Tight Homes, Lower Loads: The Link Between Air Leakage and HVAC Sizing

The Cost of Air Leaks: Why Sealing Up Saves Big

Imagine trying to heat or cool your home while leaving a window cracked all year. That’s essentially what happens when your home leaks air—and most buildings do, a lot more than you’d think.

At Full Circle Construction Services, we run the numbers every day. And when it comes to air leakage, the math is crystal clear: leaky homes cost more to heat, cool, and maintain.

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🏠 Just How Much Air is Leaking?

When we test a home’s air leakage with a blower door, we get results in ACH50 (air changes per hour at 50 Pascals). Here’s what we found for one project:

Air Leakage	Hole Size (approx.)	Heating Load	Cooling Load
5 ACH50	445 sq in (3.1 sq ft)	99,354 BTUH	46,916 BTUH
3 ACH50	267 sq in (1.85 sq ft)	86,789 BTUH	45,536 BTUH
2.5 ACH50	223 sq in (1.55 sq ft)	83,650 BTUH	45,152 BTUH
1.5 ACH50	134 sq in (0.93 sq ft)	77,365 BTUH	44,382 BTUH

📉 That’s a 22,000 BTU drop in heating load just by tightening the home from 5 ACH50 to 1.5. That’s nearly one ton of heating load reduction—the size of an entire small furnace or heat pump!

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Why Does This Matter?

Here’s what happens when your home leaks:

• Your HVAC system has to work harder to maintain comfort.
• You may need larger equipment, which costs more upfront.
• That system runs less efficiently, leading to higher utility bills.
• Comfort suffers—think drafts, temperature swings, and overworked equipment.

“It’s like trying to heat a bathtub with the drain open. You can keep pouring hot water in… but you’re wasting money doing it.”

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Sealing = Saving

By reducing leakage, you’re doing more than saving energy—you’re unlocking:

• ✅ Smaller HVAC systems (lower cost)
• ✅ Lower monthly energy bills
• ✅ Improved comfort and air quality
• ✅ Longer-lasting mechanical equipment

Every time we cut air leakage, we also cut the heating load—and that makes homes more affordable to build and to operate.

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Want to learn how to make your home or building leak less? Contact Full Circle today!

Email: amanda@fullcircleconstruction.org