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HVAC Unit Curbs Made Hassle-free
Roof Curb Systems makes it easy! Give us the HVAC unit model number and we will take it from there. We also offer project coordinating and advisory services and will work with your contractor to make sure the correct HVAC unit orientation for the roof system is selected. This will insure that the supply and return duct drops are properly coordinated with purlin spacing.
Here are a few HVAC unit hints for free:
- Always request the HVAC make and model number and ask your builder to send the factory curb drawing and specification sheets from the mechanical contractor. With HVAC units, these documents are more important than mere curb size information because the documents provide vital information such as;
a. Unit Weight
b. Corner Weights
c. Supply and return opening layout dimensions
- After you determine the best orientation for layout of the unit, double check purlin point loads. (Roof Curb Systems will assist you with orientation and weights.)
• Is the point load over 300 pounds?
• Is a double purlin required at the center purlin of a double span support system?
- Try to control the unit layout or orientation to work best with your purlin or joist spacing. This will minimize costly purlin splicing and double curbs. Units may be rotated or cantilevered to allow the duct work to drop through the purlins. (Roof Curb Systems will include this in our detailing services.)
- Recommend a flexible connection be used for duct work connection with floating standing seams.
- What is the largest duct opening that will drop through a standard 60” purlin spacing?
Example :
60” purlin spacing
– 6” for top and bottom purlin flange
– 3” for thermal movement allowance
– 4” for TDC duct connection (if required)
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= 47“
- The HVAC factory curb will often show a 14” high curb. In most cases, a lower profile standard 8” curb will work. The 14” curb usually applies to a conventional roof where 8” should be maintained above the finished roof.
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