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Integrating Radiant Cooling Systems for Energy Efficiency


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As more and more jurisdictions and building owners are placing increased emphasis on sustainable and responsible building strategies, design teams are looking beyond traditional HVAC solutions to maximize energy efficiency while maintaining occupant comfort and safety.

In-slab radiant heating systems have enjoyed popularity both here in the United States and abroad for years. Now, with the availability of improved control systems and better understanding within the design and construction community, the same concept can be applied to radiant cooling as an energy-efficient and cost-effective solution. This program will cover the radiant cooling heat transfer fundamentals, system performance and capacity, typical construction methods, and control strategies. Attendees will gain an understanding of how in-slab radiant cooling systems can be used as part of an energy-efficient design solution to reduce overall energy consumption.

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Integrating Radiant Cooling Systems for Energy Efficiency

  1. 1. Integrated Radiant Cooling Systems forEnergy EfficiencyDevin Abellon, P.E. – Business Development Manager UponorCalifornia Center for Sustainable Energy
  3. 3. LEED v3new constructionLEED Topic Possible PointsENERGY & ATMOSPHERE 26Credit 1: Optimize Energy PerformanceCredit 3: Enhanced CommissioningCredit 4: Enhanced Refrigerant ManagementCredit 5: Measurement & VerificationINDOOR ENVIRONMENTAL 6QUALITYCredit 1: Outdoor Air Delivery MonitoringCredit 2: Increased VentilationCredit 3: Construction IAQ PlanCredit 6.2: Controllability of Systems – Thermal ComfortCredit 7: Thermal Comfort – Design/VerificationINNOVATION IN DESIGN 5Credit 1: Innovation in Design
  4. 4. RADIANT COOLING High Mass Low Mass•Thermally Activated Building •Suspended or surface-mountSystem (TABS) •Faster response•Overhead slab or floor slab •Typically less surface area•Thermal mass •Colder temperatures (e.g.,55F)•Larger surface area•Moderate temperatures (e.g.,65F)
  5. 5. 2nd LAWof thermodynamicsClausius Statement:Heat generally cannot flow spontaneously from a material at lowertemperature to a material at higher temperature.
  8. 8. RADIANT TEMPERATUREAverage Uncontrolled Surface TemperatureArea weighted average of the surface temperatures of all uncontrolledsurfaceMean Radiant TemperatureAverage of the AUST and the surface temperature of the controlled surfaceOperative TemperatureAverage of the Mean Radiant Temperature and the Air Temperature
  9. 9. RADIANT TEMPERATURE Room Temp. = 78.0°F AUST = 78.0°F MRT = 72.0°F Operative Temp. = 75.0°F
  10. 10. SOLAR GAIN
  11. 11. SOLAR GAIN
  12. 12. SOLAR GAIN
  13. 13. SOLAR GAIN
  14. 14. RADIANT COOLING System Advantages• Ability to Deal with High DirectSolar Gains• Superior Human Comfort• Greater Architectural Freedom• Reduced Drafts and Noise• Energy Efficiency
  15. 15. ENERGY EFFICIENCY LBNL Findings: 100% peak power 37.5% Depending on the Fan and motor climate, a radiant cooling 57.7% system in conjunction 18.8% 1.5% - Pumps 7.5% with a dedicated outside Load from lights 9.4% air system (DOAS) could Chiller 9.3% Air transport load 1.9% save between 17% - 42% 62.5% over the baseline VAV 34.4% Other loads 34.4% system Conventional Radiant coolingSource: LBNL HVAC system HVAC system
  16. 16. ENERGY EFFICIENCYPacific Northwest National Laboratory A radiant cooling system in conjunction with a dedicated outside air system (DOAS) could save as much as 53% over the baseline HVAC systemNational Renewable Energy Laboratory /U.S. Department of Energy 50% Energy Savings over ASHRAE 90.1 can achieved using a radiant heating and cooling systemAmerican Institute of Architects
  17. 17. ENERGY EFFICIENCY Case StudiesSuvarnabhumi Bangkok Airport California Academy of Sciences Western Science Center Cooper UnionBangkok, Thailand San Francisco, California Hemet, California New York, New York30.5% Energy Savings LEED Platinum LEED Platinum LEED PlatinumNREL Research Support Facility David Brower Center The Chartwell School Portola Valley Town CenterGolden, Colorado Berkeley, California Seaside, California Portola, CaliforniaLEED Platinum LEED Platinum LEED Platinum LEED Platinum
