Can I Tap Into Existing Ductwork for Basement Heat?

A home’s basement can provide additional space for use as a gym, office, living room, game room, apartment, or bedroom.

The finished space may be completely or partially underground. Either way, the typically-concrete walls provide a damp and cool environment.

During the summer, that might be appreciated as temperatures rage outside. However, in the cooler winter months, the basement can quickly become uncomfortable or even unbearable. Inasmuch, you’ll need to find a way to provide heat to the space.

Your first thought might be to tap into the existing ductwork, and that may be a very viable option. However, there are myriad factors in deciding whether that’s the best course of action. Let’s consider the types of heating options, what it takes to duct heating to the basement, and whether it’s a good choice for your space.

Step 1 - Consider the Needs of the Basement

What do you plan to use your basement for? Will it be a frequently-used space or somewhere that’s only inhabited occasionally? If your basement will be part of your everyday living space, moderating heating and cooling will be essential.

However, if you’ll only be down there once in a while, a temporary heating solution, such as space heaters, can save you a ton of money and hassle.

Step 2 - Codes and Regulations

If you’re already undergoing any type of basement remodel, you’re probably familiar with the building codes that guide the project. There’s nothing new about applying for permits and scheduling the inspector when it comes to figuring out the heating too.

Because an improperly installed system can result in fines and perhaps even having to redo the work, it’s essential you check with the local building department at the planning stages rather than mid-project.

Knowing what the codes are can help you plan and lay out the ductwork, vent registers, and required insulation, among other aspects of the project. Remember the regulations are in place both for your safety and for energy efficiency, so pay your fee and listen to the experts on this one.

Step 3 - Evaluate Alternatives to Central Heat

Although tapping into your current system might be the first thing that comes to mind, it’s not always the best solution. So before we discuss the ins and out of expanding your ductwork, let’s talk about a few other options.

Space Heaters

Yes, the basic units that simply plug into the wall. Space heaters can be a very effective tool for, as the name suggests, heating a space. They are particularly effective in small spaces.

You can place a few throughout the basement and also make a space smaller by adding heavy curtains or room dividers, so the space heater does a better job of heating the area. Do be careful how many space heaters you put on the same circuit. You don’t want to cause an overload.

Also note space heaters can be a fire hazard, both by overloading a circuit and if they come into contact with textiles. Be sure to use a space heater with a tip sensor that automatically shuts it off, and keep it a safe distance from curtains and furniture.

Ductless Mini-Split

Mini-split heaters mount to the wall and duct directly outdoors. They are called ductless systems because they skip the need for ductwork, which makes them less labor intensive to install.

This type of system allows you to place units in spaces where heat or cooling is needed. This target approach saves you money since the central furnace is heating the entire space in order to warm a particular area. The upfront installation cost is substantially more for a mini-split, however.

A ductless may be an ideal solution for a basement, since it’s effective at heating and cooling a single space, but not an entire house. This is only true if you have a way to run the required system elements out through a basement wall.

Radiant Floor Heating

If you’re figuring out options for heating the basement during a remodel or renovation, consider adding heating to the floor.

This isn’t an ideal solution for a retrofit simply because it’s expensive to rip up existing flooring. However, radiant floor heating can make the space considerably more comfortable both underfoot and in the ambient temperature of the space.

Baseboard Heater

Perhaps not the most efficient for overall home heating, a baseboard heater might be the ideal solution for a single room space in the basement.

Baseboard heaters are easy to install and cost very little compared to other options. The overall less-efficient design, however, will cost you more in energy costs than other options.

This option also skips the need for ductwork since they work by drawing cold air up from near the floor, heating it, and allowing the heated air to naturally rise, warming the room (or at least the surrounding area).

Some baseboard heaters are hardwired into the home’s central electrical system, while others plug into an outlet like a space heater.

Also similar to space heaters, baseboard heaters can be a fire hazard, so be sure to keep furniture, curtains, and other flammable materials away.

Gas or Electric Wall Heater

Where baseboard heaters are strictly electric, wall heaters come in electric or gas options.

They are convenient for small spaces because they are built into the wall rather than sitting on the floor. However, gas wall heaters can bring the risk of carbon monoxide poisoning.

These units are typically louder than other options.

Wood Stove or Fireplace

You could also consider installing a fireplace, gas stove, wood stove, pellet stove, or other similar fuel source. Wood stoves have been a heating unit of choice for generations. New models, however, are much more efficient than the previous designs that resulted in copious smoke both inside and outside the home.

These systems are very effective at heating a basement space and may even send residual heat to the upper units of the home. Depending on your venting situation, it may be easy to install. The downside of biofuel stoves is the frequent need to source, haul, and load wood or pellets. It can be messy and expensive.

