Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
Ask a Question or Search InspectAPedia
InspectAPedia ® Home
AIR CONDITIONING & HEAT PUMP SYSTEMS
A/C - HEAT PUMP CONTROLS & SWITCHES
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR FILTER EFFICIENCY
AIR FILTERS, FIBERGLASS PARTICLES
AIR FLOW MEASUREMENT CFM
APPLIANCE EFFICIENCY RATINGS
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books
CAPACITORS for HARD STARTING MOTORS
CLEANING & Legionella BACTERIA
CHINESE DRYWALL HAZARDS
CONDENSATION or SWEATING PIPES, TANKS
DEFINITION of Heating & Cooling Terms
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST, HVAC CONTAMINATION STUDY
ELECTRIC MOTOR OVERLOAD RESET SWITCH
EVAPORATIVE COOLING SYSTEMS
FAN LIMIT SWITCH
GAS EXPOSURE EFFECTS, TOXIC
GAS DETECTION INSTRUMENTS
HEAT LOSS (or GAIN) in buildings
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HEATING SMALL LOADS
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS, A/C SYSTEMS
LEED GREEN BUILDING CERTIFICATION
LOST COOLING CAPACITY
LOW VOLTAGE TRANSFORMER TEST
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
OPERATING COST, AIR CONDITIONER
OPERATING DEFECTS, AIR CONDITIONING
REPAIR GUIDE, AIR CONDITIONERS / HEAT PUMPS
REPAIR & DIAGNOSTIC FAQs for A/C
THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
WATER COOLED AIR CONDITIONERS
WINDOW / WALL AIR CONDITIONERS
WINDOW / WALL A/C SUPPORTS
Heating & air conditioning HVAC ductwork air flow balancing: this building air supply ductwork diagnosis and repair article describes proper (and improper) balancing of heating & air Conditioning duct air flow in residential buildings and in commercial office space including high-rise buildings. Our page top photo shows how individual office occupants who are too hot or too cold can foul up carefully balanced air distribution in a building. Just push over a section of suspended ceiling.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Look for indications that the system has not been balanced for optimum air flow:
You may want your service person to review air flow in different rooms, to add manual balancing dampers in the duct system (and show you where they are located and mark on the duct just where the balancing damper levers are normally set.
Air conditioning cool air balancing in offices & commercial spaces or in homes with long HVAC duct runs
The photographs above show both supply and return ceiling registers in a commercial office space. In this case they are located too close together. The second photograph shows that a ceiling tile has been removed from a suspended ceiling over an office which uses the ceiling cavity as a common return air plenum. While this may produce more airflow in the office where this suspended ceiling tile was removed, it has unbalanced the entire air conditioning system for the rest of the offices in the building.
Many commercial spaces and offices are cooled (and sometimes heated as well) by an air handler which delivers supply air to each office area by flex duct connected to ceiling registers.
Return air is passed back to the air handler through the large common space above a suspended ceiling over the occupied space. Special vents either around the supply registers or placed separately are intended to pass return air to the common ceiling space, and their location and adjustment are important to provide balanced airflow in the work space.
These photos show a common ceiling return air plenum over commercial offices. In the first or left hand photo, notice that rectangular opening in the distance? The second photo is a closeup. Openings had been left open between the office space and the top floor hallway and also between the hallway and other office spaces in the building, so that particles, leak-related mold, or other irritating particles developing over any office will be shared among all of the tenants on this building floor.
In addition to the HVAC air duct flow balancing problems & recommendations discussed above, consider these possible causes of inadequate cool air or warm air deliver to some building areas:
Frequently Asked Questions (FAQs) About HVAC air duct balancing: how to obtain even heating or cooling air flow thorughout a building
Question: forms for commercial air duct flow balancing for a retail building?
I need forms for commercial air balancing for a retail building. - Kevin Ryan, Oct 2012
Kevin I am doubtful that "forms" will be enough to balance air flow in a retail building; the HVAC duct design has to consider quite a bit of information beyond what's in a duct layout sketch form. I'd start by making a drawing of the existing system, including duct diameters, lengths, bends, and location of supply and return registers; You may need to consult an HVAC design engineer, but some defects will become obvious simply by examining the duct layout.
Question: How do we get cool air to the more-distant, hotter end of our house?
Your site is fantastic. I am a home owner that needs a cheap but through education because of a bad remodel. My question is: my home is a one story shaped like a rectangle. We have a brand new AC unit. One end of the house is cool and very comfortable. The very end of the house is always much hotter. If we cool the entire house we have to set the thermostat at 65 degrees. So the really cool end of the house is like a meat locker and the other end is just comfortable.
I know this could be a duct problem or it could be the wrong size unit was purchased to begin with. We have a 5 ton - maybe we needed two smaller units? Did I mention I live in Phoenix AZ? What is the logical way to start? If I missed this issue on your site you could tell me where it is. thanks. - G.B. - Phoenix, AZ /p>
Reply: priority of things to try to improve cool air (or warm air flow) across a building with long HVAC duct runs
Before doing something expensive like installing a pair of new A/C units and separate HVAC cooling duct systems to make cooling distribution more effecive across yoru home, and presuming there is a complete house HVAC duct system already installed, I'd have considered these steps:
Those components should be much less costly than system replacement and redesign.
Questions & answers or comments about how to balance air delivery or air supply in duct systems for building heating and air conditioning.
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.