RADIANT COOLING SYSTEMS PRINCIPLES OF RADIANT COOLING SYSTEMS INSTALLATION, DESIGN, CONTROLS, CAPACITIES www.rehau.com Construction Automotive Industry INTRODUCTIONS PRESENTER Lance MacNevin - Manager, REHAU Academy - Senior PEX Codes and Standards Specialist - Mechanical engineer for REHAU s PEXa piping division since 1993 - Product development, system design - Develops training for installers, designers, engineers, architects, distributors, etc. - Based at REHAU Head Office in Leesburg, VA - lance.macnevin@rehau.com 27-Mar-15 Page 2 1
ABOUT REHAU UNLIMITED POLYMER SOLUTIONS SMART SOLUTIONS FOR SUSTAINABLE DESIGN REHAU was founded in 1948 in the town of Rehau, Germany - Over 18,000 employees in more than 70 countries at 170 locations around the world - Focused on polymer solutions for construction, automotive, furniture and industry REHAU is a pioneer of: - PEXa piping systems for radiant heating applications, starting in 1968 - Applications like snow and ice melting, PEX geothermal systems and radiant cooling 27-Mar-15 Page 3 PROLOGUE: RADIANT COOLING SYSTEMS DEFINITIONS - Radiant surface: an exposed building surface including a tube or piping configuration installed within for heat exchange within a conditioned space - Radiant surfaces may be for heating or cooling - Sensible cooling surface: a surface designed for sensible cooling of an indoor space through heat transfer to the thermally effective surfaces from the occupants and/or indoor space by thermal radiation and natural convection - The network of radiant surface pipes can turn the radiant surface such as floors, walls and ceilings of a conditioned space into cooled surfaces that evenly absorb sensible heat energy such as radiant energy from solar gain, people, lights and computers, in addition to convective heat transfer from the air 27-Mar-15 Page 4 2
PROLOGUE: RADIANT COOLING SYSTEMS WHAT IS A RADIANT COOLING SYSTEM? Typically designed in conjunction with radiant heating, radiant cooling systems circulate chilled fluid through the same network of pipes where warm fluid circulates during the heating season - This network of pipes can turn the floors, walls and ceilings of a conditioned space into cooled surfaces that evenly absorb heat energy - Radiant cooling works best in a tightly sealed building that integrates radiant with a downsized forced-air system to meet the building s fresh air requirements - Over 50% of high-performance buildings utilize radiant heating and cooling systems Early example: Bilbao International Airport, northern Spain 27-Mar-15 Page 5 PROLOGUE: RADIANT COOLING SYSTEMS WHAT IS A RADIANT COOLING SYSTEM? Why is this course relevant? - May 2014 ASHRAE Journal technical feature VAV vs. Radiant describes how radiant cooling helped architects and engineers achieve LEED Platinum certification in an office building in the demanding climate of Hyderabad, India - Two identical buildings were built with same loads and uses, one with radiant cooling - 34% reduction in operational costs for building with radiant cooling vs. VAV systems 27-Mar-15 Page 6 3
LEARNING OBJECTIVES OF THIS COURSE BY THE END OF THIS COURSE, PARTICIPANTS SHOULD BE ABLE TO: 1. Explain the principles of radiant cooling systems and factors affecting thermal comfort 2. Describe the four basic installation types for radiant cooling systems 3. Discuss how a radiant cooling system is combined with air handling equipment to make a hybrid radiant cooling HVAC system which can address the concern of condensation 4. Introduce control options for a radiant cooling system 5. List the factors that affect output capacity of a hybrid radiant cooling system 6. Summarize the advantages of a hybrid cooling HVAC system 7. Refer to published case studies Note: Several of the claims in this presentation have been independently published in Radiant Cooling Research Scoping Study (2006) Moore, Bauman, Huizenga, Center for the Built Environment (CBE), UC Berkley: http://www.cbe.berkeley.edu/research/pdf_files/ir_radcoolscoping_2006.pdf 27-Mar-15 Page 7 1. PRINCIPLES OF RADIANT COOLING AND THERMAL COMFORT THERMAL COMFORT BASIC PHYSICAL PHENOMENA Whenever there is a temperature difference between two objects, both objects will attempt to equalize the temperature - The energy transfer required to approach equivalent temperatures occurs through radiation, conduction and convection Radiant energy is infrared energy that travels from hot to cold through a space, without heating the space itself On a hot day the sun can provide too much radiant energy On a cool day the radiant energy from the sun can feel great 27-Mar-15 Page 8 4
