Sensible Heat Ratio Calculator

Calculate

Sensible cooling load — the portion of total load that changes air temperature

Latent cooling load — the portion of total load that removes moisture from air

Overview

A Sensible Heat Ratio Calculator determines how much of a cooling load is sensible versus latent. This page uses one fixed HVAC model: total cooling load is the sum of sensible and latent load, and SHR is the sensible portion divided by the total. A higher SHR means the load is more temperature-driven, while a lower SHR means more of the cooling duty is being spent on moisture removal and dehumidification. This is the standard HVAC definition of SHR.

Enter the sensible cooling load and the latent cooling load in either Imperial or Metric units. The calculator first adds them to find the total cooling load, then divides sensible load by total load to compute SHR. Use the result to understand whether the application is mostly sensible, balanced, or strongly latent-driven, and compare that load split against equipment SHR and humidity-control needs.

Engineering references consistently define SHR as sensible load divided by total load.

How to Use This Calculator

  1. Enter sensible load — in kW or BTU/hr.

  2. Enter latent load — in kW or BTU/hr.

  3. Click "Calculate" — get total cooling load, sensible heat ratio (SHR), sensible fraction, and latent fraction.

Compare the space SHR against the equipment's rated SHR at design conditions; if the space SHR is below ~0.65, plan for enhanced dehumidification.

Inputs & Outputs

Inputs

  • •Sensible Load (kW / BTU/hr)
  • •Latent Load (kW / BTU/hr)

Outputs

  • •Total Cooling Load (kW / BTU/hr)
  • •Sensible Heat Ratio (SHR)
  • •Sensible Fraction (%)
  • •Latent Fraction (%)

Formula

Calculator Formula

This page uses one fixed SHR model.

Step 1: Total Cooling Load

Qtotal = Qsensible + Qlatent

Where:

  • Qtotal = total cooling load (kW or BTU/hr)
  • Qsensible = sensible cooling load
  • Qlatent = latent cooling load

ASHRAE defines total cooling load as the sum of sensible and latent cooling load.

Step 2: Sensible Heat Ratio

SHR = Qsensible / Qtotal

or equivalently:

SHR = Qsensible / (Qsensible + Qlatent)

Where:

  • SHR = sensible heat ratio (dimensionless, 0 to 1)
  • Qsensible = sensible load
  • Qlatent = latent load

This is the standard SHR equation used in HVAC references.

Fixed Decision Model

This page follows one exact path:

Sensible Load + Latent Load → Total Cooling Load → SHR

That is the fixed model used on this page.

Variable Reference

Variable Meaning Units
sensibleLoad / Qsensible Sensible cooling load kW / BTU/hr
latentLoad / Qlatent Latent cooling load kW / BTU/hr
totalLoad / Qtotal Total cooling load kW / BTU/hr
SHR Sensible heat ratio dimensionless (0–1)
Sensible Fraction SHR × 100 %
Latent Fraction (1 − SHR) × 100 %

What is Sensible Heat Ratio

Sensible Heat Ratio (SHR) is the fraction of total cooling load that is associated with temperature change rather than moisture removal. If SHR is high, most of the load is sensible. If SHR is low, a larger share of the load is latent, meaning the system must do more dehumidification work. ASHRAE and other HVAC references define SHR exactly this way.

Why SHR Matters

SHR is one of the most important parameters in HVAC equipment selection and system design. Two cooling systems with identical total capacity can perform very differently in practice if their sensible/latent split does not match the actual load profile of the space.

A system with a high equipment SHR installed in a space with a low load SHR will struggle to control humidity, even though it has enough total cooling capacity. This mismatch is one of the most common causes of indoor humidity complaints in commercial and residential buildings.

Sources of Sensible and Latent Load

The sensible portion of the cooling load comes from:

  • Solar radiation — sunlight striking the building envelope and entering through windows
  • Conduction — heat transfer through walls, roof, floor, and glazing
  • Internal gains — lighting, equipment, and occupant sensible heat
  • Ventilation sensible load — temperature difference between outdoor and indoor air

The latent portion comes from:

  • Occupants — each person generates moisture through respiration and perspiration
  • Outside air ventilation — humid outdoor air introduced for ventilation carries significant moisture
  • Infiltration — uncontrolled air leakage through the building envelope
  • Process moisture — cooking, washing, swimming pools, industrial processes
  • Moisture migration — vapor diffusion through building materials

Typical SHR Ranges

While there is no single universal SHR target, typical ranges include:

  • Dry climates or sensible-heavy spaces: SHR 0.85–0.95
  • Standard comfort cooling: SHR 0.70–0.85
  • Humid climates or high-occupancy spaces: SHR 0.55–0.75
  • Natatoriums, kitchens, or process spaces: SHR below 0.60

These are general guidelines — actual SHR depends on the specific application, climate, ventilation rate, and internal loads.

Practical Tips

When using SHR for equipment selection:

  • Always compare the space load SHR against the equipment rated SHR at the actual operating conditions
  • Remember that equipment SHR varies with entering air conditions, airflow, and compressor staging
  • A low space SHR (below 0.65) often indicates the need for enhanced dehumidification — consider lower supply air temperatures, reheat, or dedicated dehumidification equipment
  • Outside air fraction has a major impact on SHR — high ventilation rates in humid climates drive SHR down significantly
  • SHR is a screening indicator, not a final design decision — always verify with full psychrometric analysis for final equipment selection

Important: This calculator provides screening estimates using a simplified ratio model. Final equipment selection should always be verified using manufacturer data, full psychrometric analysis, and professional engineering judgment.

