Under floor Air – “Plenum Construction”ASHRAE Summer Meeting - June 2009

James E. Megerson, PE, LEED® APVice President, Larson Binkley, Inc.

UFAD Supply Plenum Design & Construction

Basic supply plenum design Construction documents Controlling Leakage Construction administration documentation Real world examples along the way

Objectives

Plenum Construction

Primary Construction Materials Raised Access Flooring (RAF) Concrete Sheetrock Brick, Block

Plenum Materials

MEP Construction Documents

MEP Construction Documents

MEP Construction Documents

Architectural Drawings

Architectural Drawings

Architectural Drawings

Architectural Drawings

Leakage Types

Categories of Leakage

Type I – Leakage to interstitial (un-occupied)

Type II – Leakage to the space (occupied)

Avoid any cracks

Be Proactive

Category I

Category II

Category I

Category I

Category I

Category II

Category II

Category II

Avoiding Leakage

What can we do to make it easier?

Improve RAF specification

Execution section

Specify that RAF installer performs a pre-RAF installation inspection / meeting with General, Architect, Engineer and HVAC Contractor and obtain sign off before any RAF is installed.

Age of air gets hotter 2- 3º F / 50’

50’ to farthest diffuser on perimeter

Air Injection Points

50’

50’

Air Highways

100 ft

Air highway Example

Ductwork Example

Fabric diffusers

Shaft Extension

Shaft Extension

Large vents: dispersion in a direction more parallel with the supply sox

Smaller vents:  Increased static pressure directs airflow more perpendicular to sox

Dispersion Patterns

Installation photos

Shaft Branch Feeders

What’s wrong with this?

Shaft Branch Feeders

Maximum Depth = RAF height – 4 inches

18” floor: 14” high duct

14” floor: 10” high duct

Use Combination FSD / EOD

Mount Heat Detector on side of FSD

Mount Disconnect Switch on side

Create a shaft extension

Remove sheetrock 2” above ceiling due to restricted return air path

Seal around conduit and seal end of conduit after wire is pulled

Site Observation Reports

Questions ?