In this HVAC sensible load calculator, we will show you how to find the sensible heat load of any space in just a few seconds.
We will also help you understand what sensible load means, explain the formula used, and show you how each term in the formula works.
What is sensible heat load?
How is it different from total heat load?
How do you calculate it for your room, office, or building? Find all the answers right here!
HVAC Sensible Load Calculator
Formula: Qs = 1.08 × CFM × ΔT (BTU/hr)
Sensible Heat Load Formula Explained
The sensible heat load represents the energy required to change the temperature of air in a space. It is calculated using the formula: Qs = 1.08 × CFM × ΔT (BTU/hr)
- Qs : Sensible heat load in BTU/hr
- 1.08 : Constant accounting for air density and specific heat (for standard conditions)
- CFM : Airflow in cubic feet per minute
- ΔT : Temperature difference between outside and inside air (°F)
Real-World Applications
| Application | Example | Purpose |
|---|---|---|
| Residential AC sizing | Calculate cooling load for a 3-bedroom house | Determine HVAC unit capacity |
| Commercial building ventilation | Airflow in offices or stores | Ensure comfort and energy efficiency |
| Server rooms / data centers | Cooling load calculation for racks | Prevent overheating of equipment |
| Industrial processes | Control temperature in factories | Maintain product quality & safety |
Example Problem: Step-by-Step
Problem: A small office has an airflow of 1200 CFM. The outside air temperature is 95°F, and the inside temperature needs to be maintained at 75°F. Calculate the sensible cooling load.
- Step 1: Identify the known values
CFM = 1200, Tout = 95°F, Tin = 75°F - Step 2: Calculate ΔT
ΔT = Tout – Tin = 95 – 75 = 20°F - Step 3: Apply the formula
Qs = 1.08 × CFM × ΔT = 1.08 × 1200 × 20 - Step 4: Calculate Qs
Qs = 1.08 × 1200 × 20 = 25,920 BTU/hr - Step 5: Interpret the result
The office requires a sensible cooling load of 25,920 BTU/hr to maintain the desired temperature.
HVAC Reference Table
Common values and constants for quick reference in HVAC sensible load calculations
| Parameter | Value / Typical Range | Notes |
|---|---|---|
| Air Density (ρ) | 0.075 lb/ft³ | Standard conditions at sea level |
| Specific Heat of Air (Cp) | 0.24 BTU/lb·°F | Used in sensible heat formula |
| Formula Constant (1.08) | 1.08 | Accounts for ρ, Cp, and 60 min/hr |
| Airflow (CFM) | 0 – 5000+ | Depends on HVAC system and space size |
| ΔT (Temperature Difference) | 1 – 40°F typical | Difference between supply and return air |
| Sensible Heat Load (Qs) | 0 – 100,000+ BTU/hr | Calculated using Qs = 1.08 × CFM × ΔT |
| Conversion: BTU/hr → kW | 1 BTU/hr ≈ 0.000293 kW | Useful for energy estimation |
FAQs
What is sensible heat load?
It tells you how much cooling or heating your space needs.
How do I calculate ΔT?
ΔT is simple: subtract the inside temperature from the outside temperature. If outside is 95°F and inside is 75°F, then ΔT = 20°F.
What does CFM mean?
CFM stands for cubic feet per minute. It’s the amount of air moving through your HVAC system every minute.
Can I use this calculator for both cooling and heating?
Yes! If ΔT is positive, it’s a cooling load. If it’s negative, it’s a heating load.