2AGENDA Chilled Ceilings & Beams ? Part 1 – Passive Systems So what areChilled Ceilings & Beams ?Part 1 – Passive SystemsChilled CeilingsChilled SailsPassive BeamsPart 2 – Active systemsActive Chilled BeamsPart 3 - Reducing EnergySpace Humidity concernsDesign ConsiderationsWater System DesignSavings & LEEDPart 4 - SolutionsAll Air Core6 WayLoFloOverall 1st Costs
3So What are Chilled Ceilings & Beams? A sensible cooling only device that uses chilled water above the room dew point to remove heat from the space.They can be independent of, or combined with, a method of introducing conditioned outside air to the space to meet the ASHRAE 62 ventilation requirements
4Radiant & Convective sensible cooling independent of ChilledCeilingsRadiant & Convective sensible cooling independent ofPrimary air delivery
8Chilled Ceilings Advantages Design Issues Excellent thermal comfort Can HeatReduced space requirementsWill fit into 6-8” cavitySelf regulatingSimple controlsLow noiseLow maintenanceLow cooling output20 to 25 BTUH/FT2 100% coverage14 to 18 BTUH/FT2 70% coverageDriven by surface areaVery High costSeparate air system requiredNeeds many connections
13Chilled Sails Advantages Design Issues Good thermal comfort Reduced space requirementsFreely suspendedSelf regulatingSimple controlsLow noiseLow maintenanceCooling output40 to 50 BTUH/FT2dependent of amount of ceiling usedSeparate air system requiredHigh costCan not heatNeed good acoustic treatment to avoid hard spacesMany connectionsAesthetics ?
15Ceilings & Sails Summary - Cooling & Heating (Ceiling only)Very High thermal comfort especially on ceilingsCooling capacity up to 18 Btuh/FT2 floor space (Ceiling - average)Cooling capacity up to 40 Btuh/FT2 floor space (Sail - average)Very low ceiling cavities needed, could in installed in a 6” space.Self regulatingsimple two position controlsLow noiseLow maintenance
16Buoyancy driven sensible cooling independent of PassiveBeamsBuoyancy driven sensible cooling independent ofPrimary air delivery
22Passive beams Advantages Design Issues Good thermal comfort Low terminal velocitiesSelf regulatingSimple controlsLow noiseLow maintenanceIdeal ‘top up’ to UFAD especially at the façadeCooling output40 to 50 BTUH/FT2Separate air system requiredNeed High free area ceilingsCan not heatNeed deep ceiling cavity and space above coilNeed separate return air passage for remove primary air volume
24Passive Beams Summary - Cooling onlyGood thermal comfortCooling capacity up to 50 Btuh/FT2 floor spaceUp to 450 BTUH per LF of beamReduced ductwork, riser and plant sizesWater transports most of sensible coolingSelf regulatingsimple two position controlsLow noiseLow maintenance
25Passive beams – Perforation beware! Perforation Free AreasAre critical to passive beam performance !Painted ?Usually, perforated free areas are quoted prior to paint application !On a recent projectThe tiles were specified 28% free area 1/10” hole. These turned out to be when painted a 1/12” hole which equated to19% free area.This reduced the reduced performance by a further 20%Rule of ThumbMinimum 1/8” hole, approx 45% free area preferred, any reduction in hole size or free area reduces output therefore it costs you more because you need more beams
26Passive beams – Return air passage Passive beams need a return air passage to feed the coil, typically the same area as the coil, split along the 2 long sides of the beam.As important, the removal of the fresh or conditioned air must have aSeparate return route if the return is via the celling cavity/void. Better to have a ducted return!
