Originally Posted by paque
M'y house is equipped with a heat recovery ventilator (HRV) that makes the air circulate in the house and the basement as well... Does that prevent from the downdraft?
Not familiar with that kind of system.
But, a downdraft is air coming back down the exhaust system (chimney) of any oil or gas appliances and out through the appliance. This is cause by the interior air pressure being lower than the exterior air pressure, in this case caused by your brewing exhaust fan. If your bathroom fan or range exhaust vent to the outside the too will create negative pressure. Since they are not near the furnace that imbalance will likely be corrected through a leaky window or bad door seal.
IF you system recirculates air throughout the house the entire time you are brewing it MIGHT spread the load to the point that a down draft will not occur. But if it turns off at all you are into down draft conditions.