Misting houseplants is not an effective way to raise the relative humidity. The plant foliage dries quickly after misting. Misting would have to be done several times a day to be effective and is simply not practical. To compensate for the short days and long nights of winter, move houseplants closer to windows. However, make sure the houseplant foliage doesn't actually touch the cold window.
Supplemental lighting is another option.
Light units containing special grow lights can be purchased from mailorder companies or at garden centers. Gardeners can also build their own lighting structure. A standard fluorescent unit containing one cool white 40 watt tube and one warm white 40 watt tube provides adequate light for houseplants. Plants should be placed within 6 to 12 inches of the lights. Watering In general, houseplants require less frequent watering during the winter months than in spring and summer.