27AGENDA Active Chilled Beams Part 2 – Active systems Part 3 - Reducing EnergySpace Humidity concernsDesign ConsiderationsWater System DesignSavings & LEEDPart 4 - SolutionsAll Air Core6 WayLoFloOverall 1st Costs
28So What are Chilled Ceilings & Beams? A sensible cooling only device that uses chilled water above the room dew point to remove heat from the space.They can be independent of, or combined with, a method of introducing conditioned outside air to the space to meet the ASHRAE 62 ventilation requirements
38Active Chilled Beams 1 Way perimeter (Concealed)
39Thermal Comfort Perimeter CFD Good air movement throughout the room with ≈ 3-4:1 entrainment ratiosUniform temperatures and no drafts by thorough mixing of the primary and room air
40Active Chilled Beams 1 Way perimeter (Concealed)
41Active beams Advantages Design Issues All services in celling, integrated cooling, ventilation and heatingLower pressure than traditional induction systemsSelf regulatingSimple controlsLow maintenanceFiber tile ceilingsLower ceiling cavity, lower slab to slabCooling outputto 100 Btuh/FT2 , beam outputs up to 1800 Btuh/LFCan be 2 or 4 pipeCan heatNeed more primary air than minimal fresh are, suggest .3 cfm/SFPrimary air controls dew point
42Rule # 1The Design with the fewest number of chilled beams will be the lowest 1st cost install, therefore performance matters.
45Heat Removal Active Chilled Beam concept Airflow requirementreduced by 70%70% of sensible heat removed by chilled beam water coil30% of sensible heat removed by air
46Chilled WaterOn a Mass Flow Rate Basis:-1 lbs of chilled water (6°Δt) transports 4x more cooling energy than 1 lbs of air (20°Δt)As water weighs 800 times that of airOn a Volume Flow Rate Basis:-1 FT³ of chilled water transports 1000 more cooling energy than 1 FT³ of air (20 Δt)Transportation EnergyTransportation of a ton of cooling by air requires 7 to 10 times more energy than by chilled water.
49Fan Energy Use in Buildings “Energy Consumption Characteristics of Commercial Building HVAC Systems” - publication prepared for U.S. Department of Energy
50Heat Removal Ratio Airflow requirement reduced by 70% 70% of sensible heat removed by chilled beam water coil
51Rule # 2If your not reducing the air volume in a space by 25%, you could be installing a very expensive diffuser
52Rule # 3Even if your using chilled beams on your design, you don’t have to use them everywhere.
53Water = Efficient Transport 10”1 Ton of Coolingrequires 550 CFM of airor4 GPM of water10”¾” diameterwater pipe
54‘Water’ is a better cooling medium, than air ! ‘Water’ takes lessenergy to transportthan air !
55So a room ‘BTU/h is still a BTU/h’, however Room Load is still Room loadChilled Ceilings & Beams do not lower the heat load of a space, solar gain is still a gain, lights and equipment still give off heat and so do people.So a room ‘BTU/h is still a BTU/h’, however.
56Only enough‘chilled Water’ isChilled to 45°Fto dehumidify the reducedprimary airflow requirement.So less energy is used toproduce the beams ‘chilled water’at 58°F - saving energy
57We need lessprimary air,making100% DOAS ideal and cost effective, Improving IAQ& Ventilation effectiveness
59REHVA (Federation European Heating & Ventilation) Publication Independent PublicationsThis years 2012 ASHRAE HVAC Systems and Equipment publication covers chilled beam basicsREHVA (Federation European Heating & Ventilation) PublicationAHRI Test Standard (being worked on)Part of the European Commission ‘Energie’ program, in partnership with COSTIC (France), BSRIA (UK), ISSO (Netherlands) & IDEA (Spain).Climatic Ceilings - Technical Note: Design CalculationsClimatic Ceilings and Chilled beams - Application of low temperature heating and high temperature cooling
60Relative to room air dew point Extract From Independent ‘Energie’ Climatic CeilingsPassive+ 0.5 °C ( °F )Active- 1.5 °C ( °F)Relative to room air dew point
6164˚ Dew Point75˚/70% RH58˚ CWS75˚/50% RH55.1˚ Dew Point
62Condensation Considerations 75ºF db room design temperature at 50% relative humidity 55.1ºF dew point temperatureTheoretically condensation will form on the coil when the chilled water temperature is 55ºF.Apparent room dew point is 2-3ºF lower due to insulating effect of a water film on coil finsIn reality at this room design condition, condensation in the form of droplets will not begin to form until the water temperature is 52-53ºF.
