Sensible vs. Latent Heat Plain English
Sensible heat is the easy one: it’s the change you feel on a thermometer—sun through windows, hot appliances, people in a room. Latent heat is “hidden” in moisture. When your AC pulls water out of the air, it’s working on latent heat. On an ASHRAE psychrometric chart, sensible changes slide left/right (temperature), while latent changes move up/down (moisture). In a real home, both happen at once: the oven raises sensible load; a shower raises latent load. Good system selection respects both. If your unit only hammers temperature, you’ll get 72°F air that still feels sticky. If it only dries aggressively, winter can feel nose-bleedingly dry. Balanced equipment—and a sealed, insulated house keeps both in check.
Helpful reads: Sizing Guide
Why Humidity Control Matters as Much as Temperature
At 75°F, 70% humidity feels muggy; at 75°F, 40% humidity feels comfortable. That’s latent heat at work. High humidity slows sweat evaporation and makes your AC feel weak. Low winter humidity dries skin, warps wood, and irritates sinuses. Aim for 30–50% RH year-round. Practically, that means selecting cooling that reliably dehumidifies in summer and adding controlled humidification (or just tighter building shells and right-sized heating) in winter. Many comfort complaints—“It’s cool but sticky,” “Upstairs is swampy,” “Basement smells musty” are latent issues, not thermostat setpoints. Address the moisture, and you can often raise cooling setpoints a few degrees without losing comfort, saving energy in the process.
Explore equipment options: R32 Condensers
SHR (Sensible Heat Ratio): The 65–80% Rule of Thumb
Sensible Heat Ratio (SHR) tells you how a unit splits its effort: temperature reduction (sensible) versus moisture removal (latent). Typical residential SHR runs 0.65–0.80. An SHR of 0.75 means the system spends 75% of capacity dropping temperature and 25% removing humidity. In dry climates you can live with a higher SHR; in humid areas you want more latent muscle (lower SHR). Two identical “3-ton” systems can feel very different if their SHR differs. When we see “cool but clammy,” it’s often an oversized unit with high SHR and short run times. Ask for rated SHR data and match it to your climate and your Manual J latent load.
Learn & plan: Design Center
Climate Zones: Humid vs. Arid vs. Mixed
Your zip code shapes your load. Humid Southeast/Coastal homes take on outside moisture through infiltration and ventilation latent load is king. There, we lean toward lower SHR equipment, longer run times at low speed, and sometimes dedicated dehumidification. Arid/High-Desert regions mainly fight sensible heat; higher SHR gear is fine, and ventilation can even add comfort. Mixed climates swing seasonally think latent-heavy shoulder seasons and dry winters. For these areas, variable-speed or multi-stage systems shine by stretching runtimes and throttling capacity to match the day. If your house sits by a lake, has a damp basement, or uses high-occupancy spaces, bump latent capacity. If you’ve got big west glass and little shade, prioritize sensible.
See matched systems: R32 AC & Coils
Manual J: How Pros Size for Sensible and Latent
Skip “500 square feet per ton.” That shortcut ignores moisture. A Manual J load calculation weighs insulation, windows, shading, air leakage, occupants, appliances, and local weather to produce both sensible and latent loads—room by room. We then select equipment (Manual S) and ductwork (Manual D) that can actually deliver those numbers. The payoff is big: smaller, quieter systems that run longer at lower speed, wring out humidity, and keep temperatures even. If a contractor won’t do (or show) Manual J, you risk buying a system that short-cycles and never dehumidifies properly. Ask for the latent line item—and make sure it’s not “assumed.”
Next step: Get a Quote by Photo.
Matching Equipment to the Load You Actually Have
Once you know your loads, match the gear:
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Standard AC / Heat Pump: Works in average conditions if sized right and ducts are tight.
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Variable-Speed / Inverter: Runs longer at low speed for better dehumidification and fewer swings.
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Enhanced Dehumidification Modes: Some air handlers overcool coils for extra moisture removal.
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Whole-Home Dehumidifier/Humidifier: When latent loads are extreme or winter air is desert-dry.
Real-world pick: humid climate + leaky envelope? Consider an inverter heat pump with a whole-home dehumidifier. Tight, dry climate? A right-sized single-stage might be perfect.
