Drier air in winter is less comfortable than more humid air. Dry air leads to chapped or cracked skin, nosebleeds, and sinus problems. Moist air is better for plants and people alike. Also furniture. And pets. Lowering the temperature will increase the relative humidity, but it doesn't cause there to be more moisture in the air. Humidity level is defined relative to the maximum amount of water vapor that air can hold (air at 50% humidity contains half as much water vapor as it can; at 100% humidity there's nowhere for additional moisture to go, and you start to get rain or dew). Warmer air has more capacity than cooler air. Increasing humidity levels by lowering the temperature is a little bit like trying to raise a flag by lowering the pole it's attached to. Most indoor plants will do better with a lower night temperature, but most indoor plants are also tropical, so their idea of "low" isn't very cold at all (and in fact, a lot of them can be damaged by temperatures below 60F / 16C). I would not put a tropical plant on a windowsill in cold weather: leaves touching the window can be damaged, and the overall temperature tends to be much colder by a window. If it's not practical / permissible to use an actual humidifier, bringing plants home for the season, grouping several plants together or surrounding plants with damp moss or pebble trays, adding a glass or plastic cover for the plants, or using plants that don't care about humidity levels (and there are more of those than you'd think) are pretty much the only options. To answer the original question: the room I'm typing in right now is about 76F (24C) and 55% humidity. The humidity level is normal; the temperature is a little higher than usual.

Sharara..Which directions do your windows face? Are they obstructed by neighboring buildings, trees, curtains or blinds? Don't judge your thumb or light by a Mini Rose. They are very very difficult, if not impossible thriving indoors. Most who buy them either, 1. toss after flowering or 2. plant in their garden, if hardy. So, you're looking for a plant that has color? Other than green? Are you searching for tropicals or will succulents do? Or does it not matter? There are several ways to increase humidity..First and best choice is to buy a humidifer. They're helpful to plants, people and pets. There are several types of humidifers on the market..Consoles and smaller, 2-3 gallon filter-less types. Walgreens and Walmart sell humidifers, and now that winter is over most are on sale. Costs begin at 14.99 up to 200.00 depending on the type. Or if you're into name brands. I'm not into brand names, my concern is whether or not it does the job. Misting and showering plants increase humidity. For those with a large number of plants, grouping together. Humidity trays work fine, especially with plants growing in containers under 10" diameters. You don't have to buy anything special other than a bag of stones/pebbles for these trays. I bought a bag of pebbles at Home Depot..40 or 50 lbs for 2.50. Since you won't be needing that much, HD sells smaller bags of stones, including decorative, different colors. Heck some dollar stores sell them. 1 bag is enough for one tray. I save all types of containers, from frozen dinners to cake pans. As long as they're strong and don't crack, they work. I even have family members and friends save usable trays..lol I prefer brighter colors like silver, but any color works. Of course boiling water will humidify a house, but I doubt you'll want to boil water 8 hours per day. lol. What type of heat do you have? If you have space heaters or radiators, placing a pan of water on top works somewhat, but depending on the plant if it required a lot of humidity, a pan on the heater won't be enough. If you answer some of these questions we can narrow down plants that would work..Toni

Thanks Tigerdunes for the info. I am going to meet with my HVAC installer on Thursday to talk about how best to decrease the airflow while the compressor is on to allow sufficient water to be condensed from interior air -- with goal to keep my internal humidity below 60% (or more). Re your comments 1-4: 1. No crawlspace, house is 9 ft elevated on stilts. I do have a vapor barrier on bottom of R-38 batting in floor. 2. I never run fan in "ON" mode, however, it runs a whole lot on slow speed without compressor running in "Auto" and/or "Cool" mode -- which I think may increase the humidity like "ON" mode as noted by contributors in this forum thread. However I must solve the more major problem of not removing sufficient humidity when the compressor IS running on, first. Then address this if high humidity is still an issue. 3. I agree that attemping to re-program dipswitch settings, even with the manual, is foolhardy for a person not trained in HVAC and Trane eqpt. in particular. 4. Will attempt to get air handler air speed to be more correctly matched to dehumidification needs. Especially in light of your and ryanhughs comments: "First, that air handler will come factory set for an airflow suitable for 3.5 tons, so it should be adjusted for both the high and low stages of your 3 ton unit (4TWX6036 is a 3 ton). Second, is Comfort-R enabled?" Thanks again to all for your continuing assistance. I will post how this does (hopefully!) get resolved. KR

You might have multiple small air leaks in those rooms rather than one or two large leaks that are easier to locate. Finding air infilteration require's an organized process plus a few specailized(not necessarily complex or expensive) tools. A supply leak can result in outside air being drawn into home any place that isn't sealed.