Does your Key Largo home ever feel sticky even when the AC is running? You are not alone. Warm, salty ocean air can leave surfaces tacky, closets musty, and metal finishes spotting with corrosion. If you want a fresher, drier home year‑round, a few smart upgrades and habits make a big difference.
In this guide, you will learn how to bring in fresh air without adding moisture, when and how to use dehumidifiers, which materials hold up to salt, and the simple maintenance plan that keeps everything humming. Let’s dive in.
Why Key Largo humidity feels different
Key Largo sits in a tropical maritime climate with high outdoor humidity most of the year. Nighttime and wet‑season air often sits above 60 to 70 percent relative humidity, so moisture control is a year‑round need, not a seasonal chore. That outdoor air also carries salt that speeds up corrosion on coils, fasteners, window tracks, and exterior hardware.
Many homes are elevated for flood resistance, which changes how air moves under and through the structure. Open foundations and vented crawlspaces can draw in humid air and sea spray if they are not sealed or conditioned correctly. The big takeaway is simple: in hot‑humid coastal settings, you manage moisture by controlling sources, conditioning the air, and using materials that can take the salt.
Ventilation that keeps air fresh and dry
You need fresh air for health and odor control, but raw outside air in the Keys can add a heavy moisture load. The goal is controlled ventilation that pairs with dehumidification.
Use balanced ERV over raw intake
A balanced ventilation system with an Energy Recovery Ventilator (ERV) brings in outside air while exhausting stale air and transfers some heat and moisture between the two streams. In hot‑humid climates, an ERV can reduce the moisture you bring indoors compared with a simple outside air duct or window ventilation. Heat Recovery Ventilators (HRVs) transfer heat but not moisture, so they are usually less suitable here.
Match fresh air to dehumidification
If you add mechanical ventilation, make sure your HVAC or dehumidifier can handle the extra moisture. Use recognized residential ventilation targets such as ASHRAE 62.2 as a design basis for fresh air and size dehumidification to match. In many homes, a properly sized whole‑house dehumidifier paired with an ERV is an effective combination.
Consider demand‑controlled ventilation
Ventilation that ramps up when you are home and down when you are away can protect comfort without dragging in unnecessary humidity. Systems that respond to occupancy or indoor humidity help you fine‑tune air quality while limiting latent load.
Place intakes where salt is lower
Locate outside air intakes away from sea spray, roof runoff, and exhaust outlets. Use pre‑filters and insect screens, and avoid intakes tucked under eaves where salt deposits collect. Plan for easy filter access because coastal systems need more frequent cleaning.
Seal attics and crawlspaces when practical
Conditioned, sealed attics and crawlspaces often perform better than vented ones in the Keys. Insulating at the roofline helps keep ducts and equipment inside the conditioned space, reduces condensation on ductwork, and limits infiltration of humid, salt‑laden air. If you encapsulate a crawlspace, include a ground vapor barrier and dedicated dehumidifier.
Dehumidification you can count on
In Key Largo, dehumidification is central to comfort and durability. It controls musty odors, limits mold growth, and stops sticky surfaces.
Set targets that work in the Keys
Aim to keep indoor relative humidity below 60 percent to limit mold risk. Many homeowners find 40 to 50 percent feels best in hot climates. Pros also watch indoor dew point and often target about 60 to 62 degrees Fahrenheit or lower to avoid condensation on cool surfaces.
Whole‑house vs portable units
- Whole‑house dehumidifiers treat the entire home, can run automatically, and are usually more efficient per gallon of water removed than multiple portables. They cost more up front and must be sized and integrated correctly, with corrosion‑resistant components for coastal duty.
- Dedicated crawlspace or attic units help if those areas are sealed and tend to collect moisture.
- Portable units are flexible and lower cost, useful for problem rooms like laundry rooms or closets. They can be noisy, need frequent draining or a pump, and may struggle with very high loads.
Central AC will remove some moisture while cooling, but it is controlled by temperature, not humidity. Oversized systems short‑cycle and remove less moisture. That is why pairing right‑sized cooling with a whole‑house dehumidifier works so well here.
Size for capacity, plan for drainage
Choose dehumidifier capacity based on your home’s volume, how you live, and how tight the building envelope is. Look for corrosion‑resistant coils and fasteners, an integrated humidistat, and automatic defrost if the unit sits in a cooler space. Plan a reliable drain path. Many elevated homes need a condensate pump or a dedicated drain line to a safe discharge point.
Run it when the weather says to
In the Keys, plan to run dehumidification much of the year, especially during wet months and shoulder seasons. Use trusted sensors to monitor RH in main living areas and in moisture‑prone spots like closets. Keep garage and shed doors closed and consider small dehumidifiers or passive vents for closets that trap moisture. If you add ventilation, increase dehumidification capacity to match.
Envelope and materials that last near the ocean
The right building assembly helps you avoid condensation, limit air leaks, and fight corrosion.
Conditioned attics, ducts inside
A sealed attic with insulation at the roof plane often performs best in hot‑humid climates. Closed‑cell spray foam at the roof deck serves as both insulation and an air and vapor control layer. For re‑roof projects, rigid foam above the roof sheathing is another path. Keeping ducts and equipment inside the conditioned space reduces the risk of sweating ducts and keeps energy use in check.
Walls, windows, and flashing that dry
Use vapor‑permeable sheathing and water‑resistive barriers that allow assemblies to dry to the exterior. Avoid trapping moisture between impermeable layers. Choose corrosion‑resistant fasteners and robust flashing details around windows and doors. High‑performance windows with low solar heat gain reduce cooling loads and help your AC and dehumidifier keep up.
