AIA Chicago Presentation

Building Envelope Performance –

Quantifying and Mitigating the Impact of

Thermal Bridging

November 18, 2014

2

Presentation Overview

Thermal Bridging 101

Data – Where & How

Findings & Applications

1

2

3

Thermal Bridging 101

• Highly conductive material that by-passes insulation layer

• Areas of high heat transfer

• Can greatly affect the thermal performance of assemblies

Effective Thermal Resistance

What is a Thermal Bridge?

Existing Sources of Information

5

R-8.5 R-13.5

Parallel Path Heat flow

6

Utotal

• Area weighted average of un-insulated assemblies

• Does not tell the whole story

• Parallel path doesn’t tell the whole story

• Many thermal bridges don’t abide by “areas” ie: shelf

angle

• Lateral heat flow can greatly affect the thermal

performance of assemblies

Thermal Bridging

Addressing Lateral Heat Flow

8

Lateral Heat Flow

9

𝑅 ≅ 11.5

𝑅 ≅ 9.8

Parallel Path

With Lateral

Heat Flow

𝑅20𝑊𝑎𝑙𝑙?

Overall Heat Loss

Additional heat loss

due to the slab

oQQ slabQ

Overall Heat Loss

LQslab /

The linear transmittance

represents the additional heat

flow because of the slab, but

with area set to zero

The Conceptual Leap

Types of Transmittances

Point

Linear

Clear Field

oUpsi chi

Overall Heat Loss

Total Heat

Loss

LAUTQ o )(/

Heat Loss

Due To

Anomalies

Heat Loss

Due To

Clear Field

+=

Data – Where & How?

ASHRAE 1365-RP 2011

Goals and Objectives of the Project

15

• Calculate thermal performance data for

common building envelope details for

mid- and high-rise construction

• Develop procedures and a catalogue

that will allow designers quick and

straightforward access to information

ASHRAE 1365-RP

Calibrated 3D Modeling Software

16

• Heat transfer software by Siemens

PLM Software, FEMAP & Nx

• Model and techniques calibrated

and validated against measured

and analytical solutions

• ISO Standards for glazing

• Guarded hot box test

measurements, 29 in total

ASHRAE 1365-RP

Details Catalogue

17

• 40 building assemblies and

details

• Focus on opaque assemblies,

but also includes some glazing

transitions

• Details not already addressed in

ASHRAE publications

• Highest priority on details with

thermal bridges in 3D

Providing Results

ASHRAE Data Sheets

18

ASHRAE Data Sheets

19

Providing Results

outsideinside

outsidesurface

iTT

TTT

ASHRAE Data Sheets

20

outsideoutsideinsideisurface TTTTT )(

Providing Results

21

BETBG

Building Envelope Thermal Bridging GuideAnalysis, Applications, & Insights

Funding Partners

Private Clients

• Structural thermal breaks

manufacturer

• EIFS

• Insulated Metal Panel

• Cladding attachments

• Vacuum insulated panels (VIP)

in insulated glazed units for

glazing spandrel sections

23

More Data & Connect the Dots

Whole Building

Energy Analysis

Construction Cost Analysis

Thermal Performance

Cost Benefit Analysis

24

BETBG Layout

• Introduction

• Part 1 Building Envelope Thermal Analysis

(BETA) Guide

• Part 2 Energy and Cost Analysis

• Part 3 Significance, Insights, and Next Steps

• Appendix A Material Data Catalogue

• Appendix B Thermal Data Catalogue

• Appendix C Energy Modeling Analysis and Results

• Appendix D Construction Costs

• Appendix E Cost Benefit Analysis

Organization of Details

25

Appendix A & B

26

Visual Summary

27

www.bchydro.com/construction

28

Accounting for Details

• Standard 90.1-2004 Prescriptive Requirements for Zone 5

• Mass Wall, U-0.090 or R-11.4 ci

• Steel-Framed Wall, U-0.064 or R-13 + R-7.5 ci

Mass wall with R-11 insulation inboard; U-0.074

Steel stud with R-10 exterior insulation and horizontal girts at 24”o.c and R-12 in the stud

cavity; U-0.061

How much extra heat loss can details add?

