South Florida presents unique dehumidification challenges due to year-round humidity and heat. Understanding the right dehumidification strategy for your home protects your health and your investment.
Traditional single-stage air conditioners run at 100% capacity or off — no middle ground. This works for temperature control but is a blunt instrument for humidity management.
Two-stage systems add a low-speed stage (typically 65–70% capacity) that runs during moderate conditions. The low stage runs longer, moves air more slowly over the coil, and removes more moisture per cycle. Variable speed systems operate across a continuous range, dialing in exactly the capacity needed to maintain both temperature and humidity simultaneously. At low speeds they can run almost continuously during mild, humid shoulder-season conditions — keeping the coil active and humidity under control even when there’s no real cooling load. Variable speed systems are the gold standard for humidity control in South Florida, particularly in tightly constructed homes.
Blower fan speed matters enormously for dehumidification — and is one of the most frequently misconfigured aspects of HVAC systems in South Florida. Air needs sufficient time in contact with the cold coil to give up its moisture. Run the fan too fast and air moves through before adequate condensation occurs.
ACCA guidelines suggest blower airflow around 350–400 CFM per ton as a general target, with dehumidification-focused applications sometimes calling for lower airflow to increase coil contact time. Many modern variable speed air handlers can be configured to reduce fan speed when humidity is elevated — prioritizing moisture removal over air circulation. This is a setup decision made at installation and makes a significant real-world difference in how comfortable a home feels at any given thermostat setpoint.
How a home is constructed changes everything about its dehumidification needs. A tight building envelope — sealed penetrations, minimal air infiltration, energy-efficient construction — means the HVAC system controls nearly all moisture entering the space. This is good for energy efficiency but means the mechanical system bears the full dehumidification burden and must be designed for that role.
An older South Florida home with concrete block walls, original windows, and decades of small gaps is a leaky envelope. These homes have a higher latent (moisture) load and need systems calibrated for it. The practical implication: envelope improvements — sealing attic penetrations, replacing weatherstripping, upgrading windows — change the dehumidification math and are often more cost-effective than simply adding equipment.
Some homes are designed with systems that intentionally bring in outside air — energy recovery ventilators (ERVs), heat recovery ventilators (HRVs), or simple exhaust/supply fan arrangements. In South Florida, fresh air requires careful management because outdoor air carries enormous moisture load most of the year.
An ERV is strongly preferred over an HRV in South Florida because it transfers both heat and moisture between incoming and outgoing air streams, pre-conditioning the fresh air using the conditioned air being exhausted. An HRV transfers heat but not moisture, which can result in significant humidity spikes when running in South Florida conditions. Fresh air rates should be sized to meet ASHRAE 62.2 requirements without over-ventilating — excess fresh air means excess humidity load for everything downstream.
Even a well-designed HVAC system may not provide adequate dehumidification during shoulder seasons — periods when temperatures are comfortable but outdoor humidity is still high. Dedicated dehumidifiers fill this gap.
Inline (ducted) dehumidifiers are installed in the HVAC ductwork and operate independently of the AC — running when the dehumidistat calls for moisture removal regardless of whether the thermostat is calling for cooling. High-capacity whole-home units (Aprilaire, Santa Fe, Honeywell, Ultaire) can remove 70–130 pints of water per day. Attic dehumidifiers address South Florida’s specific attic vulnerability: unconditioned attics accumulate enormous moisture loads from stack effect, duct leaks, and roof deck temperature swings. An attic dehumidifier manages humidity at the source rather than waiting for problems to migrate down into the living space.
Modern high-efficiency heat pumps — particularly variable speed models with inverter compressors — perform well in South Florida’s mild heating season and excel at dehumidification during mild weather. Variable speed heat pumps can modulate down to very low capacity, running long slow cycles ideal for wringing moisture out of the air without over-cooling spaces that don’t need aggressive cooling.
Some advanced systems include a dedicated “dehumidify” mode that actively reduces indoor humidity while compensating for temperature change — running the cooling cycle for moisture removal while reheating the supply air to maintain thermostat setpoint. This mode is particularly useful during mild, humid shoulder seasons. For most South Florida homeowners replacing aging equipment, a properly sized variable speed heat pump paired with a dedicated inline dehumidifier represents the most capable combination currently available.
When to use a dehumidifier, what size is needed, attic dehumidification, whole-home vs. portable units, and more.
learn more
What dew point actually means, why indoor humidity stays high, how temperature affects moisture levels, and more.
AC removes some moisture — but it’s not a dehumidifier. Learn why South Florida homes can feel humid even with the AC running, and what to do about it.
Water doesn’t have to be visible to be a problem. Learn how moisture enters South Florida homes.
We’re here to help. Whether you’re trying to learn about pollutants in your home or workplace, or just want to point us toward a topic you’d like us to cover — we’d love to hear from you.
South Florida Indoor Air is an independent educational resource dedicated to helping our community breathe better and make informed decisions about the air inside their spaces.