Infiltration Heat Loss Calculation

Infiltration Heat Loss Formula:

\[ Q = CFM \times 1.08 \times \Delta T \]

Infiltration Heat Loss (Q):

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1. What is Infiltration Heat Loss?

Infiltration heat loss refers to the energy lost when outside air enters a building through cracks, openings, and unintentional ventilation, requiring additional heating to maintain indoor comfort temperatures.

2. How Does the Calculator Work?

The calculator uses the infiltration heat loss formula:

\[ Q = CFM \times 1.08 \times \Delta T \]

Where:

\( Q \) — Infiltration heat loss (BTU/hr)
\( CFM \) — Cubic feet per minute of air infiltration
\( \Delta T \) — Temperature difference between inside and outside (°F)
\( 1.08 \) — Constant factor accounting for air density and specific heat

Explanation: The formula calculates the heat energy required to warm the infiltrating outside air to indoor temperature conditions.

3. Importance of Infiltration Heat Loss Calculation

Details: Accurate infiltration heat loss calculation is essential for proper HVAC system sizing, energy efficiency analysis, building envelope assessment, and optimizing heating system performance.

4. Using the Calculator

Tips: Enter CFM value in cubic feet per minute and temperature difference in °F. Both values must be valid (CFM > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is the 1.08 constant in the formula?
A: The 1.08 constant combines the density of air (0.075 lb/ft³) and the specific heat of air (0.24 BTU/lb·°F), multiplied by 60 minutes/hour.

Q2: How is CFM measured or estimated?
A: CFM can be measured using blower door tests or estimated based on building tightness, number of air changes per hour, and building volume.

Q3: What are typical CFM values for residential buildings?
A: Typical values range from 0.1-0.5 air changes per hour for tight construction to 1.0+ for leaky older buildings.

Q4: Does this calculation account for humidity?
A: No, this basic formula only accounts for sensible heat loss. Latent heat from humidity requires additional calculation.

Q5: When is infiltration heat loss most significant?
A: Infiltration heat loss is most significant in cold climates, windy conditions, and in buildings with poor air sealing.