HVAC, IAQ & Mechanical Integration

Treat mechanical systems as part of the overall building system. Connect HVAC, ventilation, filtration, combustion safety, and pressure control back to occupant outcomes and enclosure strategy.

Builds on: P5-P10  ·  Leads to: none - this is the capstone session  ·  Cross-series: A11 Synthesis & Playbook

P/A bridge: Define who owns load calculation, ventilation verification, filtration setup, and owner handoff - these are both performance and lifecycle-cost actions.

Core Concepts

• IAQ is a system outcome, not a device. Can define targets (ventilation/filtration) and verify performance.
• Pressure relationships affect comfort and durability. Can avoid depressurization and distribution-driven moisture issues.
• Mechanical design must align with enclosure performance. Can size/commission systems based on tightness and loads.

What Good Looks Like

• Comfort: stable temperatures, controlled humidity, low noise, minimal drafts.
• IAQ outcomes: consistent ventilation strategy, filtration appropriate to goals, pollutant source control.
• Pressure sanity: avoid pulling air from garages, crawlspaces, attics, or soil.
• Efficiency and longevity: right-sized equipment that runs appropriately and lasts.
• Enclosure compatibility: mechanical operation doesn't create moisture problems in the enclosure.

Example Commissioning Checks

Specific targets depend on adopted code, ASHRAE standards, and program goals. These are categories, not prescriptive values.

1. Airflow: measure supply CFM at registers; confirm total matches Manual J/D design
2. Filtration: correct MERV rating for goals (including smoke events); owner can access and replace
3. Pressure: room-to-house differential acceptable; no combustion zone depressurized beyond safety limits
4. Duct leakage: total and to-outside tested; meets code or program target
5. Design ownership: load calc, ventilation calc, balancing, controls, and owner education each have a named responsible party

Where Things Go Wrong