Do Mechanical Plans include ventilation?

Yes. Ventilation is a core part of our Mechanical Plans — the drawing set documents both the mandatory ASHRAE 62.2 whole-building mechanical ventilation system and the local exhaust (bathroom fans and a kitchen hood). Ventilation is a separate Title 24 requirement from heating and cooling, and it is one of the most commonly missed items on incomplete ADU plans, so we design and document it explicitly.

The two layers of ventilation we show

• Whole-building (dilution) ventilation per ASHRAE 62.2 — a continuous, mechanically driven supply of outdoor air sized to the ADU's floor area and bedroom count. The plan specifies the strategy, equipment make/model, CFM, and controls. This is required in every new ADU regardless of size and is not waivable.
• Local (spot) exhaust — bathroom exhaust fans and a kitchen range hood ducted to the exterior (recirculating hoods generally don't satisfy the California Mechanical Code). These are in addition to whole-building ventilation, not a substitute.

What appears on the plan set

1. The calculated whole-building ventilation rate, derived from floor area and bedroom count.
2. The chosen strategy — continuous exhaust fan, balanced ERV/HRV, or supply ventilation through the air handler.
3. The ventilation equipment in the schedule: make, model, and rated CFM.
4. Controls confirming continuous operation.
5. Bath fan and kitchen-hood locations with duct runs to the exterior.
6. A note for HERS verification of ventilation airflow, which a rater field-measures.

Typical ADU ventilation rates

These illustrate the order of magnitude; the engineer calculates the exact target for your unit.

A clean plan check depends on showing ventilation as its own designed system — not assuming a bath fan covers it. ASHRAE 62.2 whole-building ventilation and local exhaust are distinct requirements.

Why ventilation is non-negotiable in a tight ADU

Modern ADUs are built tight to meet the energy code, which means they no longer "breathe" through gaps the way old construction did. Without deliberate mechanical ventilation, moisture, CO2, cooking byproducts, and VOCs from finishes accumulate indoors. That is exactly the problem ASHRAE 62.2 solves, and it is why a HERS rater field-measures the installed airflow — a system that looks right on paper still has to deliver the required CFM in the field. Designing it into the plans up front, with the correct controls and CFM, is what keeps both plan check and final inspection clean.

Ventilation rates and verification requirements vary by code cycle and jurisdiction — confirm current details with your local building department. Our mechanical plans include the ASHRAE 62.2 design, calculated rate, and equipment schedule, and pair cleanly with a bundled Title 24 report. See pricing or start your order.