I remember my siblings and me as children running around the house, rubbing our stocking feet on the carpet and then giving each other shocks. You could actually see the sparks! We really didn’t know what was going on, and we didn’t care, all we knew is that this was an awesome game to play. Now that I’m an adult and energy consultant (and no I don’t play this game anymore) I go into many homes during the winter months and notice that the joints on much of the woodwork have pulled apart by at least 1/16th to 1/8” inch. And yes, I occasionally get that little shock when I shake the homeowner’s hand.
These two examples indicate that the relative humidity (RH) levels are too low in the home. This is also bad for your health. Extended low RH levels can lead to nose bleeds, dry and sore throats, and cracked and dry skin.
On the other hand, I’ve gone into homes and felt like I’m in Jamaica, but without the beautiful palm trees and white sand. Instead, what I saw was white paint that turned green with mold and mildew. The worst case I ever remember of high RH in a home was on a day that was about 58°F outside. In spite of how warm it was, when I walked in, my glasses fogged up!
Having too much RH in the home can be equally as bad. It can lead to deterioration of construction materials such as paint, drywall, and lumber. It can also lead to health problems and poor indoor air quality. Controlling relative humidity is very important in helping to minimize the presence of dust mites and mold, both of which are significant sources for allergies and asthma.
So what’s the perfect relative humidity level? It depends on the outside temperature. The ideal RH is about 40-50%, which helps promote good health and comfort. In colder climates, RH may have to be below 40% to help prevent condensation on windows. Generally, 30-40% is the industry standard for colder climates during the winter months. Keep in mind, whether you’re in a cold or warm climate, keeping the RH below 50% helps to prevent the growth of mold and mildew, and dust mite infestations.
With new homes and additions being built so air-tight, it’s now more important than ever to keep an eye on the RH levels within your home. Along with fresh and clean air, proper humidity levels will provide you with healthy air to breath.
To help maintain a healthy RH level, I recommend that every home be equipped with a hygrometer. Such a device measures temperature and relative humidity levels. There are many on the market. Portable and easy to install units are readily available. You can check them out at your local “big-box” stores, such as Home Depot and Lowe’s.
Things you can do to maintain proper relative humidity levels in your home:
- Make sure the intakes to your bath exhaust fans are clean of lint and dust.
- Bath exhaust fan ducts should be vented directly to the outside, not just to the attic.
- Run bath exhaust fans for at least 30 minutes after a bath or shower.
- Change cooking exhaust fans from the recirculation type to direct vent. Use them the entire time you’re cooking.
- Check your lint trap weekly on your clothes dryer and clean as needed.
- Make sure your clothes dryer vents directly to the outside.
- If you have a humidifier on your furnace, keep adjusting it during the heating season until the desired RH level is reached.
- Make sure all of your attic vents are open to the outside and clean of debris.
- Keep gutters and downspouts clean. Use extensions on the downspouts to direct water away from the house.
- Your finish grade around the house should slope so water flows away from it. I recommend a fall of 6” for the first 10’ away from the house.
- For crawlspaces, place 6-mil Visqueen over the floor. Lap the seams 6” and go up the sides of the walls 6”. Tape all seams.
- If you have one, run your air conditioner during warm, muggy weather.
- During the heating season, use a humidifier if you fall below the recommended RH levels.