Cooling Load Calculator (Area / U-value + Infiltration)

Cooling Load Calculator (Area / U-value + Infiltration) | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Math & Numbers
Input types: textarea, select, number
Output type: json
Sample coverage: 4
API ready: Yes

Overview

Estimate a room’s cooling load with a simplified steady-state ASHRAE method. Enter envelope surface areas and U-values, indoor and outdoor temperatures, relative humidity, room volume, and ACH to calculate transmission, sensible infiltration, latent infiltration, and total cooling load in watts.

When to use

Estimate preliminary air-conditioning capacity for a room or conditioned space.
Compare cooling loads for different envelope U-values, areas, or air-change rates.
Separate transmission, sensible infiltration, and latent infiltration contributions to the total load.

How it works

1Enter one envelope surface per line using the format `area, U-value`, such as `50, 0.5`.
2Choose square meters or square feet, then provide indoor and outdoor dry-bulb temperatures and their unit.
3Enter indoor and outdoor relative humidity, room volume, and air changes per hour; ACH defaults to 0.5.
4The calculator applies the simplified formulas and returns transmission load, sensible and latent infiltration loads, total sensible load, and total cooling load in watts.

Use cases

Preliminary HVAC sizing for residential rooms, offices, and other conditioned spaces.
Building-envelope comparisons using different surface areas and U-values.
Humidity-sensitive load checks that distinguish latent infiltration from sensible heat gain.

Examples

1. Estimate the load for a 120 m³ room

HVAC designer

Background

A designer needs a preliminary cooling-load estimate for a room with two envelope surfaces and moderate outdoor heat and humidity.

Problem

Calculate the transmission, infiltration, and total cooling loads from the room’s envelope and air-change conditions.

How to use

Enter `50, 0.5` and `10, 1.8` as the envelope surfaces. Use m², indoor 24 °C and 50% RH, outdoor 33 °C and 70% RH, volume 120 m³, and ACH 0.5.

{"surfaces":"50, 0.5\n10, 1.8","areaUnit":"m2","indoorTemp":24,"outdoorTemp":33,"tempUnit":"°C","indoorRH":50,"outdoorRH":70,"volume":120,"ach":0.5,"decimalPlaces":2}

Outcome

The estimate is approximately 387 W transmission, 664.2 W sensible infiltration, 2365.41 W latent infiltration, and 3416.61 W total cooling load.

2. Repeat the estimate with square-foot inputs

Building analyst

Background

The same room data is available in square feet rather than square meters, while the volume, temperatures, humidity, and ACH remain unchanged.

Problem

Check whether entering approximately equivalent surface areas in square feet produces a comparable cooling-load estimate.

FAQ

What does the cooling load estimate include?

It includes envelope transmission, sensible infiltration or ventilation, latent infiltration, total sensible load, and total cooling load.

How should I enter envelope surfaces?

Enter one surface per line as `area, U-value`, for example `50, 0.5`. The U-value is in W/(m²·K).

Can I enter area in square feet?

Yes. Select square feet as the area unit, and the calculator converts the entered areas internally.

Which temperature units are supported?

You can use Celsius, Kelvin, or Fahrenheit. Temperature differences are used in the calculation.

What is ACH?

ACH means air changes per hour and represents the combined infiltration or ventilation rate. Its default value is 0.5.

{"surfaces":"538, 0.5\n108, 1.8","areaUnit":"ft2","indoorTemp":24,"outdoorTemp":33,"tempUnit":"°C","indoorRH":50,"outdoorRH":70,"volume":120,"ach":0.5,"decimalPlaces":2}

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Estimate the load for a 120 m³ room

2. Repeat the estimate with square-foot inputs

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