PRINCIPLES OF RADIANT COOLING AND THERMAL COMFORT THERMAL COMFORT BASIC PHYSICAL PHENOMENA People are exothermic heat generators! - Heat emission from the human body occurs via four modes of heat transfer: i. Radiation (~45%) ii. Convection (~30%) iii. Evaporation (~20%) iv. Conduction (~5%) - Our bodies radiate heat to any surface in line-of-sight which is cooler than our own surface temperature (85-90 F / 29-32 C) - Humans feel most comfortable when they can regulate at tleast t45% of ftheir heat emission i through radiation - Reducing surrounding surface temperatures draws more heat from our bodies via radiation - When the air is warm, this is a good thing! Our brains burn 500 Cal/day! 27-Mar-15 Page 9 PRINCIPLES OF RADIANT COOLING AND THERMAL COMFORT THERMAL COMFORT TEMPERATURE SET POINTS From years of adjusting thermostats, we have been conditioned to believe that air temperature alone translates to comfort, but this is not necessarily true. We have to consider: 1. Air temperature Space s air temperature, monitored by thermostat as set point temperature 2. Mean radiant temperature (MRT) Average temperature of surrounding surfaces 3. Operative room temperature Weighted average of mean radiant temperature and the conditioned space s air temperature The operative temperature is what we perceive on our skin in a room and what is most important to consider when specifying a radiant system. Higher air temperature set points during the cooling season and lower set points during the heating season are possible with radiant systems. 27-Mar-15 Page 10 5
PRINCIPLES OF RADIANT COOLING AND THERMAL COMFORT THERMAL COMFORT ASHRAE Standard 55 Thermal Environmental Conditions for Human Occupancy Boundaries for thermal comfort according to ASHRAE Standard 55 - Operative temperature: - Summer period @ 50% RH: 75-80 F - Winter period @ 30% RH: 70-77 F - Range of the floor temperature: 66-84 F - This is their so-called comfort area, where the percentage of people who are comfortable is optimized - A reasonable target t might be less than 10% dissatisfied at any moment - commercially 27-Mar-15 Page 11 PRINCIPLES OF RADIANT COOLING AND THERMAL COMFORT THERMAL COMFORT THE EFFECTS OF MEAN RADIANT TEMPERATURE ON COMFORT A lower Mean Radiant Temperature increases the radiant heat loss from human body - Surfaces are cooler with radiant cooling - Human body radiates more heat to floors, walls and ceilings - Indoor air does not have to be as cool for equivalent comfort - Indoor air temperature setpoint is elevated, or operative temperature may be too low - We typically use setpoint temperatures above 75 F for radiant cooling applications Pink area = approximate comfort zone - With cooler surface temperatures, the air can be warmer without causing discomfort, saving energy MRT comfort graph originally published in Architectural Forum, January 1939 Mean Radiant Temperature ( F) 27-Mar-15 Page 12 6
PRINCIPLES OF RADIANT COOLING AND THERMAL COMFORT THERMAL COMFORT RADIANT HEAT TRANSFER In a radiant heating system, warm fluid circulates through PEX pipes integrated in the floor structure - Heat radiates up from the warmed floor, providing a comfortable environment by warming people and objects - Warm air also rises due to natural convection - There is also conduction to feet! A radiant cooling system works with the reverse energy transfer process, providing a comfortable environment by absorbing heat from the space - In cooling mode, the same network of pipes is used as in the heating mode - Heat transferred into the floor is removed from the space via the circulating fluid - In some applications, pipes are embedded into the ceiling or even the walls or columns WARMED CONCRETE SLAB COOLED CONCRETE SLAB COOLED CONCRETE SLAB Floor Covering PEX Pipe Floor Covering PEX Pipe PEX Pipe Ceiling Exposure 27-Mar-15 Page 13 PRINCIPLES OF RADIANT COOLING AND THERMAL COMFORT THERMAL COMFORT TEMPERATURE SET POINTS Spaces with 100% forced-air systems have higher mean radiant temperatures due to solar gains and office equipment - Occupant turns down the air setpoint, t trying to counter radiant loads using more cooler air - This requires more air movement, inefficiently countering a high MRT With an air-based system in combination with a radiant cooling system, surface temperatures are naturally lower - This increases the heat emitted from the occupant to cooled surfaces via radiation - Occupant feels comfortable within the space, which removes the need for a lower air temperature and/or increased air flow - Most efficiently counters heat loads 27-Mar-15 Page 14 7
