Blower Door Calculator For Windows

Leakage Formula:

\[ Leakage = \frac{CFM50}{Window\ Area} \]

Leakage:

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1. What is Blower Door Leakage?

Blower door leakage per window area is a measurement of air infiltration through windows at a pressure difference of 50 Pascals. It helps assess the energy efficiency and airtightness of window installations in buildings.

2. How Does the Calculator Work?

The calculator uses the leakage formula:

\[ Leakage = \frac{CFM50}{Window\ Area} \]

Where:

\( CFM50 \) — Airflow in cubic feet per minute at 50 Pascals pressure difference
\( Window\ Area \) — Total window area in square feet

Explanation: This calculation normalizes the blower door test results by window area, allowing for comparison between different sized windows and buildings.

3. Importance of Leakage Calculation

Details: Measuring window leakage helps identify energy efficiency issues, assess the need for weatherization improvements, and ensure building envelope integrity for both comfort and energy savings.

4. Using the Calculator

Tips: Enter CFM50 measurement from blower door test and the total window area in square feet. Both values must be positive numbers for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is a good leakage value?
A: Lower values indicate better airtightness. Values below 0.25 CFM50/ft² are generally considered good, while values above 0.5 may indicate significant air leakage.

Q2: How is CFM50 measured?
A: CFM50 is measured using a blower door test that depressurizes the building to 50 Pascals and measures the airflow required to maintain that pressure.

Q3: Should I include all windows in the area calculation?
A: Yes, include the total area of all windows being evaluated for the leakage calculation to get an accurate normalized result.

Q4: What factors affect window leakage?
A: Installation quality, window age, weatherstripping condition, frame material, and overall window design all impact leakage rates.

Q5: When should I be concerned about high leakage values?
A: High leakage values may indicate the need for weatherstripping replacement, caulking, or in some cases, window replacement to improve energy efficiency.