ASHRAE 62.1 - Indoor Air Quality Procedure (IAQP) 2025

A Technical Explainer for Architects & Consulting Engineers

The purpose of IAQP

ASHRAE Standard 62.1 provides two compliant ventilation pathways:

1. Ventilation Rate Procedure (VRP) – prescriptive outside air volumes

2. Indoor Air Quality Procedure (IAQP) – performance-based contaminant control

The IAQP allows engineers to meet indoor air quality requirements by limiting contaminant concentrations, rather than by supplying fixed quantities of outdoor air.

This enables safe reduction of outdoor air, provided that:

• Contaminants of concern are identified

• Acceptable concentration limits are defined

• Control strategies are documented and verifiable.

  
  

Why ASHRAE 62.1 - Indoor Air Quality Procedure Matters in HVAC Design

In hot-climate regions, outdoor air dominates:

• Cooling load

• HVAC system sizing

• Energy consumption

IAQP enables engineers to decouple IAQ performance from outside air volume, unlocking opportunities to:

• Reduce ventilation rates

• Downsize HVAC equipment

• Lower peak and annual energy demand

  
  

IAQP Compliance Framework (An Engineer's Viewpoint)

Under ASHRAE 62.1 - Indoor Air Quality Procedure, the design team must demonstrate that:

1. Contaminants of Concern are identifiedTypical examples:

   • Particulates (PM2.5, PM10)

   • VOCs

   • Microbial contaminants (bacteria, viruses, mould)

   • Odours

2. Acceptable Concentration Limits are defined using:

   • ASHRAE guidance

   • WHO / EPA references

   • Owner Project Requirements (OPR)

3. Control Measures are implemented including:

   • Filtration

   • Air cleaning / purification

   • Source control

   • Ventilation (reduced but sufficient)

4. Performance is Achieved and Maintained through:

   • Independently tested technologies

   • Monitoring (optional but recommended)

   • Documented design intent

     
     

The Role of Bipolar Ionization in IAQP

When Direct Barrier Discharge (DBD) Bipolar Ionization is integrated into the HVAC system:

• Pathogens, VOCs, and fine particulates are neutralized in the air and on surfaces

• Contaminant concentrations are actively reduced, not just diluted

• IAQ targets can be met with significantly less outside air

This allows engineers to justify ventilation reductions often in the order of ~40–50%, subject to project-specific modelling and approval.

HVAC Downsizing Opportunities Enabled by IAQP

Reducing outside air directly impacts system sizing:

System Element	Impact
FAHUs	Lower airflow rates
Cooling coils	Reduced sensible & latent loads
Chillers	Smaller capacity
Ductwork	Reduced cross-sectional area
Plant rooms	Smaller footprint
Electrical	Reduced fan & chiller power

The result is lower HVAC CapEx and lower OpEx, while remaining compliant with ASHRAE 62.1.

Energy & Sustainability Implications

Typical outcomes in IAQP + air purification designs:

• ~10–15% reduction in total building energy

• Reduced peak cooling demand

• Lower carbon emissions

• Improved LEED, WELL, and Fitwel alignment

Importantly, IAQP is explicitly recognised within these certification frameworks as a valid compliance pathway.

Key Engineering Considerations

• IAQP must be documented clearly in Basis of Design (BoD)

• Air cleaning technology must be independently tested and ozone-free

• Coordination with sustainability consultants is recommended

• Early-stage integration (concept / schematic) maximises savings

  
  

Summary for Engineers

IAQP is not a workaround.It is a standards-compliant, performance-based design method that:

• Improves IAQ

• Reduces HVAC size

• Cuts energy use

• Strengthens the business case for healthy buildings

When paired with proven air purification, IAQP becomes a powerful engineering optimisation tool.