PRINCIPLES OF RADIANT COOLING AND THERMAL COMFORT SUMMARY 1. Humans feel most comfortable when they can regulate at least 45% of their heat emission through radiation 2. The operative temperature is what we perceive on our skin in a room and what is most important t to consider when specifying i a radiant system 3. A radiant cooling system works by absorbing heat from the space 4. With a radiant cooling system, surface temperatures are lower, so occupants feel comfortable within the space, which removes the need for a lower air temperature and/or increased air flow 27-Mar-15 Page 15 2. INSTALLATION TYPES OF RADIANT COOLING INSTALLATION TYPES i. Radiant Floor Heating and Cooling (FHC) ii. Thermally Activated Building Slab (TABS) iii. Radiant Ceiling Heating and Cooling (CHC) iv. Radiant Wall Heating and Cooling (WHC) 27-Mar-15 Page 16 8
INSTALLATION TYPES OF RADIANT COOLING RADIANT FLOOR HEATING AND COOLING i. Radiant Floor Heating and Cooling ( FHC ) - With insulation underneath to condition the space above - Creates a heated/cooled floor for the space above - Common in slab-on-grade buildings - Uni-directional heating/cooling 27-Mar-15 Page 17 INSTALLATION TYPES OF RADIANT COOLING THERMALLY ACTIVATED BUILDING SLAB ii. Thermally Activated Building Slab (TABS) aka Concrete Core Tempering (CCT) - Without insulation underneath - Creates a heated/cooled d floor and ceiling, to condition the spaces above and below - Common in multi-story buildings - Bi-directional heating/cooling 27-Mar-15 Page 18 9
INSTALLATION TYPES OF RADIANT COOLING RADIANT CEILING HEATING AND COOLING iii. Radiant Ceiling Heating and Cooling (CHC) Suspended panels with embedded small diameter PEX mini-pipes, plastered over Surfaces can absorb radiant heat from below and from warm air Cooled surfaces can be strategically located above warm occupied areas Ideal for factories, classrooms, stores This is Uni-directional heat transfer 27-Mar-15 Page 19 INSTALLATION TYPES OF RADIANT COOLING RADIANT CEILING HEATING AND COOLING iii. Radiant Ceiling Heating and Cooling (CHC) Suspended panels with embedded PEX mini-pipes are sometimes used Panels can absorb radiant heat from below and from warm air Panels can be strategically located above warm occupied areas 27-Mar-15 Page 20 10
INSTALLATION TYPES OF RADIANT COOLING RADIANT WALL HEATING AND COOLING iv. Radiant Wall Heating and Cooling (WHC) - Small diameter pipes are attached to walls then plastered over - Pipes may be run from the floor as the same circuit, same fluid (left) - Pipes may be run as a separate circuit (right) 27-Mar-15 Page 21 INSTALLATION TYPES OF RADIANT COOLING RADIANT FLOOR HEATING/COOLING RE-PURPOSED COMMERCIAL SPACE Pier One, San Francisco, 1999 The radiant floor heating and cooling system installed in historic Pier One in San Francisco's Embarcadero district is one of the first documented uses of a radiant floor heating system, also used to cool a building, in NA 27-Mar-15 Page 22 11
INSTALLATION TYPES OF RADIANT COOLING RADIANT FLOOR HEATING/COOLING MOTORCYCLE DEALERSHIP IN LIBERAL, KANSAS Radiant system was combined with air system to meet customer s needs for: - Optimum thermal comfort - Reduced energy consumption - Reduced noise - Avoiding local hot/cold spots 27-Mar-15 Page 23 INSTALLATION TYPES OF RADIANT COOLING RADIANT FLOOR HEATING/COOLING NATIONAL GUARD HANGER (HIGH ALTITTUDE ARMY TRAINING SITE) IN EAGLE, CO IS LEED SILVER Radiant system was combined with air system to meet customer s needs for: - Optimum thermal comfort - Energy savings - Radiant is ideal for hanger space with high ceilings and high solar gain 27-Mar-15 Page 24 12
INSTALLATION TYPES OF RADIANT COOLING RADIANT FLOOR HEATING/COOLING PLUS CEILING COOLING EARTH RANGERS CENTRE IN WOODBRIDGE, ONTARIO IS LEED PLATINUM 27-Mar-15 Page 25 INSTALLATION TYPES OF RADIANT COOLING THERMALLY ACTIVATED BUILDING SLAB IN MULTI-STORY TOWER YWCA WOMEN S SHELTER IN TORONTO, ONTARIO IS LEED SILVER YWCA Toronto Elm Tower, ON Complex includes 5-, 10- and 17- story residential towers and the new YWCA Toronto corporate offices Radiant heating/cooling in TABS design, with downsized AHU and ground-source geothermal heating/ cooling source, saves over 40% on heating/cooling costs 27-Mar-15 Page 26 13
INSTALLATION TYPES OF RADIANT COOLING THERMALLY ACTIVATED BUILDING SLAB IN MULTI-STORY DORMITORY YORK UNIVERSITY IN TORONTO, ONTARIO 27-Mar-15 Page 27 INSTALLATION TYPES OF RADIANT COOLING THERMALLY ACTIVATED BUILDING SLAB IN MULTI-STORY DORMITORY PIPES IN FLOORS, CEILING AND CERTAIN BUILDING COLUMNS - Radiant cooling pipes may be embedded in floors, ceilings, walls or other exposed surfaces - Pipes are in these columns 27-Mar-15 Page 28 Example: Pond Residence at York University in Toronto, ON 14
