Very High Efficiency Dedicated Outside Air Systems

Dedicated outside air systems (DOAS) separate heating and cooling from the ventilation system to allow for optimal control of each of these critical building functions. Building on the DOAS concept, a very high efficiency DOAS includes heat recovery ventilation and focuses on increased equipment efficiency and optimized system design. This approach has been proven to yield significant energy and cost savings in new and existing commercial buildings while providing better indoor air quality and improved occupant comfort.

System Benefits

  • Can substantially lower energy use in commercial buildings*  
  • Improves indoor air quality by using filtered 100% outside air
  • Increases occupant comfort
  • Reduces maintenance costs and requirements
  • Saves roof space through system downsizing and reduced ductwork
  • Meets 2017 Washington code requirements for new construction or retrofit HVAC installations, which require DOAS

*Based on a pilot of seven small commercial buildings throughout the Pacific Northwest, pilot participants saw an average 60% HVAC savings and 35% whole building energy savings.

How It Works

The illustration to the left demonstrates how the components of this system, installed on the roof of a commercial building, work together to maintain fresh air and consistent temperatures. The HRV pre-heats incoming supply air by recovering heat from the outgoing exhaust air in the winter. In the summer, the HRV pre-cools incoming supply air by rejecting heat to the outgoing exhaust air. This process, eliminates or significantly reduces the need for post-conditioning of the ventilation air. This system approach allows for down-sizing of the heating and cooling system and decreased run-time, resulting in a smaller heating/cooling system and which consumes less energy (lower energy cost). 

Note: This drawing is for quick-reference only and does not represent the sizing or depth of the system or frame for all manufacturers' products. Please check with manufacturer for exact measurements and specifications.


Ideal Building Applications

A very high efficiency DOAS approach is a great option for many existing and new small-to-medium sized buildings or spaces (generally up to 50,000 sq. ft.) that are commonly serviced by packaged rooftop units (RTUs), particularly the office, school and retail sector.