Radiant 101

Casey Swanson & Him Ly

Terms and Definitions

• • • AUST- Average Uncontrolled Surface Temp.

― ― Area-weighted of all interior surfaces Excluding cooled panel MRT- Mean Radiant Temp.

― (AUST+cooled panel)/2 Operative Temp.

― ― ― ― Temp. an occupant feels (MRT + room temp)/2 Winter (68F – 75F) Summer (73F – 79F) 01 May 2020 ©Uponor 2

Calculating AUST-MRT-OT

Room Temp. = 77F AUST = 78.2F

MRT = 72.1F

Operative Temp. = 74.6F

01 May 2020 ©Uponor Room Temp. = 68F AUST = 66.4F

MRT = 75.7F

Operative Temp. = 71.9F

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01 May 2020

National Building Code Requirements Refers to ASHRAE 55 on thermal comfort:

“produce thermal environmental conditions acceptable to a majority /80% of the occupants within the space.” • • • • • • Factors: Metabolic rate / activity Clothing Air Temperature Air Speed Humidity

Radiant Temperature

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Thermal Comfort…ASHRAE Standard 55

Floor Surface Temperature ,  F 80 40 30 10 4 6 66  F 84  F 41 50 59 Ref. : ASHRAE Standard 55-2004 01 May 2020 68

Design Range

77 86 95 104 ©Uponor 5

Thermal Comfort….ASHRAE Standard 55

Radiant Temperature Asymmetry, °F 80 60 40 20 10 6 4 0 9 18 Ref. : ASHRAE Standard 55-2004

Design Range

27 36 45 54 01 May 2020 ©Uponor 63 6

Thermal Comfort…ASHRAE Standard 55

80 Air Temperature Difference Between Head and Feet, °F 40 10

Design

6 6 2 4 0

Range

4 0 4 7 7 01 May 2020 ©Uponor 11 11 14 14 7

01 May 2020

Common HVAC concerns that a radiant system can solve

• • • • • • • • • • • • Inconsistent temperatures Circulation of dust and allergens High (O&M) operating and maintenance costs Aesthetics Space considerations Building heights Large glazing areas Dry air Noise Window condensation Odor circulation Damp lower levels ©Uponor 8

Radiant Overview

01 May 2020 • • A hydronic system consists of an installation of embedded tubes or surface mounted panels Radiant heating and cooling systems use the structure and surfaces of an area to transfer energy ― ― In radiant heating systems, the energy moves away from the heated surface towards the cooler area In radiant cooling systems, the energy moves towards the cooled surface from the warmer area ©Uponor 9

T oc T ih Convection Radiation Convection T sc & D p T ic T oh Ref. : ASHRAE Standard 55-2004 01 May 2020 ©Uponor 10

01 May 2020

Radiant –Efficiencies

 Water has roughly 3,500 times the energy transport capacity of air  With radiant space conditioning systems, the ventilation function is separate – The volume of air moved and component size can be up to 5 times less – Fan power and duct size is much smaller  The cost of a radiant system is comparable to traditional variable-air-volume (VAV) system *Analysis and statistics provided by the Lawrence Berkeley National Laboratory (LBNL) ©Uponor 11

The Hearst Tower, New York City 01 May 2020 ©Uponor Radiant System Economics • LBNL modeled office buildings in 9 US cities comparing radiant with ventilation and all other forced air VAV systems  Findings: – Radiant cooling, on average, saves 30% overall energy for cooling and 27% on demand – Energy savings of • • 17% in cold, moist climates 42% in warmer, dry climates 12

System Types, Strategies and Design Considerations

Types of Systems

• There are two primary types of radiant systems ― ― High Mass: incorporates the mass of the building with tubing embedded within the structure Low Mass: uses surface mounted ceiling/wall panels 01 May 2020 ©Uponor 14 Source: LBNL

High Mass Systems (cooling)

• Draws the energy from the surface toward the embedded tubing in the slab or wall ― Chilled water is circulated through the tubing • Similar installation to radiant floor heating systems ― ― Very common to incorporate a hybrid system that cools and heats based on demand Slower response times and more residual energy

Low Mass Systems

• Low mass radiant cooling systems are based on the Fanger Concept ― ― They react fairly quickly to temperature change Have little or no residual energy ― Must be used as an active system • Work well for retrofit applications 01 May 2020 ©Uponor 15

Types of Loads

• Sensible load ― Direct solar load • Latent load ― Can not address ― Mechanical system is required The Akron Art Museum, Ohio 01 May 2020 ©Uponor 16

57.7%

1.5% - Pumps Source: LBNL A typical office building in Los Angeles as modeled by LBNL 01 May 2020

Sensible Load

• ― ― ― ― The external loads account for only 42% of the thermal cooling peak 28% of the internal gains were produced by lighting 13% by air transport 12% by people 5% by equipment • • • This is the dry bulb heat or heat gain in the space Radiant cooled systems can handle a significant portion of this load Absorption is dependant upon a decreased surface temperature ©Uponor 17

Latent Load

• This is the energy that is contained in the moisture in the air, the wet bulb load or gain • A phase change is required to address this load • Radiant cooling systems can not address this load ― The ventilation system must: ― Address the latent load ― ― Balance of the sensible load if any exists Control the level of humidity within the air system  Meet the requirements of the Indoor Air Quality Standards for fresh air • Dew point is determined by the relative humidity and temperature within the space • In most cases an Rh of 50% or lower will be sufficient to prevent condensation on the cooling surface • Humidity level in the building must be controlled through the ventilation system 01 May 2020 ©Uponor 18