63Condensation Consideration Condensation after 8.5 hours on a chilled surface intentionally held 7.8F colder than the space DPT. Not one droplet fell under these conditionsChilled Ceilings in Parallel with Dedicated Outdoor Air Systems: Addressing the Concerns of Condensation, Capacity, and Cost Stanley A. Mumma, Ph.D., P.E.
64‘Active Chilled beams could be run at or below the room dew point, but that’s crazy’! Be safe, design at 2 to 3F above the dew point and control the moisture content of the primary air to control the room RH64
65Rule # 4If you can not measure and control the space humidity, and your not in the middle of the desert, don’t use chilled beams !
67Building SuitabilityBuilding Characteristics that favor Active Chilled BeamsZones with moderate-high sensible load densitiesWhere primary airflows would be significantly higher than needed for ventilationBuildings most affected by space constraintsHi – rises, existing buildings with induction systemsZones where the acoustical environment is a key design criterionLaboratories where sensible loads are driving airflows as opposed to air change ratesBuildings seeking LEED or Green Globes certification
68Building SuitabilityCharacteristics that less favor Active Chilled BeamsBuildings with operable windows or “leaky” constructionBeams with drain pans could be consideredZones with relatively low sensible load densitiesZones with relatively low sensible heat ratios and low ventilation air requirementsZones with high filtration requirements for the re-circulated room airZone with high latent loads
69Required Design Data Room Design Conditions Room Sensible Cooling LoadsRoom Latent Cooling LoadsRoom Heating Loads (if used for heating)Infiltration LoadsMinimum Outside Air Quantity per ZoneSecondary Chilled Water Conditions and FlowPrimary Air Conditions and Inlet PressureDesired Room Air Change Rate (if required)Spatial Considerations/ConstraintsRoom layout/DrawingsUnit models desired
70Role of the Primary Air Ventilate the occupants according to ASHRAE 62 Handle all of the latent load in the spacePrimary air is only source of latent heat removalCreate induction through chilled beamPressurize the building
71Primary Air Design Central AHU sized to handle: AND sensible and latent cooling/heating of the ventilation airportion of the sensible internal cooling/heating loadsANDall of the internal and infiltration latent loadsPrimary air delivered continuously to the chilled beamsVAV primary air can be considered for the perimeter if the sensible loads are highChilled beam water coils provide additional sensible cooling/heating to control zones
73CHW System Design Options Secondary loopTap into district CHW loopHeat exchanger into return – no GPM demandCan increase main plant efficiencyDedicated chiller & DXDehumidification by DX AHUSignificantly increased COP - 11+Twin chillersOne for AHU’s – 6 COPOne for chilled beam circuit – 11+ COP
74Secondary Loop Supply temperature monitor Secondary chilled water supply to beamsTPrimary chilled water supplySSCHW PumpHeat ExchangerSecondary chilled water returnPrimary chilled water return
75Dedicated Chiller To chilled beam zones Bypass Valve T Chilled water pump64°FCooling TowerGeothermal LoopDedicated chiller11+ COPGeothermal Heat Pump58°F
76District Chilled Water Loops Tap into return pipe with heat exchanger and secondary loopNo demand in district loop GPMIncreases main chiller plant COP
77Waterside EconomizerWith mid-high 50ºFs chilled water temperature serving the Active Chilled BeamsReduce chiller energy consumption through:Using a water side economizer to minimize the chiller operating hours serving the Active Chilled Beams
79Boiler Efficiency Lower Hot Water Temp Hot water typically FReduce boiler energy consumption by maximizing efficiency of a condensing boiler through very low return water temperaturesUse of water to water heat pumps(KN boiler efficiency chart courtesy of Hydrotherm)