INSTALLATION TYPES OF RADIANT COOLING RADIANT CEILING EXAMPLE APPLIED IN A UNIVERSITY LIBRARY LOYOLA UNIVERSITY IN CHICAGO, ILLINOIS IS LEED SILVER 27-Mar-15 Page 29 INSTALLATION TYPES OF RADIANT COOLING INSTALLATION TYPES i. Radiant Floor Heating and Cooling (FHC) ii. Thermally Activated Building Slab (TABS) iii. Radiant Ceiling Heating and Cooling (CHC) iv. Radiant Wall Heating and Cooling (WHC) A common factor is the poured cementitious thermal mass around the pipes No aluminum heat transfer panels are used in radiant cooling systems 27-Mar-15 Page 30 15
3. HYBRID RADIANT COOLING COMBINED WITH AIR HANDLING ADDRESSING HUMIDITY AND PREVENTING CONDENSATION Although hydronic building conditioning systems have many benefits, they usually can not work alone in commercial applications Radiant cooling systems must have an air-based component for several reasons: 1. Fresh air - The AHU is required to meet the building s fresh air requirements, staying consistent with increased building environment standards (e.g., ASHRAE 62.1, LEED) 2. Latent cooling - Downsized forced-air components must exist to counter humidity from outside air and from occupants within a building (latent t cooling) 3. Fast response time - For some applications, it is desirable to have a fast-acting air system to handle quick shifts in occupancy and transient loads 27-Mar-15 Page 31 HYBRID RADIANT COOLING COMBINED WITH AIR HANDLING ADDRESSING HUMIDITY AND PREVENTING CONDENSATION Successful radiant cooling projects center around understanding the correct balance of an air handling unit (AHU) working in conjunction with a radiant system. These are referred to as hybrid HVAC systems. Note: AHU is used to indicate any forced-air system used to condition a space (e.g., fan coil, packaged rooftop unit, DOAS). The radiant system and the AHU work together as a hybrid HVAC system, optimizing system design and performance by decoupling the following portions of the system: 1. Hydronic and air-based heat exchange 2. MRT and air temperature control 3. Sensible (dry) and latent (humid) cooling functions 27-Mar-15 Page 32 16
HYBRID RADIANT COOLING COMBINED WITH AIR HANDLING ADDRESSING HUMIDITY AND PREVENTING CONDENSATION The key to preventing condensation lies in three specific areas: 1. Infiltration - First and foremost, use a tight building envelope to reduce loads associated with non-mechanical infiltration (leakage) 2. Surface Temperature - Control surface temperatures by designing cooled surfaces to operate at specific supply temperatures to prevent the surface from reaching dew point, which might lead to surface condensation 3. Relative Humidity - Control the level of humidity in a building with the AHU to keep the dew point lower than the radiant system s operating temperatures - Spaces are typically designed for about 50% maximum relative humidity during peak cooling periods 27-Mar-15 Page 33 HYBRID RADIANT COOLING COMBINED WITH AIR HANDLING ADDRESSING HUMIDITY AND PREVENTING CONDENSATION Relative humidity: The ratio of the amount of moisture in the air at a specific temperature to the maximum amount that the air could hold at that temperature, expressed as a percentage Dew point temperature: The temperature at which dew begins to form. - Radiant cooling needs a slightly more sophisticated design approach compared to radiant heating due to solar gains, occupant loads and resulting moisture management issues, which for many climates of North America pose concerns for specifiers - We must avoid reaching the dew point When a surface temperature is lower than the dew point, condensation can form 27-Mar-15 Page 34 17
HYBRID RADIANT COOLING COMBINED WITH AIR HANDLING ADDRESSING HUMIDITY AND PREVENTING CONDENSATION The Dew Point of any atmosphere may be predicted using established means - The radiant cooling designer must utilize proper controls to keep all surfaces temperature above the dew point Example of pyschrometric chart 27-Mar-15 Page 35 HYBRID RADIANT COOLING COMBINED WITH AIR HANDLING ADDRESSING HUMIDITY AND PREVENTING CONDENSATION Radiant cooling is used in very cold climatic regions - Where specifiers have chosen radiant heating, they can easily take advantage of the cooling potential in the existing PEX network - Addition of radiant cooling minimally increases the initial cost and has many advantages during operation Sampling of radiant cooling projects in NA Radiant cooling is used in Hot/Humid climatic regions - Proper controls are available to avoid uncomfortable and dangerous condensation 27-Mar-15 Page 36 18
HYBRID RADIANT COOLING COMBINED WITH AIR HANDLING ADDRESSING HUMIDITY AND PREVENTING CONDENSATION CHALLENGING BUILDING DESIGN IN ALABAMA WITH RADIANT HEATING AND COOLING New 12,000 ft 2 Technical Center in Cullman, AL 27-Mar-15 Page 37 HYBRID RADIANT COOLING COMBINED WITH AIR HANDLING ADDRESSING HUMIDITY AND PREVENTING CONDENSATION CHALLENGING BUILDING DESIGN IN ALABAMA WITH RADIANT HEATING AND COOLING New 12,000 ft 2 Technical Center in Cullman, AL - Summertime dew point temperature can be above 80 F 27-Mar-15 Page 38 19
