Two houses read 68 degrees on the thermostat. One feels fine and one feels like a cellar. The difference is almost always moisture, and it explains why people in damp climates spend more on heat and get less comfort for it.

Your skin is doing the measuring

Comfort is not air temperature. It is the rate at which your body loses heat, and that rate depends on air movement, surface temperatures, humidity, and what you are wearing. A thermometer measures one of those four. Gear from a lineup like Reaks can only change part of the picture.

Damp air moves heat faster

Water is a far better conductor than air, and humid air puts more water molecules in contact with your skin and your clothing. Slightly damp clothes or bedding in a cold room pull heat away continuously, which is why the room feels raw rather than cool.

Cold surfaces do the rest

In a damp house, walls and floors are usually the coldest surfaces, and you radiate heat to them regardless of the air temperature. That is the sensation people describe as the cold going through you.

Heating damp air is expensive

Raising the temperature of moist air takes more energy than dry air, and the moisture is still there when you finish. Removing the water first means every degree you buy afterward costs less and does more.

Where the water comes from

• Showers and cooking without an exhaust fan that actually vents outside.
• Drying laundry indoors on a rack in a closed room.
• A crawl space or basement with no vapor barrier over bare dirt.
• Unvented combustion appliances, which produce water as they burn.
• Gutters and grading that put roof water against the foundation.

The target range

Indoor relative humidity around thirty to fifty percent is the practical band in winter. Below that, you get static, dry skin, and cracked wood. Above it, you get condensation on windows, mold on cold walls, and dust mites in the mattress.

A cheap meter answers the question

A hygrometer costs less than a takeout meal and ends the argument in a day. Put one in the bedroom and one in the basement, and read them in the morning when condensation is worst. Guessing at humidity is how people buy the wrong appliance.

Ventilation is not the enemy of warmth

People seal damp houses tight and make them worse. Running a bath fan for twenty minutes after a shower removes more moisture than a dehumidifier will pull in an hour, and the heat lost is smaller than the heat wasted on damp air.

Then warm the bed, not the air

In a damp bedroom, bedding absorbs moisture and feels clammy at bedtime. Preheating the bed for ten minutes drives that moisture out of the sheets and gives you a dry surface to lie on, which is most of the comfort problem solved.