Quick answer
Sensible heat is heat that changes the temperature of air or another material without changing its state, the part of a heating or cooling load you can measure with a thermometer.
In HVAC, sensible heat is often estimated as 1.08 × airflow in cfm × temperature change in °F. Its partner is latent heat, the energy tied up in moisture.
Quick facts
The key facts about Sensible Heat, with sources:
Key takeaways
- Sensible heat is the heat you feel as temperature.
- The common shortcut: BTU/h = 1.08 × cfm × ΔT 1.
- Cooling equipment must meet the sensible load and the latent (moisture) load separately 1.
- High humidity shifts more coil work to moisture, so the air temperature drop gets smaller 2.
- The 1.08 factor is for sea-level air; adjust it at altitude 1.
What sensible heat means
Heat comes in two forms in HVAC work. Sensible heat changes temperature: warm a room from 65°F to 70°F and you have added sensible heat. Latent heat changes water between vapor and liquid: dry humid air and you have removed latent heat, even if the thermometer hardly moves.
The word "sensible" means you can sense it. A thermometer reads sensible heat. It cannot read latent heat, which is why a home can be 74°F and still feel clammy.
In winter, nearly all of a furnace's work is sensible. In summer, an air conditioner handles both. Load calculations split the cooling load into sensible and latent parts so equipment can be picked to match both 1.
Where sensible heat comes from
- Sun through windows → sensible gain
- Heat through walls, roof and ducts → sensible gain
- People, lights and appliances → mostly sensible, plus some latent
- Outdoor air leaking in → sensible and latent gain
- Total sensible gain → removed by the coil as a drop in air temperature
How the 1.08 formula is built
- Air at standard conditions weighs about 0.075 pounds per cubic foot 1.
- It takes about 0.24 BTU to warm one pound of air by 1°F (its specific heat) 1.
- There are 60 minutes in an hour, and airflow is measured per minute.
- 0.075 × 0.24 × 60 = 1.08 1.
- So BTU per hour = 1.08 × cfm × temperature change 1.
Green Building Advisor stresses that 1.08 "looks like a constant" but is not: it must be adjusted when air density differs from sea-level, room-temperature air 1.
Sensible heat in different HVAC jobs
| Job | Sensible share | Notes |
|---|---|---|
| Furnace or heat pump heating | Nearly all | Winter heat is mostly temperature |
| Cooling in a dry climate | High | Little moisture to remove 1 |
| Cooling in a humid climate | Lower | More coil work goes to moisture 2 |
| Dehumidifier | Adds a little sensible heat | Its compressor heat stays in the room |
| Ventilation air | Varies with weather | Outdoor air brings both kinds |
Worked example: furnace output and cooling split
Example only, using the 1.08 formula at standard air 1. Part 1 checks a furnace's delivered heat; part 2 splits a cooling load.
| Step | Math | Result |
|---|---|---|
| Furnace airflow | Measured or from the blower table | 1,000 cfm |
| Temperature rise | Supply 125°F − return 68°F | 57°F |
| Delivered sensible heat | 1.08 × 1,000 × 57 | 61,560 BTU/h |
| Cooling airflow | 3 tons × about 400 cfm per ton 1 | 1,200 cfm |
| Air temperature drop across coil | Say 19°F | 19°F |
| Sensible cooling | 1.08 × 1,200 × 19 | 24,624 BTU/h |
| If total capacity is 36,000 BTU/h | 24,624 ÷ 36,000 | Sensible heat ratio about 0.68; the rest is latent |
The furnace check works only if airflow is known. A technician would measure it or use the maker's blower table.
The cooling split shows why a smaller temperature drop on a humid day is not automatically a problem: the coil may be doing more drying 2. Our delta T page explains how techs use these readings.
Where you will see the term
- In a Manual J load report: sensible and latent cooling loads listed separately.
- In Manual S equipment selection, checking that the unit's sensible capacity meets the sensible load.
- On expanded performance tables from manufacturers: total and sensible capacity at given conditions.
- On commissioning sheets: supply and return temperatures and airflow.
Why splitting sensible and latent helps
What it gets right
What goes wrong without it
- A unit sized on total load alone may cool fast but leave moisture behind.
- Oversized systems tend to satisfy the thermostat before drying the air 3.
- Wrong airflow can shift the split the wrong way for the climate.
Limits of the shortcut
The 1.08 formula assumes sea-level air near room temperature. At higher altitude, air is thinner, holds less heat per cubic foot, and the factor drops 1. Denver-area designers adjust it.
It also needs a good airflow number, which is hard to get in the field. HVAC School notes that temperatures measured at grilles can be off because ducts gain and lose heat, and recommends measuring near the equipment 2. Small errors in cfm or ΔT make big errors in BTUs.
Field data shows why this matters. DOE's review of 44 field studies found equipment oversized compared with Manual J in 31% to 93% of systems tested, and low airflow below 350 cfm per ton in 50% to 93% 5.
Both faults change the sensible and latent split the homeowner actually gets, no matter what the spec sheet says.
Where cost comes in
Sensible heat has no price, but it drives equipment size, which drives cost. A load calculation that overstates the sensible load leads to a larger, costlier unit that may also handle humidity worse.
For what moves an install price, see the cost calculator, and for sizing, the AC sizing calculator.
How designers use sensible heat
- Run a Manual J to get sensible and latent loads room by room.
- Choose equipment whose sensible capacity at design conditions meets the sensible load.
- Check the latent capacity covers the latent load 1.
