What is the Difference Between DOAS and Tempered Makeup Air Units for Restaurants?

As a restaurant owner or manager, maintaining a healthy and comfortable environment for your staff and guests is essential. Proper air quality and ventilation are key components of achieving this. Two common solutions for commercial kitchens:

But how do they compare? And which is best for your restaurant? This guide breaks down the differences and benefits of both systems.

What is a Dedicated Outdoor Air System (DOAS)?

A DOAS is a sophisticated HVAC system that uses only fresh outdoor air. It conditions the air to the perfect temperature and humidity levels before it enters your restaurant.

Key Benefits of DOAS for Restaurants:

  • Precise Climate Control: Keeps kitchen temperature and humidity stable year-round.
    • In summer: Cools and reduces humidity.
    • In winter: Warms incoming air.
  • Humidity Control: Removes excess moisture, preventing mold and mildew. Keeps staff comfortable during high-heat cooking.
  • Energy Efficiency: Uses variable-speed fans and advanced controls to adjust energy use based on needs. Lowers operating costs over time.
  • Better Air Quality: Works with your kitchen ventilation system to remove smoke, grease, and odors, while circulating fresh air.
  • Adaptable to Weather: Adjusts to extreme weather conditions, ensuring a comfortable environment all year.

What is a Tempered Makeup Air Unit?

A Tempered Makeup Air Unit brings in outdoor air to replace the air exhausted by your kitchen. It conditions the air to match your indoor temperature but doesn’t control humidity like a DOAS.

Key Differences Between DOAS and Tempered Makeup Air:

  • Climate Control:
    • DOAS: Controls both temperature and humidity for consistent comfort.
    • Tempered Makeup Air: Only adjusts temperature; no humidity control.
  • Energy Efficiency:
    • DOAS: : Reheating Ability – Unlike direct fired heaters, 100% of the air may be recirculated through an indirect fired heater as no combustion by-products are introduced into the airstream by the heating process.
    • Tempered Makeup Air: As nearly 100% of the fuel is being converted to heat, fuel consumption and operating costs are reduced. These heaters are 100% combustion efficient with an overall thermal efficiency of 92% (8% heat loss due to water formation during combustion).
  • Functionality:
    • DOAS: This dedicated supply of filtered outdoor air effectively dilutes and removes indoor pollutants, including volatile organic compounds (VOCs), odors, and airborne contaminants.
    • Tempered Makeup Air: MERV (Minimum Efficiency Reporting Value) air filters improve indoor air quality by trapping particles in the air, offering benefits like reduced allergens, improved respiratory health, and a cleaner home environment.
  • Best Use:
    • DOAS: Buildings with high occupancy and needing to prevent moisture-related issues: Schools, offices, hotels, conference rooms, churches, retail stores, multifamily housing, and nursing homes
    • Tempered Makeup Air: Environments, like commercial kitchens, where you need to balance heating and cooling, especially in situations with high exhaust rates and large airflows

Which System is Right for Your Restaurant?

If you need precise climate control, humidity management, and energy efficiency, a DOAS is your best choice. It offers the most comfort and air quality benefits for busy commercial kitchens.

If your restaurant needs basic ventilation and doesn’t require humidity control, a Tempered Makeup Air Unit may suffice.

For more information or a quote on the best air quality solution for your kitchen, contact us today. Our experts can help you choose the right system based on your needs.