ASHRAE Journal - March 2013 - 54

© Jeff Goldberg/Esto

Part Three: Making it Work

Thermally Active Floors
By Daniel H. Nall, P.E., FAIA, Member ASHRAE

A

fter the physical design of a radiant slab system has been completed, the project requires the appropriate control strategies and

the use of tested construction techniques to be successful. Control strategies
for radiant slab systems differ significantly from those of standard HVAC
components in that they must not only respond to current space conditions
but also recognize the thermal lag of the components they are controlling. The control sequences must avoid either “driving” the slab or causing
the slab system to conflict with the ventilation/dehumidification system.

Radiant Heating and Cooling
Control Sequences
The entire operating range of temperature setpoints for the radiant floor
is limited by condensation and comfort considerations to a minimum of
68°F (20°C) and a maximum of 84°F
54

ASHRAE Journal

(28.9°C). Floors colder than the minimum easily can result in temperature
contact discomfort or condensation.
Temperatures higher than the maximum
also result in contact discomfort. Control is not necessarily precise to tenths
of a degree, but must logically track
ashrae.org

the thermal conditioning requirements
of the space. Deviation of a setpoint by
a degree or two may result in a similar
space temperature deviation, but that
range is well within the operating behavior of a conventional HVAC system.
The fact that the thermally active floor
influences comfort both by moderating
the air temperature and the mean radiant temperature makes the system very
forgiving for minor temperature excursions.1
In general, the floor control system is
handled by a local panel and individual
slab temperatures are not reported back
to the building management system
(BMS). The BMS typically will recalculate floor temperature setpoints and
About the Author
Daniel H. Nall, P.E., FAIA, is senior vice president
at Thornton Tomasetti Group in New York. He is an
ASHRAE certified Building Energy Modeling Professional and High-Performance Building Design
Professional.

March 2013



ASHRAE Journal - March 2013

Table of Contents for the Digital Edition of ASHRAE Journal - March 2013

ASHRAE Journal - March 2013
Contents
Commentary
Show Coverage
Meetings and Shows
Feature Articles
2013 ASHRAE Technology Awards
Commissioning Existing Airside Economizer Systems
How Indoor Environment Affects Performance
Thermally Active Floors: Part 3: Making it Work
Technology Award Case Studies:
Data Center Dilemma
Heat Recovery for School
Standing Columns
Data Centers
Refrigeration Applications
Emerging Technologies
IAQ Applications
Engineer's Notebook
Classified Advertising
Advertisers Index
ASHRAE Journal - March 2013 - Intro
ASHRAE Journal - March 2013 - ASHRAE Journal - March 2013
ASHRAE Journal - March 2013 - Cover2
ASHRAE Journal - March 2013 - 1
ASHRAE Journal - March 2013 - 2
ASHRAE Journal - March 2013 - Contents
ASHRAE Journal - March 2013 - Commentary
ASHRAE Journal - March 2013 - 5
ASHRAE Journal - March 2013 - Show Coverage
ASHRAE Journal - March 2013 - 7
ASHRAE Journal - March 2013 - 8
ASHRAE Journal - March 2013 - 9
ASHRAE Journal - March 2013 - 10
ASHRAE Journal - March 2013 - 11
ASHRAE Journal - March 2013 - 12
ASHRAE Journal - March 2013 - 13
ASHRAE Journal - March 2013 - Meetings and Shows
ASHRAE Journal - March 2013 - 15
ASHRAE Journal - March 2013 - 16
ASHRAE Journal - March 2013 - 17
ASHRAE Journal - March 2013 - 2013 ASHRAE Technology Awards
ASHRAE Journal - March 2013 - 19
ASHRAE Journal - March 2013 - 20
ASHRAE Journal - March 2013 - 21
ASHRAE Journal - March 2013 - 22
ASHRAE Journal - March 2013 - 23
ASHRAE Journal - March 2013 - 24
ASHRAE Journal - March 2013 - 25
ASHRAE Journal - March 2013 - 26
ASHRAE Journal - March 2013 - 27
ASHRAE Journal - March 2013 - 28
ASHRAE Journal - March 2013 - 29
ASHRAE Journal - March 2013 - 30
ASHRAE Journal - March 2013 - 31
ASHRAE Journal - March 2013 - 32
ASHRAE Journal - March 2013 - 33
ASHRAE Journal - March 2013 - Commissioning Existing Airside Economizer Systems
ASHRAE Journal - March 2013 - 35
ASHRAE Journal - March 2013 - 36
ASHRAE Journal - March 2013 - 37
ASHRAE Journal - March 2013 - 38
ASHRAE Journal - March 2013 - 39
ASHRAE Journal - March 2013 - 40
ASHRAE Journal - March 2013 - 41
ASHRAE Journal - March 2013 - 42
ASHRAE Journal - March 2013 - 43
ASHRAE Journal - March 2013 - 44
ASHRAE Journal - March 2013 - 45
ASHRAE Journal - March 2013 - How Indoor Environment Affects Performance
ASHRAE Journal - March 2013 - 47
ASHRAE Journal - March 2013 - 48
ASHRAE Journal - March 2013 - 49
ASHRAE Journal - March 2013 - 50
ASHRAE Journal - March 2013 - 51
ASHRAE Journal - March 2013 - 52
ASHRAE Journal - March 2013 - 53
ASHRAE Journal - March 2013 - Thermally Active Floors: Part 3: Making it Work
ASHRAE Journal - March 2013 - 55
ASHRAE Journal - March 2013 - 56
ASHRAE Journal - March 2013 - 57
ASHRAE Journal - March 2013 - 58
ASHRAE Journal - March 2013 - 59
ASHRAE Journal - March 2013 - 60
ASHRAE Journal - March 2013 - 61
ASHRAE Journal - March 2013 - Data Center Dilemma
ASHRAE Journal - March 2013 - 63
ASHRAE Journal - March 2013 - 64
ASHRAE Journal - March 2013 - 65
ASHRAE Journal - March 2013 - 66
ASHRAE Journal - March 2013 - 67
ASHRAE Journal - March 2013 - Heat Recovery for School
ASHRAE Journal - March 2013 - 69
ASHRAE Journal - March 2013 - 70
ASHRAE Journal - March 2013 - 71
ASHRAE Journal - March 2013 - 72
ASHRAE Journal - March 2013 - 73
ASHRAE Journal - March 2013 - Data Centers
ASHRAE Journal - March 2013 - 75
ASHRAE Journal - March 2013 - 76
ASHRAE Journal - March 2013 - 77
ASHRAE Journal - March 2013 - 78
ASHRAE Journal - March 2013 - Refrigeration Applications
ASHRAE Journal - March 2013 - Emerging Technologies
ASHRAE Journal - March 2013 - 81
ASHRAE Journal - March 2013 - 82
ASHRAE Journal - March 2013 - 83
ASHRAE Journal - March 2013 - IAQ Applications
ASHRAE Journal - March 2013 - 85
ASHRAE Journal - March 2013 - Engineer's Notebook
ASHRAE Journal - March 2013 - 87
ASHRAE Journal - March 2013 - 88
ASHRAE Journal - March 2013 - 89
ASHRAE Journal - March 2013 - 90
ASHRAE Journal - March 2013 - 91
ASHRAE Journal - March 2013 - 92
ASHRAE Journal - March 2013 - 93
ASHRAE Journal - March 2013 - 94
ASHRAE Journal - March 2013 - Classified Advertising
ASHRAE Journal - March 2013 - Advertisers Index
ASHRAE Journal - March 2013 - Cover3
ASHRAE Journal - March 2013 - Cover4
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