Proper Placement of Heating or Cooling Registers & Ducts InspectAPedia® -
How to Locate Heating or Cooling Registers & Ducts
Air Conditioning (or Heating) Duct Defects
Duct installation defects, safety hazards
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This chapter of "How to Inspect the Central Air Conditioning or Cooling System" describes the
Proper Placement of Heating or Cooling Registers & Ducts and addresses problems such as misplaced or missing air conditioning cool air supply
or return air registers, improper cooling duct routing, cooling (or heating) air duct corrosion, and
defective heating or cooling duct work.
The master document, of which this is a chapter, describes the inspection of residential air conditioning systems (A/C systems) to inform home buyers, owners, and
home inspectors of common cooling system defects.
Asbestos in or on HVAC ducts is a possible hazard for which we provide links to a separate document - see "Asbestos HVAC Ducts" at below left.
LOCATION OF REGISTERS & DUCTS - Location of air conditioning return or supply outlets
Supply and return too close together
You don't have to be
an HVAC design engineer to see that in the photograph at page top and shown again here the air conditioning supply register is above and just
a few feet from the central air conditioning return grille. Cool air delivered to this attic room
will mostly fall down to be simply drawn right back into the return.
Poor supply and return duct
locations like this can severely reduce the effectiveness of the cooling system and increase its
operating costs.
In this particular home the installer was confronted with a shoehorn retrofit
of the air handler and duct work into a sub-standard attic bedroom closet in an area where s/he
was not permitted to open cathedral ceilings nor to construct a delivery duct along the ceiling or
under the floors. It was a costly to operate and poor performing air conditioning installation.
Location of Heating or Cooling Return Registers in Basements
The photograph shows a basement door into which an installer cut two return air inlets to feed basement air
back to an air return located at the basement air handler.
As we discussed at INCREASING RETURN AIR,
this is a poor design that increases heating or cooling system operating costs.
In addition to that issue, placement of return air inlets in basements, depending on their location, risk other potential hazards including:
Carbon monoxide hazards: Return air registers too close to oil or gas fired equipment may draw combustion gases or carbon monoxide into the
air duct system, sending dangerous gases into the living space
Carbon monoxide production may be increased and heating fuel combustion incomplete at nearby heaters, water heaters, or even gas clothes dryers, if
the air handler is pulling return air from a confined space where combustion equipment is also located.
Air-starved equipment may not
only work improperly, but may be unsafe, producing dangerous carbon monoxide. We've also found this problem in basements where the
owner, attempting to improve basement air quality, ran powerful exhaust fans continuously.
Placement of Air Returns at Outside Walls
Heating or cooling return air duct systems which place the return register at outside building walls
may perform poorly. Some
heating authorities opine that more effective and economical design places
these registers on the interior walls - the outside walls and perimeter of
some rooms may be chilly even when the heat is operating.
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Additional technical contributors & reference sources for this article are listed below.
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Thanks to Mark Cramer, Tampa Florida, for assistance in technical review of the "Critical Defects"
section and for the photograph of the deteriorating gray Owens Corning flex duct in a hot attic. Mr. Cramer is a Florida home inspector and
home inspection educator.
Thanks to Jon Bolton, an ASHI, FABI, and otherwise certified Florida home inspector who provided photos of failing Goodman gray flex duct in a hot attic.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
"Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
Carson Dunlop, Associates, Toronto, have provided us with (and we recommend)
Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).
More Information on Building Diagnostic Inspections and Repairs
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The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems
Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.
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