Air Sealing & Ventilation

Air sealing is the single highest-ROI move you can make on a new build, and it's also the easiest one to mess up. A leaky house doesn't just waste energy — it pulls humid summer air into wall cavities, lets winter heat escape through the top plate, and routinely strips insulation of half its rated performance. The Passive House standard targets 0.6 ACH50 for a reason: below that threshold, your envelope behaves the way the spec sheets say it will, and your mechanical ventilation can actually do its job.

Once you build tight, you have to ventilate right. That's where balanced mechanical ventilation comes in — an ERV in mixed and humid climates, an HRV where winters are long and dry. Sizing isn't intuitive: too little airflow and you trap CO2 and moisture indoors; too much and you over-ventilate, dump conditioned air outside, and drive humidity in the wrong direction. ASHRAE 62.2 gives you a starting point for residential ventilation rates, but climate and occupancy matter as much as the standard.

This hub walks through both halves of the equation — sealing and ventilating — with these as good entry points:

• ERV vs. HRV — climate-driven choice between heat-only and enthalpy recovery.
• Safer alternatives to spray foam — air-sealing without the off-gassing trade-offs.
• Air sealing calculator for ACH50 targets, and the ERV/HRV sizing calculator for matching CFM to your floor plan.

The honest tradeoff: cheap air sealing — careful detailing of penetrations, sill plates, rim joists, and top plates with gasketing and acoustic sealant — outperforms expensive air sealing applied as an afterthought. DOE Energy Saver covers the basics, but you'll get further by running a mid-construction blower-door test and chasing the leaks while the framing is still exposed.