View Full Version : Extractor fan... with no inlet?

12-17-2012, 12:28 PM

I live in a condo (new construction) and we have several problems that the contractor still cannot understand: dust coming from nowhere, cold air coming in even from the smallest cracks in the windows, cold floor near dryer exhaust, etc. I tried looking up, and it always comes up that there might be a negative pressure problem.

This week-end, I disconnected the HRV and tried to find where the negative pressure could come from. I found air tends to go towards the laundry room. I did not find where it is, but there is definitely something there that is sucking air... but with no inlet.

Is that supposed to be? This fan would be running 24/7 with no inlet, I'm assuming this could be the cause for the negative pressure situation, am I right?


12-17-2012, 12:46 PM
What kind of heating appliance(s) do you have? Anything that burns natural gas? Air that goes out the flue needs a source of combustion air to replace it. Was the dryer running? Is your boiler or water heater in there?

12-17-2012, 12:55 PM
We have an electric washing machine, an electric dryer and an electric water heater.

Could there be an extractor vent that is somehow tied to the hallway system? Again, why would they install an extractor fan with nothing to push air?

12-17-2012, 04:08 PM
If you light a candle then blow it out, it will smoke for a bit...it can be an easier way to visualize the air movement. Even though the dryer is electric, it still is blowing out LOTS of air when it is running - that air has to come from somewhere. If you have a hood vent on the stove that actually vents, rather than filters and recirculates, that makeup air has to come from somewhere. If the duct sizes on the ERV are not proper, that could generate problems. If you open a door, is there a breeze that either pulls it open or pushes it closed? That can give you an idea of air movement that may help isolate the source of the problem.