HVAC, IAQ & Mechanical Integration
The enclosure and the mechanical system are one combined performance system. This session focuses on right-sizing, distribution, and pressure management—and how they connect to comfort, durability, and indoor air quality.
Potential agenda
- Intro (2 min): “Comfort complaints are usually systems complaints.”
- Desired outcome (6–8 min): What good mechanical integration delivers
- Common failures (6–8 min): Oversizing, poor distribution, duct leakage, bad pressure regimes
- Core concepts (6–8 min): Loads, airflows, filtration/ventilation basics, controls/commissioning
- Takeaways (2–3 min): The few “must-do” fundamentals
- Discussion (30–45 min): Prompts embedded below
Desired outcome
- 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.
Discussion prompt
- “Good HVAC”: What’s the most common reason homeowners complain even when equipment is “new”?
Common failures
Mechanical integration failure patterns These often look like “comfort” problems but have clear root causes
- Oversized equipment: short cycling, poor humidity control, uneven comfort.
- Bad distribution: rooms that never match the thermostat; high static; noisy airflow.
- Duct leakage: energy loss, pressure problems, and pollutant pathways.
- Pressure-driven contamination: depressurization pulls in soil gases or garage air.
- Uncommissioned controls: “works on day 1” but not across seasons and use cases.
Examples (worked into failures)
Example — “One room is always hot/cold”
Distribution, balancing, or duct design issues—often compounded by enclosure weak points or solar gains.
Example — “Musty smell after sealing/renovation”
Enclosure got tighter, but ventilation/dehumidification didn’t adapt; pressure regimes change; pollutants and moisture linger.
Discussion prompt
- Commissioning: What do you wish was always measured/verified before handoff?
Core concepts
Right-sizing is about comfort and control
Oversizing isn’t a safety margin; it often creates worse comfort and worse moisture control.
Distribution is the product
Equipment can be perfect; distribution can still make the house uncomfortable.
Ventilation is intentional, not accidental
Air leakage is not ventilation. Choose a strategy and execute it consistently.
Pressure control prevents surprises
Pay attention to exhaust, returns, and duct leakage so you don’t create pollutant pathways.
Takeaways
- Mechanical success is loads + distribution + controls + commissioning.
- A tighter enclosure changes the “rules”—systems must be designed for the new behavior.
- Most comfort complaints are fixable when you treat the enclosure + mechanicals as one system.
- This closes the loop: P01 outcomes → P06–P10 enclosure control → P11 integration and operation.
Further reading
Optional links will be added here (short, high-credibility readings that match the session focus).