Air sealing

Where the leaks actually are

Most homeowners picture windows and doors when they think about drafts. In practice, the bigger losses are almost always in the attic: top plates, plumbing and wiring penetrations, recessed can lights, attic hatches, and chimney chases. These are harder to see and easier to ignore, which is exactly why they matter.

• Top plates where interior walls meet the attic
• Plumbing stacks and electrical penetrations
• Recessed lighting fixtures not rated for insulation contact
• Attic access hatches and whole-house fan openings
• Band joists at the rim of the floor system

Air sealing versus insulation

These solve different problems. Air sealing stops uncontrolled air movement through gaps and cracks. Insulation slows heat transfer through the materials themselves. A well-insulated house with major air leaks will still perform poorly, and a well-sealed house with too little insulation still loses comfort. You need both, and air sealing should generally happen first.

What a blower door test tells you

A blower door depressurizes the house and measures how much air is moving through the building envelope. It turns "the house feels drafty" into an actual number, and it will find leaks that are completely invisible on a walkthrough. It is standard equipment on a real home energy audit.