Healthy Indoors Magazine
Issue link: https://hi.iaq.net/i/509496
May's Ways Continued from previous page 34 May 2015 install a sump pump. Before installing a French drain system, however, check conditions out- side your home that may be causing water- intrusion problems in your basement. For example, many water problems in base- ments are caused by poor control of roof water at the exterior. Keep your gutters and down- spouts clean, and check to be sure downspouts are connected properly and are directing wa- ter away from the foundation. If needed, add splash blocks or insert the downspouts into underground piping by installing 4-inch solid PVC piping buried about two inches below the soil, and extending to daylight downhill from the house or to the edge of a landscape furrow. An easy way to test for drainage problems is to run water from a hose at the end of a downspout and see if water enters the basement. Mold can also grow in basements that haven't had water intrusion. Basements are naturally cool and damp. As air cools, its relative humid- ity (RH) rises. Some mold species can flour- ish when the RH exceeds 80%, even in the absence of liquid water from water intrusion or pipe leaks. All below-grade (below ground-level) spaces must therefore be dehumidified in the humid season (in a four-season climate, that means approximately mid-April to mid-October). Use a dehumidifier that's adequate for the space. Attach the machine to a condensate pump so that it drains directly into a sink, sump or to the exterior so the machine won't turn off when the reservoir is full. Measure the RH separately with a thermo-hygrometer, available in many home supply stores. In an unfinished basement, the RH should be at or below 50%, whereas it should be at or below 60% in a finished base- ment. Air conditioning can control the RH, but if your thermo-hygrometer confirms that the RH is over 60%, add dehumidification. You do not need to dehumidify a basement (fin- ished or unfinished) in the heating season, but you must heat a finished basement when you heat the rest of the house – whether you are using the space or not. Otherwise, the RH will most likely rise high enough for mold growth to occur. This growth can be barely visible white or yellow splotches on the bottom foot or so of finished basement walls, especially in exterior corners, and on a basement ceiling and the bot- toms or backs of furniture facing the cool floor walls. Mold can also flourish in the dust cap- tured in carpeting laid on a cool, concrete floor. Mold growth on a paneled basement ceiling (left). Photomicrograph of mold hyphae on carpet fibers (right). Believe it or not, mold can subsist on the dust captured in fiberglass insulation, which is often installed below-grade. That's one of the reasons it's not a great idea to saw wood in a basement; biodegradable sawdust can collect on walls, ceilings, the floor, and even in exposed fiber- glass. Mice love to nest in exposed fiberglass. Mouse burrows and droppings in fiberglass insulation And where there are mice, there can be shrews. These animals look a little like mice but have