You might consider cutting into existing ductwork to extend your HVAC system to a finished basement, converted attic or garage, or home addition. But is this a good idea? Well, you can tap into your existing ductwork if the system isn’t at its full capacity.
However, if it’s at maximum output, exceeding capacity can cause performance issues. The system will struggle to maintain a constant temperature in your home. You’ll have hot and cool spots, and the system will use more energy than necessary. The extra work can also lead to wear and tear damage and costly repairs.
But let’s consider that cutting into existing ductwork is an option for you:
Determine If Your Ductwork Can Support the Airflow
Unless you run a small duct off the main trunk to serve a small bath or home office, capacity will likely be an issue. It is measured in cubic feet per minute (CFM). Exceeding the blower’s airflow rating will reduce the amount of air that reaches each vent.
For example, you have a blower with a 1,600 CFM rating. If there are eight vents, you’ll get 200 CFM per vent, but adding two more will reduce that to 160 CFM per vent. Adding even more vents reduces airflow per vent even further, which reduces the comfort level throughout your home.
How to Cut Into Ductwork
We’ll now assume you’ve decided to cut into existing ductwork. It requires cutting a physical hole into a metal duct. To get started, mark the duct where you will make the hole, knowing the dimensions of the opening you need. You can then drill with a step bit around the line you’ve drawn, or use a flat screwdriver. Place the screwdriver at a 45-degree angle and hammer it into the sheet metal.
Once you have a large enough hole, cut out the desired material with a tin snip. Use a right-hand tin snip (which is easier to hold in the left hand) to make sharp right-hand turns at corners. Left-hand tin snips help make sharp left-hand turns using your right hand. Alternating the tools will help complete the cut.
The hole must be the same size as the duct you bolt to the opening. You can also use flexible ductwork, which is easier to run from the main line or trunk to the vent opening. Flexible ducts should be stretched tight to avoid compressed sections that increase air friction and static pressure.
Is Cutting Into Existing Ductwork Necessary to Get More AC
If this process sounds like more than you can handle, here are alternatives to cutting into your expensive ductwork:
- Zone Your HVAC System: Zoning lets you get more out of the equipment you have. By adding dampers, you can configure your system to handle, for example, eight vents, whether you close two, four, or more vents in unoccupied areas. Manual or motorized dampers are available.
- Use a Portable Unit: A portable electric AC or space heater can be used in a finished basement that’s not used frequently. But a new bedroom, for example, should have a more permanent heating/cooling solution.
- Install Baseboard Heaters: It’s easier to install baseboard heaters than new ducts. They’re effective at providing warmth. However, you’ll need an electrician to install a dedicated 220-volt circuit.
- Install a Radiant Floor Heater: If redoing a floor is part of your project, installing a radiant floor heater may be practical. It heats the room from the bottom up, which works because heat rises.
- Go Ductless: Installing a ductless heat pump is not the cheapest option. But a smaller, single-zone ductless system is less expensive than zoning your ductwork. It’s also one of the most efficient and effective types of air conditioning. It may be just the right solution for a home addition or finished basement, garage, or attic.
We recommended contacting an HVAC specialist before cutting into existing ductwork or considering any other option.
Call Sky Heating & Air Conditioning
We provide a range of ductwork services in Portland and The Dalles, so we can help if you need any advice or service. Our technicians are trained to install the latest ductless systems, which are compact, efficient, and ideal for home additions. These also provide aesthetic benefits and can improve indoor air quality.
Our team helps with every step of installation and can add zoning capabilities, integrate wireless controls, and provide 24/7 emergency repairs. For more information, call (888) 961-4282.