82Call Center, Kentucky Case Study Call center, 350,000 sq ft2200 occupantsLEED designConsidered radiant ceilings and passive beam systemsArticle in ASHRAE Journal, December 2009
83Call Center, Kentucky Case Study Real energy results based on comparison with another building on the same campusEnergy usage data collected over 1 yearElectrical energy consumption reduced by 41%Natural gas consumption reduced by 24%
84First Costs Compared to VAV “Energy Consumption Characteristics of Commercial Building HVAC Systems” - publication prepared for U.S. Department of Energy
85Maintenance No moving parts No filter No condensate pumps No consumable partsUp to 4 year inspection & cleanEasy maintenance access
86(Minimum 40 points needed for certification out of 100 maximum) LEED CertificationOptimize Energy Performance - up to 48% (new) or 44% (existing)more efficient than ASHRAE 90.1 (EA Credit 1) - up to 19 pointsIncreased Ventilation - 30% more outdoor air than ASHRAE 62 (IEQ Credit 2) - 1 pointControllability of Systems - individual temperature control (IEQ Credit 6.2) pointThermal Comfort - meet ASHRAE 55 (IEQ Credit 7.1) point(Minimum 40 points needed for certification out of 100 maximum)
89Active Chilled Beam Low Cost Core Solution When the sensible load densities in the interior zones are relatively low, the zone sizes large and the first cost of an Active Chilled Beam system is an issue consider:An Active Chilled Beam perimeter system in the high sensible load density perimeter zonesA single duct VAV interior system in the low sensible load density interior zonesLow supply air temperature to the single duct VAV with induction diffusers to increase the supply air temperatureThis needs separate air handers for perimeter & internal/core areas
90Interior Zones Induction Diffuser 277 cfm48ºF277 cfm75ºF555 cfm60ºF
91Lower airflows and fan energy consumption in the interior VAV system through use of lower temperature primary air - 20% reduction if temperature lowered from 55ºF to 50ºF - 26% reduction if temperature lowered from 55ºF to 48ºFImproved comfort through increased air movement in the low load interior zonesIncreased latent cooling capacity and improved humidity control
92Latent 640 BtuhLatent 1408 Btuh2.2 times latent capacity for same sensible capacity with 26% less primary air
952 or 4 Pipe Chilled Beams? Higher coil performance 4 pipe performance is compromised75% Cooling (12 pipes)25% Heating (4 pipes)Fewer or shorter beamsLower hot water temperatures90°F for 2 pipe130°F for 4 pipe
962-Pipe Beams and Terminal Heating Chilled Water SupplyTerminal Heating CoilHot Water Supply2-Pipe Active Chilled BeamsHot Water ReturnSTChilled Water ReturnS
105AdvantagesReduced pipeworkHigher system Delta TReduced pumping flow and horse powerIncreased flexibilityEliminate flow control valve and balancing valvesReduced commissioningMultiple water temperaturesIncreased capacity at chilled beam (no 4-pipe req.)Used in conjunction with 6 way valveLMB requires no maintenanceOne LMB for each zone (multiple ACB’s)Simple cartridge replacement
106DisadvantagesPower required to each LMBRequires low temperature water at thermal plant
108Viterbo School of Nursing, WI New $15.8m facility (original estimate $20m)68,000 ft2, 7 floorsConsists of labs, lecture halls and classroomsLEED Silver CertificationCompletion fall 2011
109HVAC First Costs Savings Compared to VAV Smaller AHU’sSmaller ductworkControlsSimple two position zone valvesElectrical infrastructure costsIncreased pump HP more than offset by reduced fan HP
110HVAC First Costs Increases Compared to VAV More terminals (beams)More distribution pipingMore piping insulationRequirement depends on chilled water temperature and dewpointOverall HVAC cost increase = $300,000 compared to VAV