If you’re replacing a rooftop unit (RTU), upgrading an HVAC system, or working on a tight project deadline, you’ve probably come across curb adapters. But what exactly do they do, and how can you make sure you’re ordering the right one?
At Madon Sheet Metal, we specialize in precision-engineered, union-made curb adapters that make HVAC installations faster, easier, and more reliable. Below, we answer some of the most common questions contractors, facility managers, and mechanical engineers ask about curb adapters.
1. What is a curb adapter, and why do I need one?
A curb adapter is a custom-fabricated metal transition piece that allows a new RTU to be installed on an existing roof curb without modifying the ductwork below. Instead of costly roof and duct modifications, a curb adapter ensures a perfect fit—saving time, labor, and installation headaches.
2. How do I know if I need a curb adapter?
If you’re replacing an RTU and the new unit’s supply and return air openings don’t match the existing curb dimensions, you need a curb adapter. Instead of cutting into the roof or modifying ductwork, a curb adapter bridges the gap and ensures proper airflow.
3. How do I measure a curb adapter?
Accurate measurements are crucial for ensuring a proper fit when ordering a curb adapter. Here’s a step-by-step guide to help you measure effectively:
If the RTU model number or manufacturer’s information is visible, take note of it. You can now order online using our Curb Adapter Portal.
🔗 Learn how to use our curb adapter portal
If you can’t find the old RTU model number, you can follow these steps.
Step 1: Measure the Existing Roof Curb
- Outside Dimensions: Measure the exact outside dimensions of the original roof curb that is integrated into the building. Avoid measuring the unit itself, its base rail, or any existing adapter curbs.
- Supply and Return Duct Openings: Measure the sizes of the supply and return duct openings on the original roof curb.
- Duct Location: Determine the distance from the outside edge of the roof curb to the edges of the supply and return duct openings.
Step 2: Assess the Levelness of the Unit
- Check for Level: Verify if the existing unit is level. If it’s not, indicate the direction and degree of the slope, as this can often be corrected in the curb adapter design.
Step 3: Identify Potential Obstructions
- Tight Clearances: Note any nearby obstructions, such as adjacent units, roof fans, gas piping, electrical conduits, walls, or roof edges, as these can impact the design and installation of the curb adapter.
Step 4: Document with Photographs
- Visual Records: Take comprehensive photographs of the existing setup from multiple angles. These images provide valuable context and can prevent miscommunication during the design and fabrication process.
Step 5: Avoid Common Mistakes
- Do Not Stack Adapters: Avoid installing a new curb adapter on top of an existing one. Always install the adapter on the original factory roof curb to prevent structural issues and unnecessary static loss in the duct system.
- Measure the Curb, Not the Unit: Focus on measuring the original roof curb, not the unit’s base rail or any existing adapter curbs, to ensure accurate dimensions.
By following these steps, you can ensure that your new curb adapter fits perfectly, facilitating a smooth installation and optimal HVAC performance.
However, if you are new to measuring curbs or if you are measuring for an unusual curb adapter, it can get tricky. Don’t struggle with it alone or order the wrong adapter. Instead, just call us and a union sheet metal worker will walk you through the whole process or schedule a time that we can come measure for you.
📞 Call (224) 300-7995 for expert advice
4. How long does it take to get a curb adapter?
At Madon Sheet Metal, we understand that time is money. That’s why we offer:
⏳ Instant pricing & spec sheets for over 20,000 curb adapters via our Curb Adapter Portal
⚡ Custom curb adapter designs in less than 24 hours if your model isn’t in our database
🚚 Fast fabrication & shipping—we deliver in days, not weeks
Other companies might take weeks to turn around an order, but we prioritize speed without sacrificing quality.
5. What materials are curb adapters made from?
At Madon Sheet Metal, we fabricate curb adapters using:
🔩 Galvanized steel – Durable, corrosion-resistant, and cost-effective. Usually, we use 16 or 18 gauge Galvanized steel
All our curb adapters are built to last and crafted with precision by certified union welders.
6. What’s the difference between an insulated and non-insulated curb adapter?
Insulated curb adapters help prevent heat loss, condensation buildup, and noise transfer, making them ideal for:
✔️ Cold climates
✔️ High-efficiency HVAC systems
✔️ Noise-sensitive environments (offices, hospitals, schools)
Non-insulated curb adapters are more cost-effective and are used when insulation isn’t required for performance.
🔗 Read our full breakdown of insulated vs. non-insulated curb adapters
7. Do curb adapters affect airflow or HVAC performance?
Only if they are designed incorrectly! A properly designed curb adapter ensures that the supply and return airflow remain balanced, preventing pressure drops or inefficiencies.
That’s why it’s essential to work with a trusted fabricator like Madon Sheet Metal, where we:
✔️ Offer instant design verification through our Curb Adapter Portal
✔️ Ensure every adapter is built to match manufacturer specifications exactly
8. How do I order a curb adapter from Madon Sheet Metal?
Ordering is fast and easy:
1️⃣ Check our database – Visit our Curb Adapter Portal for instant pricing and drawings
2️⃣ Upload your measurements – If your unit isn’t in the system, send us your specs, and we’ll design it in under 24 hours
3️⃣ Get your curb adapter in days – We fabricate and ship fast, so you can keep your project moving
9. Why choose Madon Sheet Metal over other curb adapter manufacturers?
Not all curb adapters are created equal. Here’s why contractors, engineers, and facility managers trust us:
🏆 Union-Certified Quality – Every curb adapter is crafted by experienced, union-trained welders
⚡ Fastest Turnaround in the Industry – Instant pricing, 24-hour designs, and rapid shipping
📍 Midwest-Based, Nationwide Shipping – Conveniently located for fast deliveries anywhere in the U.S.
🔗 Our Curb Adapter Portal is a game-changer – No more waiting for quotes!
Final Thoughts: Get the Right Curb Adapter, Faster
Choosing the right curb adapter doesn’t have to be complicated. At Madon Sheet Metal, we make it easy, fast, and reliable. Whether you need an RTU retrofit, custom HVAC curb, or an insulated adapter, we’ve got you covered.
🚀 Get started today!
🔗 Order now via our Curb Adapter Portal
📞 Call (224) 300-7995 for expert advice
🌐 Visit Madon Sheet Metal Online