Shop options: R32 AC & Gas Furnaces
Variable Speed: Longer Runs, Drier Air
Why do techs love variable speed? Because time on coil dries air. Running at lower CFM over a colder coil increases moisture removal. Instead of blasting cold air for 8 minutes then shutting off (leaving humidity behind), an inverter unit cruises for 30–60 minutes, shaving both temperature and humidity gently. That steadier operation also quiets the system, reduces hot/cold spots, and typically lowers energy use. If you’re the “it feels sticky unless I set it to 70°F” homeowner, this is your fix. Bonus: variable indoor blowers can change airflow per mode, helping noise control and comfort tuning.
Popular picks: Ductless Mini-Splits (DIY & pro install)
Tighten the Envelope Before You Oversize the Unit
Your building shell drives both sensible and latent loads. Insulation and air sealing lower sensible gains; controlled ventilation and vapor management keep latent in check. Typical high-impact fixes: seal attic penetrations, add attic insulation, weather-strip doors, seal rim joists, and address crawlspace moisture. These upgrades let you choose smaller equipment with better runtimes and humidity control. They also protect indoor air quality by reducing mold-friendly conditions. If your basement smells musty, fix drainage and sealing first, don't just crank the AC. Then pick equipment that matches the new, lower loads.
Tools & parts: Accessories
Energy Savings: Why 76°F Can Feel Like 72°F
Humidity changes how we feel temperature. Get RH down around 45% and you can often set cooling 2–4°F higher without losing comfort. That lowers runtime and cuts bills. On the heating side, avoiding bone-dry air means you can keep the thermostat a touch lower and still feel okay. The big saver is right-sizing: oversized systems short-cycle (poor latent control, wasted energy), while matched systems cruise efficiently. Variable-speed compressors and ECM blowers sip power at low speed and only ramp up when needed. Combine that with a sealed envelope and smart thermostat schedules, and you’ll see steady comfort with fewer spikes on your utility bill.
Budget help: HVAC Financing
Common Sizing Mistakes (and How to Avoid Them)
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Square-foot rules: Ignore moisture and infiltration—skip them.
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Ignoring ducts: Leaky or undersized ducts wreck capacity and humidity control.
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No Manual J/SHR check: You’ll cool fast but stay clammy.
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Chasing “bigger is better”: Bigger units short-cycle; humidity hangs around.
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Skipping envelope fixes: You’ll pay for more tonnage forever.
How to avoid: demand a Manual J with both sensible and latent loads, verify duct design (Manual D), and choose equipment with runtime and moisture control in mind. If you’re replacing like-for-like after insulation or window upgrades, downsizing may be correct.
Start right: Sizing Guide
Quick Homeowner Checklist (Before You Buy)
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Get a room-by-room Manual J with sensible/latent loads.
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Ask for the unit’s SHR and how it fits your climate.
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Verify duct design & sealing; measure static pressure.
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Consider variable-speed or dehumidification features if RH runs high.
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Address insulation/air sealing first; compare loads before/after.
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Plan for maintenance: filter sizes, coil access, drain protection.
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Match equipment to lifestyle: bedrooms humid at night? Longer runtimes help.
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Review warranty and parts availability.
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Confirm thermostat compatibility and dehumidify-on-demand settings.
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Keep future add-ons in mind (ERV/HRV, whole-home dehumidifier).
Browse systems: R32 Heat Pumps
FAQ
What’s a good indoor humidity target?
Aim for 30–50% RH. In humid summers, closer to 45%; in winter, avoid dropping below ~30% to protect health and woodwork.
How do I know if my system is oversized?
Short cycles, uneven temps, and “cool but clammy” rooms are red flags. A Manual J and data-logging hygrometer can confirm it.
Will a bigger AC remove more humidity?
Usually no. Bigger units cycle off faster, so they don’t stay on the coil long enough to wring out moisture.
What if my basement is always damp?
Fix water entry and air leaks first, then consider a dedicated dehumidifier tied into the duct system.
Is SHR listed on every unit?
Not always plainly. Ask your contractor for performance data at your design conditions and compare to your latent load.
Do mini-splits control humidity well?
Inverter mini-splits run long and low, great for dehumidification. Select models with dry modes or latent-friendly airflow settings. See Ductless Mini-Splits.