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 ?
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