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ASHRAE Standard 62.1-2025
ASHRAE 기준 62.1-2025
주요 변경 사항 시각화
Indoor air quality standards shape every building you enter. The 2025 update rewrites several of the rules — here's what that means in practice.
Based on "What's New in ASHRAE Standard 62.1-2025" by Brendon Burley, Ph.D., P.E., Member ASHRAE
Extended Allowable Excursion Period for Dew-Point Compliance
The limit: Dew-point temperature must stay at or below 60°F (16°C).
12-Hour Excursion Window
Any exceedance of the 60°F (16°C) dew-point limit had to be corrected within 12 hours. Compliance was evaluated continuously. Humidity sensors were expected in occupied spaces throughout the building.
60-Hour Excursion Window
The allowable window is now 60 hours (2.5 days) — five times longer. Compliance is evaluated against a 30-day rolling average dew-point temperature. Individual room-level sensors are no longer required.
Also added: HVAC zones served by evaporative cooling systems now carry a dedicated 65% relative humidity (RH) ceiling.
Many commercial buildings shut down HVAC systems over weekends to reduce energy costs. The previous 12-hour rule created a compliance problem even when actual air conditions were within acceptable health parameters. The 30-day average evaluation method reflects real operating patterns without changing the underlying health standard.
Ventilation Rates Now Account for Elevation and Real Occupancy
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School Corridors — New Occupancy Category Added School hallways experience extreme occupancy swings — crowded between classes, empty otherwise. Some also function as locker areas, introducing air quality variables not present in standard corridors. A dedicated occupancy category has been added so ventilation is sized to actual use patterns rather than a generic hallway assumption.
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Laboratories — Minimum Exhaust Rate Reduced by 65% The minimum exhaust airflow for laboratories has been reduced from 1.0 to 0.35 cfm/ft² (5.1 to 1.8 L/s·m²). Supported by research indicating safe operation at 2 air changes per hour for many lab types. For hospitals and universities with significant laboratory space, this reduction in required fan load has direct implications for energy consumption over the building's lifetime.
65% reduction in minimum required laboratory exhaust airflow · Hover bars for detail
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Altitude — Density Correction Now Mandatory Above 515 ft (157 m) Air at higher elevations contains fewer molecules per cubic foot (per litre) than air at sea level. A ventilation system delivering the same air volume at altitude delivers less air mass to occupants than the same system at sea level. The 2025 edition requires a mandatory density correction factor for any building with an outdoor air intake above 515 ft (157 m) above sea level — covering more than 70% of all land on Earth. A normative appendix has been added to guide engineers through the correction calculation.
*Heights shown for scale reference only. The 515 ft (157 m) threshold refers to outdoor air intake elevation above sea level — not building height. Hover bars for details.
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Occupancy Density Defaults — Recalibrated All default occupancy figures have been cross-referenced against model building code occupancy limits and reduced where previously set too high. Fresh air calculations are now based on more accurate baseline assumptions.
Buildings above 515 ft (157 m) — the majority of the world's land area — are now required to apply a density correction that was not previously mandatory. Laboratories in hospitals and universities may reduce exhaust airflow requirements, with corresponding reductions in fan energy consumption over the building's operational life.
Updated Chemical References and End-of-Life Air Cleaner Efficiency Requirements
1,1,1-Trichloroethane
Removed as a design reference compound. References to the relevant regulatory authorities were updated. The allowable limits for phenol and PM₂.₅ were also adjusted.
In-Field Measurement Methods
New testing methods for acetaldehyde and acetone allow for in-field measurements rather than laboratory analysis — reducing testing timelines during construction and commissioning.
Air Cleaner End-of-Life Efficiency — Now Required
Under the previous standard, filtration equipment was evaluated only at initial peak performance. The 2025 edition requires calculations to also account for air cleaner efficiency at end of useful life — specifically for formaldehyde and one nonpolar compound. The system must demonstrate it meets the design indoor air quality target throughout its full maintenance cycle.
Buildings that rely on filtration to meet ventilation requirements may have been compliant at installation while falling short as filters aged. The end-of-life requirement ensures the design air quality standard is maintained across the full service period of the equipment — not only when filters are new.
Ventilation Control Emergency Mode Requirements
CO₂ Demand Control — Differential Method
Demand-control ventilation systems use CO₂ concentration as an occupancy proxy — as occupancy rises, CO₂ increases, and the system responds by increasing fresh airflow. The updated methodology, based on ASHRAE Research Project RP-1547, measures the difference (Δ) between indoor zone CO₂ concentration and outdoor ambient CO₂ concentration, rather than monitoring the absolute indoor level alone. Outdoor CO₂ concentrations are not constant — in dense urban areas, near traffic, or near industrial zones, outdoor CO₂ may already be elevated. An absolute indoor reading in those conditions cannot accurately isolate occupant-generated CO₂ from background levels. The differential method accounts for that variable baseline. Table 6-1 now includes an allowable CO₂ concentration rise limit for each occupancy category.
Values shown (400 ppm outdoor / 900 ppm indoor) are illustrative examples only — not values specified by the standard.
Emergency Ventilation Modes — Now Required in All New Buildings
Economizer Lockout
An automatic setting to disable the airside economizer when outdoor air quality is hazardous — wildfire smoke, chemical releases. The building stops pulling in compromised outdoor air for cooling.
Maximum Ventilation Override
A separate control that opens outdoor air dampers to the designer-specified maximum. Intended for infectious disease scenarios where maximum fresh air dilution is the design priority.
72-Hour Auto-Reset
All emergency modes disengage automatically within 72 hours (3 days). Reactivation is unlimited — but each reactivation requires a deliberate decision. No building remains in emergency mode indefinitely.
Before this update, emergency ventilation protocols were not standardized across buildings. The COVID-19 pandemic and increasing wildfire smoke events demonstrated the consequences of that gap. Every new mechanically ventilated building must now be equipped with documented, testable emergency response capabilities — with a built-in safeguard against indefinite emergency operation.
Maintenance Requirements Consolidated Across Two Standards
Two Overlapping Standards
ASHRAE Standard 62.1 and Standard 180 both contained maintenance requirements that did not always align. Facility managers were required to navigate both documents and reconcile any conflicts independently.
One Unified Reference
Section 8 now incorporates all of Standard 180's requirements plus 18 additional ventilation-specific items. New Table 8-1 maps every task to the exact compliance section it supports.
Maintenance compliance depends on clarity. When requirements are distributed across two partially conflicting documents, tasks get misunderstood or missed. Table 8-1 provides a single cross-referenced lookup — each task is directly linked to the compliance section it supports, removing ambiguity from routine maintenance decisions.
Who's Affected & How Much?
| Change | Who's Affected | Impact | Key Outcome |
|---|---|---|---|
| Humidity 60-hr window | Mechanically cooled commercial buildings | High | Operational flexibility without sacrificing compliance |
| Altitude correction | Any site above 515 ft (157 m) | High | More fresh air required — covers 70%+ of land |
| Emergency ventilation modes | New buildings with mechanical ventilation | High | Emergency response built into every new building |
| Air cleaner end-of-life rating | Buildings using filtration for compliance | Medium | Filter performance must hold through full lifecycle |
| CO₂ differential method | Buildings with demand-control ventilation | Medium | More accurate, occupancy-specific fresh air control |
| Lab exhaust reduction | Hospitals, universities, research facilities | Medium | Significant energy savings over building lifetime |
| School corridor category | K-12 and higher education facilities | Lower | Ventilation sized to actual use patterns |
| Maintenance Table 8-1 | Facility managers & building operators | Lower | Single cross-referenced compliance checklist |