Understanding Wall Insulation and Whole Building Energy

Report
Wall Insulation and Whole Building
Energy Performance
John Swink, PE, LEED-AP
Acme Brick Company
[email protected]
817-714-9523
Wall Insulation and Whole Building
Energy Performance
• Avoid disinformation about saving energy in
buildings.
• Understand real thermal performance of wall
systems
• Demystify whole building energy analysis.
Learning Objectives
1. Learn the TRUE U and R values of many common
wall systems.
2. Learn how to calculate true U and R values for
complex building envelope components.
3. Learn how eQuest and Simergy can help you
design high performance buildings to meet
sustainable goals.
4. Learn to integrate economical building
envelopes with high performance mechanical
systems for the most cost-effective energy
performance.
1. True U and R Values in Building Walls
Introduction – The LEED® Mandate
Rising energy costs and concern for the environment have led
many groups, including AIA, ASHRAE, USGBC and ICC to support
much higher expectations for building energy performance. There
have been many predictions and endeavors to build zero-energy
and near-zero energy buildings.
But there are practical limits on building performance. Today
we will look at the entire building envelope to optimize the wall
systems, including opaque and glazed areas, to see what those
limits are, and how best to design buildings for optimum
performance and value.
1. True U and R Values in Building Walls
Introduction – The LEED® Mandate
Traditionally, heating and cooling of buildings has been the
purview of mechanical engineers on the design team. But choices
made by architects and structural engineers have a significant
impact on the energy performance of our buildings. So we need
to understand as fully as possible how those choices can help or
hurt the building’s overall energy performance.
Today we will investigate the impact of various types of
building envelope construction on the performance of those
buildings.
1. True U and R Values in Building Walls
Introduction – The LEED® Mandate – ever-decreasing energy
demand for buildings.
1. We examine popular wall systems for ACTUAL heat flow
a. All include air and moisture barriers
b. Alternates for glazing area considered.
c. Mass not included in calculations, but will benefit
2. eQUEST or Simergy lets you quickly study the effects of
different wall systems on whole building energy performance.
Occupancy types are critical for effective evaluation of building
performance. Energy demands vary widely:
Session Outline
1.
2.
3.
4.
5.
Dispel some popular myths about R values
Compare popular wall systems
Detailed look at wall system heat flow
ORNL study of mass walls in a model house
Proposed mass house for optimum energy
performance
6. School energy performance study at
University of Louisville
Those “R” Lies
“Oh, what a tangle web we weave
when first we practice to deceive!”
Sir Walter Scott
Let’s look and some misinformation
– or is it disinformation? –
that is commonly reported.
• Misinformation – erroneous information that is
passed on through ignorance.
• Disinformation – deliberate lies or distortions
used to promote one’s cause or agenda.
OXYMORON – “TRUE” R VALUE
• Fiberglass industry only reports R value of batt
insulation that is:
– Perfectly placed
– No studs, fasteners, wiring, etc.
– No stapled facings
– Batts must be in contact with all surfaces
– Never happens in the field
– FALSE R values reported
– True R values MUCH lower
OXYMORON – “TRUE” R VALUE
• Wood industry reports R value of batts, not the
wall assembly.
– Does not include heat flow through studs
– Ignores air gaps from imperfect placement.
• Stapled facings leave gaps
• Wiring leaves gaps
– False R values reported
– True R values MUCH lower
MASONRY – TRUE R VALUE
• NCMA
– Calculates or tests true R value of wall assembly
– Only reports True R values
– Notes the effects of mass in reducing heat flow, but
only as recognized by ASHRAE and supported by
analysis.
Those “R” Lies
Lie #1 – ICF walls have an R value of 50
– Some say “Equivalent R Value of 50.”
– Equivalent to what?
