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Is there a Connection Between Ponding Water and HVAC Units?


Having more than one HVAC unit on your roof increases your risk of ponding water. Flat commercial roofing is known for having ponding issues, especially when multiple HVAC units are positioned on the roof. Many people do not realize that the HVAC units themselves could be contributing to the ponding problem along with a lack of drainage on the flat roof. Roof top units like HVAC units, skylights, and cooling towers can cause ponding if they are not protected by crickets. Crickets are triangle-shaped structures that are designed to divert water away and without them, water can accumulate. HVAC units also regularly produce condensation which additionally should drain away but cannot if there is no cricket, this does not happen.

Is there a Connection Between Ponding Water and HVAC Units?

The weight of the HVAC unit also contributes to the problem of deck deflection. The presence of any low spots around the unit as a result of poor or aging insulation can damage the roof membrane. The structure of HVAC units can also pose as obstacles that trap debris and accumulated debris interferes with water flow into the gutters causes ponding. Rooftop HVAC units are ideal because it keeps these bulky items out of sight but with the risk of ponding water being high, there are things you should know to effectively prevent this from happening. You first need to make sure that no interior damage or structural damage has occurred before repairing any low spots. Then, make sure all gutters and downspouts are cleared of debris so water can flow without interference.

Keeping Your Roof Dry

Once the flow of water has been corrected and there is a minimal risk for ponding, you need to look for ways to prevent future ponding. The best way to avoid low spots is to fix smaller problems before they turn into larger ones. When there is any rain, be sure to schedule inspections right away to check for ponding. The sooner you find and address issues, the fewer problems you will have in the long run.


Having your HVAC units on the roof keeps the noisy and unsightly equipment out of the way, but they can contribute to low spots and accumulating water. Ponding water causes serious damage to the interior and exterior of your roof and building but can be prevented with proper maintenance and regular inspections. If you have a rooftop HVAC unit, be sure to inspect the surface regularly and take care of all repairs right away. Preventative care is the best way to keep your roof dry and free of ponding-related damage.



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