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  1. Air
  2. Displacement ventilation

Displacement ventilation

Features>Air>21. Displacement ventilation

21. Displacement ventilation

By providing ventilation at the normal breathing zone, displacement ventilation enhances air change effectiveness. Since heat in a room is naturally stratified, displacement ventilation ensures that air is not delivered and pushed through the return air path (often the dirtiest portion of the air stream) and also tends to concentrate some pollutants near the ceiling. Once there, the pollutants are out of the breathing zone and can be more easily removed. Displacement ventilation supplies air at very low velocity levels at or near floor level. Air then rises and returns to the ceiling level.

This feature supports a thermally comfortable indoor environment through a carefully designed and efficient displacement ventilation system.

Part 1: Dedicated Outdoor Air Systems

The following requirements are met:

a. Dedicated outdoor air systems are used for heating and/or cooling systems.
b. The project achieves ASHRAE 55-2013 standards for thermal comfort for at least 75% of all regularly occupied space.
c. A detailed design review of the proposed system is conducted by an independent, qualified and registered professional mechanical engineer (not employed or compensated by the mechanical engineer on record). The review addresses thermal comfort (temperature, humidity, air velocity, etc.) and ventilation rates, as well as overall serviceability and system reliability. Report must demonstrate satisfactory compliance with all applicable ASHRAE standards and codes.
Part 2: System Performance

The following requirements are met:

a. A Computational Fluid Dynamics (CFD) analysis is conducted for the displacement ventilation system.
b.92 The displacement ventilation system meets ASHRAE 55-2013 (Thermal Environmental Conditions for Human Occupancy) for comfort for at least 75% of all regularly occupied space.
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Applicability Matrix

Core & Shell Tenant Improvement New Construction
Part 1: Dedicated Outdoor Air Systems - O O
Part 2: System Performance - O O
Commercial Kitchen Schools Multifamily Residential Restaurant Retail
Part 1: Dedicated Outdoor Air Systems O O O O O
Part 2: System Performance O O O O O

Verification Methods Matrix

Letters of Assurance Annotated Documents On-Site Checks
PART 1 (Design)
Dedicated Outdoor Air Systems 		MEP
PART 2 (Design)
System Performance 		MEP

37

American Society of Heating, Refrigerating and Air-Conditioning Engineers. UFAD Guide: Design, Construction and Operation of Underfloor Air Distribution Systems. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers; 2013.
21.1.b

ASHRAE's Underfloor Air Distribution Guide provides recommendations for underfloor air distribution systems.
41

ASHRAE. Performance Evaluation and Development of Design Guidelines for Displacement Ventilation, RP-949. Atlanta, GA: American Society of Heating, Refrigerating, and Air-Conditioning Engineers; 1999.
21.1.a

The Performance Evaluation and Development of Design Guidelines for Displacement Ventilation document recommends air supply temperatures.
92

ASHRAE. Standard 55: Thermal Environmental Conditions for Human Occupancy, Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers; 2013: 4; 8-13.
21.2.b

ASHRAE Standard 55 provides guidelines for displacement ventilation systems for thermal environmental comfort.
Features>Air>21. Displacement ventilation