Musty No More!

With recent hot temperatures, high humidity and occasional downpours, you may be experiencing musty odors wafting up form your old house basement. Your first inclination may be to open your basement windows for some fresh air, but not so fast! Beverly Thomas, Program Director at the N.H. Preservation Alliance offers some tips and first-hand experience.

Many old house owners have water or moisture issues in their basements and are not quite sure how to handle the problem. Even though some owners have expressed that they don’t have major water issues, i.e. water entering their cellars through the stone foundations or up through dirt floors due to high water table (that’s another article!), they do have high humidity levels resulting in very damp musty cellars. An unhealthy condition that supports mold, mildew and bacterial growth.

Getting the relative humidity in check in older cellars is of utmost importance for your family’s health as well as that of the structure.

Recent best practices have shown that closing the cellar windows and using a dehumidifier greatly improves the ability to control the relative humidity at healthy levels. When warm moist air enters a cool cellar, the moisture-laden warm air condenses when it hit the surfaces of cold water pipes and other cool surfaces including the stone foundation. I learned this early on in my dirt-floored damp basement. After the first summer living in our 1870s farmhouse, I proved to myself that leaving the windows open to air out the basement on a hot summer day resulted in condensation on all our cold water pipes causing a rainforest affect with water droplets creating a grid pattern on the dirt floor.

Assuming you don’t have significant ground water or drainage issues and your high basement relative humidity is from condensation, controlling the higher than desirable moisture level can be attainable. If you have a dirt basement and not able to finance a new concrete basement floor, best practices say to install at least a 6mil vapor barrier over the entire floor (and crawlspace) to keep ground moisture from entering up through the ground. If you occasionally have standing water issues, you should consider installing drainage pipe and crushed stone under the vapor barrier. And if you have a sump pump, make sure it drains into a sealed basin.

With the cellar windows and all vents closed, you are now ready to install a dehumidifier to reduce and maintain the desired humidity level. Your target relative humidity levels should be 50% in winter and 55% in summer. Go to your local hardware store to purchase an inexpensive hygrometer to help monitor the RH. Most dehumidifiers can be set to turn on at a specific RH and go off automatically when that target is reached. To save time and many trips up and down cellar stairs, discharge the drain hose of your dehumidifier into your sump pump basin or directly outside far away from your foundation wall. And for fire safety reasons, best practices say not to use extension cords to run appliances like dehumidifiers, but if you must, make sure it is heavy duty!

Humidity can have an effect on multiple areas of your life.

Reducing relative humidity levels in your cellar is not only important for your family’s health, but also for your structure to minimize deterioration due to rot or bug infestation (most destructive wood boring bugs thrive in moist conditions). And if you struggle with exterior paint adhesion problems, you’re likely to see improvement on that front too! Managing moisture will make your historic home more comfortable, healthier to live in and more durable too.

If you are worried about possible damage to your cellar due to humidity, check out our online Directory for contractors with experience working on older homes. You can also reach out to us for advice or with questions, we’d love to hear from you!