Q. We live in a house that is essentially built into the side of a hill and as a by-product of this our basement always requires dehumidification. At a recent street fair I was exposed to a product called Humidex. The product seems to work like a large exhaust fan sucking the cold moist air that is at the bottom of the basement floor to the outside via a vent.
I wonder if you have any experience with this product or if you can offer us some ideas on how to make our basement more usable without the expense of a dehumidifier. The Humidex product boasts many claims which I could not substantiate with any Internet search.
A. Neither could I substantiate their claim through their website. Nowhere did I find how the make-up air comes from.
Humidex claims that while the unit exhaust the “dirty, polluted” air from the basement, this dirty air is replaced with clean air. How? Sucking a lot of air from the basement floor to the outside will require that the negative pressure created be equalized. That means that the make-up air will either come from outdoors or get down to the basement through the basement or upstairs windows in warm weather when they are open. That make-up air from outside will be warm and moist, and will be brought into a basement that is kept cooler because it is underground, which compounds the problem. It could lead to condensation on the floor and on the lower parts of the walls.
Since it is not clear whether the unit has an intake as well as an exhaust, I called them and asked the question. The answer is what I suspected: the make up air comes from upstairs through grilles installed in the floor. They claim that the system works very well, that they have sold many units over 26 years with a money-back guaranty.
But of much greater concern is that, if the Humidex does not provide make-up air through the unit, as an air-to-air heat exchanger does, and if the house is reasonably tight and the windows are closed (like in the winter time), the make-up air is very likely to come as a back-draft through chimneys, including the heating appliances – a serious safety problem during the heating season since it will pull into the house the combustion gases that contain carbon monoxide!
Asked that question, the sales person answered that there are enough leaks in a house to provide the make-up air. Knowing that air, like water, moves through the easiest paths, their answer does not satisfy me because the closest source of make-up air is likely to be from the furnace or boiler located in the basement as well. The sales person insists that this is not the case.
At this point, it is up to each prospective purchaser to decide whether or not to buy. I would not for myself.