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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)
59
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
top related