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Building for Comfort and Efficiency: Passive House Design and Ventilation
Reading time: 5 minutes
Comfort
Passive House construction is gaining momentum across North America as builders, engineers, and HVAC contractors look for ways to deliver homes that are energy-efficient, durable, and comfortable for occupants. At its core, Passive House focuses on airtightness, super-insulation, thermal bridge-free construction, high-performance windows, and controlled mechanical ventilation. While many builders borrow Passive House principles for high-performance projects, formal certification through PHI or PHIUS provides third-party verification that the home actually meets the rigorous performance targets and not just design intent. Whether pursuing certification or applying the core principles to improve efficiency, builders can significantly reduce energy use, improve indoor comfort, and create durable, resilient buildings.
This article highlights key strategies for Passive House-inspired design, with a spotlight on ventilation systems. The Bay View House, a compact waterfront home designed with high-performance living in mind, provides a practical example of these strategies in action.
What is Passive House?
Passive House, or “Passivhaus,” is a performance-based building standard originally developed in Germany. It is defined not by specific materials or aesthetics, but by measurable energy and comfort targets:
Sources: Passive House Accelerator, PHIUS
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Airtightness: ≤0.6 air changes per hour at 50 Pascals (ACH50), verified via blower door testing.
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Space Heating Demand: ≤15 kWh/m²/year (~4,750 BTU/ft²/year).
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Primary Energy Limit: ≤120 kWh/m²/year (~38,000 BTU/ft²/year) for all energy use.
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Thermal Comfort: Maximum indoor temperature variance of 20°C (68°F), even in winter.
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Mechanical Ventilation with Heat Recovery (MVHR): Continuous supply of fresh air with heat recovery from exhaust air.
For builders and HVAC contractors, these targets translate into practical design strategies: sealing the building envelope precisely, selecting high-performance insulation and windows, and integrating a well-sized heat recovery ventilation system.
Why Certification Matters
Although many high-performance homes draw inspiration from Passive House principles, certified Passive House buildings undergo a rigorous, third-party verified process that ensures the building performs as designed. Certification provides:
Verified airtightness through blower door testing (≤0.6 ACH50)
Verified energy modeling using PHI or PHIUS-approved software
Verified ventilation design, including HRV/ERV sizing and performance
Verified commissioning, ensuring systems operate to specification
For builders and engineers, certification removes guesswork: it confirms that design goals translate into measurable performance outcomes. Passive House-inspired approaches can significantly improve comfort and efficiency, but certification guarantees compliance, quality, and long-term performance.
Ventilation: The Lungs of a Passive House
Even the most airtight home cannot maintain healthy indoor air quality without mechanical ventilation.
Why Ventilation Matters
Airtight construction traps moisture, VOCs, and other indoor pollutants.
Proper ventilation prevents condensation, mold growth, and unhealthy indoor air.
It supports consistent indoor temperatures and occupant comfort.
HRV vs. ERV
Heat Recovery Ventilator (HRV): Transfers heat between incoming and outgoing air to minimize energy loss.
Energy Recovery Ventilator (ERV): Transfers both heat and humidity, which can be advantageous in humid climates.
Sizing & Efficiency
Passive House design typically requires 0.3–0.5 air changes per hour of continuous fresh air.
For a single-family home, this often equates to 150–250 CFM, depending on size and layout.
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A real-world example is the Bay View House. Designers incorporated a HERO 150H-EC Fresh Air Appliance, an ENERGY STAR®-certified HRV providing 175 CFM of continuous filtered outdoor air while recovering up to 80% of heat from outgoing air. This high-efficiency ventilation system maintains indoor comfort and air quality in a tightly sealed, energy-efficient home, supporting both performance and occupant health.
Design Strategies to Support Ventilation and Efficiency
Builders and engineers must implement holistic strategies that complement ventilation systems to achieve high-performance results. For Passive House-certified homes, each strategy must meet specific, measurable criteria and is reviewed and verified by an independent certifier. Even in high-performance homes that are not pursuing certification, applying these strategies can dramatically improve comfort, efficiency, and indoor air quality, though the results are not third-party verified.
