should be used for this application and it can be more expensive than normal cabling. And finally, a cable popping out of a floor register is not the most professional look. In many cases you can fix this and make everything look nice and professional, but this will take extra work and could turn what was originally thought of as a great cabling shortcut into just as much work as running the cable through an attic or crawl space.

Let’s go over each of these considerations to see if your situation is a good candidate for running your Ethernet cables through the air vents.

Problems Ethernet cables Could Cause in your Air Ducts

One of the biggest problems that installing network cabling, or anything else for that matter, in your ductwork is the negative impact that it can have on your HVAC (heating, ventilation, and air conditioning) system. It is not obvious right away that such a small wire could really cause problems in an air vent, especially when the vent is on the larger side, but the truth is that there are a few different ways that the Ethernet cable can cause problems.

The first major problem that you might run into is probably the most obvious. Depending on the size of the air vent a cable can be enough to get in the way of airflow and make the vent less efficient. Admittedly if you are careful and keep the cable straight and tight throughout the entire duct this should not be much of a problem but I have seen tangles of wire in all sorts of places where they shouldn’t be over the years. Even if the cable is installed well and taking up as little space in the duct as possible there are still other issues that it might cause.

The second thing that you will need to look out for is the fact that as dust and debris travel through the duct they can start to build up on the cable rather than the air filter like they should. This can cause the duct to get dirtier faster and hurt the efficiency of your HVAC system. In addition to a less and less effective heating and cooling system over time dirty ducts can harbor all kinds of particulates including mold. These particulates can increase symptoms of allergies and in some people they can even contribute to more serious health problems.

The last major problem you can have with a cable in this situation shows up when it is time to have the duct cleaned. The National Air Duct Cleaners Association (NADCA) recommends that you have your ducts cleaned and inspected every 3 to 5 years to remove the allergens and other particulates mentioned earlier. Most of the time this cleaning is done with a rotating brush that simply cannot be used if there is a cable in the duct. The cable could either be damaged or else it could become tangled with the brush.

Brushes like these can easily damage cables inside of air ducts.

Even with the issues above there are still some situations where you might want to run an Ethernet cable through your ductwork. Perhaps there is no better option or the cable will only need to stay there for a couple of years so most of the issues I mentioned earlier will not become a problem before the cable can be removed. If these problems will not be an issue for your installation continue reading on and I will touch on a couple of things you should know before you get started.

What is Plenum Cable and Why You Might Need It

It is important to know that according to the NEC (National Electrical Code) all cabling that runs in an air return space must be plenum rated rather than the cheaper  alternatives. You might ask if that really applies to you. The answer is yes. If a contractor were to run a cable through the air vents of a new home being built and they failed to use plenum rated cable it could defiantly fail its fire inspection.

Even if you are not in a situation where a building inspector would cause you problems for using cheaper cabling inside of an air vent I would still recommend that you spend the extra money to use the right materials. The reason that you should use plenum cable in this situation is because there are a few situations where the cheaper style of  cable (often called riser cable) can be dangerous.

The first major concern with riser cable is that it can have carcinogenic plastics in its coting. Only plenum rated cable is guaranteed not to use any of the plastics that may cause cancer so it is not recommended that you put riser cable in a space that mixes with the air you breath all day long.

The second big feature of plenum cable is that is does not burn in the same way that riser cable does. Some of the cheaper cables put off really toxic fumes if they melt or catch on fire. They can also burn well enough to allow fire to travel along the cables and though spaces that would normally be relatively fire resistant if plenum cabling would have been used.

Because of these two safety reasons I would definitely recommend that if you are going to run cabling through the ductwork of your home you use plenum rated cable.

To learn more about plenum check out my article on the subject.

How to Get the Cable from the Air Vent to the Wall

One last thing to think about before you choose an air vent as the pathway for your network cable you should really consider what you are going to do with the cable on ether end of the air duct. Having a cable poking out of your air duct is not the most professional of looks.

A lot of people look to run the cable through vents because they do not want to have to go through the hassle of cutting holes into walls but if you would like to have a nice face plate with an Ethernet port in it you are going to have to find a way to get the cable from the air vent and into the wall. I would really recommend taking a moment to look at your situation. If you go through to work of finding a way to get cable though your floor or ceiling and then up or down your wall will it really be that much more work to find a better pathway for the cable?

If the room you are in is over a crawl space or under an attic the answer is likely no. This is not to say that there are no situations that the vent is not the best option. In fact I have used this method myself before. I will however say that it is often not the short cut that some people hope that it is going to be.

Who Should Consider Options other than Running Ethernet Through Vents

When looking for a pathway for your network cabling it is often nothing more than looking for the option that has the fewest problems with it. I would recommend that anyone who is looking at an air duct as a possible pathway take a moment and look around.

  • Are you in a room over a crawl space?
  • Is there an attic space directly above you?
  • Is there crown molding in this room?
  • Would it be easier better to utilize a closet or utility space?

If there are any options that might work better, even if you think they might be more work, I would recommend looking at them closer. By the time you get a cable through an air vent, into the floor on both sides, and up the walls and into terminations it is very likely that one of the other options would have been about the same amount of work and will end with a much better outcome.

When Running Ethernet Through Vents Might be the Best Option

There are some situations where, try as you might, you just cannot find a better pathway for a cable. The last time I resorted to using an air vent as a pathway was because I could not find a better way to get into a room. It was in the vault of a bank that had thick concrete walls. My team and I ended up running a half dozen or so cables into the room through an air vent for security cameras. We could have rented the tools needed to drill through the concrete but this was too expensive for the bank’s IT department so they agreed to just deal with the problems that come along with having the cables in the ductwork.

You very well could be in a similar situation. In multi-story homes sometimes the only way to get all the way from the basement to one of the upper levels without cutting a lot of holes in a lot of walls is though the cold air return. Maybe the trouble you would need to go through to get a better pathway set up is just not worth it and you would rather deal with the problems that can come up down the road from having the network cabling installed in an air duct.

Another situation where I have chosen to run cabling though air vents in the past was when I was doing so temporarily. I once lived in an apartment where I wanted to run a cable from the living room where we had a router upstairs to my bedroom. Because I was only going to live there for a few years I did not have to worry about dust and debris building up in the vent or having to find a way to clean it with a cable still inside. I also could not cut network locations into the walls anyway because I did not own the property so having a cable poking directly through the air register in my floor really was the best looking option I was going to get anyway.


At the end of the day you know your home and your situation best. As long as you are aware of the risks and problems associated with installing Ethernet inside of air vents it can be a solution that works well for you. It really comes down to whether you can find a better alternative or not.