What Is ASHRAE?
ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) is an international professional organization that develops standards for HVAC systems, indoor air quality, and building performance. Founded in 1894, ASHRAE standards are widely adopted in building codes and industry practice.
For mold prevention, ASHRAE standards are critical because they define minimum ventilation rates and humidity control requirements that directly impact whether buildings develop mold problems.
Key ASHRAE Standards for Mold Prevention
Standard 62.1: Commercial Ventilation
Ventilation for Acceptable Indoor Air Quality — Sets minimum ventilation rates and humidity control requirements for commercial and institutional buildings. Referenced in most commercial building codes.
Standard 62.2: Residential Ventilation
Ventilation and Acceptable Indoor Air Quality in Residential Buildings — Specifies exhaust fan capacities, whole-building ventilation rates, and moisture control for homes. Essential reference for residential builders.
Standard 55: Thermal Comfort
Thermal Environmental Conditions for Human Occupancy — Sets humidity ranges for occupant comfort (typically 30-60% RH), which aligns with mold prevention thresholds.
Standard 160: Moisture Analysis
Criteria for Moisture-Control Design Analysis in Buildings — Provides criteria for analyzing moisture in building assemblies. Used by engineers to design walls, roofs, and foundations that resist mold.
Humidity Requirements
ASHRAE standards address humidity control as part of indoor air quality:
| Parameter | ASHRAE Requirement | Mold Impact |
|---|---|---|
| Upper RH limit | 65% RH or 0.012 lb/lb | Above mold threshold |
| Comfort range (Std 55) | 30-60% RH | Ideal for mold prevention |
| EPA/IOM recommendation | Below 60% RH | Aligned with ASHRAE |
Key Alignment: ASHRAE humidity recommendations align with EPA and building science consensus: keep indoor RH below 60% to prevent mold growth.
Ventilation Rates (Standard 62.2)
| Location | Intermittent | Continuous |
|---|---|---|
| Bathroom | 50 CFM | 20 CFM |
| Kitchen | 100 CFM over range | 5 ACH |
| Whole-building | — | 0.15 CFM/sqft + 7.5 CFM/person |
What This Means for Homeowners
- Proper ventilation is essential for mold prevention — not optional
- Bath fans should be used during and 15-20 minutes after showering
- Kitchen exhaust should be used during all cooking (especially boiling/steaming)
- Whole-house ventilation may be needed in tight modern homes
- HVAC systems should control humidity, not just temperature
- Undersized or oversized equipment causes humidity problems
Oklahoma Context
High Cooling Loads
Oklahoma’s hot summers mean extensive A/C runtime. Systems must be properly sized — oversized units short-cycle and fail to dehumidify. This is a common cause of high indoor humidity even with working A/C.
Code Adoption
Oklahoma’s building codes reference ASHRAE standards for commercial construction. Residential codes vary by jurisdiction but typically require bathroom exhaust. Newer energy codes increase ventilation requirements.
Older Home Challenges
Many Oklahoma homes predate modern ventilation standards. Bath fans may be undersized, improperly ducted, or absent. Upgrades to meet ASHRAE 62.2 can significantly reduce mold risk in older homes.
Resources & Citations
- ASHRAE.org — Access standards and publications
- ASHRAE Standard 62.2-2022: Ventilation and Acceptable Indoor Air Quality in Residential Buildings
- ASHRAE Standard 55-2020: Thermal Environmental Conditions for Human Occupancy
- ASHRAE Standard 160-2021: Criteria for Moisture-Control Design Analysis in Buildings