- To make offices safe during COVID-19, buildings need a breath of fresh air
Gensler technical director Ambrose Aliaga Kelly said, “Underfloor ventilation creates safer and better air quality with the added benefit of being more sustainable.”
- Engineering healthy workplaces – considerations in response to Covid-19
Buro Happold said, “To better incorporate strategic pressurization in workplaces to induce airflow that will lead to improved air quality, underfloor air displacement (UFAD) systems should be considered. These systems introduce clean supply air at the floor and accept return air at the ceiling, resulting in a once through pathway of airflow across the breathing zone of occupants before the air is returned to the central filtration system or exhausted directly out of the building.”
- Can Better Indoor Air Fight Covid-19?
David Cooper, mechanical engineer and president of global property and buildings at WSP, said, “The issue is that increased air motion may cause the virus to carry further than it normally would in still air,” He also discussed how that traditional displacement or underfloor air distribution (UFAD) systems can minimize air currents and the horizontal movement of air.
Underfloor Air Distribution (UFAD) systems distribute cool, clean air through the plenum below the raised floor instead of through overhead ductwork. Through convection, air is naturally lifted from the supply at the floor level to the occupied zone and then finally to a return at the ceiling, which results in a single direction airflow. Traditional overhead systems supply cool, clean air at the ceiling level, and intentionally mix the clean air with the existing air in the space that contains contaminants, CO2
and possibly even infectious aerosols. This negatively impacts the quality of the air throughout the space. In a UFAD system, airflow mixing is minimized because air is supplied at low velocity from the floor and uses natural convection to move the air in one direction from the floor to the ceiling. By moving the air upward toward a ceiling return, you pull contaminated air away from occupants instead of mixing it with clean air, improving the ventilation effectiveness and creating better indoor air quality.
Another benefit of Underfloor Air Distribution is the ability to supply clean air directly to the occupied zone through in-floor diffusers. Diffusers can be strategically placed throughout the floor to best serve occupants directly at their individual desk areas. Each diffuser can be equipped with personal comfort controls so that occupants can manually adjust the direction of airflow in their space and volume adjustment is available either with manual or automatic control via thermostats and connection to the BAS. Typical design allows for one diffuser per occupant, creating a sort of individually controlled micro-environment for every occupant.
Many studies have been conducted to evaluate and prove the benefits of Underfloor Air Distribution. One such study by ASHRAE, the American Society of Heating, Refrigerating and Air-Conditioning Engineers, compared underfloor and overhead air distribution systems in an office building. The study shows that underfloor systems have 3.5–4.5 times less particles per cubic meter than overhead systems, concluding “The underfloor system was lower in both concentration of mass and total number of airborne particles than the overhead system,” and “Measurements of the local ventilation effectiveness and local air change index showed that the ventilation performance of the underfloor system was better than that of the overhead system
.” Another ASHRAE study tested the effectiveness of stratified air distribution systems and stated that, “Under-Floor Air Distribution (UFAD) systems are becoming more popular because they can create better indoor air quality (Chen and Glicksman 2003, Bauman and Daly 2003).”
As more companies prepare for the return to the office, there are many decisions to make to ensure the office environment is safe. One of the most important steps you can take is to assess your indoor air quality. Apart from its indoor air quality benefits, Underfloor Air Distribution has also been shown to improve thermal comfort and enhance productivity, decrease absenteeism and improve a building’s value. If you’re considering UFAD to help provide your customers and employees with a safe environment, we’re here to help! Contact us today to discuss the potential benefits and options for your building.
 Comparison of Underfloor Vs. Overhead Air Distribution Systems in an Office Building
H. Fukao, Dr.Eng.; M. Oguro; M. Ichihara; S. Tanabe, Ph.D.
 Air Distribution Effectiveness with Stratified Air Distribution Systems
Kisup Lee; Zheng Jiang, PhD; Qingyan Chen, PhD