What is Ductwork Heating?

After considering all the options for heating your basement, you decide you want to incorporate the space into the home’s central heating system. What exactly is ductwork heating, though? How does it work?

Your forced air furnace creates a mostly-closed system wherein air is pumped through the furnace, throughout the house, and back to the furnace.

That pumped air runs through metal tubes or corridors known as ducts. The ductwork encompasses everything from the point where air leaves the furnace to the vents in each room that provide an entry space for air to flow into the room.

If you look at your furnace, you’ll see the metal ductwork around it. The same is true if you lift a vent register out of place. Some homes have exposed, or partially exposed, ductwork, while other homes have it almost completely hidden inside the walls.

Since the ductwork snakes throughout the home, it makes sense some of it may be relatively easy to tap into in order to divert air into the basement.

If you’ve ever diverted rainwater from a downspout, it’s kind of the same idea.

Can I Tap Into Existing Ductwork?

So we go back to the original question. The answer is ‘probably’ but not certainly. There are several factors to consider.

The primary consideration is the capability of your current system. Furnaces are equipped with a blower motor that is responsible for pushing the air throughout the system. Blower motors are rated by their capacity to do this job. Measurements are labeled by cubic feet per minute, or CFM.

Your current system may be too large for your current uses. If this is the case, you’re probably good to go for the additional space in the basement. However, if your system merely adequately meets your current demands, it will overtax the furnace to extend the ductwork into the basement.

The more workload you add to your blower, the less efficiently it will function. It’s best to have an HVAC professional evaluate the system to decide if it’s up to the task.

Basically, he or she will consider the rating of the system. Then calculate the number of registers you're currently using. Each vent you add reduces the amount of air that can be delivered to other vents in the home if your blower is being stretched to capacity.

While it’s not uncommon for a builder to have installed a system larger than what’s required for the home, it’s inefficient and considered wasteful nowadays. For this reason, older homes may have a better chance of having a furnace blower that can manage the task than newer homes. Get a professional evaluation to be sure.

How to Tap Into Existing Ductwork

If everything checks out with the furnace and you find you have nearby ductwork that’s accessible to tap into, you can hire a professional to do the job, or tackle it DIY style.

Safety Note—When working with metal, always protect yourself with eye protection and use ear protection when using loud power tools. Also wear a mask when cutting through drywall or handling insulation.

Step 1 - Identify Plan and Install Ductwork

This is easiest during a remodel or renovation. If you’re in the throes of a basement facelift, install the ductwork alongside electrical and plumbing. Once the walls and ceiling are finished, it's a much more labor-intensive job.

One option to make the job easier is to leave the ductwork exposed in the basement. The feature can contribute to an industrial design look. It certainly is easier than enclosing it all. However, you can also consider a drop ceiling option that covers it with less work than drywall.

To configure your system, you’ll need to evaluate the route the air duct will take. Also calculate how many vent registers you will be adding.

With the map drawn out, cut into the existing ductwork at the proper location.

You’ll rely on a series of elbows, connectors, tees, and reducers to build out the ductwork system. How many and what types depend on the layout of your system and obstacles in your home.

The ductwork needs to meet local code, so be sure to check before beginning work.

When using duct sheeting, which is a thick, rigid, boxy material meant to be durable, you will need to plan for corners. Pre-formed corner pieces attach to the straight portions of the ductwork. Measure and cut the straight, rectangular ducting to length up to the point the corner piece will be installed.

Then install the corner piece and continue to the next corner in the same manner, connecting straight lengths together as necessary.

You can also use flexible ducting if it meets code and the needs of the job. It’s easier to work with and will require fewer connections. Be sure to pull the material tight as you work.

Step 2 - Create Holes for Vents

After you’ve identified the locations for your intake vents, carefully measure the length and width of your chosen vents.

Make sure to cut the opening to the size of the actual vents, not to the size of the entire vent. In other words, cut the hole smaller than the vent so the outer part of the vent can attach to the wall via the screw mounting holes.

Double check all measurements and then cut through the wall or ceiling surface to the right dimensions. Once the hole is cut, test fit the vent. Install it when everything is lined up.

Conclusion

Your ductwork is an integral part of your home. It provides heated and cooled air to every corner of the house. If you want it to expand into the basement, you’ll need to ensure your furnace blower can manage it, or you’ll cost yourself hassle and a shortened lifespan for your furnace, which adds up to big expenses.

Find out more about Repairing Heating and Cooling Ducts and check out our Duct Work and Ventilation Q and A for more information. Also get a better understanding of how heat is produced in your home in our article Heating Systems Explained.