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Comfort & Moisture

Humidity and HVAC Energy Use

How indoor humidity affects comfort, air-conditioning operation and the temptation to lower thermostat settings.

The Practical View

Reduce the load before chasing a rating

Temperature is only part of summer comfort. High indoor humidity reduces the body's ability to cool through evaporation and can make a reasonable air temperature feel uncomfortable.

When the home feels damp, occupants often lower the thermostat, increasing cooling runtime without necessarily correcting the underlying moisture problem.

Air-conditioning dehumidification depends on coil conditions, airflow and run time, while building moisture sources and outdoor-air leakage also affect indoor humidity.

Energy Factors

What affects HVAC operating cost

Latent load

Cooling equipment must remove moisture as well as sensible heat.

Runtime

Longer stable cooling cycles can provide more opportunity for moisture removal.

Oversizing

Excess cooling capacity can satisfy temperature quickly and reduce dehumidification time.

Air leakage

Humid outdoor air entering the building adds moisture load.

Duct leakage

Return leaks in humid spaces can add moisture directly to the HVAC air stream.

Controls

Some systems use airflow or capacity strategies specifically to improve humidity control.

Efficiency vs. Consumption

They are not the same thing

Equipment efficiency describes how effectively equipment performs under defined conditions. Your utility consumption also depends on weather, thermostat settings, building heat gain or loss, ductwork, system sizing, maintenance and how many hours the equipment operates.

Best Investment

Fix obvious waste first

Before replacing functioning equipment solely for a higher efficiency rating, evaluate low-cost problems such as thermostat schedules, dirty filters, blocked airflow, duct leakage and building-envelope deficiencies. Major equipment replacement should be evaluated on installed cost, expected savings, comfort and remaining equipment life.

Related Resources

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Planning a Replacement?

Compare efficiency as part of the complete project

Use the Buying Guides and Homeowner Tools to evaluate equipment efficiency, system age, replacement budget and contractor proposals together.

HVAC Efficiency Buying GuideHomeowner Tools
Homeowner IAQ Tool

Not sure which IAQ solution fits the problem?

Use the IAQ Device Selector to compare practical options for filtration, air cleaning, humidity, moisture and ventilation—and see when an in-home evaluation makes more sense.

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