8 T E S T I N G A D J U S T I N G A N D B A L A N C I N G B U R E A U T h e P r o f e s s i o n a l ’ s C h o i c e

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UFAD’s proponents certainly talk the talk, creating atidal wave of interest. When it comes to facts—likeactual performance of real-world installations—the

100-year-wave resembles a splash in the kiddie pool.

By A. Lee Chichester

Behindthe

UFAD TSUNAMI

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Underfloor air distribution sys-tems (UFAD) were being includ-ed in plans for numerous U.S.

buildings still in the design stage.According to a tabulation performednear mid-year, UFAD was incorporatedinto buildings representing 20 million

square feet of future construction.With that increasing popu-

larity, UFAD loomed large onthe radar screen of the

Emerging MarketsTask Force of the

National Energy Management Institute(NEMI—see www.nemionline.org).

As with any “hot” market, the TaskForce moves in a closer look. What theyfound was somewhat alarming: A sur-prising lack of documentation forclaims of versatility and advantages ofUFADs over traditional systems.

So they looked harder.

Tsunami du jour What the heck was the cause of thistsunami of interest in UFAD? This tech-nology is neither “new” nor “cuttingedge” by any definition; ThomasJefferson designed and installed such asystem more than 200 years ago at hisshowplace home, Monticello.

A call for help went out to sourcesfamiliar with HVAC systems perform-ance measures, research, education, andtesting. The Task Force looked withinNEMI’s resources, as well as those of theTesting, Adjusting, and BalancingBureau (TABB) and The BuildingDiagnostics Research Institute, Inc.

Tsunamis start with earthquakes;what was behind the UFAD boom?Apparently, commercial real estateprofessionals and building ownerslooking for cost savings.“Expandable infrastructure” is

the key.

Flexible, retrofit-ready workspacesare the bottom line. This siren songcame from (among others), AlanWebber, Mike Vance, and VivianLoftness.

Those speakers talked about“expandable infrastructure” at a 2002meeting of the InternationalDevelopment Research Council (a glob-al association of corporate real estateprofessionals). The speakers bring withthem a fair amount of prestige: Webberonce served as editorial director of theHarvard Business Review; Vance is theformer dean of Walt Disney University;and Loftness chairs the ArchitectureDepartment at Carnegie MellonUniversity.

As savvy building owners seek tominimize the cost of tenant improve-ment work, UFAD is not alone. Ownersare looking at many infrastructure vari-ations, including those that make cubi-cle partitions/walls easier to move.

UFAD strengths—initial claims oflower installation costs plus energy sav-ings—fed the tsunami! Recently, howev-er, rumblings about UFAD’s weakness-es—discovered in research and otherplaces—have become loud enough to befound regularly on the Web (see accom-panying story).

‘I want to know’Combined with the Task Force’s explo-

ration, the rumblings led to action.NEMI and TABB, working withthe New York City and LongIsland chapters of the Sheet Metal

and Air-conditioning ContractorsNational Association

(SMACNA) NYCand SMACNALong Island,

scheduled a New York-area semi-nar for engineers and architects.

Purpose: To bring forwardsome major UFAD concerns—and

highlight ways they might beaddressed in the design stage. Event

invitations noted its purpose was to

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“explore the expected performance ofUFAD systems as alternatives to conven-tional air distribution (CAD) systemsduring design.”

Can you counter a tsunami withfacts? While only 50 invitations weremailed, attendance swelled to 135—including commercial building safetyofficials. Speakers at the spring 2004event included Dr. James E. Woods ofThe Building Diagnostics ResearchInstitute, Inc., and John Hamilton ofTABB.

Most participants came to learnmore— they were relatively few whoobviously brought with them an “axe togrind.” What drew such an overflowcrowd? “There’s a lot of talk in theindustry about this system being at theforefront of design,” said Damian Payne,EIT, a mechanical systems engineer forLoring Consulting Engineers of NewYork City.

“I wanted to know more.”

First, seek solutions! Simon Wu, P.E. with Arthur Metzler &Assoc. Consulting Engineers (New YorkCity) felt about the same way as Payne—when the seminar began. “When I came,most of what I’d heard about UFADs waspretty positive,” Wu noted.

“But now, hearing some of thechallenges of the systems, I’m not sosure. It was a great seminar.”

First, the seminar explored the verylimited documentation of UFAD pro-ponents’ claims. There also isn’t muchresearch or data, attendees learned, fromreal-world UFAD installations—per-formance, testing, and cleaning issues.

“UFADs are simply one more toolin the kit,” said Dr. Woods. “They aren’tthe silver bullet some would have usbelieve. The issues we’ve discussed hereneed to be addressed at the design stage,not over the life cycle of the building.

“Please, please—architects andengineers—work together at the begin-ning to incorporate solutions to theseissues into the design of the systems.”

Questions & answers A flavor of the event’s atmosphere ofvigorous inquiry was seen in the Q-and-A in the seminar room. While there’snot enough space here for all of thequestions and answers, here is a smat-tering—a feel:

‘Bathtub effect’—If a UFAD is installed in a building

with a sprinkler system, and that systemgoes off, the water will collect in theunder-floor plenum or cavity. Do we haveto structurally design more weight loadfor the floors of multi-story buildings?

—Not necessarily, but possibly.Prevention of the “bathtub effect” is thebest strategy. So the design of the sys-tems should include rapid drainage pos-sibilities, water detection sensors, andlevel indicators.

It needs to be dealt with very quick-ly to avoid a pancaking building duringa fire or other emergency.

