Analysis of Underfloor VAV System

With growing attention on greener buildings and smarter energy use, the air-conditioning field is placing a strong focus on developing more innovative system solutions.

In this article, we take a closer look at a highly efficient Underfloor VAV System and explore how its unique design delivers both significant energy savings and improved indoor comfort.

The Underfloor VAV system uses a “supply from below and return from above” airflow strategy. Fresh air is delivered through the underfloor plenum directly into the occupied zone, and as the warm air naturally rises, it returns through the ceiling to complete an efficient circulation cycle. Compared with traditional ceiling-based air distribution, this approach shortens the air-delivery path and significantly improves heat-exchange efficiency.

Key Advantages

Easy and Flexible Installation: The system skips complex duct networks; primary air directly supply to the under-floor’s plenum box—cutting installation costs. When room functions change, the end devices can be quickly reconfigured, making the system highly adaptable.

Boosted Energy Efficiency and Comfort: In cooling mode, supply air can be raised to 16–18°C, and in heating mode lowered to 22–24°C, reducing energy use. The airflow directly reaches the occupied zone, solving the “temperature stratification” problem common in traditional ceiling-based systems.

Smart Control Strategy

Single-Zone AHU Supply: Maintains stable underfloor plenum static pressure with a variable frequency drive (VFD) for fan, ensuring consistent and comfortable airflow throughout the space.

Multi-Zone AHU Supply: The main duct uses constant static pressure control combined with zone dampers to achieve independent pressure control for each area.

Terminal Unit Selection Guide

Select pressure-dependent terminal units flexibly based on space requirements, for example:

Open-plan office areas: Underfloor fan powered VAV terminal or swirl diffusers are recommended to achieve uniform air distribution.

Individual rooms: Underfloor fan powered VAV terminal or single-duct VAV terminals are suitable.

Perimeter zones with heating demand: Fan-powered terminal units with electric heating or fan coil units can be configured to provide heating.

RSV-UFFP Underfloor Fan Powered VAV Terminal

RSV-UFD Underfloor Swirl Diffuser

RSV-UFDC Underfloor Single Duct VAV Terminal

RSV-UFFC Underfloor Fan Coil Unit

In short, the Underfloor VAV System provides an efficient and flexible way to deliver comfortable indoor air. By sending air directly to occupied areas and using smart controls, it saves energy while improving comfort—making it an ideal solution for modern, sustainable buildings.

Royal Service Air Conditioning specializes in HVAC systems. With 50 years of experience as a trusted air conditioning manufacturer, we are committed to providing high-quality products and reliable service to customers across the United States and worldwide. Over the years, Royal Service has grown into a leader in the HVAC industry, serving manufacturing facilities, office buildings, hospitals, and business centers.