Thermal Management Load Calculator

Calculator Inputs

Fields are sensible-only. Add latent loads separately if required.

Project name

Used on downloads and report header.

Mode

Loads use |ΔT| for magnitude.

Safety factor (%)

Typical range: 5–15%.

Outdoor design temperature (°C)

Use local summer/winter design values.

Indoor setpoint temperature (°C)

Typical: 24°C cooling, 20°C heating.

Supply air ΔT (°C)

For airflow estimate, common 8–12°C.

Conditioned floor area (m²)

Used for internal gains calculations.

Average ceiling height (m)

Volume = floor area × height.

Air changes per hour (ACH)

Tighter buildings: 0.2–0.6.

Envelope Areas and U-values

U-value is W/m²K. Use consistent units.

Wall area (m²)

Wall U-value (W/m²K)

Roof area (m²)

Roof U-value (W/m²K)

Floor area (m²)

Use slab/ground-contact area, if relevant.

Floor U-value (W/m²K)

Window area (m²)

Window U-value (W/m²K)

Solar and Internal Gains

Solar applies to window area only.

Solar irradiance (W/m²)

Pick a peak value for design checks.

SHGC (0 to 1)

Shading factor (0 to 1)

Lower means more shading.

People (count)

Sensible watts per person

Office activity is often 70–90 W.

Lighting density (W/m²)

Equipment density (W/m²)

Computers and plug loads vary widely.

Reset

Example Data Table

Illustrative values for a mid-size conditioned building.

Mode	Outdoor (°C)	Indoor (°C)	Area (m²)	Height (m)	Walls A/U	Roof A/U	Windows A/U	ACH	People	LPD	EPD	SHGC/Shade	Irr (W/m²)	Safety
Cooling	40	24	250	3.0	300 / 0.60	250 / 0.35	40 / 2.60	0.8	18	8	10	0.55 / 0.85	500	10%

Paste these values into the form to reproduce a baseline scenario.

Formula Used

All results are sensible-only and use consistent SI units.

Temperature difference: |ΔT| = |T_out − T_in|
Envelope conduction (each surface): Q = U × A × |ΔT|
Total conduction: Q_cond = Σ(U × A × |ΔT|)
Infiltration sensible: Q_inf = 0.333 × ACH × V × |ΔT|
Solar through windows: Q_solar = I × A_win × SHGC × Shading
Internal gains: Q_int = (People × W/person) + (LPD × Area) + (EPD × Area)
Total sensible load: Q_total = Q_cond + Q_inf + Q_solar + Q_int
Design load: Q_design = Q_total × (1 + Safety/100)
Airflow estimate: m³/h = Q_design / (ρ·c_p·ΔT_supply) × 3600, using ρ·c_p ≈ 1200 J/m³K
Conversions: BTU/hr = W × 3.412; Tons = (BTU/hr) / 12000

How to Use This Calculator

A quick workflow for early-stage sizing and comparisons.

Choose Cooling or Heating based on your design case.
Enter outdoor and indoor temperatures to define the driving |ΔT|.
Provide conditioned area and average height to estimate volume.
Fill envelope areas and U-values from drawings or specifications.
Set ACH based on airtightness or ventilation assumptions.
Add solar inputs for window heat and apply shading reductions.
Estimate internal gains using people, lighting, and equipment density.
Apply a safety factor and review the design kW, BTU/hr, and tons.
Use the airflow estimate to sanity-check distribution assumptions.
Export CSV or PDF for project records and coordination.

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