Healthy Indoors Magazine
Issue link: https://hi.healthyindoors.com/i/1227696
Healthy Indoors | 55 that moisture isn't condensing on the sheathing or roofing nails. If moisture is migrating from the house into the attic, consider reducing the humidification. (Drip marks at or below sheathing nails are an indica- tion of excess moisture.) Rust at nails and wood stains indicate condensation May Indoor Air Investigations LLC Drip stains on pull-down stairs leading to attic May Indoor Air Investigations LLC • Take steps to minimize the flow of moist air from the house into the attic by covering the access hatch or pull-down stairs with an airtight insulated box, or by insulating the in- side of a door leading to permanent stairs. Be sure that such a door is airtight (add gaskets or a sweep as needed). • If you have an air handler in the attic and the unit has a central humidifier, be sure that the handler and the attic ducts are not leaking air into the attic. The filter holder should be airtight, and the ducts should not have any gaps or, if the flexible type, punctures or holes. • Measure the RH separately with a thermo-hygrometer, available at many home-supply stores (like Home De- pot). Keep the RH at or below 40%. In very cold weather, keep the RH below 35%. Central humidifiers: In almost every furnace humidifier I see that has a water reservoir, the tray that holds the water is full of microbial growth and its byproducts: substances that mold and bacteria contain and excrete and that can make some people sneeze, cough and wheeze. These sub- stances are in water droplets that the humidifier releases into the air in the mechanical system. When the droplets evaporate in the air, the particles that were within the droplets still remain suspended in air and can be inhaled. Even when these particles settle onto sur- faces, they can become airborne again when the surfaces are disturbed by human activities (moving objects, walking across floors, wiping surfaces, etc.). There's another reason I don't like central humidifiers with water reservoirs. Most of them that I have inspected have two modes of operation: broken in the "on" position, and broken in the "off" position, so the humidifiers either cease to function or overflow into the duct system. I encourage people who want central humidification to choose either a trickle- or steam-type humidifier, neither of which has a water reservoir in which mold, bacteria and/or yeast can grow. Should you humidify your home? If humidification makes the air in your home more comfort- able, then the answer is yes, but follow these tips: • Choose the right kind of humidifier. • Inspect the humidifier at least once a month and clean the device as needed. • Be sure that the device is not leaking. If you have cen- tral humidification and the device is leaking, water may soak into exposed fibrous lining material in the ducts or furnace, fueling mold growth within the system. Exposed fibrous lining material contaminated with microbial growth May Indoor Air Investigations LLC • Check your attic sheathing on a cold night to be sure