body {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
background-color: #f8f9fa;
color: #333;
line-height: 1.6;
margin: 0;
padding: 20px;
}
.loan-calc-container {
max-width: 800px;
margin: 30px auto;
background-color: #ffffff;
padding: 30px;
border-radius: 8px;
box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
}
h1, h2 {
color: #004a99;
text-align: center;
margin-bottom: 20px;
}
.input-group {
margin-bottom: 20px;
padding: 15px;
border: 1px solid #e0e0e0;
border-radius: 5px;
background-color: #fdfdfd;
}
.input-group label {
display: block;
margin-bottom: 8px;
font-weight: 600;
color: #004a99;
}
.input-group input[type="number"],
.input-group select {
width: calc(100% – 22px);
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1rem;
margin-top: 5px;
}
.input-group input[type="number"]:focus,
.input-group select:focus {
border-color: #004a99;
outline: none;
box-shadow: 0 0 5px rgba(0, 74, 153, 0.3);
}
button {
display: block;
width: 100%;
padding: 12px 20px;
background-color: #004a99;
color: white;
border: none;
border-radius: 5px;
font-size: 1.1rem;
cursor: pointer;
transition: background-color 0.3s ease;
margin-top: 20px;
}
button:hover {
background-color: #003366;
}
#result {
margin-top: 30px;
padding: 20px;
background-color: #e7f3ff;
border-left: 5px solid #28a745;
border-radius: 5px;
text-align: center;
}
#result h3 {
margin-top: 0;
color: #004a99;
}
#result-value {
font-size: 2.5rem;
font-weight: bold;
color: #28a745;
}
.article-section {
margin-top: 40px;
padding: 25px;
background-color: #ffffff;
border-radius: 8px;
box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
}
.article-section h2 {
text-align: left;
color: #004a99;
margin-bottom: 15px;
}
.article-section p, .article-section ul {
margin-bottom: 15px;
}
.article-section ul {
padding-left: 20px;
}
.article-section li {
margin-bottom: 8px;
}
.formula {
background-color: #eef7ff;
padding: 10px 15px;
border-left: 3px solid #004a99;
margin: 15px 0;
font-family: 'Courier New', Courier, monospace;
font-size: 0.95rem;
overflow-x: auto;
}
@media (max-width: 768px) {
.loan-calc-container {
padding: 20px;
}
h1 {
font-size: 1.8rem;
}
#result-value {
font-size: 2rem;
}
}
Understanding HVAC CFM and Air Changes per Hour (ACH)
In the realm of Heating, Ventilation, and Air Conditioning (HVAC), Cubic Feet per Minute (CFM) is a critical metric. It represents the volume of air that an HVAC system can move per minute. This value is essential for properly sizing an air conditioner, furnace, or ventilation system to ensure it can effectively heat, cool, and ventilate a given space.
The CFM requirement for a space is directly related to its size and the desired rate of air exchange. This is where Air Changes per Hour (ACH) comes into play. ACH refers to how many times the entire volume of air within a room or building is replaced by fresh or conditioned air in one hour. Different applications and building codes specify different ACH rates:
- Standard Residential: Typically ranges from 8 to 12 ACH. This ensures adequate comfort and air quality for most homes.
- Commercial Spaces: May require higher ACH rates (e.g., 10-20 ACH or more) depending on occupancy, activities, and specific ventilation standards.
- Specialized Environments: Areas like laboratories, clean rooms, or hospitals might have much higher ACH requirements to maintain strict air purity and safety standards.
How to Calculate Required CFM
The calculation for CFM is straightforward and involves determining the volume of the space and the desired air exchange rate.
First, calculate the volume of the room in cubic feet:
Volume (cu ft) = Room Length (ft) × Room Width (ft) × Room Height (ft)
Next, determine the total air volume to be moved per hour based on the desired ACH:
Total Air Volume per Hour (cu ft/hr) = Volume (cu ft) × ACH
Finally, convert this hourly volume to CFM by dividing by 60 (since there are 60 minutes in an hour):
Required CFM = (Volume (cu ft) × ACH) / 60
Example Calculation
Let's consider a living room with the following dimensions:
- Room Length: 18 feet
- Room Width: 14 feet
- Room Height: 9 feet
- Desired ACH: 10 (for good residential ventilation)
1. Calculate Volume:
Volume = 18 ft × 14 ft × 9 ft = 2,268 cubic feet
2. Calculate Total Air Volume per Hour:
Total Air Volume per Hour = 2,268 cu ft × 10 ACH = 22,680 cu ft/hr
3. Calculate Required CFM:
Required CFM = 22,680 cu ft/hr / 60 min/hr = 378 CFM
Therefore, for this living room, an HVAC system capable of delivering approximately 378 CFM would be suitable to achieve the desired 10 air changes per hour.
Important Note: This calculation provides a baseline. Factors like ductwork design, system efficiency, climate, and specific occupancy needs can influence the final system sizing. It is always recommended to consult with a qualified HVAC professional for precise system design and installation.
function calculateCFM() {
var roomLength = parseFloat(document.getElementById("roomLength").value);
var roomWidth = parseFloat(document.getElementById("roomWidth").value);
var roomHeight = parseFloat(document.getElementById("roomHeight").value);
var ach = parseFloat(document.getElementById("ach").value);
var resultDiv = document.getElementById("result");
var resultValueDiv = document.getElementById("result-value");
if (isNaN(roomLength) || isNaN(roomWidth) || isNaN(roomHeight) || isNaN(ach) ||
roomLength <= 0 || roomWidth <= 0 || roomHeight <= 0 || ach <= 0) {
resultValueDiv.innerHTML = "Invalid Input";
resultDiv.style.display = "block";
resultDiv.style.backgroundColor = "#ffebee"; // Light red for error
document.getElementById("result-unit").style.color = "#d32f2f";
return;
}
var volume = roomLength * roomWidth * roomHeight;
var cfm = (volume * ach) / 60;
resultValueDiv.innerHTML = cfm.toFixed(2);
resultDiv.style.display = "block";
resultDiv.style.backgroundColor = "#e7f3ff"; // Light blue for success
document.getElementById("result-unit").style.color = "#28a745"; // Green for unit
}