Q&A – Flue penetration concerns

With conflicting information from different sources, this homeowner came to our experts to get an outside perspective on their ductwork. 

We recently had a homeowner from Virginia reach out with a question concerning their ductwork. This is what they asked: 

We had our HVAC company come out to do some ductwork repair and the attic, and they noticed that you can see light coming through around the flue and suggested that it needs to be replaced and yet when I contacted a roofer that came out to do an inspection not that long ago, he said the flue is fine and that it’s normal to see light around it. I did do some AI research and they say it is not normal to see any light around the flue so now I don’t know who to believe and I don’t want to have to get somebody else out there to do another inspection.

One of our residential roofing experts, Luis with Wagner Roofing​​​​, took a look at their question and shared some thoughts:

In general, it is not typical to see daylight around a flue penetration. While visibility can vary depending on the type of vent or pipe, the penetration should always be properly flashed and sealed to prevent water intrusion and air leakage.

Rather than focusing solely on the presence of light, it is more important to evaluate any signs of moisture or staining on the surrounding plywood or framing, as those are indicators of an active or past issue. When sealant fails or a flashing was not installed correctly, gaps can develop and lead to the conditions you’re describing.

Based on the interior photo alone, the most appropriate recommendation would be to replace the pipe flashing to ensure a watertight seal. A photo of the penetration from the exterior roof surface would be helpful to confirm the condition and identify the exact corrective action, but replacing the flashing is typically the proper solution in cases like this.

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