- Set airflow per ton for the climate 1.
- Size ducts to deliver that airflow.
- At start-up, measure airflow and temperatures to confirm.
Keeping the sensible side working
- Change filters; low airflow lowers capacity and can freeze the coil.
- Keep coils clean so heat transfers well 4.
- Keep vents open and unblocked.
- Shade west-facing windows; sun is a large sensible gain, and exterior shades or awnings block it before it gets inside the glass.
- Have a tech check airflow during tune-ups 4.
Signs the sensible load is not being met
- The house will not reach the setpoint on hot afternoons.
- Supply air feels only slightly cool on a dry day.
- Rooms with big windows run much hotter.
- The system runs nonstop on mild days, which may point to a fault.
- Call a pro to check airflow, charge and ducts.
Standards that use it
Sensible heat is a physics term, not a regulated value. It appears in the industry methods codes rely on: ACCA Manual J (load calculation) and Manual S (equipment selection). The International Residential Code requires heating and cooling equipment to be sized by Manual J and S in many adopting jurisdictions; adoption varies by state.
Energy efficiency ratings such as SEER2 measure total cooling, not the sensible split, so two units with the same SEER2 can handle humidity differently.
Sensible heat vs latent heat
| Feature | Sensible heat | Latent heat |
|---|---|---|
| What it changes | Temperature | Moisture (state of water) |
| Measured by | Thermometer | Humidity readings (grains, RH) |
| Formula (standard air) | 1.08 × cfm × ΔT 1 | 0.68 × cfm × Δgrains 1 |
| Main sources | Sun, walls, roof, ducts | People, cooking, showers, outdoor air |
| More detail | This page | Latent heat |
Common misconceptions
- Myth If the temperature drop is small, the AC is weak.
- Reality On humid days more work goes to moisture, so the drop shrinks 2.
- Myth 1.08 is a fixed constant.
- Reality It depends on air density 1.
- Myth Tonnage tells you sensible capacity.
- Reality Tonnage is total capacity; the sensible share varies with conditions.
- Myth Sensible heat is only a summer issue.
- Reality All heating is sensible heat added to air.
Climate and the sensible share
Dry Southwest climates have high sensible shares, so systems can run more airflow per ton 1. Humid Southeast climates have more latent load and benefit from slower airflow. Degree days show how much heating and cooling your area needs overall.
When it matters to you
It matters when you get a load calculation or a replacement quote. Ask to see the sensible and latent loads, and the equipment's sensible capacity at your design conditions.
Next step: if your home is humid even when cool, read the dehumidification page and ask about airflow settings.
Questions about Sensible Heat
What is the difference between sensible and latent heat?
Sensible heat changes temperature, which a thermometer shows. Latent heat changes water between vapor and liquid without changing temperature. An air conditioner removes both: it cools the air (sensible) and dries it (latent).
What is the sensible heat formula?
For air at standard conditions, BTU per hour ≈ 1.08 × cfm × temperature change in °F. The 1.08 comes from air density (0.075 lb per cubic foot), specific heat (0.24) and 60 minutes per hour. Adjust it for altitude.
What is sensible heat ratio?
It is the share of total cooling that goes to lowering temperature. A ratio of 0.75 means 75 percent sensible and 25 percent latent. Humid climates need equipment with a lower ratio, meaning more moisture removal.
Why does my AC cool but not dry the house?
It may be oversized, running short cycles that satisfy the thermostat before much moisture is removed. Airflow may also be set high for a dry climate. A technician can check sizing, airflow and fan settings.
How do I calculate furnace output from temperature rise?
Multiply 1.08 by airflow in cfm by the temperature rise. For example, 1,000 cfm with a 57°F rise is about 61,560 BTU per hour. The answer is only as good as the airflow number, which a technician should measure.
Is sensible heat the same as dry-bulb temperature?
Not quite. Dry-bulb temperature is what a normal thermometer reads. Sensible heat is the energy that changes that temperature. A change in dry-bulb temperature tells you sensible heat was added or removed.
Does sensible heat matter for heat pumps?
Yes. In heating, nearly all of a heat pump's output is sensible heat. In cooling, it splits its capacity between sensible and latent like any air conditioner. Equipment data lists sensible capacity at different conditions.
Why is 1.08 different at high altitude?
Thinner air weighs less per cubic foot, so each cfm carries less heat. The factor in the formula drops in proportion to air density. Designers in high-altitude areas use a corrected factor.
What are the biggest sources of sensible heat in a house?
In summer, sun through windows is often the largest, followed by heat through the roof and attic, walls, and ducts in hot attics. People, lighting and appliances add more. Shading west windows, sealing and insulating ducts, and attic insulation all cut the sensible load.
Sources
- Green Building Advisor, Converting Heating and Cooling Loads to Air Flow Needs, retrieved .
- HVAC School, What Should the Air Delta T Be? (Air Temperature Split), retrieved .
- U.S. DOE Energy Saver, Central Air Conditioning (archived copy, 2025), retrieved .
- ENERGY STAR, Maintenance Checklist (heating and cooling), retrieved .
- U.S. DOE Building Technologies Office, Residential HVAC Installation Practices: A Review of Research Findings (June 2018), retrieved .
Expert review
Written by the HyreHVAC Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: The 1.08 and 0.68 factors and their derivation are from Green Building Advisor's building-science article; the humidity effect on temperature split is HVAC School's. The worked example multiplies illustrative airflow and temperature readings, labelled as such.
Suggest a correction. We fix errors and say what changed.