Hi Paul: I hope you are doing well in these times. Mister Condo sent me from his website. I have a condo unit on the 16th floor facing north in Toronto. I have an issue with the exhaust fan above the stove. When fan is turned off, I can still hear the fan spinning and it makes a loud “chopping” sound cutting through the air. This is most prevalent during windy days. Do you know what the issue could be, or any recommendations on how to fix it? Thanks, LL.
LL: I am sorry to hear about your situation. It must be annoying. I do not know how tall your building is, but I suspect it might be on one of the top floors where the prevailing winds will be stronger. If this noise just started recently then probably the cause could be some damage to the damper (the flap) that prevents outside air from entering the vent system. Depending on where the damper is located, it may be more difficult to locate the problem. This might be the culprit. If your fan exhausts from your unit directly to the outside, it may be considered a unit issue and depending on your governing documents your responsibility or the corporation’s. If it feeds into a multi-unit exhaust system, it would most definitely be a corporation matter.
I would encourage you to keep a log for a week or two diarizing the time of day when you turn off the fan and check the wind speed and direction if you can. This will provide you with some evidence and will help determine the cause. I am not an air exhaust expert, but as a homeowner this is the place I would start looking.
Have you spoken to any of your neighbours in the adjoining suites? Are they having the same issue? Ask your building manager/ maintenance person to check it out.
If you were on the main floor, I would suggest that you inspect the damper to determine if it is too light and does not remain shut on windy days. If it is not heavy enough it will flap in the wind enough to let air in. Unless the exhaust damper is accessible, it may be challenging to inspect. In some buildings, it may exhaust on your balcony or very close to it giving you access. If it exhausts up to the roof of the building the turbine cap on the conduit leading up to the roof may again be too light and lets air in, or it may be damaged. If you search on the internet you will see that may people have written about this problem and attempted various solutions with only moderate success. Whatever you do, you should not block the exhaust since this could cause dirt and dust to build up inside the conduit and result in a vent fire. If you check with a local heating/plumbing company, they may have a heavier flap that closes when wind pushes it from the outside and it is light enough to open the flap when air is pushed out.
Be Well! Stay Safe!