  18. 18. RADIANT COOLING Performance Sensible Cooling A radiant cooling system can effectively manage a portion of building’s sensible load 12 – 14 BTUH/SF Direct Solar Loads In areas with high direct solar loads, the systems capacity can significantly increase to 25 – 32 BTUH/SF
  19. 19. RADIANT COOLING Typical Parameters Tubing Cross-linked polyethylene (PEX) barrier tubing 5/8” diameter 6” to 9” on center spacing Maximum tubing length per loop – 350’Operating Water Temperatures 55°F to 58°F 5°F to 8°F temperature differentialSurface Temperature Minimum 66°F
  20. 20. RADIANT COOLING Typical Construction Slab on Grade Flooring Structural Slab PEX Tubing Wire Mesh / Rebar Insulation Compacted Grade
  21. 21. RADIANT COOLING Typical Construction Suspended Slab Structural Slab PEX Tubing Wire Mesh / Rebar Metal Deck Insulation
  22. 22. RADIANT COOLING Typical Construction Topping Slab Topping Slab PEX Tubing Wire Mesh Insulation Structural Slab
  23. 23. RADIANT COOLING Typical Construction Wood Deck Flooring Topping Slab PEX Tubing Wood Deck Insulation
  24. 24. RADIANT COOLING Manifolds
  25. 25. RADIANT COOLING Manifold Locations
  26. 26. RADIANT COOLING Piping DiagramsMixing with Heating/Cooling Switchover
  27. 27. RADIANT COOLING Piping DiagramsPrimary/Secondary Piping
  28. 28. RADIANT COOLING Piping DiagramsLocal Secondary Injection
  29. 29. CONTROLS Control Points 24vac ON CAT5 TX TX Port RUN RX RX 1 10 Thermostats per controller Digital Zone Control Modules FILED MODULES Port Link Ethernet DZCM 2 Port OAS• Space Temperature Active uponor 3 To Building Service Network Port 4• Indoor Relative Humidity uponor uponor Port 5 Modem Port 1• Operative Temperature Port 2 24vac uponor DZCM Field Modules• Operating Water Port 3 Port 4 24vac uponor ZVDCTemperatures TX TX Router Port 5• Slab Temperature ON RUN RX Secondary1 Mix1 HOT WATER RETURN uponor• Control Valves HOT WATER SUPPLY Secondary2 Mix2 COLD WATER RETURN COLD WATER SUPPLY Mix3• Circulating Pumps Secondary3 DIVERTING GLOBE VALVE GLOBE VALVE / VALVE / Secondary4 Mix4 CIRCUIT DIVERTING VALVE CIRCUIT SETTER SETTER Outdoor Temperature Secondary5 Snowmelt 1 Snowmelt 2 Mix5• Outdoor Relative Humidity Supply Temp LOW LOSS Snowmelt 4 HEADER / 3WAY MODULATING Snowmelt 3 DECOUPLER VALVE Uponor Return Temp Supply Water Controller
  30. 30. CONTROLSControl Strategies • Base load with radiant cooling system and operate as a differential to air setpoint • Utilize indoor adaptive rest strategy to optimize target water temperature for maximum effectiveness • Continuously monitor indoor relative humidity for condensation control
  31. 31. RADIANT COOLING Condensation Concerns Condensation Surface condensation will occur if the surface temperature drops below the dew point Solution Continuously monitor indoor relative humidity and maintain supply water temperature 2 degrees above dew point at all times
  32. 32. CONTROLSControl StrategiesResponsiveness • High thermal mass provides “inertia” against temperature fluctuations • Heat transfer from the thermal mass to the space is instantaneous whenever there is a temperature difference • Thermal mass evens out fluctuations in internal temperature • Secondary system used to handle high load densities
  33. 33. COSTTypical Cost Factors No Cost • Structural Slab already part of the construction budget • Chilled water source typically already part of the budget Additional Cost • Cost of tubing, manifolds, fittings, circulators • Insulation • Increased Labor Reduced Cost • Smaller air handling units, ductwork, diffusers, etc. • Reduced ceiling space requirements may allow for reduced floor to floor heights • Potential to reduce electrical service size Reduced Maintenance Cost • Less airside equipment to maintain
  34. 34. COSTTypical Cost Factors Pacific Northwest National Laboratory Study • Average cost of the radiant system, including central plant • $9.31/ SF (7-8 year payback) 2010 R.S. Means Cost Data • Average cost of materials & labor (excluding chilled water source) • $4.25 - $5.43/ SF Innovations for Reduced Cost • Big Box Retailer • 2-1/2 year payback
  35. 35. RADIANT COOLINGSummary Benefits • Can be used to dramatically reduce overall building energy use • Superior Human Comfort • Improved architectural freedom Performance • 12-14 BTUH/SF Sensible, up to 25-32 BTUH/SF with direct solar for radiant floor installations Important Considerations • Controls • Installation Methods • Installation and Life-Cycle Costs
  36. 36. Questions?