HYBRID RADIANT COOLING COMBINED WITH AIR HANDLING ADDRESSING HUMIDITY AND PREVENTING CONDENSATION CHALLENGING BUILDING DESIGN IN ALABAMA WITH RADIANT HEATING AND COOLING New 12,000 ft 2 Technical Center in Cullman, AL includes: - Radiant heating and cooling, geothermal heat exchange, smart controls, pre-insulated pipe, PEX plumbing and outdoor snow and ice melting - 2,900 ft of 5/8 PEX tubing @ 6 inch spacing (in 10 circuits) for heating/cooling in the Academy classroom - When it opens in 2015, this facility host seminars for architects, engineers, contractors and distributors who will travel to Cullman to see these innovative technologies in action 27-Mar-15 Page 39 HYBRID RADIANT COOLING COMBINED WITH AIR HANDLING ADDRESSING HUMIDITY AND PREVENTING CONDENSATION CHALLENGING BUILDING IN ALABAMA WITH RADIANT HEATING AND COOLING New 12,000 ft 2 Technical Center in Cullman, AL 27-Mar-15 Page 40 20
HYBRID RADIANT COOLING COMBINED WITH AIR HANDLING ADDRESSING HUMIDITY AND PREVENTING CONDENSATION CHALLENGING BUILDING IN ALABAMA WITH RADIANT HEATING AND COOLING New 12,000 ft 2 Technical Center in Cullman, AL - Radiant heating/cooling slab system uses 2,900 ft of 5/8 PEX at 6 in. spacing - 10 circuits connected to central manifold - Maximum circuit length 300 ft. - Designed for maximum ΔT of 10 F 27-Mar-15 Page 41 HYBRID RADIANT COOLING COMBINED WITH AIR HANDLING ADDRESSING HUMIDITY AND PREVENTING CONDENSATION CHALLENGING BUILDING IN ALABAMA WITH RADIANT HEATING AND COOLING New 12,000 ft 2 Technical Center in Cullman, AL (current status) 27-Mar-15 Page 42 21
HYBRID RADIANT COOLING COMBINED WITH AIR HANDLING ADDRESSING HUMIDITY AND PREVENTING CONDENSATION SUMMARY 1. A hybrid radiant cooling system uses the correct balance of an air handling working in conjunction with a radiant system 2. Hybrid radiant systems must have an air-based component for fresh-air supply, to dehumidify and for localized fast response 3. Examples of radiant cooling in humid climates demonstrate the effectiveness 27-Mar-15 Page 43 4. CONTROL OPTIONS FOR RADIANT COOLING SYSTEMS BUILDING CONTROL STRATEGY Typical elements: - Outdoor temperature sensor on the northern side of the building, not exposed to direct sunlight - Humidity and temperature sensor(s) in each zone to monitor dew points and set points - Floor temperature sensor in the upper level of the thermal mass - Supply and return fluid temperature sensors in the piping network 27-Mar-15 Page 44 22
CONTROL OPTIONS FOR RADIANT COOLING SYSTEMS BUILDING CONTROL STRATEGY ZONE CONTROL STRATEGY - Humidity sensor/s in several rooms to measure RH% - Air sensing thermostats in each zone to control air supply for rapid response cooling and local dehumidification - Both sensors are often combined in one unit 27-Mar-15 Page 45 CONTROL OPTIONS FOR RADIANT COOLING SYSTEMS SUMMARY The right controls are available - Several firms have the know-how to design, build and program building management controls to include radiant cooling - Appropriate PC-based smart control systems are economically feasible for high-end residential and light commercial applications 27-Mar-15 Page 46 23
5. FACTORS AFFECTING OUTPUT CAPACITIES RADIANT COOLING CAPACITIES PERFORMANCE OF RADIANT FLOORS AND CEILINGS The capacity of a radiant cooling system depends on factors such as insulation, radiant emissivity, pipe spacing, fluid flow rates, floor construction, floor covering, room set-point temperature and others - Floor surface temperatures less than 66 F (29 C) are to be avoided for comfort reasons - Radiant cooling systems in poured floors or ceilings typically use PEX pipes at 6-8 in. pipe spacing, fluid temperatures in the range of 55 F to 60 F, fluid Delta-T of 10 F or less, and higher flow rates than radiant heating systems - Pipe size is determined by coverage areas and circuit lengths - Under optimal design conditions, radiant cooled floor capacities of up to 16 BTU/(hr-ft²) can be achieved*, with more typical capacities in the 8 to 12 BTU/(hr-ft²) range * Olesen, Bjarne. Radiant Floor Cooling Systems, ASHRAE Journal, September 2008 Compared with radiant floor heating systems: - Floor surface temperatures over 84 F are to be avoided for comfort reasons - Under optimal design conditions, capacities of up to 34 BTU/(hr-ft²) can be achieved 27-Mar-15 Page 47 FACTORS AFFECTING OUTPUT CAPACITIES RADIANT COOLING CAPACITIES PERFORMANCE OF RADIANT FLOORS AND CEILINGS For effective radiant cooling in poured slabs, a higher than normal concentration of radiant pipes is required - 6 on-center spacing is typical to eliminate striping and provide faster response time Radiant floor being built in the REHAU MONTANA Ecosmart House research project 27-Mar-15 Page 48 24
