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

Estimate the cooling load of a room by the simplified ASHRAE steady-state method. Transmission sensible load Q_trans = Σ(A_i·U_i·ΔT) over envelope surfaces entered one per line as 'area,U' (U in W/(m²·K)). Infiltration/ventilation sensible Q_s = 1.23·ACH·V·ΔT and latent Q_l = 3010·ACH·V·ΔW (W), where ΔW is the indoor-outdoor humidity-ratio difference derived from dry-bulb temperature and relative humidity via the Magnus saturation fit. Total cooling load = total sensible + total latent. Temperature in °C/K/°F (only differences matter), area in m²/ft².

> Canonical page: https://elysiatools.com/en/tools/cooling-load-calculator

- **Category:** Math & Numbers

- **Keywords:** cooling load, refrigeration load, U-value, thermal transmittance, infiltration, latent load, sensible load, ACH, humidity ratio, ASHRAE

## 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.

## Inputs

- **Envelope Surfaces (area, U-value per line)** (textarea): One envelope surface per line as 'area,U-value'. U in W/(m²·K). Area in the selected Area Unit. Example line: 50, 0.5
- **Area Unit** (select)
- **Indoor Dry-bulb Temp** (number): Indoor dry-bulb temperature, in the selected Temperature Unit.
- **Outdoor Dry-bulb Temp** (number): Outdoor dry-bulb temperature, in the selected Temperature Unit.
- **Temperature Unit** (select)
- **Indoor Relative Humidity** (number): Indoor relative humidity (%).
- **Outdoor Relative Humidity** (number): Outdoor relative humidity (%).
- **Room Volume V** (number): Room (conditioned space) volume V in m³.
- **Air Changes per Hour (ACH)** (number): Air-change rate ACH (1/h), combined infiltration/ventilation. Default 0.5.
- **Decimal Places** (number)

## 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

- Enter one envelope surface per line using the format `area, U-value`, such as `50, 0.5`.
- Choose square meters or square feet, then provide indoor and outdoor dry-bulb temperatures and their unit.
- Enter indoor and outdoor relative humidity, room volume, and air changes per hour; ACH defaults to 0.5.
- The 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.

## Frequently asked questions

### 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.

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