In the HVAC industry, installing a heat pump or central system isn’t enough to guarantee customer satisfaction. The air duct network plays a crucial role in system performance. Poorly sized ducts can lead to:
- Reduced energy efficiency (overheating of the unit, short or long cycles).
- Hot or cold spots in the home.
- Increased noise from excessive air velocity.
- Comfort complaints, or even premature equipment wear.
💡 In short: poorly designed ducts can ruin the performance of even the most efficient heat pump.
1. Calculate the Heating and Cooling Load (BTU)
Before sizing a duct, you need to know how much air has to circulate. This is based on the heating and cooling load (BTU) of each room.
👉 Example: A room requiring 6,000 BTU of heating/cooling will need an appropriate airflow (expressed in CFM – cubic feet per minute).
2. Respect Air Velocity
- Ideal velocity in main ducts: 600 to 900 feet per minute.
- In branch ducts: 400 to 600 feet per minute.
Too high = noise + discomfort.
Too low = poor air distribution.
3. Minimize Pressure Losses
Every elbow, reduction, or extension adds resistance to airflow.
✅ Use long-radius elbows instead of sharp ones.
✅ Avoid ducts that are too long or undersized.
✅ Opt for smooth, well-insulated ducts to reduce air leaks.
4. Choose Proper Grilles and Registers
Even a properly sized duct can lose efficiency if the grilles are undersized.
💡 Always make sure the grille or diffuser matches the required airflow.
Benefits for the Homeowner
A properly sized duct network means:
- ✅ Even comfort in all rooms.
- ✅ Energy savings (less waste, better system performance).
- ✅ Longer equipment life thanks to balanced workload.
- ✅ Fewer service calls and happier customers.
How Flex Distribution Supports You
At Flex Distribution, we know that a successful installation isn’t just about the heat pump. That’s why we provide contractors with:
- Clear technical sheets to help you size ducts properly.
- Training and practical tips to avoid common mistakes.
- A full range of high-efficiency WILLIS HVAC products, designed to perform at their best when paired with a properly installed duct network.
👉 Our mission: give you the tools to deliver efficient, reliable installations that build customer loyalty.
Conclusion
Proper duct sizing is a key element of energy efficiency and residential comfort. By following best practices and using the right tools, you maximize your chances of success on every project.
With support from Flex Distribution and the WILLIS brand, you have all the resources you need to deliver optimized, long-lasting solutions to your clients.
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