FACTORS AFFECTING OUTPUT CAPACITIES RADIANT COOLING CAPACITIES PERFORMANCE OF RADIANT FLOORS AND CEILINGS For effective radiant cooling in poured slabs, a higher than normal concentration of radiant pipes is required - 6 on-center spacing is typical to eliminate striping and provide faster response time 27-Mar-15 Page 49 FACTORS AFFECTING OUTPUT CAPACITIES RADIANT COOLING CAPACITIES THE MATH PART... Specific heating/cooling capacity in W/m² or Btu/(h ft 2 ) Heat transfer coefficient (HTC) Average surface temperature q HTC T SURFACE T AIR Air temperature Floor Ceiling Heating Cooling 11 W/m 2 K 7 W/m 2 K 1.9 Btu/(h ft² F) 1.2 Btu/(h ft² F) - ~ 60% greater potential to absorb heat from ceiling cooling system vs. floor cooling system based solely on HTC Heating 6 W/m 2 K 1.1 Btu/(h ft² F) - Reverse for delivering heat in heating mode Cooling 11 W/m 2 K 1.9 Btu/(h ft² F) Heat transfer coefficient (HTC) values can be approximated based on values from DIN EN 1264 and 15377 27-Mar-15 Page 50 25
FACTORS AFFECTING OUTPUT CAPACITIES RADIANT COOLING CAPACITIES PERFORMANCE OF RADIANT FLOORS AND CEILINGS Radiant Heating Output Potential Formula: - (Panel surface temp - Indoor air temp.) x HTC = Heat Output in BTU/hr(ft 2 ) - HTC = Combined Radiant/Convective Heat Transfer Coefficient Approximate HTC values for heated panels: - Radiant Floors: 1.9 BTU/(h ft² F) (35-40% heat is transferred via natural convection) - Radiant Walls: 1.4 BTU/(h ft² F) (less natural convection than floors) - Radiant Ceiling: 1.1 BTU/(h ft² F) (very little natural convection) Example: 80ºF heated floor potential output - (80ºF - 68ºF) x 1.9 = 23 BTU/hr(ft 2 ) The potential output of a 80ºF heated floor 27-Mar-15 Page 51 FACTORS AFFECTING OUTPUT CAPACITIES RADIANT COOLING CAPACITIES PERFORMANCE OF RADIANT FLOORS AND CEILINGS Radiant Cooling Output Potential Formula: - (Indoor air temp - Surface temp) x HTC = Cooling capacity in BTU/hr(ft 2 ) Notes: - Floor surface temperatures less than 66 F are to be avoided for comfort reasons - Indoor air set-points for radiant cooling may be as high as 77ºF Example: 66ºF cooled ceiling potential output (76ºF - 66ºF) x 19 1.9 = 19 BTU/hr(ft 2 ) The potential ti capacity of a 66ºF cooled ceiling Notes: - In arid climates this output may be possible, but we also have the limit of dew point - The emissivity of the actual ceiling surface may also reduce heat transfer - The actual radiant cooling capacity of each system is based on many variables 27-Mar-15 Page 52 26
FACTORS AFFECTING OUTPUT CAPACITIES RADIANT COOLING CAPACITIES PERFORMANCE OF RADIANT FLOORS AND CEILINGS For comfort, ASHRAE Standard 55 limits floor temperature range to: - Equal to or greater than 66 F (19 C) in cooling mode - Less than 84 F (29 C) in heating mode Typical capacities based on setpoints adjusted for radiant systems: T SURFACE OUTPUT Floor Ceiling Heating 78-84 F 19-31 Btu/(h ft 2 ) Cooling 66-70 F 8-12 Btu/(h ft 2 ) Heating 78-84 F 11-17 Btu/(h ft 2 ) Ceilings are not limited by the ASHRAE 55 floor limit; ceiling values are used only to Cooling 66-70 F 15-24 Btu/(h ft 2 ) show capacity comparison Obtaining a designed surface temperature from a radiant floor system depends on factors such as average fluid temperature, pipe spacing, pipe placement, floor covering, room set point temperature 27-Mar-15 Page 53 FACTORS AFFECTING OUTPUT CAPACITIES SUMMARY 1. The capacity of a radiant cooling system depends on factors such as insulation, radiant emissivity, pipe spacing, fluid flow rates, floor construction, floor covering, room set-point temperature and others 2. The math for calculating l capacities is understood d and is sometimes easily applied 3. Direct solar gain can increase specific capacities of chilled ceilings or floors 27-Mar-15 Page 54 27
6. ADVANTAGES OF HYBRID RADIANT COOLING HVAC SYSTEMS INCREASED THERMAL COMFORT MAKE CUSTOMERS HAPPIER Radiant cooling and heating systems are integral in creating hybrid systems that reach higher levels of thermal comfort than their 100% forced-air system counterparts Increased Thermal Comfort: 1. The human body feels most comfortable when it can regulate at least 45% of its heat emission via radiation achieved through a radiant system 2. Radiant cooling optimizes the surface temperatures of the occupants surroundings, providing a even and comfortable environment 3. Comfortable cooling is provided with reduced ventilation air and little to no flow noises 4. Improved thermal comfort may aid in LEED certification - LEED NC 2009 Energy and Atmosphere category up to 1 point for Thermal