Finishes that handle washing and salt
Select marine‑minded materials where you can. Stainless or aluminum hardware, coated HVAC coils, and corrosion‑resistant fasteners hold up better in salt air. Inside, mold‑resistant drywall and moisture‑resistant backers in wet rooms are smart upgrades. Tile, washable paints, PVC trim, and composite decking make regular rinsing and cleaning easy.
Ductwork that resists leaks and condensation
Keep ducts in conditioned space whenever possible. Seal and insulate ducts thoroughly, and use corrosion‑resistant fittings. In coastal settings, coils and condensate pans need frequent inspection and cleaning to maintain efficiency and avoid leaks.
Flood‑smart foundations and under‑home spaces
Elevated homes are common in Monroe County. Use ground covers and positive drainage under the structure, raise mechanicals above expected flood levels, and protect wiring and equipment from splash and spray. Where codes and design allow, an encapsulated, conditioned crawlspace with a dedicated dehumidifier can stabilize moisture and improve indoor comfort.
Your Keys humidity maintenance plan
A steady, light touch beats big fixes later. Use this simple rhythm to stay ahead of moisture and salt.
Weekly to monthly
- Check RH in the living room, primary bedroom, and a closet. Note the values.
- Empty portable dehumidifier buckets or confirm the condensate pump is working.
- Walk the home for musty odors, stains, or early signs of corrosion.
Quarterly
- Replace HVAC and ERV filters and clean the ERV core as the manufacturer recommends. Coastal homes often need this more frequently.
- Rinse outdoor HVAC condenser fins with fresh water to remove salt deposits. Follow dealer guidance.
- Inspect exterior caulking and flashing around windows, doors, and utility penetrations.
Biannual
- Schedule HVAC tune‑ups in spring and fall. Ask for coil cleaning, refrigerant checks, condensate pan and drain inspection, and a dehumidifier performance check.
- Inspect attics and crawlspaces for damp spots, standing water, or mold. Confirm vapor barriers are intact.
Annual
- Service whole‑house dehumidifiers and ERVs. Test the condensate pump, review setpoints, and verify controls.
- Check and touch up protective coatings on exterior metals. Inspect mechanical equipment for corrosion. Clean and lubricate moving parts.
- Clean gutters and downspouts and confirm drainage moves water away from the foundation.
Shopping checklist for upgrades
When you plan improvements or hire a contractor, ask for these items so your system is right for the Keys.
HVAC
- Manual J load calculation and Manual D duct design.
- Coils with hydrophilic or corrosion‑resistant coatings.
- Reliable condensate drainage with proper slope and protection.
Dehumidifiers
- Whole‑house capacity sized by pints per day for your conditioned volume and lifestyle.
- Corrosion‑resistant construction and an integrated humidistat.
- Built‑in pump or planned gravity drain to a safe discharge.
Ventilation
- ERV sized to recognized residential ventilation rates for your home and occupancy.
- Accessible filters and washable cores for easy, frequent maintenance.
Insulation and envelope
- Sealed roofline assembly with closed‑cell spray foam or continuous exterior rigid insulation during re‑roofing.
- Vapor‑permeable, water‑resistive wall assemblies and careful flashing.
The real estate angle: protect comfort and value
Managing humidity in Key Largo is not only about comfort. It also protects finishes, reduces odors, and keeps your home showing its best. If you are selling, a drier, well‑maintained home photographs better and feels better during showings. If you are buying or upgrading, investing in moisture control pays you back in lower maintenance and longer‑lasting systems.
If you want a property that fits your lifestyle and is set up for Keys conditions, or you need referrals for local pros who understand coastal construction, connect with the team that lives this every day. Reach out to Island Welcome Real Estate to talk through your plans. Start Your Island Search.
FAQs
Can central AC alone control humidity in Key Largo homes?
- AC removes some moisture while cooling, but it is temperature‑driven, so in hot‑humid conditions it often cannot hold ideal RH; pairing right‑sized AC with a whole‑house dehumidifier gives better year‑round control.
Is it smart to open windows at night in the Keys?
- Outdoor humidity is often high at night in Key Largo, so opening windows can raise indoor RH and bring in salt air, which may feel cooler briefly but leads to condensation, stickiness, and corrosion.
Is closed‑cell spray foam worth it at the roofline?
- Closed‑cell spray foam is an effective air and vapor control layer for a sealed attic, helps keep ducts inside the conditioned space, and is a strong option for hot‑humid coastal homes when installed by qualified pros.
Whole‑house dehumidifier or multiple portable units?
- Whole‑house systems typically provide more consistent results with less maintenance and better efficiency, while portables are useful for spot treatment in areas like laundry rooms or closets.
How do I stop musty closets in a humid home?
- Encourage a little air exchange or add a small dehumidifier, avoid storing damp items, and monitor RH; aim for about 40 to 50 percent in closets to limit odors and mold.
How often should HVAC coils be cleaned near salt air?
- In coastal environments, many contractors recommend coil cleaning and corrosion checks every 6 to 12 months; follow manufacturer guidance and schedule regular service.
What indoor humidity target should I use in Key Largo?
- Keep indoor RH below 60 percent to reduce mold risk, and aim for 40 to 50 percent for comfort when possible; many pros also target about a 60 to 62 degree Fahrenheit indoor dew point.
