DIY Blower Door Test: How to Check Your Home’s Air Leaks: 1 Minute to Master Home Energy Efficiency with a Blower Door Test

Air leaks are small on the surface and costly over time. I’ve measured homes where a few unsealed penetrations around plumbing, recessed lights, and attic hatches translated into drafty rooms, uneven temperatures, and unnecessary energy spend. To frame the impact, Steelcase workplace research associates air movement and thermal discomfort with a measurable drop in focus; when thermal comfort declines, cognitive performance can falter by 5–15% depending on severity of discomfort. WELL v2 sets performance targets for air tightness to support thermal and acoustic comfort, reinforcing that leak control is not just about efficiency—it’s about everyday livability.

In terms of energy, infiltration can contribute 25–40% of heating and cooling load in leaky homes, and small cracks often add up to several square inches of equivalent leakage area. Herman Miller’s research on environmental comfort notes that stable temperature and low drafts improve task persistence and reduce perceived fatigue—translating airtightness improvements into tangible wellness benefits. A blower door test quantifies your home’s leakage via ACH50 (air changes per hour at 50 Pascals). While professional testing is ideal, a careful DIY approach can help you identify high-risk leakage points and prepare for targeted sealing before scheduling a formal test.

What a Blower Door Test Measures

At its core, a blower door depressurizes (or pressurizes) the home using a calibrated fan and measures the airflow needed to maintain a set pressure (commonly 50 Pa). That airflow, converted to ACH50, reflects total leakage. Lower ACH50 values signal tighter construction; higher values indicate more paths for unwanted air exchange. Typical older homes can exceed 10 ACH50; post-2000 construction often ranges 3–7 ACH50; high-performance homes may target ≤ 1.5 ACH50. While your DIY setup won’t give lab-grade numbers, it can reveal dominant leaks and guide remediation.

DIY Setup and Safety Basics

I always start with safety. Turn off combustion appliances (gas furnaces, water heaters, fireplaces) and extinguish pilot lights to avoid back-drafting. Close exterior doors and windows; leave interior doors open for even pressure. Seal large openings like pet doors temporarily. If you have a heat recovery ventilator (HRV) or energy recovery ventilator (ERV), disable it during testing.

Creating a DIY Pressure Difference

Without a professional blower door kit, you can approximate pressure differentials to locate leaks. Two practical methods:

1. Box-fan in a door: Mount a box fan in an exterior door with cardboard or foam board shrouds to reduce bypass. Run the fan exhausting air from the home to create a slight depressurization. You won’t reach 50 Pa, but you’ll exaggerate infiltration at gaps.
2. Exhaust stack method: Run multiple exhaust fans (kitchen hood on low, bathroom fans) while ensuring make-up air is limited. This will gently depressurize the space, enough to highlight drafts.

Use an inexpensive differential pressure gauge or a smartphone-connected anemometer at suspected leaks to compare airflow between baseline and depressurized conditions. The goal isn’t perfect numbers, but consistent relative readings room-to-room.

Room-by-Room Leak Hunt

My usual sweep follows the building envelope from basement to attic:

1. Basement and crawl: Rim joists, sill plates, utility penetrations, and masonry-to-wood interfaces. Cold seasons reveal telltale cobweb movement—a sign of air currents.
2. Main floor: Window sashes, trim-to-drywall joints, outlets on exterior walls, recessed lights, chimney surrounds, and plumbing chases behind vanities.
3. Kitchen: Range hood ducts, under-sink penetrations, and toe-kicks. If the hood backdraft damper rattles, you likely have pressure imbalances.
4. Bathroom: Fan housings, supply/return grilles, and plumbing penetrations around tubs and toilets.
5. Attic: Hatch or pull-down stair perimeters, can lights, bath fan ducts, and top-plate gaps under insulation. Air sealing here often yields the biggest energy gains.

Carry incense sticks or a smoke pencil; watch for smoke drawn into cracks under depressurization. Alternatively, use a thermal camera or a phone-compatible IR attachment during temperature extremes—cooler streaks in winter or warmer streaks in summer often track infiltration paths.

Translating Findings into Targeted Sealing

I prioritize leaks by impact and ease. Start with attic and basement interfaces, then move to windows and doors. For gaps ≤ 1/4 inch, use high-quality acrylic-latex or silicone sealants; for larger perimeter gaps, low-expansion spray foam is safer around windows/doors. Weatherstripping for door thresholds and window sashes prevents recurring drafts. At chimneys or flues, use high-temperature sealants and metal collars. Keep materials compatible with substrates to avoid adhesion issues and off-gassing concerns.

