Your home's return plenum is a part of your HVAC (heating ventilation and air conditioning) system that is out of site and usually out of mind. The word plenum means a chamber intended to contain air, gas, or liquid at positive pressure. Simply put, its the box the air travels through. In this case the return plenum is where home's ambient air returns to the HVAC system to be heated or cooled. Since its hidden, most homeowners never look inside this part of the house. This area often becomes a repository for all sorts of material such as dust, debris, pet hair, dust bunnies and even the dead bodies of pests.
The return plenum gets dirty for two primary reasons:
- Improper sealing - The ducting and/or plenum is not sealed properly. This is very common and renders an air filter mostly useless
- Deferred maintenance - Air filters haven’t been changed regularly or the filter becomes so dirty, blow-by occurs (more)
The return plenum is often located behind a metal grill on a wall, in the ceiling or in rare cases, on the floor of older homes. This area is the chamber behind or below the air filter depending on if the filter is located behind the grill or located under the air handler unit.
Cleaning out this area is very easy. Simply open or remove the grill (which ever applies). Then, using a good flashlight, survey the area to determine if any build up is present and just how dirty it actually is. Carefully vacuum out the box. Having the return plenum sealed while you have it open will reduce debris build up as well as dramatically increases the air quality of the home. A sealed plenum reduces cleaning and maintenance on the HVAC system's coil and ducts. Sealing the plenum is easy but depending on how tight the space is, it may take some time to cover all the seams and joints with a sealant. If your return plenum was built correctly, it will be lined with drywall or another approved material like fiberboard. You shouldn't see framing like studs or the sole plate of the wall or any fiberglass batt material. Be sure to choose a sealant that is approved for indoor use by reading the product label. You will be breathing the sealant fumes until the sealant cures.
While you're at it, look for water stains in this area and check to see if air is getting past your air filter. This section might not apply to those of you who have an inline HEPA filter. If your air filter is located below the air handler, remove and look into the lower panel on the air handler to see if it's dirty in the fan area. If you filter is located behind the grill, the 1" lip where the filter sits will show dust that has missed the filter (blow-by). If you find dirt has bypasses the filter, consider relocating the filter from the under air handler to a return grill filter type. If you already have a return grill filter, consider weather stripping the 1" lip so the stripping is between the filter and frame. This will form a good seal and prevent blow-by.
If your air handler/furnace/coil are located directly above this area, there is a good change water has overflowed or will over flow the A/C's primary drain line. Consider installing a primary drain overflow kill switch especially if you have any carpet or wood flooring you don't want destroyed if the primary drain does overflow. Maintaining your primary drain by pouring about a cup of bleach in the beginning of the primary drain will help prevent these overflows.
Frequency: Check every three years
Difficulty: Easy
Tools Required: Household vacuum cleaner and a screwdriver
Completion Time: 15 minutes
Regardless of they type of house you have, there are some necessary tasks you will have to do stay on top of things. Learn more and keep up with your house with a free My Healthy House.com profile. Stay tuned and make your house the best it can be.
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© Healthy House, Inc. 2009
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