.cooling-load-calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 800px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e0e0e0;
border-radius: 10px;
background-color: #f9f9f9;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}
.cooling-load-calculator-container h2 {
color: #2c3e50;
text-align: center;
margin-bottom: 25px;
font-size: 1.8em;
}
.cooling-load-calculator-container .input-group {
margin-bottom: 18px;
display: flex;
flex-wrap: wrap;
align-items: center;
}
.cooling-load-calculator-container .input-group label {
flex: 1;
min-width: 200px;
margin-right: 15px;
color: #34495e;
font-weight: 600;
font-size: 0.95em;
}
.cooling-load-calculator-container .input-group input[type="number"] {
flex: 2;
min-width: 150px;
padding: 10px 12px;
border: 1px solid #ccc;
border-radius: 5px;
font-size: 1em;
color: #333;
box-sizing: border-box;
}
.cooling-load-calculator-container .input-group span.unit {
margin-left: 10px;
color: #555;
font-size: 0.9em;
}
.cooling-load-calculator-container button {
display: block;
width: 100%;
padding: 12px 20px;
background-color: #3498db;
color: white;
border: none;
border-radius: 5px;
font-size: 1.1em;
font-weight: bold;
cursor: pointer;
transition: background-color 0.3s ease, transform 0.2s ease;
margin-top: 25px;
}
.cooling-load-calculator-container button:hover {
background-color: #2980b9;
transform: translateY(-2px);
}
.cooling-load-calculator-container #result {
margin-top: 30px;
padding: 20px;
border: 1px solid #dcdcdc;
border-radius: 8px;
background-color: #eaf4f9;
color: #2c3e50;
font-size: 1.1em;
line-height: 1.6;
}
.cooling-load-calculator-container #result h3 {
color: #2c3e50;
margin-top: 0;
margin-bottom: 15px;
font-size: 1.4em;
border-bottom: 1px solid #b3d9ee;
padding-bottom: 10px;
}
.cooling-load-calculator-container #result p {
margin-bottom: 8px;
}
.cooling-load-calculator-container #result p strong {
color: #1a5276;
}
@media (max-width: 600px) {
.cooling-load-calculator-container .input-group {
flex-direction: column;
align-items: flex-start;
}
.cooling-load-calculator-container .input-group label {
margin-bottom: 5px;
width: 100%;
}
.cooling-load-calculator-container .input-group input[type="number"] {
width: 100%;
}
}
function calculateCoolingLoad() {
var roomArea = parseFloat(document.getElementById('roomArea').value);
var ceilingHeight = parseFloat(document.getElementById('ceilingHeight').value);
var outdoorTemp = parseFloat(document.getElementById('outdoorTemp').value);
var indoorTemp = parseFloat(document.getElementById('indoorTemp').value);
var numOccupants = parseFloat(document.getElementById('numOccupants').value);
var lightingWatts = parseFloat(document.getElementById('lightingWatts').value);
var applianceWatts = parseFloat(document.getElementById('applianceWatts').value);
var windowArea = parseFloat(document.getElementById('windowArea').value);
var wallRoofUValue = parseFloat(document.getElementById('wallRoofUValue').value);
var windowUValue = parseFloat(document.getElementById('windowUValue').value);
var windowSHGC = parseFloat(document.getElementById('windowSHGC').value);
var solarRadiationFactor = parseFloat(document.getElementById('solarRadiationFactor').value);
var infiltrationACH = parseFloat(document.getElementById('infiltrationACH').value);
// Validate inputs
if (isNaN(roomArea) || isNaN(ceilingHeight) || isNaN(outdoorTemp) || isNaN(indoorTemp) || isNaN(numOccupants) ||
isNaN(lightingWatts) || isNaN(applianceWatts) || isNaN(windowArea) || isNaN(wallRoofUValue) ||
isNaN(windowUValue) || isNaN(windowSHGC) || isNaN(solarRadiationFactor) || isNaN(infiltrationACH) ||
roomArea < 0 || ceilingHeight < 0 || numOccupants < 0 || lightingWatts < 0 || applianceWatts < 0 ||
windowArea < 0 || wallRoofUValue < 0 || windowUValue < 0 || windowSHGC 1 ||
solarRadiationFactor < 0 || infiltrationACH < 0) {
document.getElementById('result').innerHTML = 'Please enter valid non-negative numbers for all fields. Window SHGC must be between 0 and 1.';
return;
}
var tempDiff = outdoorTemp – indoorTemp;
if (tempDiff < 0) { // Cooling load only applies if outdoor is hotter than indoor
tempDiff = 0; // No heat gain from conduction/infiltration if outdoor is cooler
}
var totalVolume = roomArea * ceilingHeight;
// Constants for calculation
var sensibleHeatPerPerson = 230; // BTU/hr/person (approximate)
var latentHeatPerPerson = 190; // BTU/hr/person (approximate)
var wattsToBTUhr = 3.41;
var applianceUsageFactor = 0.75; // Assumes appliances are not always at peak load
