ASHRAE 62.2: Complete Guide to Ventilation and Acceptable Indoor Air Quality in Residential Buildings

ASHRAE Standard 62.2 specifies minimum ventilation rates and indoor air quality requirements for low-rise residential buildings. This standard addresses the unique characteristics of residential buildings, including intermittent occupancy, diverse contaminant sources, and varied construction types. Understanding ASHRAE 62.2 is essential for residential HVAC designers, builders, and homeowners seeking to maintain healthy indoor air quality.

The standard provides requirements for whole-house ventilation, local exhaust ventilation, and natural ventilation options. It addresses the balance between energy efficiency and indoor air quality, providing practical solutions for residential applications. This comprehensive guide covers ventilation requirements, calculation methods, system design, and practical application examples.

Introduction to ASHRAE 62.2

Purpose and Scope

ASHRAE Standard 62.2 serves multiple critical functions:

Health Protection:

• Minimum ventilation for acceptable IAQ
• Dilution of indoor contaminants
• Moisture control
• Odor management

Code Compliance:

• Building code requirements
• Energy code compliance
• Health department regulations
• Green building standards

Design Guidance:

• Ventilation system sizing
• System selection
• Installation requirements
• Operation guidelines

Performance:

• IAQ improvement
• Energy efficiency
• Occupant comfort
• System reliability

Scope of Application

ASHRAE 62.2 applies to:

Building Types:

• Single-family detached homes
• Townhouses
• Multi-family low-rise (≤ 3 stories)
• Manufactured homes
• Modular homes

Exclusions:

• High-rise residential (ASHRAE 62.1)
• Hotels and motels (ASHRAE 62.1)
• Institutional buildings (ASHRAE 62.1)

Whole-House Ventilation

Ventilation Rate Calculation

Basic Formula:

Where:

• $Q_{fan}$ = Required ventilation rate (L/s)
• $A_{floor}$ = Conditioned floor area (m²)
• $N_{br}$ = Number of bedrooms

Alternative (IP Units):

Where:

• $Q_{fan}$ = Required ventilation rate (cfm)
• $A_{floor}$ = Conditioned floor area (ft²)
• $N_{br}$ = Number of bedrooms

Minimum Ventilation Rate:

• Minimum: 7.5 L/s (15 cfm) per bedroom + 1
• Maximum: Not specified (use calculated value)

Ventilation Rate Examples

Typical Homes:

Local Exhaust Ventilation

Kitchen Exhaust

Requirements:

• Range hood or exhaust fan
• Minimum flow rate: 100 L/s (200 cfm)
• Maximum flow rate: 150 L/s (300 cfm) for recirculating
• No maximum for ducted exhaust

Operation:

• Intermittent operation
• Manual or automatic control
• Ducted to outdoors
• Proper installation

Bathroom Exhaust

Requirements:

• Exhaust fan in each bathroom
• Minimum flow rate: 25 L/s (50 cfm) intermittent
• Minimum flow rate: 20 L/s (40 cfm) continuous
• Ducted to outdoors

Operation:

• Intermittent or continuous
• Timer or humidity control
• Proper installation
• Quiet operation

Other Local Exhaust

Requirements:

• Clothes dryers: Ducted to outdoors
• Combustion appliances: Proper venting
• Garage: Separation and exhaust if attached

Ventilation System Types

Exhaust Ventilation

System Description:

• Exhaust fans remove air
• Outdoor air enters through leaks
• Simple and low cost
• May cause pressure imbalances

Design Requirements:

• Central exhaust or multiple fans
• Proper distribution
• Outdoor air inlets
• Control system

Advantages:

• Low cost
• Simple installation
• Effective moisture removal

Disadvantages:

• Pressure imbalances
• No air filtration
• No preconditioning

Supply Ventilation

System Description:

• Supply fans bring in outdoor air
• Indoor air exits through leaks
• Positive pressure
• Can include filtration and conditioning

Design Requirements:

• Central supply fan
• Distribution system
• Filtration
• Optional conditioning

Advantages:

• Positive pressure
• Filtration possible
• Preconditioning possible

Disadvantages:

• Higher cost
• More complex
• May increase heating/cooling load

Balanced Ventilation

System Description:

