j366 thermally active structures for green buildings

Syska Hennessy Group

J366

THERMALLY ACTIVE STRUCTURES FOR GREEN BUILDINGS TASGB2015

Daniel H. Nall, PE, FAIA, FASHRAE, LEED Fellow, BEMP, HPDP Date

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Course ID: 0920005379

THERMALLY ACTIVE

STRUCTURES FOR GREEN

BUILDINGS

By ASHRAE

Approved for:

1 General CE hours

0 LEED-specific hours

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permission of the speaker is prohibited.

Syska Hennessy Group

©Syska Hennessy Group 2015

Copyright Materials

Thermally active structure is an evolving strategy that has become a popular system in green buildings. Originally implemented for heating only, as radiant heating floors, this strategy has, over the past 20 years been implemented also as a cooling strategy. The addition of cooling capability adds a number of design constraints and potential operational problems to the successful implementation of the system. This presentation explores the many design, construction and operational issues of thermally active heating and cooling structures. Issues addressed include • Most effective applications of the technology • Design tools • Case studies of successful implementations • Design issues • Construction issues • Constraints and limitations • How-to tips

Course Description

Learning Objectives

1. Identify projects that might be appropriate for thermally active structures and which

might not be appropriate.

2. Recognize design issues for this technology and design tools that can help identify

and overcome these issues.

3. Recognize construction issues for this technology and learn how to avoid them.

4. Understand how the technology is implemented in different types of buildings

based upon presentation of successful case studies.

At the end of the this course, participants will be able to:

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THERMALLY ACTIVE STRUCTURES FOR GREEN BUILDINGS

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• Reduction of ductwork and air handling unit size to meet space

loads

• Incorporation of the thermal mass of the structure into the

driving force of the conditioning system

• Improved human comfort through MRT control

• Removal of solar heat gain directly from mass without additional

air flow

• Separating space temperature control from humidity control

• Reduced heat transport energy using water compared with air

• Reduction in energy expended for conditioning areas where

people aren’t

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WHY RADIANT HEATING/COOLING

• Controlling the Temperature of the Building Structural Mass

instead of the Air

• Dedicated Ventilation/Dehumidification System

• Polyethylene Tubing Imbedded in Slab Circulates Hot or Cool Water to Alter Slab Temperature

• Direct Removal of Absorbed Solar Heat gain from Floor Slab

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RADIANT HEATING/COOLING Sunspace Conditioning

• Ventilation

• Dehumidification

• Changeover from Heating to Cooling

• Condensation Avoidance

• Capacity Control

• Construction

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RADIANT HEATING/COOLING ISSUES…

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RADIANT HEATING FLOOR SCHEMATICS

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DARTMOUTH MCLAUGHLIN TUBING INSTALLATION

• Two Dimensional Floor Heat Transfer

• Shortwave Radiant Fluxes on Floor

• Room Thermal Stratification

• Radiant Coupling between Room Surfaces

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RADIANT HEATING/COOLING DESIGN TOOLS…

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MARIA’S RADIANT FLOOR MODELLER

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COMPUTATIONAL FLUID DYNAMICS

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ST. MEINRAD ARCHABBEY CHURCH

• Built circa 1900, Gothic church construction

• 75 foot high nave, 30 ft. high aisles

• 12,000 square foot floor plate

• 500 persons for holy day services

• Daily usage at low occupancy

• Groin vault roofs and bearing wall construction precluded

overhead air

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• Radiant heating/cooling floor

• Perimeter displacement ventilation

• Floor temperature control from wall sensor

• VAV air control by space air sensor

• Large displacement diffusers surround entries

• Return air bypass air handling unit for dehumidification and

leaving temperature

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ST. MEINRAD ARCHABBEY CHURCH DESIGN

APPROACH

Existing Heating Scheme

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ST. MEINRAD CHURCH

Computational

Fluid Dynamics Images:

Cooling and Heating

with Radiant Floor

Displacement,

No Radiant

Floor; Cooling

Displacement,

Radiant Floor;

Cooling

Radiant

Floor;

Heating

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2nd Generation CFD Finite

volume modeling

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Supply and Return Hydronic Manifolds for Radiant Floor

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Radiant Floor Piping on Insulation

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Displacement Diffusers in fascia of benches

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At Crossing Looking

Toward Apse

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Nave looking Toward Entry

• Should have used CO2 sensors for demand controlled

ventilation

• Maximum velocity through displacement diffusers

• Fan operation during chiller plant shut-down season

• Ventilation of enclosed choir carrels

• Facilities manager and monks very pleased with comfort and

operation

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ST. MEINRAD ARCHABBEY CHURCH CAVEATS

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VIRGINIA HAND CALLAWAY DISCOVERY

CENTER

Callaway Gardens, GA

• 34,000 sq. ft. floor area

• Middle Georgia location

• Multi-use program

• Educational component

• Peak crowd of 200 persons

• Large shaded glazed area

• Variable occupancy

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CENTER…

• Conventional ventilation in closed areas

• Radiant heating/cooling floor in circulation areas

• Air flow from closed areas is thru circulation space

• VAV air control by space air sensor

• Demand controlled ventilation with CO2 sensors in return air

• Reverse cycle heat pump with lake heat exchangers

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CALLAWAY DISCOVERY CENTER DESIGN