var sensibleInfiltrationFactor = 0.018; // BTU/hr/cuft/°F/ACH (approximate for air density * specific heat)
var latentInfiltrationFactor = 0.03; // BTU/hr/cuft/ACH (simplified estimate for latent heat from humidity difference)
// 1. Heat Gain from Walls/Roof (Conduction Sensible Load)
var wallRoofSensible = wallRoofUValue * roomArea * tempDiff;
// 2. Heat Gain from Windows (Conduction Sensible Load)
var windowConductionSensible = windowUValue * windowArea * tempDiff;
// 3. Heat Gain from Windows (Solar Sensible Load)
var windowSolarSensible = windowArea * windowSHGC * solarRadiationFactor;
// 4. Heat Gain from Occupants (Sensible Load)
var occupantsSensible = numOccupants * sensibleHeatPerPerson;
// 5. Heat Gain from Occupants (Latent Load)
var occupantsLatent = numOccupants * latentHeatPerPerson;
// 6. Heat Gain from Lighting (Sensible Load)
var lightingSensible = lightingWatts * wattsToBTUhr;
// 7. Heat Gain from Appliances (Sensible Load)
var applianceSensible = applianceWatts * wattsToBTUhr * applianceUsageFactor;
// 8. Heat Gain from Infiltration/Ventilation (Sensible Load)
var infiltrationSensible = totalVolume * infiltrationACH * sensibleInfiltrationFactor * tempDiff;
// 9. Heat Gain from Infiltration/Ventilation (Latent Load – simplified)
var infiltrationLatent = totalVolume * infiltrationACH * latentInfiltrationFactor;
// Total Loads
var totalSensibleLoad = wallRoofSensible + windowConductionSensible + windowSolarSensible +
occupantsSensible + lightingSensible + applianceSensible + infiltrationSensible;
var totalLatentLoad = occupantsLatent + infiltrationLatent;
var totalCoolingLoadBTUhr = totalSensibleLoad + totalLatentLoad;
// Convert to Tons of Refrigeration (1 Ton = 12,000 BTU/hr)
var totalCoolingLoadTons = totalCoolingLoadBTUhr / 12000;
// Display results
var resultHTML = '
Cooling Load Calculator
sq ft
ft
°F
°F
people
Watts
Watts
sq ft
BTU/hr·sqft·°F
BTU/hr·sqft·°F
(0-1)
BTU/hr·sqft
ACH
Cooling Load Calculation Results:
Enter the details above and click "Calculate" to see the estimated cooling load for your space.
Cooling Load Calculation Results:
'; resultHTML += 'Total Sensible Load: ' + totalSensibleLoad.toFixed(2) + ' BTU/hr'; resultHTML += 'Total Latent Load: ' + totalLatentLoad.toFixed(2) + ' BTU/hr'; resultHTML += 'Total Cooling Load: ' + totalCoolingLoadBTUhr.toFixed(2) + ' BTU/hr'; resultHTML += 'Required Cooling Capacity: ' + totalCoolingLoadTons.toFixed(2) + ' Tons'; resultHTML += '(1 Ton of refrigeration = 12,000 BTU/hr)'; document.getElementById('result').innerHTML = resultHTML; }Understanding Cooling Load Calculations for Optimal HVAC Sizing
Properly sizing an air conditioning system is crucial for comfort, energy efficiency, and the longevity of your HVAC equipment. An undersized system will struggle to cool your space, leading to high energy bills and discomfort, while an oversized system will cycle on and off too frequently (short-cycling), resulting in poor dehumidification, uneven temperatures, and premature wear and tear. This is where a cooling load calculation becomes indispensable.
What is a Cooling Load?
A cooling load refers to the amount of heat energy that needs to be removed from a space to maintain a desired indoor temperature and humidity level. This heat comes from various sources, both inside and outside the building, and is measured in British Thermal Units per hour (BTU/hr) or Tons of Refrigeration (where 1 Ton = 12,000 BTU/hr).
Why is a Cooling Load Calculation Important?
- Accurate Sizing: Ensures your HVAC system is neither too big nor too small for your specific needs.
- Energy Efficiency: A correctly sized system runs optimally, consuming less energy.
- Enhanced Comfort: Maintains consistent temperatures and appropriate humidity levels, preventing clammy or overly dry air.
- Equipment Longevity: Reduces wear and tear on the system, extending its lifespan.
- Cost Savings: Avoids the higher initial cost of an oversized unit and lower operating costs over time.
Factors Affecting Cooling Load
The cooling load of a space is influenced by numerous factors, which can be broadly categorized into sensible and latent heat gains:
Sensible Heat Gain:
Sensible heat is the heat that causes a change in temperature. Our calculator considers the following sources:
- Walls/Roof Conduction: Heat transfer through the building envelope (walls, roof, floor) from warmer outdoor air to cooler indoor air. This depends on the surface area, the temperature difference, and the material's U-value (a measure of heat transfer).