29

Accounting for Details

Typical Building

30

• 10 floors

• 20% glazing

• Standard details

Mass Concrete Wall

o Exposed concrete slab

o Un-insulated concrete parapet

o Punched window in concrete

opening

o Steel-Framed Wall

o Exterior insulated structural steel floor

intersection

o Insulated steel stud parapet

o Punched window in steel stud

opening with perimeter flashing

Accounting for Details

31

Transmittance

Type

Mass Concrete Wall Exterior Insulated Steel Stud

Heat Loss

(BTU/hr oF)% of Total

Heat Loss

(BTU/hr oF) % of Total

Clear Wall 118 52 % 98 67 %

Slab 92 40% 24 17 %

Parapet 9 4% 4 3 %

Window transition 8 4% 19 13 %

Total 227 100 % 145 100 %

Accounting for Details

32

Performance Metric

Mass Concrete Wall Exterior Insulated Steel Stud

ASHRAE

Prescriptive

Requirements

Overall

Performance

ASHRAE Prescriptive

Requirements

Overall

Performance

U

(Btu/hrft2oF)0.09 0.14 0.064 0.091

“Effective” R

(hr ft2 oF/BTU)R-11 R-7 R-15.6 R-11

% Difference 44 % 35%

33

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

R-3.9

R-4.5

R-5.0 R-5.3R-5.2

R-10.2

R-14.3R-16.7

Co

ntr

ibu

tio

n o

f T

her

ma

l P

erfo

rma

nce

of

Wa

ll A

ssem

bly

to

En

erg

y U

se(G

J/m

2o

f F

loo

r

Are

a)

Clear Wall Only Including Poor Details Including Efficient Details

Additional building energy use based on thermal performance of the building wall assembly for

varying amounts of nominal exterior insulation for a mid-rise MURB in Edmonton (overall

assembly thermal resistance in ft2·ºF·h/Btu also given)

U0.26

U0.10

Findings & Applications

Vertical Z-Girts Horizontal Z-Girts Mixed Z-Girts Intermittent Z-Girts

CLADDING ATTACHMENTS

36

Clip Systems

37

Effect of Thermal bridging in 3D

38

ASHRAE 90.1 2010

39

Proprietary Systems Thermal

vs Structural Performance

Slab Edge Interfaces

45

≈ ≈

Concrete Walls

SI (W/m∙K)

IP (BTU/hr∙ftoF)

0.81 0.47

46

Think about it!

An R10 wall would have a transmittance of 0.1

BTU/hr∙ft2oF. One linear foot of this detail is the same

as 4.7 ft2 of R10 wall (or 7.3 ft2 of R15.6 wall)

Slab Edges – Balcony

SI (W/m∙K)

IP (BTU/hr∙ftoF)

0.59 0.34

Slab Edges – Shelf Angle

SI (W/m∙K)

IP (BTU/hr∙ftoF)

0.47 0.27

Slab Edges – Shelf Angle

SI (W/m∙K)

IP (BTU/hr∙ftoF)

0.31 0.18

Slab Edges – Exterior Insulated

SI (W/m∙K)

IP (BTU/hr∙ftoF)

0.16 0.09

50

Slab Edges – Balcony

SI (W/m∙K)

IP (BTU/hr∙ftoF)

0.21 0.12

Thermal break

(image courtesy of Halfen)

Structural thermal break

(image courtesy of Fabreeka)

Structural thermal break

(image courtesy of Schock)

Balcony connection

(image courtesy of Lenton)

Structural Thermal Breaks

• Glazing area is major determinant of overall heat loss

• U value of opaque spandrel closer to “glazing” values

• Improvements can and are being made…

Curtain Wall

57

Glazing Spandrel Areas

Curtain Wall Comparison

58

No Spray Foam Spray Foam

Glazing Spandrel Areas

3.4

4.24.8 5.0

7.4

8.2

8.8 9.1

0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30

Sp

an

dre

l S

ec

tio

n R

Va

lue

Back Pan Insulation

Detail 22 (Air in Stud Cavity) Detail 23 (Spray Foam in Stud Cavity)

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Glazing Spandrel Areas

No Spray Foam Spray Foam

60

Unitized System

61

62

Vacuum Insulated Panels

Vacuum Insulated Panels

63

Glazing Spandrel Areas

3.4

4.24.8 5.0

7.4

8.2

8.8 9.1

0

1

2

3

4

5

6

7

8

9

10

0 5 10 15 20 25 30

Sp

an

dre

l S

ec

tio

n R

Va

lue

Back Pan Insulation

Detail 22 (Air in Stud Cavity) Detail 23 (Spray Foam in Stud Cavity)

64

40

5

Placement of Insulation

65

Curtain Wall System

66

Traditional Captured

Stick Built

Structurally

Glazed Unitized

High Performance

Captured Stick Built

Traditional Spandrel Insulation

Stick Built Curtain Wall

Vacuum Insulated Spandrel

Stick Built Curtain Wall

Major thermal break at verticals

69

High Performance Curtain Wall

Vacuum Insulated Spandrel

Unitized Curtain Wall

Condensation Resistance

73

“Window Wall”

Window Wall Spandrel

77

How to Improve?