APPROACH…

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CENTER

Siting at lake’s edge;

exterior sun-shading

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CENTER

Circulation space and entry

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CENTER

Circulation and

Exhibit Spaces

Outside Closed areas

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CENTER

Lake Source Heat

Exchangers for Annual

Cycle Heat Pump

storage

• Attachment of piping with staples to board insulation

• Post-pouring slab cuts and piping integrity

• Controls of radiant floor

• Sizing of lakeside heat exchangers

• Winter lake temperatures and minimum leaving chilled water

temperature

• No floor condensation, good environmental control so far

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CALLAWAY DISCOVERY CENTER CAVEATS…

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HEARST TOWER

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HEARST TOWER

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HEARST HEADQUARTERS

Radiant Heating/Cooling Floor - Displacement Ventilation

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HEARST HEADQUARTERS

Lobby Temperature Sections

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HEAST HEADQUARTERS


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HEARST HEADQUARTERS


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HEARST HEADQUARTERS

Radiant Heating/Cooling Floor – Geometry and CFD Results

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HEARST HEADQUARTERS

Chilled Water Feature

Radiant Floor Tubing

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DARTMOUTH COLLEGE McLaughlin Hall (2006)

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DARTMOUTH COLLEGE McLaughlin Hall (2006)

Radiant Floor CFD Analysis

Geometry

Cooling

Heating

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THE WILLIAM JEFFERSON CLINTON PRESIDENTAL

CENTER

LEED NC 2.1 Silver

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THE WILLIAM JEFFERSON CLINTON PRESIDENTIAL

CENTER

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CENTER

Computational Fluid

Dynamics Studies of

Museum Area -

Temperature, Flow and

Ventilative Effectiveness

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CENTER

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SYRCAUSE UNIVERSITY SCHOOL OF

MANAGEMENT

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SYRACUSE UNIVERSITY SCHOOL OF

MANAGEMENT

• Radiant Floor Tubing

Radiant Floor Tubing

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GAYLORD NATIONAL HARBOR HOTEL

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GAYLORD NATIONAL HABOR HOTEL

CFD Analyses for Cooling

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SAP AMERICAS HEADQUARTERS EXPANSION

LEED NC 2.2 Platinum

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Thermally Active Lobby Floor

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Atrium Ground Coupled Thermally Active Slab System

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Thermally Active Slab in Construction

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PAVILION AT BROOKFIELD PLACE

Principles of Design

• The system does not provide ventilation or dehumidification – A conditioned air system is required to provide these functions

• The system is a low temperature difference, large active area conditioning system, so highly accurate temperature control is not required for comfort maintenance

• A chilled floor enhances stratification, providing greater comfort where the people are – A heated floor minimizes stratification, also minimizing overheating high in

the space

• Chilled floors are most effective at removing solar heat gain as it is absorbed into the slab, reducing air flow necessary for cooling

• System does not require quick response because direct control of building mass in the space precludes rapid change of load magnitude

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RADIANT/HEATING COOLING GUIDELINES

Principles of Design

• Floor is controlled to be the right temperature for a given space condition – Floor is controlled by resetting set-point temperature

• Heating cooling changeover should be a rare event and controlled to avoid driving the floor from one mode to another

• Variable flow control (multi-zone pulsed constant flow) with constant inlet temperature (in a mode) allows inexpensive individual zone control – Constant flow with variable inlet temperature requires a pump for each

zone

• Time constant of floor temperature reset stimulus should be longer than that of the floor itself

• Floor capacity is dependent on absorbed solar radiation – Solar radiation absorbed by non-active surfaces must be removed by

alternate means

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Design Process

• Calculate cooling loads with both radiant and convective components and locate them within the room volume

• Explicitly calculate solar heat gain patches on floor for size, location and intensity – Separate solar heat gain absorbed by windows from that transmitted

through windows

• Use two dimensional heat transfer calculations to determine temperature of solar irradiated radiant floor – Incorporate floor finish and topping slab conductances in calculation

– Calculate for range of flow rates and inlet temperatures

• Use CFD analysis with calculated radiant and convective internal heat gains and solar heat gain patches calculated above

• Configure radiant loop zoning to match pattern of solar heat gain

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Radiant System Layout 1

• Configure isolated radiant loop with heating and cooling heat

exchangers to minimize fouling in the tubing

• Magnitude of space and use will determine if flow modulation is applied to individual zone loops or to manifolds for flow

temperature control

• Establish minimum zoning based upon use and solar exposure

• Layout tubing in double serpentine pattern to minimize temperature differences across the floor

• Locate manifolds to minimize home run distance to controlled

floor area

• Layout loops based on 300 ft. roll size

– Base loop zoning size on centerline tubing spacing and homerun length

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Radiant System Layout 2

• Locate floor temperature sensors to be representative of zone

• Use separate heat exchangers for heating and cooling or single heat exchanger with four-pipe change-over valving

• Control temperature of heat exchanger secondary outlet temperature by modulating primary flow volume

• Allow variable flow in radiant loop with variable speed circulating pump or pressure controlled bypass.

