How to install ductwork in existing walls

New Ducts Are for When Patches and Repairs Arent Enough

When we work on ducts, we often repair or replace sections that have become damaged for various reasons. But if your home is old or your duct system hasn’t been maintained, sometimes your entire network of ducts is full of issues. In this case, the best thing to do is to replace all your ducts instead of trying to repair them.


A hole cutter works great in tight spots when replacing ductwork

Aviator snips work fine to cut holes in a trunk line, but only if there’s enough space. If you’re dealing with close quarters and you own a right-angle drill or attachment, you may want to invest in a sheet metal hole cutter. Otherwise you might have to take down the trunk line.

Where Are The Best Places To Put Return Ducts

You are probably thinking since the purpose of a return duct is to suck the air back into the system they should be located right across from the supply vents. This is somewhat true and somewhat not true. Yes, this would be an effective setup, but it doesn’t necessarily have to be done this way.

Installing a return duct in each room where there is a supply vent would be more than feasible but isn’t always the best case. In fact, when installing return ducts it is always advisable to avoid putting them in bathrooms or kitchens. This would just simply cause the heating and air system to circulate cooking odors and moisture throughout the system. This would be a recipe for disaster and bad smells.

When it comes to two-story homes things can get a bit more complex, but the general rule of thumb is to install the return as close as possible to the thermostat. This is the general rule of thumb because it will allow the thermostat to monitor and record the temperature that is being circulated back through the system. In addition to this, the thermostat is usually installed in a centralized location.

Centralizing the thermostat and return duct will mean that you draw circulation and temperature readings from every part of the home. Unfortunately, this might not be an ideal setup for all home designs. In these cases, it might be entirely necessary to install returns in each room of the home except for the bathrooms and kitchen.


Establish a location for the grill. This may be at the ceiling or on the face of another wall. Use the square end of the rigid duct as a guide to mark for the hole in the ceiling or wall finish. Cut the hole with the reciprocating saw. If you encounter framing members, move the location either way so the hole is between the members.

How Cleaning Air Ducts Can Help For Allergies

Throughout springtime and also early summertime, the wind is more likely to kick up as well as blow around various particles. These particles can…


Set up a reciprocating saw with the appropriate blade for the wood paneling or drywall finish. For walls, make vertical cuts at each side of the grill opening, staring at the bottom edges of the opening and continuing to the ceiling. Remove the section of wall finish with a nail bar and a hammer. Skip this step if the grill opening is at the ceiling.

Step 5: Weighing Up The Cost of Installing Central Air Conditioning

Cost is one of the biggest factors homeowners take into consideration when installing a central air conditioner in an older home. If your home already has ductwork, installation is easier and will cost less. If your home needs this done, the cost can double.

With the ductwork in place, installing a new AC system in an old house will cost less. However, the cost can be higher depending on the brand, size of the unit, and the SEER rating. The SEER rating tells you how energy efficient the system is. The higher the rating, the higher-priced the unit will be. However, you will reap the additional cost over time with the money you save on lower energy bills. If you want additional systems fitted, like a humidifier or air purifier, the price goes up even more.

Take your time when selecting the type of unit you want. While cost is a big consideration, now is the best time to consider other factors such as energy efficiency, additional systems that can improve your home’s indoor air quality, and products that offer convenience, such as a smart thermostat. Choosing a good quality HVAC unit is worth the additional cost if it offers a good return on investment in terms of overall comfort and cleaner air. You just need to get the air ducts cleaned regularly to maintain them.

Make two marks for cutting when replacing ductwork

When cutting pipe, Bob likes to mark the size he needs on each side of the open seam with a marker. Flat metal is easier to cut than curved, so he uses his knee to support and flatten the pipe while he opens it up. Then you just sight on the far mark while you make the cut. It’ll be straight and perfect every time. Bob prefers snips made by Malco, which cost less than $35 online. Unless you enjoy trips to the ER, wear gloves when cutting pipe—the stuff is razor sharp.

Step 3: Installing New Ductwork

Some older homes do not have a system of ducts to deliver conditioned air. This means an HVAC contractor will have to install new ductwork. Homes with existing ducts that are old and leaky will also benefit from ductwork replacement.

The biggest challenge in installing new ductwork is often space. Older homes were not designed to house bulky central air systems. Traditional split system HVAC systems consist of an outdoor condenser unit, an indoor evaporator unit, and duct system that delivers air through the house. In most cases, the technician will put the indoor unit in the attic or basement. And then the ductwork runs from the unit to the rest of the house.

If your house has enough space, it will be fairly easy for your contractor to install an AC unit and add the ductwork. But prepare for the disruptions, though. Installing a new duct system is labor-intensive and usually adds an extra 2-3 days to the job. If you have a two-story home, the installation will take longer.

HVAC ductwork installation cost factors

Project difficulty

Project difficulty heavily influences ductwork installation costs.

Ductwork installation complexity essentially comes down to how easily HVAC contractors can access the installation site.

Easier projects Tougher projects
New construction Existing ductwork replacement
Home addition New install in a finished home
Adding a vent to existing ductwork Retrofits

Easier ductwork installation

Installing ductwork for new construction, home addition, or a home remodel, for example, is relatively straightforward.

It’s not DIY-friendly per se, but without walls and insulation in the way, installers can seamlessly place ductwork where necessary and build around it.

Open areas like basements, attics, and crawl spaces also make for easier installation.

Tougher ductwork installation

On the other hand, completing new ductwork or a full-on duct replacement costs more, takes longer, and requires more labor.

Fitting ductwork between concealed studs and joists requires intricate drywall labor costs substantially.

Additionally, sizing ductwork can prove difficult for retrofits. Older homes may not have adequate space between framing members to accommodate correctly sized ductwork.

Further complicating installation, some old homes still have asbestos, which adds a whole new series of challenges.

Such projects can easily exceed $10,000 without even including the cost of HVAC installation.

How much does ductwork cost per square foot?

Ductwork costs between $0.33 and $2.26 to install per square foot on average.

By “square foot,” we mean the house size – not the ductwork dimensions.

Home size Low-cost estimate High-cost estimate
1,000 sq. ft. (110 linear feet of ductwork) $330 $2,260
2,000 (220 linear feet of ductwork) $660 $4,520
3,000 (330 linear feet of ductwork) $990 $6,780
4,000 (440 linear feet of ductwork) $1,320 $9,040

We based these estimates on the cost to install ductwork per linear foot.

A typical house needs 110 linear feet of ductwork per 1,000 square feet.

As every home has more or less a unique configuration, this ratio should serve as a rough guide.

A house with a wide footprint (more spread out) will often require more ductwork than a compact, multi-story home of the same square footage, for instance.

How much does it cost to install ductwork per linear foot?

Per linear foot, ductwork installation costs range between $2.96 and $20.59 per linear foot.

The exact cost per linear foot depends largely on whether you use rigid or flexible ducts. Many ductwork systems involve both types of ducts, which makes estimating total costs tricky.

Material Cost to install, per linear foot
Flexible $2.96 – $19.25
Galvanized steel $5.00 – $5.74
Aluminum $8.56 – $20.59

Ask About R-Value

The R-value of your duct insulation determines how resistant it is to temperature changes (i.e., how much heat or cold it will let escape as the air travels through the system). A higher R-value means a better insulated system. Most climates, including Georgia, need R-4 to R-8, though if you’re very concerned about it, we can discuss ductwork with a higher R-value.

We can add R-value to your ducts one of two ways: either by wrapping them with insulation or by constructing them out of duct board, which is already insulated. Your home’s idiosyncrasies will help us figure out how to best insulate your ducts.

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