AC duct and air handler temperature measurement points (C) Carson Dunlop AssociatesImprove Cool Air Supply from Air Conditioning or Heat Pump Systems
How to find and fix the cause of weak or too-warm air from air conditioning supply registers

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Diagnose & fix weak / warm air conditioner output:

This article describes the common causes of too-weak or too-warm air supplied from an air conditioner or heat pump system (in cooling mode).

Before deciding to buy a bigger or more powerful or higher BTU-rated air conditioner or before changing the blower fan here are some basic and usually low-cost things to check that could make a big difference in how well an air conditioner is delivering cool air to the occupied rooms in your building.

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Check and Fix These Existing Air Conditioning Problems Before Trying to Improve its Cooling Capacity

Photograph of client using tissue to look for air conditioning air flow

Watch out: It could be a mistake to spend on any costly air conditioning improvement if the original system actually already had the needed capacity, but simply needed maintenance (like replacing a filter - A/C Filter Problems) or repair (like repairing a leaky duct - A/C Air Duct Problems).

FIRST: review all of the air conditioning performance diagnosis suggestions here to be sure there is not something that needs to be repaired or corrected with the system.

For example we have seen cool air output significantly improved by finding and fixing a disconnected cool air duct that no one had noticed in a hard-to-access crawl area.

Certainly some central air conditioning systems, especially retrofit designs, have less than optimum duct design, such as inadequate central return air registers, room doors that are so tight that it is difficult to blow cool air into the room when the door is closed, inadequate supply ducts or less than optimum supply register placement such as only in floors.

But redesigning and installing for an optimum air conditioning duct system can be costly, so it might be worth taking some other steps.

SECOND: make sure that other energy-savings steps have been taken in the building, such as proper insulation, sealing un-wanted drafts, etc.
See ENERGY SAVINGS in BUILDINGS - those suggestions apply to both heating and cooling costs.

If your HVAC service technician is sure that the present cooling system is working as intended, then if you are not considering supply or return air duct improvements, or a replacement air conditioner system of higher capacity, you might consider a stronger blower fan (discuss what you could do with your HVAC tech), or booster fans individual registers.

Watch out - just boosting air conditioner air flow by installing a higher capacity blower fan is not that simple - if the blower moves air through the duct system faster than the design speed for the system ,the cooling coil may be insufficient in capacity, the air will not be dehumidified (and the building will be less comfortable - A/C Not Dehumidifying), or you might get annoying duct or equipment noises. Discuss these possibilities with your HVAC service company.

How to Get More Cool Air Flow from Floor-Level Air Conditioning Supply Registers

How can I improve cold air delivery from my air conditioner?

Older Florida home with air handler under house in crawl space. Air is ducted to floor registers. Not very efficient as cold air doesn't rise much. House has a flat roof no attic space to get up into. Any thoughts on how to improve? - D. (Anon).

Reply: Checklist of Air Conditioner Airflow Improvements

A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem. That said, here are some things to consider in improving cool air flow in your home:

We agree completely that cool air works better delivered from ceilings than from floors since cool air tends naturally to fall through the occupied space. It takes more energy to blow cool air "up" than to drop it into a room from supply registers mounted high on walls or in the ceilings. We discuss this further

But the cost of changing ductwork is rather high and the work disruptive so that's not your first choice.

Here are some A/C cool air flow improvement steps:


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