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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 more easily removed. Displacement ventilation supplies air at very low velocity levels at or near floor level. Air then rises and returns at the ceiling level.

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

Part 1: Displacement Ventilation Design and Application

One of the following is met for projects implementing a displacement ventilation system for heating and/or cooling:

a) Low side wall air distribution with the air supply temperature slightly cooler or warmer than the desired space temperature. The system must use the System Performance Evaluation and ASHRAE Guidelines RP-949 as the basis for design.
b) Underfloor Air Distribution (UFAD) with the air supply temperature slightly cooler or warmer than the desired space temperature. This system must use ASHRAE's UFAD Guide (Design, Construction and Operations of Underfloor Air Distribution Systems) as the basis of design. Displacement ventilation applied as part of an underfloor air distribution system must be installed at a raised floor height whereby the under floor area can be cleaned on an annual basis.
Part 2: System Performance

The following requirements are met:

a) A Computational Fluid Dynamics (CFD) analysis is conducted for the displacement ventilation system.
b) 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 New Construction WELL Interiors
Part 1: Displacement Ventilation Design and Application - O O
Part 2: System Performance - O O
Commercial Kitchen Education Multifamily Residential Retail
Part 1: Displacement Ventilation Design and Application - - O O
Part 2: System Performance - - O O

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

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