Thread: Manage your Home's Humidity to Feel More Comfortable and Save $$$

When you think about your home's climate control, you think about temperature. Generally people like their house to stay between 68 and 74 degrees. We would consider this a "comfortable" temperature. But what is missing is humidity. If your house is too humid, you may feel warm, even at a lower temperature. Too dry and you will feel cooler, be more prone to getting sick, dry skin, etc.



The problem is, when it is summer and you're paying to cool down, it is generally too humid. In the winter and you're paying to stay warm, it is generally too dry. Before we go into ways to control humidity, let's do a quick humidity 101.

For humidity, we measure "relative humidity" which is a percentage of moisture in the air relative to the maximum water vapor that the air can hold at that temperature. So for example, at 68 degrees, 1 cubic meter of air can hold 20 grams of water. So if there was 8 grams of water in the air, the relative humidity would be 40% (8 / 20 = 0.4 or 40%). But lets say the same air cools to 50 degrees. Now the air can only hold around 8 grams of water. Assuming no water was lost, the relative humidity would now be 100% (8 / 8 = 100%). So let's just assume that the outside humidity is always 70% (which it isn't, but let's just pretend). When it is cold outside, 70% isn't much water. Say it is 50 degrees. 70% of 8 = 5.6 grams. Warm that air up to 68 degrees where the air can hold 20 grams and the relative humidity is now only 28%. And if you have a gas furnace, you probably burned up some of the water while heating the air, which would make the relative humidity even lower.

OK, enough explanation and examples. Generally speaking, we ideally want relative humidity to be between 40 and 50%. Much over 50% and you open the door for mold growth. And if it is summer, you have to keep it cooler to stay comfortable, which get's expensive. Too dry and you run into problems as well. Caulking starts to crack around the trim, hardwood floors start to separate, you are more prone to getting sick, nasal passages and skin are dry, and you have to keep it warmer to feel comfortable.

So now how to control it:

1. Seal air leaks. The more air you bring in from outside, the more likely moist summer air or dry winter air will infiltrate. If you want extra fresh air, get an air exchanger that brings in fresh air in a controlled way. Air leaks are usually found around doors and windows, but also can be found around recessed lighting, air vents and even around baseboards. An energy audit can help you identify leaks, but you may be able to identify the easy things yourself.
2. Use, but don't overuse the exhaust fans. Down drafts and bathroom exhaust fans can help control humidity. When you shower, using the exhaust fan can prevent the steamy air from getting into the rest of your house. But keep in mind what is happening. Your house has to keep a pressure equilibrium. And when you are pumping air out of your house, the pressure goes down compared to the pressure outside. So to reach equilibrium, the only way for that to happen is to bring in air from outside. So you got rid of some steamy air and brought in some fresh air (that in the summer is also humid). Even in well sealed homes this will inevitably happen. The longer you leave the fans on, the more air comes in. So use the exhaust fans, but don't abuse them.
3. Use humidifiers in the winter. Winter air is dry. And most furnaces dry out the air further. If your humidity is too low, use a humidifier. A whole house humidifier is great, but if that doesn't make sense, get some room humidifiers. They aren't too expensive and they work well.
4. In the summer, use a dehumidifier if necessary. If sealing the house didn't work, consider a dehumidifier. A/C units remove humidity, but often not enough, especially in very humid climates. If you need a boost, consider a dehumidifier. There are whole house systems and single room units. Room units are great especially for basements. They aren't cheap, but can pay for themselves if they reduce your A/C usage.

All of these ideas are great, but I missed the true first step...Buying a cheap hygrometer to measure your humidity. If you don't know your relative humidity, you have no idea if you have a problem. First check it, then decide if you need to take action.

Good luck!