Direct Solar Load

• Short wave radiation (sun, electrical lights) ― Energy transferred independent of room temperature and surrounding surfaces • Amount of energy absorbed depends on absorbtivity of material • In spaces with high solar gain 25 – 32 Btu/h/ft 2 • If Solar load exceeds cooling capacity ― ― Increases the floor surface temperature Emits long wave radiation back into space ` The Los Angels Federal Building, California 01 May 2020 ©Uponor 19

Direct Solar Load

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Surfaces

Carpet dark Black metallic surfaces (asphalt, carbon, slate, paper..) Tile or plaster, white or light cream Red tile, stone or concrete, dark paints (red, brown, green, etc.) White painted surfaces Table: Absorptances for Solar Radiation, Source ASHRAE Fundamentals, 1996

Absorptance

for Solar Radiation

______ 0.85 - .98

0.30 ─ 0.50

0.65 ─ 0.80

0.23 ─ 0.49

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Mode Total Heat Exchange Coefficient Heating Surface Btu/h · ft 2 · ° F W/m 2 · º K Cooling Btu/h · ft 2 · ° F W/m 2 · º K Floor 1.9

11 1.2

7 Wall Ceiling 1.4

1.2

8 7 1.4

1.9

8 11 01 May 2020 ©Uponor 21

q(tot) = q(con) + ql,(rad) + qs,(rad) q(tot) = h(tot) x (to – ts) + qs,(rad)

q(tot) – total space heat flux (Btu/sq ft) q(con) – convective heat flux (Btu/sq ft) ql(rad) – long wave radiative heat flux (Btu/sq ft) qs(rad) – short wave radiative heat flux (Btu/sq ft) h(tot) – heat exchange coefficient to – operative temperature ts – floor surface temperature 01 May 2020 ©Uponor 22

Design Considerations

• Radiant energy to condition a space is only a few degrees different from the temperature of the conditioned space • The supply water temperature to the floor needs to

be 2 degrees above the dew point

• In highly humid areas ― Buildings need to be moderately well air-sealed ― Ventilation air would need some dehumidification • Cross section of the cooling surface needs to be big enough to deliver the cooling at a small water temperature differential 01 May 2020 ©Uponor 24

Design Considerations

• Keep the total loop lengths within standard coil lengths of 300 or 1,000 feet ― Two or three loops per 1,000 foot coil ― ― ― One loop per 300 foot coil Work out a straight forward, standardized basis of design Keep things consistent and repeatable ― 5/8” hePEX™ plus tubing at 6 or 9 inches on center • Always design for the best possible system performance • Remember, radiant cooling enhances, it is not a stand alone system • Allows the downsizing of HVAC equipment and ductwork • Design differential temperatures ― ― 5 - 8 o F for cooling 10 - 20 o F for heating 01 May 2020 ©Uponor 25

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System Strategies

• Active systems are systems that run during the occupied time ― They provide a nearly steady set-point ― Typically cost more to operate • Passive systems also called activated core or activated concrete systems They operate most often during the unoccupied time ― Occupants may experience a slight drift in set point temperature across the day ― Take advantage of off-peak energy rates to lower operating costs ©Uponor 26

The Water + Life Building, Southern California 01 May 2020 ©Uponor Common Design Results • Most radiant cooling designs fall within the following parameters  12 to 14 Btu/h/ft 2 of sensible cooling  Up to 32 Btu/h/ft 2 of solar absorption  66 o F minimum floor surface temperature  76 o F to 78 o F room set point temperature  55 o F thru 58 o F supply fluid temperature 27

The Copenhagen Opera House 01 May 2020 ©Uponor Common Radiant Applications • • • • • • • • • • Museums Institutional, educational and recreational facilities High-rise hotels / offices Manufacturing & retail spaces Hospitals/health care and assisted living facilities Dormitories, barracks & prisons Churches Wineries Airports Residential 28

Featured Project

01 May 2020 ©Uponor

Bangkok International Airport

• Outdoor Temperature at 77-95°F and year round high RH relative humidity • The annual horizontal solar radiation total is more than 1,500 kWh/m²a, results in a solar radiation of 1,000 W/m² • 45,708 m 2 (492,000 ft 2 ) radiant cooling • Humidity is conditioned in the airport to 50-60% • Ventilation is four air changes/hour 30

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Bangkok International Airport

• Radiant Cooling Supply Water Temp is 13°C (55°F) • Return Water Temperature of 19°C (66°F) • Cooling capacity of 80 W/m² (25.5 btu/ft²) • 40% of the total load Airport Load is handled by the radiant cooling • Total cooling load energy savings = 30.5 % 31

Bangkok International Airport

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01 May 2020

Bangkok International Airport Temperature Distribution

55 o C (131 o F) 21 o C (70 o F) ©Uponor 33

Bangkok International Airport

Comparison of cooling loads for the entire airport Original Concept Optimized Concept Total Load: 275 GWH/a 739 kWh/m 2 a 01 May 2020 ©Uponor Total Load: 191 GWH/a 513 kWh/m 2 a 34

Design Services •Assist in radiant systems design

― Design Parameters ― Heating/cooling sensible loads ― Solar gain ― Space setpoint and relative humidity ― Construction details

•Radiant schedule •CAD loop layout •Bill of materials

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Thank you

Questions?