Healthy Indoors Magazine
Issue link: https://hi.healthyindoors.com/i/917400
Healthy Indoors | 21 It's also important to prevent a central air-condi oning system from becoming contaminated with construc on dust and debris if construc on or renova on work is occurring in the summer by closing supplies and re- turns in the work space and depending on window air condi oners for cooling, if necessary. Filtration: Good filters help keep your system clean. Consider installing coarse filtering material (available in building supply stores) cut to size under the return grilles. If the main return is in a hallway ceiling and has a large filter, replace the filter if it looks dusty. Have a technician check your furnace and change the furnace filter as needed. Be sure the filter is the proper size, and that the filter holder is airtight to prevent air from by- passing the filter. If you have an open filter slot, get a mag- netic "Filter Lock" to cover the slot (or use duct tape). I recommend a pleated-media filter with a MERV rating of at least an 8; for those with environmental sensitivities, a rating of 11 is preferable. Change the filter on the recom- mended schedule, if not more frequently. Central humidification: If you have a central humidification system attached to your furnace, be sure it's the once- through trickle type (with a metal-mesh evaporative pad); humidifiers with a rotating sponge pad inevitably get moldy. Air-to-air heat exchangers: Many newer houses with hot-air heat have air-to-air heat exchangers (HRVs) that supply fresh air into the inside environments. Such equipment often becomes moldy. If you have an HRV, inspect it and clean as needed. Moldy dust in an HRV — May Indoor Air Investigations LLC attic checked to be sure they are not leaky (this can lead to ice damming in the winter). If you live where there are cold winters, and you have a ducted system in the attic that only serves as an attic air-conditioning unit, be certain to close all supply grilles and cover the return grilles in the winter. This will prevent moist house air from migrating into the duct system, possibly lead- ing to condensation and mold growth in the duct dust. Ducts in a crawl space: If you have ducts in a crawl space (a practice I don't recommend, since crawl spaces are so often musty), the ducts should be airtight so they don't entrain musty air. Ducts in crawl spaces should also be insulated at the exterior so condensation will not occur within the ducts – a situation that can lead to mold growth in the summer, if the temperature of the crawl space is below the dew point of the house air inside the duct. Construction and renovation: Don't assume that just be- cause you are living in a newly constructed or renovated home, the components of your duct system will be clean. Unfortunately, many contractors run a duct system while construction or renovation work is on-going. Then dust and construction debris can collect in the ducts, leading to mold growth. Construction debris in flexible duct in newly constructed home May Indoor Air Investigations LLC If you are having renovation work done in your home in the late fall, winter or early spring, close and cover the sup- plies and returns where work is ongoing. Depend on sup- plementary heat, if necessary, such as oil-filled radiators. Have the duct system in your newly constructed or renovat- ed home inspected and cleaned as needed.