The relative part of humidity, technically, is the percentage of moisture in the air relative to the maximum amount the air can hold at that temperature. It’s not an intuitive concept. But it’s clear what happens as the percentage climbs: hot weather that was bad enough feels worse.
Indoors, the natural response is to dial up more AC. It makes the air cooler and drier— in a range of 30 to 50 percent relative humidity that works for most households, with 40 percent being the target to control mold growth. But many variables can increase dampness that causes condensation on cold surfaces, fosters mold and musty odors, and swells wood; doors and drawers that used to work smoothly barely budge.
Cooking, washing clothes, showering, and of course, sweating, all contribute to the impact. When they gang up and the humidity inside exceeds 55 or 60 percent, full-blast air conditioning can produce condensation— the way a can of soda from the fridge sweats on a hot day. The upshot is that AC is only part of the solution. To keep the house from sweating, consider one or more of these improvements.
•Check the AC. If you haven’t already, change the air filter, or wash a replaceable filter. A cleaner system runs more efficiently and inexpensively. You can always call in a service technician,which is the best approach if there’s trouble with the electric controls or the compressor is running excessively— often a sign that the system needs more refrigerant. But, sometimes, what seems like a system-wide failure is only a temporary stoppage triggered by safety features in the appliance. That can happen on the hottest days when heat and pressure build up in the compressor and trip the high-pressure limit switch, which keeps the compressor from shorting out. You can reset it (following manufacturer’s instructions) after the compressor cools down. Then, if the compressor restarts and holds you’re in business. If not, you need a service call.
•Exhaust moisture. Household operations like cooking and washing can produce up to 10 gallons of moisture a day— a lot of dampness when the weather is damp already. The AC will deal with it eventually, but you can lighten the load by venting some of the moisture where it’s produced with exhaust fans in the kitchen, baths and laundry area. Because those spaces are air conditioned, some cool air will be exhausted, too. But it’s a good tradeoff, especially if you replace standard fan switches with timer switches so venting time is limited.
•Increase air circulation. Central air systems are designed to deliver cool air to rooms then bring it back for filtering and re-cooling through a return duct. A fan powers the loop in cycles when cooling is called for by the thermostat. Some systems provide continuous air circulation by running the fan between cycles at very low speed, stirring the air somewhat. But even if your system works that way, portable fans and ceiling fans will enhance the cooling effect by creating more of a breeze, more so if you have room units. Some studies show that ceiling fans increase comfort by about four degrees — They allow you to cut energy costs by turning up the thermostat four degrees without feeling any warmer.
•Run a dehumidifier. There’s a tradeoff with this option because a humidifier generates heat inside the home that adds to the AC load. Then there’s the investment, typically $150 to $200 for a dehumidifier that removes 20 to 25 pints of water from the air per day. That should be enough to handle a laundry area, a home shop where tools can rust, or open areas up to about 400 square feet. Capacity depends on how wet it gets and how dry you want it. Bear in mind that with a large unit, say with a 70-pint capacity, you’ll be emptying a large container holding almost nine gallons of water that weighs about 75 pounds. Most units shut down automatically when the container is full, so if regular emptying isn’t on your to-do list, the water will gradually evaporate and become humidity again.
Copyright © 2011, Chicago Tribune
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