What is a Blower Door Test?
A blower door test measures how much air is leaking through the building envelope by using a calibrated fan temporarily mounted in an exterior doorway. The fan depressurizes the home, making it easy to detect and quantify air leakage through gaps around windows, doors, attic bypasses, rim joists, and other common problem areas.
This test is required by the IECC energy code (in most states) for new construction and is also essential for accurate Manual J HVAC sizing. Without a blower door test, a home's airtightness is based on , guesswork leading to oversized HVAC systems, poor performance, and potential inspection failures. Blower door testing provides real data so builders, designers, and homeowners can make informed decisions.
Why Airtightness Matters:
1. Moisture Control: Leaky homes allow humid air into wall cavities, leading to condensation, mold, and reduced material durability
2. Indoor Air Quality (IAQ): Air leaks pull contaminants from attics, crawlspaces, and wall voids into your breathing space
3. Comfort & Efficiency: Air leakage leads to drafts, uneven temperatures, and higher utility bills.
4. HVAC Accuracy: Load calculations (Manual J) are only accurate if air leakage is measured and controlled
In Summary:
Uncontrolled air movement bypasses insulation, air barriers, and moisture control systems, compromising the home’s durability, energy efficiency, comfort, and indoor air quality. Excess air leakage can lead to hidden moisture buildup, mold growth, uneven temperatures, high energy bills, and HVAC system strain. Without blower door testing, these issues are often missed, leading to code compliance failures or expensive corrections after construction.
It is essential to have testing performed by a certified professional. A RESNET HERS Rater or BPI Certified Building Analyst has the training and tools to measure air leakage accurately, interpret results, and ensure the home meets performance and code standards.
This test is required by the IECC energy code (in most states) for new construction and is also essential for accurate Manual J HVAC sizing. Without a blower door test, a home's airtightness is based on , guesswork leading to oversized HVAC systems, poor performance, and potential inspection failures. Blower door testing provides real data so builders, designers, and homeowners can make informed decisions.
Why Airtightness Matters:
1. Moisture Control: Leaky homes allow humid air into wall cavities, leading to condensation, mold, and reduced material durability
2. Indoor Air Quality (IAQ): Air leaks pull contaminants from attics, crawlspaces, and wall voids into your breathing space
3. Comfort & Efficiency: Air leakage leads to drafts, uneven temperatures, and higher utility bills.
4. HVAC Accuracy: Load calculations (Manual J) are only accurate if air leakage is measured and controlled
In Summary:
Uncontrolled air movement bypasses insulation, air barriers, and moisture control systems, compromising the home’s durability, energy efficiency, comfort, and indoor air quality. Excess air leakage can lead to hidden moisture buildup, mold growth, uneven temperatures, high energy bills, and HVAC system strain. Without blower door testing, these issues are often missed, leading to code compliance failures or expensive corrections after construction.
It is essential to have testing performed by a certified professional. A RESNET HERS Rater or BPI Certified Building Analyst has the training and tools to measure air leakage accurately, interpret results, and ensure the home meets performance and code standards.
© 2023. All Rights Reserved.
© 2023. All Rights Reserved.