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View Full Version : Evaporative Humidifier to Supplement A/C?



jjakucyk
06-07-2010, 02:56 AM
I was thinking of posing this as a hypothetical situation, but I'll just come right out and give the real situation. I live in a nearly 100 year old apartment building in Cincinnati with solid brick walls and original windows that have rather old aluminum storms. I'm on the fourth (top) floor, and with a broad westerly exposure the place gets absolutely blasted by the late afternoon and evening sun. In my part of the city, summer temperatures usually top out in the upper 80s, with lows at night rarely dropping below 70º. Being a very dark red brick building, needless to say the heat gain can be pretty significant. The conditioned space is about 650 square feet, spread mostly between two large rooms with a small kitchen, bath, closet, and front entry. I have a sun room that I use as a greenhouse, but I keep it closed off.

There's two window A/C units, the main one in the living room is 10,000 BTU and the smaller one in the bedroom (which the landlord only begrudgingly installed after I insisted that the one unit was woefully insufficient) is 6,000. There's a large bi-fold door between the rooms, so they're basically one large space. The two units do ok maintaining 78º during the day, which is comfortable for me. However, if I turn the temperature up to 80º while I'm out and come back in the evening to turn it down to 76º for bedtime, it can take hours to cool down to the set point even on relatively mild but sunny days.

Now, I have all the windows and doors pretty well weather-stripped, so even though it gets very humid here (dew points in the summer are usually close to 70º) the A/C units actually can make it pretty dry inside. During the day the RH usually hovers between 40-45% but when I turn the temperature down in the evening, the constant running of both units can actually get the indoor RH to drop to near 30%.

So with a still undersized A/C setup and mostly sensible loads, would running an evaporative humidifier be advantageous? I've done it on and off, but I can't really quantify whether it's helping or not. It doesn't seem to hurt, but I just don't know. It cuts off at about 45% RH, so I'm not worried about the place getting overly humid, but I just can't tell if it's actually helping to cool the place down quicker. Since it's already pretty dry, a little adiabatic cooling seems like it should be ok, and the humidifier does spit out air at about 63º. Does that adversely affect the regular A/C units in a way I might not expect? I suppose the extra condensate could be a benefit to cooling the condenser coils, but at such a high outdoor RH I don't know that it would really benefit there much. Should I try bumping up the humidifier to 50 or 55%, or would that just be asking for trouble? What do you all think?

Yuri B.
06-07-2010, 05:21 PM
Hello.
From the description I induce a heavy, dense, dark-coloured construction scorched by afternoon-evening sun. If the target is efficient (economical) way of cooling down the flat in such a "house" (like the one in which I live, by the way) I would think about walls (insides)/ ceilings/floors fine insulation.
(The A/C s are toiling now so intensely - no wonder the RH gets that low!).

If vapour of the humidifier(s) could be extracted from the space, then, maybe this would help, otherwise You are going to turn Your flat into Turkish bath, I am afraid.

jjakucyk
06-07-2010, 05:28 PM
Well, being that it's a rented apartment, insulation isn't really an option. I'm sure the landlords would love to add insulation to take the edge of their huge winter gas bills, but since it's solid brick construction it's not really feasible. To add any insulation they'd have to construct a new framed wall inside the existing solid wall. That in and of itself isn't so terrible, except then they'd have to redo all the window and door casings, baseboards, electric outlets, and maybe even move and re-plumb all the radiators. That's a huge task.