Raised floor height?—Is the design height of the raised

floor a formula or an experiential meas-urement?

—Height of the floor is dependent

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Backwash On Purported Savings In a February 2004 article posted to the ASHRAE Ottawa Valley Chapter Website, Soheil Rastan, an indoor environments and healthy building technologyspecialist, posed many of the questions raised at the seminar.

Rastan is a consultant to Public Works and Government Services Canada.You can find his thoughts at www.ashrae.ottawa.on.ca—take the link to the “arti-cles” section.

The title: “Some Thoughts on UFADs.”Before we present (with permission) one excerpt of special note, please first

read Rastan’s own caveat:The issues raised in this commentary do not, in any way, reflect PWGSC’s stand

or opinion on UFADs. These are but personal opinions of an individual to be sharedwith ASHRAE’s Ottawa Chapter colleagues and generate some sort of dialogue.

Rastan’s report“Plenum systems may be good leverage idea for return air. However, I have tothink twice before acknowledging plenums as an effective system for supply air.This concern is for both indoor air quality as well as HVAC velocity-pressurecontrol quality.

“Plenums (ceilings or floors), as we all know, are used not only for air butalso for electrical and communication wirings, plumbing, auxiliary fans, evapo-rators, etc. The premise of return air passing by these exposed items and carry-ing whatever these wires and fans emit has been accepted (though reluctantly) byacknowledging the fact that such air will eventually pass through the filtration ofthe HVAC system (though with very limited removal efficiency) before it is deliv-ered as a supply air.

“In such a case, the plenum air is at least being filtered after ‘being-in-con-tact’ with all the plenum-based gears. If we decide to go with a UFAD system, wemay need to add filters on each floor supply diffuser. This entails that we recal-culate pressure drops in the design of UFAD fan capacities.

“The latter may well eliminate some of the fan-based energy savings that arebeing claimed by UFAD advocates.”

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upon the reason you’re raising it—yourflexibility requirement, and if you’reputting electrical wiring, plumbing, andother equipment under there along withthe air handling systems; or not.

Disappearing savings? —After hearing all this, are the cost

savings that are being touted really thereat all?

—This issue is how you design thesystem required by your application. Ithink you’ll find, once you’ve taken intoaccount all the solutions you’ve got todesign into the systems to address theseconcerns, there will be very little costdifference between UFAD and CAD.

Risk & contamination —It sounds as if there’s a very scary

concern regarding contamination issueswith these systems.

—You have to do a risk analysis ofyour space. Are you building in a high-risk area? If so, you might want to re-think the potentially more vulnerableUFAD system.

Goods news—and bad The full day of discussions concludedwith these comments.

From an invitee: “I see a big liabili-ty for engineers in designs of these sys-tems. Who is going to be the authorityhaving jurisdiction over the inherentproblems we’ve discussed here? Is itworth it for cost savings, given that itappears the cost savings won’t be thatgreat?”

Dr. Woods: “Know everything youcan about the tools at your disposal.Basically, document every step of theprocess. Assure that your owner under-stands all issues and warnings in all the

choices you’re making about a construc-tion project. Document discussions andrecommendations.

“Cover yourselves.“UFADs are a good news/bad news

type of thing. Both good and bad newsis that the decision goes back to youengineers and architects. It’s your indi-vidual choice given your knowledge ofthe systems, their application in eachcase, and the capacities of all the tools atyour disposal—not just UFADs, butCADs as well.” n

Chichester, a Virginia-based free-lancer, writes frequently on electricaland HVAC issues.

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Dr. James Woods of the Building Diagnostics ResearchInstitute, Inc. (www.buildingdiagnostics.org) conducted aliterature search on UFAD in the fall of 2002. Here’s what hefound:

1. He was able to find only 65 buildings that clearly usedUFAD systems. Of these:• 33% were in the West or Northwestern U.S. (mean-

ing they had light latent loads);• 47% were in the Midwest and East (meaning large

heat losses & large sensible heat loads in summer),and

• 18% were located in the South (e.g., light sensibleheat losses and large sensible and latent heat loads insummer).

2. The 65 buildings ranged in size from 2,000 sq. ft. to 3million. The UFAD system installation generally didnot extend to each building’s entire floor space.

3. Only 30% were installed during new construction.4. Occupant discomfort was reported for thermal, lack

of air movement, drafts, noise, dust, and dirt. No ill-nesses or symptoms were reported; however, Dr.Woods noted that he has personally investigated suchcomplaints in connection with UFAD.

5. Building occupants and managers reported UFADsystems were not in compliance with relative humid-

ity and air movement criteria. Gas and particulateconcentrations were more frequently in compliance

6. UFAD system problems included insufficient latentheat capacity, lack of controllability of temperature,pressurization, and compartmentalization

7. Energy and first-cost justifications were not validated

What’s the meaning of this?Here are Dr. Woods’ interpretations:

• While they may present attractive alternatives, thereare more limitations on UFAD application than pro-ponents and marketing materials may suggest.

• There are many variations of UFADs. As it is not “onesize fits all,” investigators as well as proponents are pre-cluded from providing simple characterization ofadvantages and disadvantages

• General claims of superior performance of UFADs areprobably meaningless

• One would expect, based on the limited data, thatUFAD non-compliance with evaluation criteria wouldbe similar to that for conventional air distribution.

• Engineers and architects should await more specificdesign guidance on the use of UFADs. This shouldarrive via LEED 2.1 and GSA PBS-P100-2003.

Researching UFAD: What Washed Up

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