Super-Tight Building Envelope
Seal all junctions, windows, doors, and penetrations meticulously.
Target ≤0.6 ACH50 to ensure MVHR systems operate efficiently.
High-Performance Insulation and Thermal Bridge-Free Design
Use continuous insulation on walls, roof, and floors to prevent heat loss.
Minimize thermal bridges at framing intersections with insulated headers and proper detailing.
Window Placement and Passive Solar Gains
Triple-glazed windows reduce heat loss.
South-facing windows (in the northern hemisphere) capture winter solar energy.
Operable windows and clerestory placement provide natural cross-ventilation in mild climates, reducing reliance on mechanical systems.
Integrated Mechanical Systems
Heat pumps for heating and cooling work synergistically with HRV/ERV.
Duct layout should minimize static pressure to allow balanced airflow.
Energy modeling software (e.g., WUFI Passive, PHIUS+) optimizes system selection and placement.
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Bay View House: A Case Study in Practical Application
The Bay View House demonstrates how these strategies come together in a real project:
Envelope & Orientation: Super-tight envelope carefully oriented to existing trees and landscape, optimizing passive solar gains.
Materials: Low- to no-VOC materials, formaldehyde-free cabinetry, and durable, recyclable standing-seam metal roofing.
Ventilation: HERO 150H-EC HRV provides continuous fresh air while recovering up to 80% of heat, enhancing comfort and indoor air quality.
Heating & Cooling: Combination of a tight envelope, passive solar optimization, and HRV allowed the home to eliminate a central heating system in favor of a ductless mini-split heat pump.
Net Zero Ready: PV solar rough-ins enable future renewable energy integration.
This example shows how builders can adopt Passive House-inspired strategies without full certification, achieving high-performance outcomes.
Energy Modeling and Lifecycle Considerations
Energy modeling is a critical tool for builders and HVAC contractors and required for Passive House certification:
Predict annual heating and cooling loads.
Optimize insulation, window placement, and ventilation sizing.
Evaluate energy savings compared to code-compliant homes.
For the Bay View House, modeling revealed significantly reduced operational energy use, demonstrating the cost-effectiveness of investing in envelope performance and efficient ventilation. Proper modeling also ensures systems are correctly sized and installed, minimizing surprises during construction and operation.
Tips for Builders and Contractors
To successfully apply Passive House-inspired strategies, focus on several key considerations:
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Plan ventilation early: Mechanical ventilation layout affects duct runs, pressure loss, and energy efficiency.
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Coordinate envelope and mechanical systems: Tight envelopes demand precise ventilation, or indoor air quality suffers.
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Size systems correctly: HRV/ERV must match home volume and occupancy.
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Select durable, low-emission materials: Supports occupant comfort and long-term IAQ.
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Leverage modeling: Software tools can guide design decisions and prevent costly post-construction adjustments.
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Consider certification when clients want guaranteed performance: Certification adds accountability, documentation, and long-term assurance that the home meets stringent Passive House standards.
Common Misconceptions About Passive House
Despite growing interest, several myths persist:
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“It’s only for small homes”: Passive House principles scale to any size or type of building.
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“Mechanical ventilation isn’t necessary”: Airtight homes require ventilation to prevent moisture and pollutants.
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“It’s too expensive”: Investing in envelope and ventilation efficiency often reduces long-term operational costs, offsetting initial expenditures.
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"Certification isn’t necessary": While Passive House principles can improve any project, certification ensures the building is tested, modeled, and verified, significantly reducing the performance gap between design intentions and real-world outcomes
Understanding the reality behind these misconceptions helps builders and contractors adopt high-performance strategies with confidence.
Design Insights for High-Performance Homes
Builders, engineers, and HVAC contractors can benefit from applying Passive House principles in any project. However, Passive House certification remains the most reliable pathway to guaranteeing airtightness, ventilation performance, thermal comfort, and energy efficiency are all achieved as designed.
The Bay View House illustrates how an inspired approach can deliver meaningful improvements, but certified Passive House projects undergo rigorous verification that ensures measurable, predictable results. By understanding both pathways, building professionals can select the right approach for each project and client.
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