Better Glass

+Better Thermal Break

+More Insulation?

Vision

Opaque

U-0.4, R-2.5 U-0.26, R-3.8

U-0.27, R-3.7 U-0.25, R-4.0

78

How to Improve?

Add R-12 Spray Foam?

Vision

Opaque

U-0.4, R-2.5 U-0.4, R-2.5

U-0.27, R-3.7 U-0.23, R-4.4

79

How to Improve?

Better Deflection Header?

Vision

Opaque

U-0.21, R-4.7 U-0.21, R-4.7

U-0.21, R-4.8 U-0.14, R-7.2

80

Further Improvements?

+ Bigger thermal break at deflection header

+ VIP insulation (R-40) aligned with thermal

break

+ Insulation outboard framing using clips

and rails to support cladding (hybrid)

81

How to Improve?

36 inch

high spandrel

82

Full Height Spandrels

Standard U-0.17, R-5.8

U-0.10, R-9.9+ R-12 SPF

83

How to Improve?

Standard U-0.17, R-5.8

U-0.13, R-7.9+ more insulation

+ large thermal break

U-0.11, R-9.4

+ more insulation

+ large thermal break

+ deflection header

84

How to Improve?

Standard U-0.17, R-5.8

U-0.08, R-12.5+ more insulation

+ large thermal break

+ R-18 SPF

U-0.06, R-16.0

+ more insulation

+ large thermal break

+R-18 SPF

+ deflection header

85

How to Improve?

88

Energy and Cost Analysis

Cost Benefit Analysis

• The Impact of Interface Details

• Thermal Bridging Avoidance

• The Effectiveness of Adding More Insulation

• Ranking of Opaque Thermal Performance

Archetype Buildings

89

• 8 Archetype Buildings

• 2 Glazing Ratios per Archetype

• 3 Climate Zones

• 10-20 assembly / detail scenarios each

• Over 500 discrete examples for energy and cost

analysis

• Great place for practice…

Cost Benefit Analysis

90

Sample Scenario

91

92

We’re Not Building What We Think

ASHRAE Zone 5 Mass Wall Requirement

Non-Residential

Residential

Energy Curves

93

Payback and ROI

94

• Current envelope payback is flawed

• Starting R-value is unrealistically high

• Actual R-values lower, more savings

• Adding insulation not cost effective if

details not improved

• Thermal performance is not always

driving the cost of the envelope

Multifamily High Rise Example

95

96

Multifamily High Rise Example

• “Expensive” options can look attractive when compared to

the cost effectiveness of adding insulation

• The cost to upgrade to thermally broken balconies and

parapets for the high-rise MURB with 40% glazing may

require two to three times the cost of increasing effective

wall assembly R-value from R-15.6 to R-20, but

• Seven times more energy savings

• Better details AND adding insulation

translates to the most energy savings

and the best payback period

• Curtain Wall and Split

Insulated Steel Stud

• What is ROI on high

performance options?

• Triple Glazing? VIP?

Commercial Building Example

97

ROI

98

125

130

135

140

145

150

155

Baseline More Insulation Triple Glazing AIM withDouble Glazing

AIM with TripleGlazing

AIM with TripleGlazing and

Improved StudWall

An

nu

al E

ne

rgy

(ekW

h/m

2)

54 yrs 59 yrs 38 yrs Simple Payback

U = 0.064 BTU/hr ft2

oF (0.36 W/m2K) per ASHRAE 90.1-2010

51 yrs 18 yrs-

• 10 stories, 100,000 sq ft

• ~$50 million dollar project

• Chicago climate

• ASHRAE 90.1-2010

Commercial Building Example

99

100

The Role of Energy Codes and

Standards

• Industry needs a level playing field

• Requiring that thermal bridging at

interface details be considered will be

the catalyst for market transformation

• Incentivize effective solutions

• The guide can be leverage to help lead

the way to constructive changes

• Changes to code are on the way

• Making the data in the guide dynamic

• Analysis has been ongoing, method of

maintenance… “there’s an app for that”

• Push authorities to adapt code requirements to

include more clear approach on opaque envelope

• Make informed, data-driven decisions on your

next project!

Next Steps

101

Questions