Air can not be transported efficiently without correctly designed ductwork, resulting in higher energy bills and a shorter HVAC lifespan. Improper duct sizing needs replacement to ensure the home is comfortable and the HVAC system works correctly.
Understanding how to spot improper ductwork sizing, how to size ductwork and what to look for in a replacement can offer significant savings in the long term.
Table of Contents
- Duct Sizing Basics
- Calculating HVAC Duct Sizes
- Determining What Size Main Duct to Use for Heat Pump Systems
- How To Tell If Your Ductwork Is Sized Correctly
- What Happens If Your Ductwork Is Undersized?
- Cost of Replacing Ductwork
- Why Custom Ducts Make Installation Easier
Determining Duct Sizing
Sizing ductwork is a critical part of the HVAC process — it ensures everything will fit and lets your HVAC team know what ductwork you need. These factors influence the budget and HVAC abilities.
Duct sizing depends on the following:
- Airflow
- Air weight
- Home layout
- HVAC size
- Home size
Ductwork needs to fit your HVAC’s size to ensure it can efficiently transport air through your home without strain. Calculating ductwork correctly involves several complex factors, and it’s easy for inexperienced installers to get it wrong.
Ductwork CFM – Calculating Common Duct Sizes
Selecting the correct duct size is critical for any HVAC project. Properly sized ducts ensure balanced airflow, efficient operation and reduced noise. Many contractors perform detailed calculations and reference tools like a duct CFM chart to determine the right dimensions for each branch and main line. Understanding how to do CFM calculations for duct layout can prevent underperforming systems and save time in the field.
Sizing HVAC systems involves considering cubic feet per minute (CFM), square footage and the friction loss rate. These three factors work together to give your HVAC professionals an idea of what duct size you’ll need:
- Cubic feet per minute: Calculating the CFM involves taking the HVAC unit’s size in tons and multiplying it by 400. Next, divide that total by your home’s square footage. That result gives you the CFM, which is used with the following factors to get the HVAC duct size you need.
- Square footage: HVAC technicians will look at floor plans or measure your home to get its square footage. Calculating square footage involves taking the length and width of every room and multiplying them together. Rooms are divided into smaller rectangles to get the most accurate measurement if they’re oddly shaped. Adding all those totals together gets you your home’s square footage.
- Friction loss rate: Measuring the friction loss rate is difficult if you aren’t a professional. The friction loss rate is the pressure loss in a channel — it’s affected by coil number, duct length, grilles, filters, turns, dampers and registers. The friction loss rate has a significant impact on your ductwork’s airflow. Without accurate measurements, your ducts won’t work as efficiently as needed.
Determining What Size Main Duct to Use for Heat Pump Systems
Selecting the right size main ducts is essential for proper distribution. Using a combination of CFM requirements, static pressure considerations and airflow balancing, contractors can select main ducts that maintain system performance and comfort. Hennemuth’s expert staff can assist in reviewing layouts and suggesting duct configurations that optimize airflow, ensuring that the system operates efficiently from the start.
How To Tell If Your Ductwork Is Sized Correctly
Finding the appropriate duct size is vital for your HVAC’s function. You want your duct system to work correctly so your HVAC can avoid working overtime to heat and cool your home. If you think your ductwork is sized incorrectly, you’ll want to get it looked at to restore your system to maximum function and efficiency. Here are some signs your ductwork is sized incorrectly:
- Odd noises: If you notice lots of whistling, rattling or other constant HVAC noises, your ductwork is probably undersized. The ductwork can’t handle the HVAC load being pushed through it.
- High energy bill: A higher-than-expected energy bill can be a sign of oversized ductwork. If your ducts are oversized, your HVAC system must work harder than it should. More HVAC work means higher energy bills as the system uses more power to get the air to you.
If you aren’t dealing with these issues, your ductwork is sized correctly, and you can wait to replace your ductwork until the recommended time.
At Hennemuth Metal Fabricators, we help HVAC professionals by providing custom rectangular and spiral ducts built to precise specifications. Our in-house fabrication allows us to produce lengths and fittings that match project blueprints exactly, reducing on-site adjustments and simplifying installation.
Contractors appreciate the convenience of our in-stock inventory, which can be delivered across a 200-mile radius around Pittsburgh, PA. Many competitors do not offer the same reach or quick turnaround, making Hennemuth a reliable partner for fast-moving projects.
Ductwork Undersized? Give Us A Call
What Happens If Your Ductwork Is Undersized?
Undersized ducts happen when the ductwork has been incorrectly measured. Your HVAC system needs the right ductwork size to ensure it efficiently and correctly pushes air throughout your home. If your ductwork is undersized, you’ll hear odd, intrusive sounds from your vents as the HVAC system struggles to move too much air through too-small ductwork.
Additionally, this added HVAC strain increases its energy use and decreases its lifespan. The harder your HVAC system has to work, the more energy it will use. Over time, this constant overworking will shorten your HVAC system’s life. You’ll need to pay for an HVAC replacement much earlier than expected. Getting the right-sized ductwork can help you avoid these issues and save money.
Cost of Replacing Ductwork
If you’re dealing with a duct system that doesn’t fit, you’ll need to invest in a replacement system. While this can be a significant investment upfront, you’ll save lots of money and stress going forward, and your home will be more comfortable.
There are several factors influencing your ductwork replacement cost. While there’s no entirely accurate ductwork replacement cost calculator, you can get an estimate from your contractor depending on your ductwork.
Get a Free Estimate for Ductwork Replacement
Your total ductwork cost will depend on the following:
- Size: The larger your home, the more ducts it will have and the more expensive your ductwork replacement will be. Since you’ll need ductwork based on your home’s size, expect to pay more for a larger home. Additionally, if your ductwork is more complex, it will be more of an investment to replace.
- Location: If your ductwork is harder to access, replacing it will cost more. The job will also cost more if you have ductwork in cramped crawlspaces or if it’s in your ceilings and is challenging to get to. You’re paying for the increased difficulty — HVAC professionals want to get your ductwork as accurate as possible. Increased difficulty means more work to get it right, so you’ll pay more for the replacement services — especially if you want correctly sized ductwork.
- Labor: Paying for professional ductwork replacement will add to your total cost. While DIY-ing is technically cheaper, it’s extremely difficult to get right without professional experience — you’re more likely to perform the replacement incorrectly. Then, you’ll need to pay a professional to correct any errors made during the DIY.
- Material: There are several options for ductwork material. Fiberglass, aluminum and galvanized steel are popular. Picking a more expensive material will raise your ductwork costs.
Why Custom Ducts Make Installation Easier
High-quality, correctly sized ductwork can dramatically reduce challenges during installation. Our spiral duct and rectangular options are fabricated in-house for accuracy and consistency. Contractors can rely on pieces that fit seamlessly, minimizing field adjustments and wasted materials. Pre-assembled fittings, custom lengths and the ability to tailor connections make it easier to maintain proper airflow and avoid bottlenecks in the system.
Partner With Hennemuth Metal Fabricators
For over 40 years, Hennemuth has been providing HVAC installers and other professionals with ductwork that combines fit and quality. Our friendly and knowledgeable team is available to discuss projects and help determine the right duct sizes for both residential and commercial systems. With quick lead times and the ability to deliver within our service area, contractors get the products they need without delay.
Whether you are planning a new installation or replacing sections of an existing system, Hennemuth’s custom ductwork helps contractors complete jobs faster and more efficiently. For more information or to request materials, contact us today.