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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
f 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
- [email protected]
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
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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
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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
l t att least
l
t 45% off th
their
i h
heatt emission
i 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.
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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
bl ttargett might
i ht b
be lless th
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
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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
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
Floor Covering
PEX Pipe
WARMED CONCRETE SLAB
Floor Covering
PEX Pipe
COOLED CONCRETE SLAB
PEX Pipe
COOLED CONCRETE SLAB
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
O
t turns
t
down
d
the
th air
i setpoint,
t i t trying
t i tto
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
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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
i
important
t t to
t consider
id when
h specifying
if i a radiant
di t system
t
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.
ii.
iii.
i
iv.
Radiant Floor Heating and Cooling (FHC)
Thermally Activated Building Slab (TABS)
Radiant Ceiling Heating and Cooling (CHC)
R di
Radiant
W
Wallll H
Heating
i and
dC
Cooling
li (WHC)
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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
C
a heated/cooled
/
ffloor for
f 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
C
ah
heated/cooled
d/
l d floor
fl
and
d ceiling,
ili
to
condition the spaces above and below
- Common in multi-story buildings
- Bi-directional heating/cooling
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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
S f
can absorb radiant heat from
f
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
P
Panels
l can b
be strategically
i ll llocated
d above
b
warm occupied
i d areas
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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
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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:
p
thermal comfort
- Optimum
- 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:
p
thermal comfort
- Optimum
- Energy savings
- Radiant is ideal for hanger space with
high ceilings and high solar gain
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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 17story 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
Example:
Pond Residence
at York University
in Toronto, ON
27-Mar-15 Page 28
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.
ii.
iii.
i
iv.
Radiant Floor Heating and Cooling (FHC)
Thermally Activated Building Slab (TABS)
Radiant Ceiling Heating and Cooling (CHC)
R di
Radiant
W
Wallll H
Heating
i and
dC
Cooling
li (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
d ffrom occupants
t within
ithi a building
b ildi (l
(latent
t t cooling)
li )
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 R
3.
Relative
l ti H
Humidity
idit
- 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
h ti
heating,
th
they can easily
il ttake
k advantage
d
t
off
the cooling potential in the existing PEX
network
- Addition of radiant cooling minimally
increases the initial cost and has many
advantages during operation
R di t cooling
Radiant
li
is
i used
d in
i “Hot/Humid”
“H t/H id”
climatic regions
- Proper controls are available to avoid
uncomfortable and dangerous condensation
Sampling of radiant cooling projects in NA
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 ft2 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 ft2 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 ft2 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
f off 5/8”
/ ” PEX tubing @ 6 inch spacing ((in 10 circuits)) ffor 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 ft2 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 ft2 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.
f
- 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 ft2 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
bi d in
i one unit
it
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
design,
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·ft2)
Heat transfer coefficient (HTC)
Average surface temperature
Air temperature

q  HTC TSURFACE  TAIR
Floor

Heating
11 W/m2K
1.9 Btu/(h·ft² F)
Cooling
7
W/m2K
1.2 Btu/(h·ft² F)
- ~ 60% greater potential to absorb heat from
ceiling cooling system vs
vs. floor cooling
system based solely on HTC
Heating
6 W/m2K
1.1 Btu/(h·ft² F)
- Reverse for delivering heat in heating mode
Cooling
11 W/m2K
1.9 Btu/(h·ft² F)
Ceiling
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(ft2)
-
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(ft2) 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(ft2)
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 1.9
1 9 = 19 BTU/h
BTU/hr(ft
(ft2)
Th
The potential
t ti l capacity
it off a 66ºF cooled
l d ceiling
ili
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:
Floor
TSURFACE
OUTPUT
Heating
78-84°F
19-31 Btu/(h·ft2)
Cooling
66-70°F
8-12 Btu/(h·ft2)
Heating
g
78-84°F
11-17 Btu/(h·ft
( 2)
66-70°F
Btu/(h·ft2)
Ceiling
Cooling
15-24
Ceilings are not limited by the ASHRAE 55
floor limit; ceiling values are used only to
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
2.
Th math
th for
f calculating
l l ti capacities
iti is
i understood
d t d and
d is
i sometimes
ti
easily
il applied
li d
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
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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 di
d outdoor
d
air
i system (DOAS)
with energy recovery wheel
 Cooling tower
 Ceiling fans
Advantages
- Smaller
S ll mechanical
h i l equipment
i
t ffootprint
t i 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
t i bl technologies
t h l i
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
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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
B ildi
already
l d b
being
i d
designed
i
d with
ith radiant
di t h
heating
ti systems
t
- 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