Comfort Design 27-Mar-15 Page 55 ADVANTAGES OF HYBRID RADIANT COOLING HVAC SYSTEMS REDUCED ENERGY CONSUMPTION WASTE LESS MONEY Hybrid HVAC systems utilizing radiant heating and cooling can help to reduce energy consumption when compared with 100% AHU systems Reduced Energy Consumption: 1. Radiant cooling allows a higher space set-point temperature, while still maintaining the same level of cooling comfort compared to a traditional AHU 2. Superior heat transfer properties of water compared to air allows the hydronic portion of the system to efficiently distribute energy to conditioned spaces 3. Operating with moderate supply water temperatures allows the integration of renewable systems such as geothermal heat pumps at maximum efficiencies 27-Mar-15 Page 56 28
ADVANTAGES OF HYBRID RADIANT COOLING HVAC SYSTEMS LOWER INVESTMENT COST COMPARISON SPEND LESS MONEY A radiant cooling system has significant benefits when used in a hybrid HVAC system to reduce initial investment costs and increase economic efficiency for a building Reduced Investment Costs: 1. Higher setpoints reduce building s required cooling load, which results in less cooling capacity from total HVAC equipment 2. Often additional ducting becomes unnecessary and air systems can be downsized to only serve the fresh air requirements 3. Radiant cooling can lead to a reduction in costly forced air components of an HVAC system 27-Mar-15 Page 57 CASE STUDY - COMMERCIAL SIDE-BY-SIDE BUILDINGS FOR INFOSYS IN HYDERABAD, INDIA - May 2014 ASHRAE Journal technical feature VAV vs. Radiant describes how radiant cooling helped architects and engineers achieve LEED Platinum certification in an office building in the demanding climate of Hyderabad, India: - 99% Heating ODT = 59 F ; 1% Cooling DB = 102 F; Dew Point = 75 F - Two identical buildings were built with the same loads and occupancy - Data showed a 34% reduction in operational costs for Radiant Cooling vs. VAV buildings - Radiant system was less expensive to build and operate and delivered better comfort 27-Mar-15 Page 58 29
CASE STUDY - COMMERCIAL SIDE-BY-SIDE BUILDINGS FOR INFOSYS IN HYDERABAD, INDIA VAV Cooling Radiant Cooling 27-Mar-15 Page 59 CASE STUDY - COMMERCIAL CONCEPT AND DESIGN 27-Mar-15 Page 60 30
CASE STUDY - COMMERCIAL RADIANT MODULES BUILT ON SITE USING PEXa PIPES ON MATTS 27-Mar-15 Page 61 CASE STUDY - COMMERCIAL PEX PIPE INTEGRATED IN SLABS 27-Mar-15 Page 62 31
CASE STUDY - COMMERCIAL CIRCUITS CONNECTED TO BALANCING MANIFOLDS 27-Mar-15 Page 63 CASE STUDY - COMMERCIAL HYBRID RADIANT FORCED-AIR CONFIGURATION Hybrid System Components Radiant slab installed as a thermally activated building system (TABS) Dedicated d outdoor air system (DOAS) with energy recovery wheel Cooling tower Ceiling fans Advantages - Smaller mechanical equipment footprint t - Lower initial cost - Lower operating cost 27-Mar-15 Page 64 32
CASE STUDY - COMMERCIAL HYBRID RADIANT FORCED-AIR CONFIGURATION Thermal image of radiant cooled ceiling in Infosys SDB-1 27-Mar-15 Page 65 CASE STUDY - COMMERCIAL ANNUAL ENERGY CONSUMPTION 27-Mar-15 Page 66 33
CASE STUDY - COMMERCIAL SIDE-BY-SIDE BUILDINGS FOR INFOSYS IN HYDERABAD, INDIA The Infosys SDB-1 project proved that a hybrid forced- air / radiant system in a hot, humid climate can: 1. Reduce HVAC energy consumption 2. Increase thermal comfort 3. Reduce initial costs over optimized VAV system 27-Mar-15 Page 67 CASE STUDY - COMMERCIAL ENERGY EFFICIENCY AND THERMAL COMFORT REALIZED 27-Mar-15 Page 68 34
CASE STUDY - RESIDENTIAL REHAU MONTANA ECOSMART HOUSE An architect s own home is also a research project and demonstration of reaching near-net-zero with sustainable technologies Building envelope - Insulated Concrete Forms - Structural Insulated Panels - Compression-Seal Technology upvc windows and doors Mechanical systems and controls - Thermal Solar - Ground Source Heat Pump - Radiant Heating - Radiant Cooling - Snow and Ice Melting 27-Mar-15 Page 69 CASE STUDY - RESIDENTIAL RADIANT HEATING AND COOLING Radiant systems work by circulating warm or chilled fluid through PEX pipes placed in or under a building s floors, walls or ceilings - Warm fluid circulating through the pipes during the heating season gently warms the space, virtually eliminating cold spots and temperature fluctuations - Chilled fluid circulating through the pipes during the cooling season allows the cooled surface to remove heat energy from the room - Two radiant installation techniques are used in this project: Pipes embedded in structural concrete slabs Pipes embedded in suspended wood floor overpour 27-Mar-15 Page 70 35
CASE STUDY - RESIDENTIAL RADIANT FLOOR HEATING OVER ICF FLOOR SYSTEM ON MAIN FLOOR 27-Mar-15 Page 71 CASE STUDY - RESIDENTIAL RADIANT FLOOR HEATING OVER ICF FLOOR SYSTEM ON MAIN FLOOR 27-Mar-15 Page 72 36