Truth – Typical ICF walls are R16 to R20
Those “R” Lies
Lie #2 – 6” Steel stud walls are R 19
– Steel stud conducts much heat through the wall
– R19 batts are only R19 if perfectly placed with no
gaps
Truth – 6” steel stud walls have typical R 7.03
according to AHSRAE 90.1
Those “R” Lies
Lie #3 – 6” Wood stud walls are R19
– Wood studs conduct less heat than metal studs
– Wood studs conduct more heat than insulation
– R19 batts are only R19 if perfectly placed with no
gaps
Truth – typical 5.25” wood stud walls are R11.4
or less
Those “R” Lies
Lie #4 – 4” Wood stud walls are R13
– Wood studs conduct more heat through the wall
than insulation
– R13 batts are only R13 if perfectly placed with no
gaps
Truth – perfectly built 3.5” wood stud walls
actually R 8.4.
Truth – many 3.5” wood stud walls
R5 or less
Detailed Look at Wall Systems
• Now let’s look at these wall systems in more detail
and calculate their actual R value using the
ASHRAE series-parallel method:
• When DIFFERENT wall components are in the
SAME LAYER, we add the heat flows (U values) for
each component in that layer. (PARALLEL)
– Accounts for thermal bridging that bypasses insulation.
– R for that layer = 1/(Sum of U values)
• When wall components are in SEPARATE LAYERS,
simply ADD the R values. (SERIES)
• Here are examples of walls designed for true R19
A. True U and R Values in Building Walls
In this session we will compare each of the following wall systems.
Each has peculiar advantages that can make them appropriate
choices, but it is important to understand their limitations.
1. Wood Stud Walls
2. Steel Stud Walls
3. Insulated Concrete Form Walls
4. Tilt-up Concrete Walls
5. Single-Wythe Masonry Walls
6. Masonry Cavity Walls
1. Wall Systems – Wood Stud
Advantages
• Moderate cost
• Ease of routing wiring and
other utilities
Disadvantages
• Fire destroys it
• Water damage – mold and rot
• Air and moisture barriers
REQUIRED to prevent damage
• Air leaks cause poor energy
performance
• Thermal bridging cause poor
thermal performance
1. Wall Model – 4” Wood Studs
Calculate actual R value
Series/parallel method
R 3.5 – wood stud
U 0.286 x 15% = 0.043
R 13.0 – batt
R 9.1 reduced 30% for imperfect fill
U 0.109 x 85% = 0.093
U Total = 0.043 + 0.093 = 0.136
R = 7.33 average stud cavity
R = 1.11 2x 0.625” gyp board
R = 8.4 average opaque wall
1. Wall Model – 4” Wood Studs
Calculate actual R value
Series/parallel method
R 3.5 – wood stud
U 0.286 x 15% = 0.043
R 12.6 – spray foam, sprayed cellulose, or
aminoplast foam filled
U 0.079 x 85% = 0.0675
U Total = 0.043 + 0.0675 = 0.111
R = 9.05 studs and insulation layer
R = 1.11 2x 0.625” gyp board
R = 10.2 total when stud cavities
are filled with insulation, no gaps
1. Wall Model – 4” Wood Studs
Calculate actual R value
Series/parallel method
R 3.5 – wood stud
U 0.286 x 15% = 0.043
R 16 –aminoplast foam filled
U 0.063 x 85% = 0.053
U Total = 0.043 + 0.053 = 0.96
R = 10.4 studs and insulation layer
R = 1.11 2x 0.625” gyp board layer
R = 11.5 total when stud cavities
are filled with insulation, no gaps
1. Wall– 6” Wood Studs
Calculate actual R value
Series/parallel method
R 5.5 – wood stud
U 0.286 x 15% = 0.027
R 17.4 – compressed R 19 batt
R 12.2 reduced 30% for imperfect fill
U 0.085 x 85% = 0.070
U Total = 0.027 + 0.070 = 0.097
R = 10.3 average stud cavity
R = 1.11 2x 0.625” gyp board
