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Underfloor low-velocity air displacement (UFAD) is a form of heating and cooling which circulates hot or cold air beneath flooring at a very low speed to regulate indoor temperatures. Climate-controlled air is pumped or allowed to flow through vents in the floor. The cooled air rises as it warms up, keeping the occupied space cool. The mechanisms for heating and cooling operate much like traditional air conditioning, but save energy by retaining air beneath the insulated floor and controlling release through vents rather than letting it disperse. Slow-moving air requires less energy to circulate at low speeds.
Traditional HVAC systems pump cold air down from vents in the ceiling. These systems require significantly more space for air ducts and are much less efficient since the cold air is vented from the ceiling and will warm as it moves through the room.
In the UFAD system, the cold air rises as it warms up and is allowed to vent back into the ceiling, using natural heat cycles to circulate air through the space. Only the occupied space (the first six feet) needs to be cooled, and as the cold air is pumped directly into the living space without mixing with the hot air, the cooling air can be up to 10o warmer than a traditional HVAC. UFAD systems replace ceiling ducts with elevated floors, which makes them a difficult retrofit project.
UFAD systems may also contribute to better air quality, since pollutants are circulated upwards with rising air and trapped close to the ceilings rather than mixing in with the air flow.
Potential regulatory touchpoints in Boston and Massachusetts include: