What Is a Blower Door Test — And Why Does It Matter?

If you’ve ever wondered how builders measure a home’s true energy performance, the answer often begins with a blower door test.

At Performance By Design, we rely on blower door testing to confirm that homes meet airtightness and efficiency goals — especially in cold climates where performance matters most. It’s a simple diagnostic tool that delivers powerful insight.

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What Is a Blower Door Test?

A blower door test uses a temporary, calibrated fan installed in an exterior doorway. When the fan depressurizes the home, outside air is pulled through any cracks, gaps, or weak points in the building envelope.

This process turns invisible problems into measurable data — and often makes the hidden issues easy to see and feel.

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What the Test Reveals

A blower door test helps identify:

• Air leakage points

• Noticeable drafts

• Envelope weak spots

• Missing or inconsistent insulation

• Areas contributing to heat loss or moisture intrusion

You also receive a numerical airtightness rating (ACH50), which determines whether the home meets modern energy codes and aligns with Housing 2.0 and high-performance building principles.

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Why Airtightness Matters

Uncontrolled air leakage leads to:

• Higher heating costs

• Cold, drafty rooms

• Moisture entering walls

• Ice dams

• Reduced indoor comfort

A tighter home delivers:

• Predictable heating performance

• Better humidity and moisture control

• More consistent room temperatures

• Lower utility bills

Simply put, airtightness directly impacts comfort, durability, and long-term operating costs.

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Connection to Thermal Bridging

While thermal bridging involves heat transferring through building materials, air leakage often occurs near the same problem areas — such as corners, rim joists, framing intersections, and penetrations.

Blower door testing helps locate these vulnerable spots so builders can seal, insulate, or reinforce them correctly. It’s one of the most effective ways to validate a high-performance building envelope.

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Why Performance By Design Uses Blower Door Testing

We use blower door testing to:

• Verify airtightness against code and performance targets

• Ensure quality craftsmanship

• Improve long-term energy efficiency

• Identify issues early, before finishes are installed

• Deliver homes designed for cold-climate performance and resilience

It’s a key part of building smarter, stronger, more durable homes that perform through every season.

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Bottom Line

Whether you’re building new or upgrading an existing home, a blower door test is one of the smartest tools available. It reveals what you can’t see — and gives homeowners and builders confidence that a home is truly performing the way it should.

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Build Smarter With Performance By Design

Ready to understand your home’s performance — or build a home that exceeds modern energy expectations?

Performance By Design is here to guide you.

From blower door testing to full envelope strategy, SIP guidance, and Housing 2.0 design principles, we help homeowners and builders create strong, efficient, and resilient homes.

👉 Contact PBD today to schedule a consultation.

Let’s build a better home — by design.