Learn · Building Science

Home Infiltration & Air Leakage

Why “how tight is this house?” matters as much as tonnage — and how sneaky outdoor air loads up your AC in Polk County humidity.

By Billy Gregus, Owner · Last updated July 2026

The Short Answer

Infiltration is uncontrolled outdoor air leaking in through gaps, cracks, attic penetrations, and leaky returns. In Central Florida that air brings humidity and heat that your system has to remove again and again. Measuring and managing leakage — not just cranking the thermostat — is how premium comfort work actually gets done.

What is infiltration?

Infiltration is outdoor air that enters the home without being planned or filtered — through gaps around windows and doors, recessed lights, attic hatches, plumbing penetrations, and leaky duct returns that pull from hot attics or wall cavities.

Ventilation is different: measured fresh air you choose to bring in (for example through an ERV). Infiltration is accidental. In a muggy Florida climate, accidental outdoor air is mostly a humidity problem wearing a comfort costume.

Why tightness matters in Florida

Humid outdoor air raises indoor RH and can leave rooms clammy even when the thermostat reads “cool.”
Leaky returns can pull dusty attic air into the living space and starve supply airflow.
An oversized AC short-cycles and cannot wring moisture out; leaky envelopes make that failure worse.
Energy bills climb when the system re-conditions the same outdoor air all day.

When homeowners should care

Rooms that never feel dry, even with a newer AC.
Dust that returns quickly after cleaning, especially near returns.
Hot/cold spots that move with wind or attic heat.
You are planning a replacement and want the load calculation to match the real house — not the old nameplate.

How Integrity approaches it

We treat envelope tightness as part of the comfort system, not a side hobby. Our team includes engineering-minded diagnostics — the kind of analytical work most companies skip — so we can look at infiltration, duct leakage, equipment sizing, and humidity together instead of selling a bigger box.

Tightening a home always pairs with a plan for intentional fresh air. Seal the accidental holes, then ventilate on purpose. That is the building-science order of operations.

Premium building-science work is what separates a comfort plan from a parts swap. Integrity's engineering-minded team diagnoses Winter Haven homes from every angle — envelope, ducts, humidity, and fresh air — then designs the fix.

Request a Building Science Consult

FAQ

Common Questions Answered

Is a tighter home always better in Florida?

Tighter is better for controlling humidity and energy — as long as you add planned ventilation. Sealing leaks without a fresh-air strategy can raise indoor pollutants. Integrity designs both sides: reduce infiltration, then bring in measured outdoor air when the home needs it.

Can I see air leaks myself?

You can spot obvious ones — daylight around doors, attic hatch gaps, missing weatherstripping — but most of the load is hidden. Blower door testing and duct leakage testing put numbers on the problem so repairs are prioritized, not guessed.

Does infiltration affect AC sizing?

Yes. Manual J load calculations include envelope leakage assumptions. A leaky home needs more capacity to stay comfortable than a tighter one. Measuring the real house keeps you from oversizing “just in case.”

Keep Reading