Healthy Indoors Magazine

HI October 2017

Healthy Indoors Magazine

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MAY'S WAYS— October 2017 22 empty the reservoir, and will prevent the machine from shutting off when the reservoir is full. Do not isolate finished basement spaces from the de- humidification. Keep doors open or install louvered doors. Use fans to increase airflow. Acquire a duct kit if available. Air conditioning can help dry air, but measure the RH in any case, and add dehumidification as needed. And in the winter, finished basement rooms must be consistently heated, wheth- er in use or not, with the thermostat set at a minimum of 58°F. Crawl spaces should be isolated from the exterior and dehumidified; otherwise, when the weather is humid, moist air will flow into the space, moisture will condense on cool surfaces, and mold will begin to grow. A basement exhaust system is not a dehumidifier. If air is sucked out of a basement, air must flow back in. This "make-up air" comes either from the rooms above the basement or from the exterior, or a combination thereof. On a hot and humid day, the air from the house (unless there is central air conditioning) and from the exterior will have a high moisture content, and thus will introduce more moisture into the basement. This moisture can condense on cool basement surfaces, leading to mold growth. If the house is air conditioned, the air from the rooms above the basement will be cool and dry, but humid air will be drawn into the house to replace the air that flows into the basement. This outdoor air must then be cooled and dried, so the cost for "exhaust dehumidification" is hidden in the higher cost of the A/C operation. Remove the wall-to-wall carpeting, even if new. If the RH has not been consistently controlled in your finished basement, and/or if the basement has ever experienced leaks or water intrusion, and the carpet got damp, there is probably mold growth in the carpet. This mold is subsisting on the dust that is captured in the carpet fibers. (Even outdoor-type carpeting captures dust.) It's best to avoid carpeting below-grade; vinyl or ceramic tiles are preferable. Control the relative humidity (RH). Certain kinds of mold can flourish when the RH is above 80%. Basements are naturally cool and damp, so they must be dehumidified in the humid season (in New England, generally from mid-April to mid-October). Measure the RH separately with a thermo-hygrometer. In unfinished basement spaces and in finished basements that do not have insulated walls, the RH must be kept at or below 50%. In finished basement spaces with insulated walls, the RH must be kept at or below 60%. Use a dehumidifier adequate for the purpose, and attach it to a condensate pump so that the machine can drain into a sink, sump or to the exterior. This will save you from having to Eight Healthy Home Tips for Below-Grade (Below Ground-Level) Spaces ©2017 Jeffrey C. May Condensation on stone foundation and mold growth on a duct in a crawl space May Indoor Air Investigations LLC If you have a duct system, consider installing central dehumidification (but only with pleated media filtration).

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