CASE STUDY - RESIDENTIAL RADIANT FLOOR HEATING OVER ICF FLOOR SYSTEM ON MAIN FLOOR 27-Mar-15 Page 73 CASE STUDY - RESIDENTIAL RADIANT FLOOR HEATING OVER WOOD SUBFLOOR ON SECOND FLOOR 27-Mar-15 Page 74 37
CASE STUDY - RESIDENTIAL RADIANT DISTRIBUTION MANIFOLDS, CIRCULATOR, MOD/CON BOILER 27-Mar-15 Page 75 CASE STUDY - RESIDENTIAL RADIANT COOLING OPERATING IN FLOOR OF GROUND LEVEL AND IN CEILING OF THE CLASSROOM SPACE Shaded areas indicate the regions where Radiant cooling is available Left Floor areas with radiant cooling Right Ceiling area with radiant cooling 27-Mar-15 Page 76 38
CASE STUDY - RESIDENTIAL RADIANT COOLING PANELS Radiant cooling panels utilize hydronic technology to lower surrounding surface and air temperatures - Moderate chilled water circulates through mini-pexa pipes embedded in ceiling panels - System delivers a comfortable and cost-effective means of cooling room occupants - Radiant cooling is gaining widespread popularity in Europe, USA and Canada because of its comfort (no direct air flow) and modern efficiency 27-Mar-15 Page 77 CASE STUDY - RESIDENTIAL RADIANT COOLING PANELS ABOVE CLASSROOM SPACE Suspended panels with embedded PEXa mini-pipes Panels can absorb radiant heat from below and from warm air Panels can be strategically located above warm occupied areas, such as a classroom 27-Mar-15 Page 78 39
CASE STUDY REHAU MONTANA ECOSMART HOUSE A research contract between project sponsor and MSU Department of Mechanical Engineering began in April 2013 to evaluate the efficiency and effectiveness of the sustainable systems, especially when used together 27-Mar-15 Page 79 CASE STUDY REHAU MONTANA ECOSMART HOUSE Figure 1: Relative Humidity (RH%) and Temperature vs. Time, Ceiling + Floor Cooling RH never goes above 45%, even when cooling the air into the low 70 s 27-Mar-15 Page 80 40
CASE STUDY REHAU MONTANA ECOSMART HOUSE Figure 1: Surface Temperatures and Dew Point, Ceiling + Floor Cooling Dew point was always below 50 F, while cooled surfaces never approached that temperature 27-Mar-15 Page 81 CASE STUDY REHAU MONTANA ECOSMART HOUSE Test Conclusions: 1. The radiant cooling ceiling performed well and was able to cool the 80 F test room to 75 F quickly, using 60 F supply water fluid to the manifold. 2. Considering the moderate entering fluid temperature of 60 F to power the radiant cooled ceiling, there is potential to increase EER s from ground source heat pumps. 3. The cooled radiant floor by itself also performed well, even though the cooling capacity was less than the ceiling; a 66 F test fluid temperature was used for the floor. 4. When coupled with a cooled floor, the cooling capacity of the ceiling was enhanced. 5. There was a risk-free condensation scenario with dry to normal air humidity conditions. 6. The vast radiant area of the cooled floor surface contributed to the good response. 27-Mar-15 Page 82 41
CONCLUSIONS 1. Radiant surface cooling allows for more efficiently-sized forced-air systems to meet a building s fresh air and dehumidification requirements to address latent heat loads, resulting in increased operating energy savings. 2. Architects, engineers and other specifiers note the following from experience - Radiant cooling is suitable for most commercial, industrial and institutional applications with careful engineering design of total HVAC solution - Radiant cooling is not practical for most residential applications due mainly to humidity control and cost issues 3. Scenarios where radiant cooling is most advantageous: - Buildings already being designed d with radiant heating systems - High performance buildings where lower heating and cooling loads can be largely accommodated by radiant capacities - Atriums with large glass exposures; counter solar gains directly with cooled floor - Buildings where peak electrical rates are favorable toward thermal storage 27-Mar-15 Page 83 LEARNING OBJECTIVES OF THIS COURSE SUMMARY BY NOW, PARTICIPANTS SHOULD BE ABLE TO: 1. Explain the principles of radiant cooling systems and factors affecting thermal comfort 2. Describe the four basic installation types for radiant cooling systems 3. Discuss how a radiant cooling system is combined with air handling equipment to make a hybrid radiant cooling HVAC system which can address the concern of condensation 4. Introduce control options for a radiant cooling system 5. List the factors that affect output capacity of a hybrid radiant cooling system 6. Summarize the advantages of a hybrid cooling HVAC system 7. Refer to published case studies 27-Mar-15 Page 84 42
RADIANT COOLING SYSTEMS THANK YOU FOR YOUR TIME! www.rehau.com Construction Automotive Industry 43