Keeping Cool Basement Dry
When it comes to the kind of basement dampness that sets in
during hot, humid summer days, a dehumidifier is the only way to make things drier. Opening windows and boosting
ventilation just makes matters worse because outdoor air is the source of moisture in the first place. Trouble is, some
basements and crawl spaces are so cool that the coils inside a dehumidifier freeze up during use, rendering the machine
almost useless. Here’s a solution! My own struggles with this problem let to the discovery of a method for managing
dehumidifiers so they operate effectively in the kind of very cool basements that need dampness control the most. It’s a
system that boosts the amount of water removed from the air, while also reducing the amount of electricity consumed in the
bargain. Besides the dehumidifier, all you need is an oscillating household fan and a plug-in electric timer of the
sort used to control table lamps when you’re away from home. But to understand how all this works, you need some
technical back round.
Dehumidifiers are really just small, portable refrigeration units.
Air is forced over cooling coils within the machine by an internal fan, causing airborne moisture to condense and drip
into a collection bucket or drain pipe. All this works fine until ambient air temperatures drop to about 15 C. When that
happens, condensed water begins to freeze on the cooling coils, plugging them up with ice and preventing further airflow
and dehumidification. Some dehumidifiers have systems designed to sense internal icy conditions and deal with them,
but in many cases the problem results in a huge decrease in the amount of water removed from the air each day.
My approach eliminates ice-up before it happens, even in
basements as cool as 9 C. By placing an oscillating room fan a few feet away from the back of the dehumidifier, more air is
directed past the cooling coils than would otherwise happen via the internal fan only. This keeps the coils warmer and
much less prone to frost build up. The action of the oscillating fan also stirs up ambient basement air as it sweeps from side
to side, resulting in more uniform dehumidification by eliminating pockets of still, damp air in corners.
Although supercharging the airflow over dehumidifier coils
greatly reduces ice build up, it doesn’t always eliminate it in very cool basements. Solving this problem is where the timer
comes in. By setting the controls so your dehumidifier shuts off for about 15 minutes each hour, you let any frost that
present on the coils melt. Besides eliminating ice, this pause in operation allows all the water that’s trapped within the
coil’s cooling fins to drain away down into the collection bucket. Dry, ice-free coils boost dehumidification when the
machine comes back on again. Intermittent operation of this sort saves 25 per cent of the electricity used with continuous
operation, less the tiny amount of hydro consumed by the fan. The savings increase even more if you set your
dehumidifier to remain off all night, as I do.
I’ve used this system for the last three summers and I’m
amazed at how well it works. Twelve hours of intermittent operation each day removes more that eight litres of water
from the air, keeping a large, very cool 1,200 sq ft basement acceptably dry even when outdoor humidity levels approach
100 per cent. This is important because our climate in most parts of Canada makes a real mess of basements that
regularly experience relative humidity levels over 80 per cent. That’s the kink of thing that leads to musty basement
syndrome and the moulds and mildews that come with it. Keep basement humidity levels between 65 per cent and 70
per cent and you’ll eliminate these problems without using any more electricity than necessary to do the job.
Article written by Steve Maxwell, and published in the August
2005 REM Magazine
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