R = 11.4 average opaque wall
1. R19 Wall – 4” Wood Studs
R 0.17 – outside air boundary layer
R 0.33 – Masonry veneer
R 1.0 – Air space
R 10.0 – 2” XPS insulation
R 8.4 – Wood Studs with R 13 batts*
R 0.68 – inside air boundary layer
R 20.6 – Total
10.4 inches total wall thickness
1. R19 Wall – 6” Wood Studs
R 0.17 – outside air boundary layer
R 0.3 – Masonry veneer
R 1.0 – Air space
R 5.0 – 1” XPS insulation
R 10.3 – Wood Studs with R 19 batts*
R 0.68 – inside air boundary layer
R 19.5 – Total
11.9 inches total wall thickness
2. Wall Systems – Steel Studs
Advantages
• Moderate cost
• Ease of routing wiring and
other utilities
• Noncombustible
Disadvantages
• Subject to water damage –
rust and mold
• Air and moisture barriers
required to prevent damage
• Air leaks cause poor energy
performance
• Batt insulation less effective,
cannot be well placed
2. R19 Wall– 6” Steel Studs
R 0.17 – outside air boundary layer
R 0.3 – Masonry veneer
R 1.0 – Air space
R 10.0 – Continuous insulation
R 7.03 – Steel studs with R 19 batt
(ASHRAE Handbook of Fundamentals)
R 0.68 – inside air boundary layer
R 19.1 – Total
12.9 inches total wall thickness
3. Wall Systems – Insulated Concrete Form
Advantages
• R15 to R19 insulation built in
• Strong reinforced concrete
core
• Low air infiltration
• STC50+ sound barrier
Disadvantages
• Combustible forms must be
protected by fire barriers
both sides
• Mass of concrete is isolated
from building interior
• Thicker walls reduce floor
space
• Toxic gases in fires
• Blowouts and other
construction issues
3. R19 Wall– Insulated Concrete Form
R 0.17 – outside air boundary layer
R 0.3 – 3” Masonry veneer
R 1.0 – 1” Air space
R 9.5 – 2.5” EPS insulation form
a
R 0.48 – Concrete pour
R 7.5 – 2.5” EPS insulation form
reduced by electrical cut-outs
R 0.4 – ½” gyp board
R 0.68 – inside air boundary layer
R 19.4 – Total
15.3 inches total wall thickness
4. Wall Systems – Tilt-up Concrete
Advantages
Disadvantages
• Some general contractors have
carpenters as permanent
employees to build forms
• 24’ tall 6” walls
• Hard concrete surfaces require
low maintenance
• Very durable
• Not damaged by water
• Low air infiltration
• Very high strength
• Non-combustible and very fire
resistant
• STC 50 sound barrier
• 100 Year Life
• Limited insulation
• Continuous insulation it cavity
wall is only way to reach
prescriptive
R values in energy code
• Limited finishes and profiles
• Higher cost
• Utilities must be in place and
slab poured before walls can
be cast
• Heavy cranes required
• More space required onsite
• Level site required
4. R19 Wall – 6” Tilt-up Concrete
R 0.17 – outside air boundary layer
R 0.5 – 6” Tilt-up Concrete
Negative side dampproof coating
R 10.0 – Continuous insulation
(Seldom used – R10.3 without ci)
R 9.0 – 6”x25ga Steel studs, R 19 batts
(ASHRAE Handbook of Fundamentals)
R 0.68 – inside air boundary layer
R 20.3 – Total
15.6 inches total wall thickness
4. R19 Tilt-up Concrete Sandwich Panel
R 0.17 – outside air boundary layer
R 0.2 – 2” Concrete
R 14.0 – Continuous insulation
2” polyisocyanurate
R 0.5 – 6” Concrete
R 0.68 – inside air boundary layer
R 15.6 – Total
10.0 inches total wall thickness
5. Wall Systems – Single-Wythe CMU
Advantages
• Very Low cost
• 24’ tall 8” walls
• Hard masonry surfaces
require low maintenance
• Very durable
• Not damaged by water
• Low air infiltration