- Window Conduction: Similar to walls/roof, heat transfers through window panes based on their area, U-value, and temperature difference.
- Window Solar Gain: Solar radiation passing through windows directly heats the interior. This is influenced by window area, the Solar Heat Gain Coefficient (SHGC) of the glass (how much solar radiation it lets through), and the intensity of solar radiation.
- Occupants: People generate heat through their body metabolism. This is a significant factor, especially in crowded spaces.
- Lighting: All forms of lighting (incandescent, fluorescent, LED) convert electrical energy into light and heat.
- Appliances: Electronic devices, kitchen appliances, and other equipment generate heat during operation.
- Infiltration/Ventilation: Hot outdoor air leaking into the building through cracks, gaps, or intentional ventilation systems contributes to the sensible load.
Latent Heat Gain:
Latent heat is the heat associated with changes in moisture content (humidity) rather than temperature. Removing humidity requires energy, even if the temperature doesn't change.
- Occupants: People release moisture through respiration and perspiration.
- Infiltration/Ventilation: Humid outdoor air entering the building increases the indoor moisture content.
- Other Sources: Cooking, showering, and indoor plants can also contribute to latent heat.
How to Use the Cooling Load Calculator
Our calculator provides a simplified estimate of your cooling load by considering the most critical factors. Here's how to use it:
- Room Area (sq ft): Enter the total floor area of the space you want to cool.
- Ceiling Height (ft): Input the average height of the ceiling. This helps determine the room's volume.
- Outdoor Design Temperature (°F): This is the typical peak outdoor temperature for your location during the hottest part of the cooling season. You can find this data from local weather stations or HVAC design guides.
- Desired Indoor Temperature (°F): Your target comfortable indoor temperature.
- Number of Occupants: The maximum number of people typically present in the space.
- Total Lighting Wattage (Watts): Sum of the wattage of all light fixtures in the room.
- Total Appliance Wattage (Watts): Sum of the wattage of heat-generating appliances (TVs, computers, refrigerators, etc.).
- Total Window Area (sq ft): The combined area of all windows in the room.
- Wall/Roof U-Value (BTU/hr·sqft·°F): A measure of how well your walls and roof insulate. Lower values indicate better insulation. (e.g., well-insulated wall: 0.05-0.15, poorly insulated: 0.2-0.4).
- Window U-Value (BTU/hr·sqft·°F): A measure of a window's insulating properties. Lower values mean better insulation. (e.g., single pane: ~1.0, double pane: 0.3-0.6, triple pane: 0.2-0.3).
- Window Solar Heat Gain Coefficient (SHGC): A value between 0 and 1 that indicates how much solar radiation passes through a window. Lower SHGC means less solar heat gain. (e.g., clear glass: 0.7, low-e glass: 0.25-0.4).
- Peak Solar Radiation Factor (BTU/hr·sqft): Represents the intensity of solar radiation hitting your windows. This varies significantly with orientation, shading, and time of day. Use a higher value for south/west-facing windows with no shading (e.g., 100-150) and lower for shaded or north-facing windows (e.g., 50-80).
- Air Changes per Hour (ACH): Estimates how many times the air in a room is replaced by outdoor air per hour due to infiltration or ventilation. (e.g., very tight home: 0.3-0.5, average home: 0.5-1.0, leaky home: 1.0-2.0+).
Example Calculation
Let's consider a small office space with the following parameters:
- Room Area: 200 sq ft
- Ceiling Height: 8 ft
- Outdoor Design Temperature: 95 °F
- Desired Indoor Temperature: 75 °F
- Number of Occupants: 2
- Total Lighting Wattage: 150 Watts
- Total Appliance Wattage: 300 Watts
- Total Window Area: 30 sq ft
- Wall/Roof U-Value: 0.08 BTU/hr·sqft·°F
- Window U-Value: 0.5 BTU/hr·sqft·°F
- Window SHGC: 0.4
- Peak Solar Radiation Factor: 100 BTU/hr·sqft
- Air Changes per Hour (ACH): 0.5
Using these values in the calculator, we get:
- Total Sensible Load: Approximately 3846.75 BTU/hr
- Total Latent Load: Approximately 404.00 BTU/hr
- Total Cooling Load: Approximately 4250.75 BTU/hr
- Required Cooling Capacity: Approximately 0.35 Tons
Based on this, an HVAC professional might recommend a 0.5-ton (6,000 BTU/hr) or 0.75-ton (9,000 BTU/hr) unit, allowing for a safety margin and considering available equipment sizes.
Disclaimer
This calculator provides a simplified estimate for educational and preliminary planning purposes. Actual cooling load calculations performed by HVAC professionals involve more detailed analysis, including specific building materials, orientation, duct losses, local climate data, and advanced psychrometrics. Always consult with a qualified HVAC technician for precise sizing and installation of your air conditioning system.