Topic

Ventilation

Heat-recovery ventilation unit in a closet, its insulated ducts rising to the ceiling.

People, cooking, showers, furniture, and the ground all add to indoor air: carbon dioxide, moisture, odors, chemicals, and sometimes radon. Leaks and open windows can't be counted on to remove them: windows work only when wind and weather allow, and get shut when they don't. A Passive House ventilates continuously.

Every room people live in still has a window that opens, and opening it is fine: in monitored Passive Houses, residents who opened windows often used only a little more heat than their neighbors. On summer nights, open windows do the cooling. Fresh air every hour of the year takes the mechanical system, working with the airtight enclosure.

The system is balanced: one fan brings in fresh air, and another takes out the same amount. Fresh air usually goes to bedrooms, living rooms, offices, and classrooms, and stale air leaves from the kitchen, bathrooms, and utility rooms. It is planned as a cascade so the air crosses the halls and areas between the supply and exhaust. The two streams pass through a heat exchanger: in winter, the outgoing air warms the incoming air; in summer, it cools it; and in hot, humid climates, an energy recovery unit can also keep moisture out.

PHI requires at least 12 cfm of fresh air per person (and 0.30 air changes an hour), at least 75% heat recovery from a certified unit, fans that use no more than about 0.77 W per cfm, and bedrooms and living rooms no louder than 25 dB(A). Incoming air passes a fine filter, minimum MERV 13, which helps against wildfire smoke and traffic pollution. In monitored Passive Houses, carbon dioxide stays mostly below 1,000 parts per million.

Heat recovery doesn't cool the rooms, so the unit needs a summer bypass. And the system performs as designed only if it's balanced at handover and its filters are changed every three to six months.

Training on this topic

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13 courses and sessions

Specialized courses 2

Paid sessions 7

  • Session · Mechanicals and ventilation

    Mechanical Mastery

    Matthew McGovern, Tower Enterprises; Faiz Malek, Swegon; Zachary Koch, Mitsubishi; Dylan Martello, Steven Winter Associates (moderator)

    1.25 AIA LU · 1 PHI credit

    $19

  • Session · Mechanicals and ventilation

    Mechanical Control

    Robb Aldrich, Steven Winter Associates; Andrew Peel, Peel Passive House; Narasimha Rao, Yale University (moderator)

    1.25 AIA LU · 1 PHI credit

    $19

  • Session · Mechanicals and ventilation

    Deep Multifamily

    Crystal Ng, Curtis + Ginsberg Architects; Mark Ginsberg, Curtis + Ginsberg Architects; Elias Dagher, Pennoni; Lois Arena, Steven Winter Associates (moderator)

    1.25 AIA LU · 1 PHI credit

    $19

  • Session · Mechanicals and ventilation

    Keep it Fresh

    Eric Richards, Systemair; Szabi Fekete, Zehnder America; Andrew Peel, Peel Passive House (moderator)

    1.25 AIA LU · 1 PHI credit

    $19

  • Session · Certification and verification

    Lessons Learned

    Sarah Lewis, Passivhaus Trust; Beth Campbell, Passive House Massachusetts

    1.25 AIA LU · 1 PHI credit

    $19

  • Session · Resilience

    Passive House & Resilient Design in the Face of Fire

    Andrew Michler, Hyperlocal Workshop

    1 AIA LU · 1 PHI credit

    Watch free · credit $1.99

  • Session · Mechanicals and ventilation

    Multifamily Ventilation Duct Leakage: Targets, Strategies, and Lessons Learned

    Kelly Fisher, Peel Passive House Consulting; Michael Schmidt, Steven Winter Associates

    1 AIA LU|HSW · 1 PHI credit

    Watch free · credit $1.99

Free sessions 4

Writing on ventilation 4

  • Articles · July 22, 2026

    When the air outside is dangerous…

    When air quality alerts go out across New York City—as they did last week, with smoke from wildfires burning in Canada settling over the…

  • Articles · September 30, 2024

    Are You Healthy? Passive House and the Hygiene Standard

    An unhealthy environment? In your standard building? It’s more likely than you think.

  • Articles · March 1, 2021

    Ventilation Unit Test Data: A New Report

    As our climate emergency bears down, the importance of ventilation data and performance only rises. Passive House practitioners have been frustrated by the lack…

  • Articles · November 26, 2019

    Open Windows and Ventilation

    Several construction concepts exist that intend to dramatically reduce building energy consumption. Among the concepts is Passive House, which describes ways to design and…