• Compare cooling diversity flow requirements with non-diverse heating flow requirements to size pumps and heat exchangers

– Max heating may take on 1.0-1.5 gpm per loop

– Max cooling takes up to 2.0 gpm per loop, but is diverse because of solar patches

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Measures to Avoid Condensation

• Supply generous amounts of dehumidified air for ventilation

• Keep chilled water supply temperature well above design

interior dew-point temperature

• Design exterior wall to minimize infiltration

• Specially treat entrances and exits with dehumidified air

• Delete radiant piping from area immediately surrounding

entrances

• Use chilled water for interior water features

• Shut down circulating pump upon detection of high interior

dew point temperature

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Measures to Improve Comfort

• Outside air system configured to provide adequate ventilation,

well distributed around the space

• Limit temperature range of floor between 68 DegF and 80 DegF

• Limit temperature range of displacement ventilation between

66 DegF and 85 DegF

• Limit velocity through displacement diffusers to 60 fpm

• Zone floor to accommodate solar shadowing patterns

• Control floor to offset impact of cold surfaces on mean radiant

temperature

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Construction and Coordination Caveats

• Insure tops of manifolds are located higher than floor tubing to

facilitate air elimination

• Monitor ferrous metal in radiant loop

– Verify that tubing has oxygen barrier

– If not, verify that pumps, heat exchanger, air eliminator, valves, strainers, etc. are all completely non-ferrous

– Non-ferrous air eliminators are limited in size

– Consider using two in parallel

– Beware ferrous nipples on expansion tanks

• Beware topping slab and finish substitutions

– Insure 120 lb./cf concrete to insure good heat transfer

– Monitor carpet or flooring submittals

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• Topping slab detailing under some floor finishes, especially terrazzo should be coordinated with the architect and structural engineers – Glass fiber reinforcement in the topping slab is especially effective in limiting

cracking

• Thermally active floors demonstrate markedly lower temperature variation than passive floors – Active floors vary between 68 DegF and 80 DegF

– Passive floors can go over 100 DegF in bright sunlight and under 65 DegF on cold days

• Explicitly locate tubing on design documents – Tie down tubing to make sure it stays where it is initially placed

– Use nylon wire tires to wire mesh or barbed staples into slab insulation

• Preferred sub-topping slab insulation is 100 psi polystyrene foam, available only in 2”depths

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• Plan for Partition construction and relocation if likely to occur

− Partition bottom channels will likely be secured to concrete slab with shot fasteners

− Fasteners can penetrate tubing imbedded in topping slab

− If partitions will not move, plan tubing routing to enter rooms through door rather than crossing walls

• If partitions may be moved or installed later, consider increasing depth of topping slab, or specifying short fasteners used in conjunction with mastic to secure bottom channel to slab

• Coordinate location of slab sensors and conduit connected to them with radiant tubing layout

• DO NOT CROSS EXPANSION JOINTS WITH PEX TUBING

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St. Meinrad Archabbey Church William Jefferson Clinton Library Architect – Woollen Molzan Partners, Indianapolis, IN Architect – Polshek Partners., New York, NY Building Services Engineers – Building Services Engineers – Roger Preston + Partners, Atlanta Flack + Kurtz, NYC Virginia Hand Callaway Center Cromwell Architects, Engineers, Little Rock, AR Architect - Robert Lamb Hart, NYC Pier 1 Building Services Engineers – Architect – SMWM Architects, San

Roger Preston + Partners, Atlanta and Francisco, CA Creative Engineering Design, Atlanta Building Services Engineers – IBT Headquarters Flack + Kurtz, San Francisco, CA Architect – Murphy Jahn, Chicago, IL Dartmouth College McLaughlin Residences Building Services Engineers – Architect – Bruner Cott, Boston, MA, and Flack + Kurtz, San Francisco, CA Moore, Ruble, Yudell, Architects, Santa Monica,CA Hearst Headquarters Building Services Engineers –Flack + Kurtz, NYC Architect – Foster and Partners, London, UK Gaylord National Harbor Hotel Building Services Engineers Architect - Gensler Flack + Kurtz, NYC Building Services Engineer – WSP Flack + Kurtz, NYC

Syracuse University School of Management SAP Corporate Headquarters Architect – F X Fowle, NYC Architect – F X Fowle, NYC Building Services Engineers - Flack + Kurtz, NYC Building Services Engineers - Flack + Kurtz, NYC

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ACKNOWLEDGEMENTS

References:

Nall, D. H., “Lessons Learned in the Design, Construction and

Operation of Thermally Active Floors, Part 1: Design of the Systems”, ASHRAE Journal, Atlanta, GA, January 2013


Operation of Thermally Active Floors, Part 2: Design of the

Systems”, ASHRAE Journal, Atlanta, GA, February 2013.


Operation of Thermally Active Floors, Part 3: Making it Work”,

ASHRAE Journal, Atlanta, GA, March 2013.

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Daniel H. Nall, FAIA, PE, FASHRAE, LEED Fellow, HBDP, BEMP

[email protected]

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j366 thermally active structures for green buildings

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