Key Facts

  • SHR is a dimensionless ratio between 0 and 1 under normal cooling conditions.
  • An SHR near 1.0 means almost all cooling is sensible and very little is latent.
  • An SHR near 0.5 means moisture removal is a major part of the load.
  • In equipment selection, SHR matters because two units with similar total capacity may behave very differently for humidity control if their sensible/latent split differs.
  • HVAC references distinguish SHR from room sensible heat factor and other related load ratios — this page uses the simple total-cooling-load SHR definition.

Applications

  • Comfort cooling load split checks
  • Coil selection screening
  • Humidity-control review
  • Outside-air latent burden checks
  • Equipment SHR comparison
  • DOAS and dehumidification planning
  • High-occupancy space load analysis
  • Humid-climate HVAC sizing reviews

Example Calculation

Imperial Example

Given:

  • Sensible Load = 24,000 BTU/hr
  • Latent Load = 8,000 BTU/hr

Step 1: Total cooling load

Qtotal = 24,000 + 8,000 = 32,000 BTU/hr

Step 2: SHR

SHR = 24,000 / 32,000 = 0.75

Result:

  • Total Cooling Load = 32,000 BTU/hr
  • SHR = 0.75
  • Sensible Fraction = 75%
  • Latent Fraction = 25%

This means 75% of the total cooling load is sensible and 25% is latent.

Metric Example

Given:

  • Sensible Load = 7.0 kW
  • Latent Load = 2.0 kW

Step 1: Total cooling load

Qtotal = 7.0 + 2.0 = 9.0 kW

Step 2: SHR

SHR = 7.0 / 9.0 = 0.778

Result:

  • Total Cooling Load = 9.0 kW
  • SHR = 0.778
  • Sensible Fraction = 77.8%
  • Latent Fraction = 22.2%

This means the load is primarily sensible, with a smaller but still meaningful latent share.

Standards & References

  • ASHRAE Handbook — Fundamentals{target="_blank" rel="noopener noreferrer"} — sensible and latent cooling load; SHR methodology
  • ASHRAE 62.1 — ventilation for acceptable indoor air quality (outside-air moisture contribution to latent load)
  • ASHRAE Handbook — HVAC Systems and Equipment — coil selection and sensible/latent capacity matching
  • ACCA Manual J — residential sensible and latent load estimation

Limitations

  • This calculator is a screening tool, not a full psychrometric design engine.
  • It does not calculate: room RH directly, coil leaving-air condition, apparatus dew point, bypass factor, ventilation-air mixing, infiltration generation, process moisture sources, or equipment net sensible and latent capacity at real conditions.
  • A correct SHR does not by itself prove that the selected equipment will control indoor humidity under actual operating conditions.
  • Final selection still depends on psychrometrics, outdoor air fraction, coil performance, and equipment data.
  • The SI and Imperial formulas are identical in structure — only the load units change.

Common Mistakes to Avoid

  • Assuming a high total cooling capacity automatically means good humidity control — equipment with a high rated SHR may underperform on latent removal.
  • Confusing SHR with sensible load percentage in a loose conversational sense without actually checking the latent component.
  • Entering loads in mixed units or forgetting that SHR must stay between 0 and 1 for a normal cooling-load case.
  • Treating SHR as a final equipment-selection answer instead of a screening indicator that must still be matched against actual rated equipment sensible and latent performance.
  • Ignoring outside-air and infiltration moisture contributions when estimating the latent portion of the load.

Frequently Asked Questions

What does an SHR of 0.75 mean?
It means 75% of the total cooling load is sensible and 25% is latent. The load is mostly temperature-driven, but moisture removal is still significant.
What is the formula for sensible heat ratio?
The fixed formula is: SHR = Sensible Load / (Sensible Load + Latent Load). This is the standard HVAC definition.
What is a good SHR for comfort cooling?
There is no single universal 'good' SHR. Comfort-cooling applications often fall in a middle range, but the right value depends on climate, outside air, infiltration, occupancy, and humidity target. Lower SHR means more latent burden; higher SHR means mostly sensible load. This is an engineering interpretation, not a fixed code limit.
What happens when SHR is low?
A low SHR means a larger share of the cooling load is latent, so the system needs stronger dehumidification performance. That may influence coil selection, dew point, and equipment latent capacity.
What happens when SHR is close to 1.0?
It means the load is almost entirely sensible with little latent component. That can happen in drier applications or processes where temperature change dominates moisture removal.
Can SHR be greater than 1?
Under a normal cooling-load definition, no. Since total load equals sensible plus latent load, SHR should stay between 0 and 1. Values outside that range usually indicate invalid inputs or a nonstandard use case.
Is SHR the same as room sensible heat factor?
Not exactly. They are related ideas, but room sensible heat factor refers specifically to the room load split, while SHR can refer more generally to the sensible-to-total ratio for a process or cooling condition. This page uses the simple sensible / total SHR definition.
Can I use SHR alone to pick HVAC equipment?
No. SHR is useful for screening and load interpretation, but final equipment selection also depends on total capacity, airflow, coil conditions, entering air state, ventilation load, and actual manufacturer performance data.

Frequently Used Together

Engineers often use these calculators in combination for complete project workflows:

Coil Capacity Calculator

Condensate Pump Sizing

Supply Air Temperature Calculator

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