How DOAS Systems Improve Indoor Air Quality and HVAC Efficiency

Builders face growing pressure to protect occupant health while controlling energy costs. These demands are reshaping HVAC design. One system that addresses both challenges is the Dedicated Outdoor Air System, or DOAS.

A DOAS is a specialized HVAC system that delivers outdoor air to occupied spaces. The DOAS filters, dehumidifies and conditions the air before it enters the building. But how does a DOAS system work, and why is it becoming essential in modern building design?

The Case for Dedicated Ventilation

Traditional HVAC systems rely on mixed‑air strategies to manage temperature and humidity. These systems recirculate indoor air and add outdoor air only when required. While this approach can be energy efficient, it often reduces indoor air quality.

In tightly sealed, high‑occupancy buildings, contaminants can build up quickly. These include volatile organic compounds (VOCs), excess humidity, and airborne pathogens.

A DOAS solves this issue by supplying continuous, controlled outdoor ventilation. The outdoor air delivered by a DOAS is:

• Filtered to remove particulates and pollutants
• Dehumidified to control moisture and prevent mold growth
• Tempered to meet space‑specific temperature requirements.

As a result, DOAS systems provide:

• Stable ventilation rates regardless of occupancy changes
• Lower concentrations of indoor air pollutants
• Improved comfort and healthier indoor environments.

Engineering Around the Efficiency Barrier

While DOAS systems significantly improve indoor air quality, they also introduce engineering challenges. Designing a system and integrating it demands thoughtful engineering. These systems must balance energy use, space limitations, and system integration.

Thermal Load Management in DOAS Systems

Conditioning outdoor air can be energy‑intensive. This is especially true in hot, cold, or humid climates. In these locations, outdoor conditions vary. To manage this added thermal load, modern DOAS units often include:

• Heat recovery technologies, such as enthalpy wheels or plate heat exchangers
• Variable‑speed EC fans to adjust airflow and reduce power consumption
• Smart control systems that respond to occupancy levels and weather conditions
• These solutions help maintain efficiency while meeting ventilation requirements.

Mechanical Footprint Optimization

DOAS equipment must often fit into existing buildings or compact rooftop spaces. Limited space is a common design constraint. To overcome this, engineers use:

• Low‑profile fan arrays that maintain airflow while minimizing unit height
• Modular cabinet designs for flexible installation
• Noise‑attenuated components for sound‑sensitive environments

This calls for:

• Advanced control logic to manage staging and sequencing
• Communication protocols (BACnet, Modbus) for seamless BMS integration
• Redundancy strategies to ensure uptime in mission-critical applications

Key Design Considerations for DOAS Systems

DOAS units are excellent for air quality, but they face several engineering challenges:

• Energy Consumption: Conditioning outdoor air requires careful significant energy. Planning for energy efficiency is a must.
• Space Constraints: DOAS units must fit into existing rooftop layouts. They also need to work within tight mechanical spaces.
• System Integration: They must work together with parallel HVAC systems.

This is where advanced airflow technology, like COPRA electronically commutated fans, can make a significant difference.

These qualities make COPRA a strong choice for high‑performance DOAS systems. They are especially effective in space‑constrained installations.

COPRA fans support DOAS systems across many applications. These include schools, hospitals, data centers, and commercial buildings. COPRA can deliver cleaner air, lower energy costs, and quiet operation.

Connect With the Experts at Nicotra Gebhardt to Optimize Your DOAS System

Looking to optimize your DOAS project? Talk with our airflow specialists to learn how COPRA EC fans can strengthen your ventilation design and indoor air quality performance.