Ventilation, Comfort, and Health

A tighter home shouldn’t feel stuffy. Aim for controlled ventilation rather than uncontrolled leakage. WELL v2 emphasizes adequate fresh air, low VOCs, and balanced thermal comfort across seasons. Pair air sealing with verified ventilation rates—bath fans at 50–80 cfm, kitchen hoods at 150–300 cfm on low—for routine source control, and consider continuous low-flow ventilation or HRVs in colder climates to maintain fresh air without sacrificing efficiency.

Lighting and Acoustics During the Hunt

I use neutral lighting around 4000K when scanning surfaces; glare exaggerates shadows and can hide fine cracks. Good task lighting reveals paint hairlines and joint separations. Acoustically, a depressurized space sometimes produces whistling at window weep holes or door seals; those audible cues can be surprisingly precise.

Thermal Comfort and Color Perception

Drafts reduce perceived warmth even at stable thermostat settings. In rooms with persistent infiltration, occupants gravitate to warmer color palettes that feel cozy; that psychological lift is real. Verywell Mind’s discussion on color psychology highlights how warm hues can enhance perceived comfort, but sealing leaks remains the foundation for achieving actual comfort rather than relying on visual cues alone.

When to Call a Pro

If you suspect significant leakage or combustion safety risks, book a professional blower door test. Pros will deliver ACH50, identify zone imbalances, and can perform pressure diagnostics at individual rooms. They often combine infrared imaging with duct leakage testing to ensure HVAC distribution isn’t undermining your envelope efforts.

Document Your Findings

Photograph leaks, note locations, and track materials used. A simple spreadsheet of room, leak type, and sealant or foam brand helps for future maintenance. If you’re rethinking furniture or partition layouts to mitigate drafts or improve circulation around supply grilles, try an interior layout planner to visualize changes with a room layout tool: room layout tool.

FAQ

What is ACH50 and why does it matter?

ACH50 is the number of air changes per hour at a 50 Pa pressure difference. It standardizes tightness across homes. Lower ACH50 typically indicates better energy performance and more stable comfort.

Can a DIY test damage my home?

Not if performed carefully. Use moderate fan speeds, avoid extreme depressurization, and shut down combustion appliances to prevent back-drafting. Seal large openings temporarily rather than forcing higher pressures.

How do I estimate leak severity without pro equipment?

Use relative methods: incense smoke movement, handheld anemometers at outlets or window trims, and thermal imaging during temperature extremes. Compare rooms under consistent fan settings to prioritize fixes.

Should I seal every leak I find?

Prioritize the envelope first: attic hatches, top plates, rim joists, and duct connections. Tackle windows and doors next. Balance sealing with adequate mechanical ventilation to maintain indoor air quality.

Will tighter homes feel stuffy?

Not with planned ventilation. Pair air sealing with bath and kitchen exhaust, and consider continuous low-flow systems or HRVs/ERVs to provide fresh air with minimal energy penalty.

Which materials work best for typical gaps?

Use acrylic-latex or silicone caulk for small joints; low-expansion spray foam for larger perimeter cracks; high-temperature sealants near flues; and EPDM weatherstripping at doors and operable windows.

Is there a best time of year for testing?

Cold or hot extremes accentuate temperature differentials, making IR imaging and draft detection easier. Choose a calm day to avoid wind-driven pressure that can skew readings.

How do leaks affect noise and odors?

Infiltration can carry outdoor noise and odors indoors; sealing reduces whistling at windows and drafts that spread cooking smells or garage fumes into living spaces.

What about recessed lights and attic leaks?

Recessed fixtures can be major leakage points. Use airtight IC-rated housings and seal trim rings. In attics, seal the hatch perimeter and any visible top-plate gaps before adding insulation.

Do window replacements solve drafts?

Not always. Poor installation or unsealed frames can leak even with new glazing. Start with sash weatherstripping and perimeter sealing; replace only when the frame or glazing has failed.

Could leaks be coming from the HVAC system?

Yes. Supply and return duct leaks depressurize or pressurize rooms, driving infiltration. A duct blaster test or mastic sealing on joints often delivers quick comfort gains.

When should I get a professional blower door test?

After your initial DIY sealing, schedule a pro test to verify ACH50 and identify remaining issues. Pros can also confirm combustion safety and ventilation adequacy.