• Separate supply and exhaust
• Balanced airflow
• Can include heat recovery
• Best performance

Design Requirements:

• Supply and exhaust fans
• Distribution systems
• Heat recovery (optional)
• Control system

Advantages:

• Balanced pressure
• Heat recovery possible
• Best IAQ control
• Energy efficient (with HRV/ERV)

Disadvantages:

• Highest cost
• Most complex
• Requires more space

Heat Recovery Ventilation (HRV)

System Description:

• Balanced ventilation with heat recovery
• Sensible heat exchange
• Energy efficient
• Suitable for all climates

Efficiency:

• Typical: 60-80% sensible efficiency
• Reduces heating/cooling load
• Energy savings

Energy Recovery Ventilation (ERV)

System Description:

• Balanced ventilation with energy recovery
• Sensible and latent heat exchange
• Moisture transfer
• Suitable for humid climates

Efficiency:

• Typical: 50-70% total efficiency
• Moisture recovery
• Reduces dehumidification load

Natural Ventilation

Natural Ventilation Option

Requirements:

• Openable area: ≥ 4% of floor area
• Operable windows in each room
• Cross ventilation possible
• Automatic controls (optional)

Limitations:

• Not reliable in all climates
• No filtration
• No preconditioning
• Dependent on weather

Application:

• Mild climates
• Low pollution areas
• Supplemental ventilation
• Mixed-mode operation

System Design Requirements

Distribution

Air Distribution:

• Uniform distribution
• Supply to living spaces
• Exhaust from wet spaces
• Avoid short-circuiting

Duct Design:

• Proper sizing
• Low pressure drop
• Sealed ducts
• Insulated (if needed)

Controls

Control Requirements:

• Continuous operation capability
• Intermittent operation option
• Manual override
• Status indication

Control Strategies:

• Continuous operation
• Timer-based
• Occupancy-based
• Demand-controlled (CO₂)

Filtration

Filtration Requirements:

• Minimum MERV 6 for supply air
• Higher MERV for better IAQ
• Regular replacement
• Proper installation

Compliance Methods

Prescriptive Method

Requirements:

• Meet minimum ventilation rates
• Provide local exhaust
• Follow installation requirements
• Document compliance

Simplest Method:

• Straightforward
• Code-compliant
• Easy to verify

Performance Method

Alternative Compliance:

• Demonstrate equivalent IAQ
• Contaminant control
• Performance testing
• Documentation

More Flexible:

• Design optimization
• Alternative approaches
• Requires analysis

Practical Application Examples

Example 1: Single-Family Home

Home:

• 3 bedrooms
• 150 m² (1,615 ft²) floor area
• Exhaust ventilation system

Ventilation Rate:

System:

• Central exhaust fan: 35 L/s (74 cfm)
• Kitchen exhaust: 100 L/s (200 cfm)
• Bathroom exhausts: 25 L/s (50 cfm) each
• Outdoor air inlets

Example 2: Townhouse with HRV

Home:

• 4 bedrooms
• 200 m² (2,153 ft²) floor area
• Heat recovery ventilation

Ventilation Rate:

System:

• HRV system: 45 L/s (95 cfm)
• Sensible efficiency: 75%
• Kitchen exhaust: 100 L/s (200 cfm)
• Bathroom exhausts: 25 L/s (50 cfm) each

Best Practices

Design Practices

System Selection:

• Match system to home
• Consider climate
• Evaluate energy use
• Plan for maintenance

Installation:

• Proper duct sizing
• Sealed ducts
• Correct fan sizing
• Proper controls

Operation Practices

Maintenance:

• Regular filter replacement
• Duct cleaning
• Fan maintenance
• System inspection

Monitoring:

• Check operation
• Monitor IAQ
• Verify airflow
• Document performance

Conclusion

ASHRAE Standard 62.2 provides essential requirements for residential ventilation and IAQ. Key aspects include:

Ventilation Requirements:

• Whole-house ventilation
• Local exhaust
• Minimum rates
• System types

Design and Operation:

• System selection
• Installation requirements
• Control strategies
• Maintenance needs

By understanding and applying ASHRAE 62.2, designers and builders can ensure acceptable indoor air quality in residential buildings while maintaining energy efficiency.