• Very high strength
• Non-combustible and very
fire resistant
• STC 50 sound barrier
• 100 Year Life
Disadvantages
• Limited insulation capacity
limits use in some climate
zones
• More difficult to run wiring
5. Wall Model – Single-wythe CMU
R 0.17 – outside air boundary layer
R 5.7 – Core insulated CMU with
grouted cells at 32” minimum and
bond beams at 48” min spacing
(per IECC prescriptive tables)
R 0.68 – inside air boundary layer
R 6.55 – Total
7.63 inches total wall thickness
6. Wall Systems – Masonry Cavity Wall
Advantages
• Moderate cost
• Unlimited insulation
• Hard masonry surfaces
require low maintenance
• Very durable
• Not damaged by water
• Low air infiltration
• Very high strength
• Non-combustible and very
fire resistant
• STC60+sound barrier
• 100+ Year Life
Disadvantages
• Slightly higher cost
6. R19 Masonry Cavity Walls
R 0.17 – outside air boundary layer
R 0.3 – 3” Masonry veneer
R 2.5 – Foil-faced 1” air space
R 14 – 2” foil-faced polyiso board
a
R 2 – 6” CMU uninsulated
R 0.68 – inside air boundary layer
R 19.5 – Total
11.3” inches total wall thickness
6. Wall Model – Masonry Cavity Walls
R 0.17 – outside air boundary layer
R 0.30 – Masonry veneer
R 2.5 – Foil-faced 1” air space
R 10.5 – 1.5” foil-faced polyiso board
a
R 5.7 – 8” CMU grouted 48” c/c
R 0.68 – inside air boundary layer
R 19.9 – Total
12.8 inches total wall thickness
Summary: R values, Thickness and Cost
R Value
Thickness
1a. 4” Wood Studs with Brick Veneer
R 20.6
10.4”
1b. 6” Wood Studs with Brick Veneer
R 19.5
11.9”
2. 6” Steel Studs with Brick Veneer
R 19.1
12.9”
3. Insulated Concrete Form with Brick Veneer
R 19.4
15.3”
4. Tilt-up Concrete with Insulated Studs
R 20.3
15.6”
5. 8” Single-wythe CMU Wall
R 7.6
7.62”
6a. 6” CMU Masonry Cavity Wall with Brick Veneer
R 19.5
13.3”
6b. 8” CMU Masonry Cavity Wall with Brick Veneer
R 19.9
12.8”
$ / sq ft
Notes:
1.
2.
3.
4.
5.
6.
7.
Every wall system in this list requires continuous insulation to achieve R19.
Consider aesthetics. Most of the above do not have finished masonry inside and out.
Consider durability. Masonry and concrete will last indefinitely.
Consider maintenance. Masonry and concrete surfaces require very little maintenance.
Consider Life Cycle Cost, not just first cost.
Consider fire resistance. Wood buildings burn to the ground in 20 minutes or less.
Finally consider overall value. Masonry cavity walls give most for your money.
True Mass Effect
• Many wall systems, including masonry, tilt-up,
and ICF’s claim a benefit from mass in the wall
system to improve energy performance.
• Computer simulations at ORNL show where
mass should be placed for maximum benefit.
• This debunks claims of some wall systems to
benefit from mass.
Oak Ridge National Laboratory Study
• This recent study at ORNL found significant
improvement in energy performance of a
1500 sf house with properly placed mass
elements in the walls.
WALL 1
WALL 2
WALL 3
WALL 4
MASS INSIDE
INSULATION OUTSIDE
MASS OUTSIDE
INSULATION INSIDE
(TILT-UP WITH INSIDE
INSULATION)
MASS NOT EFFECTIVE
WALL 5
2” EPS
6” Conc
2” EPS
3” EPS
6” Conc
1” EPS
6” Conc
4” EPS
4” EPS
6” Conc
2” Conc
4” EPS
4” Conc
3” Conc
4” EPS
3” Conc
HDD / CDD
WALL 6
MASS BURIED IN
INSULATION (ICF)
MASS NOT EFFECTIVE
ORNL Study – Energy Use in Houses
http://www.ornl.org/sci/roofs+walls/staff/papers/Effect%20of%20Insulation%20and%20Mass%20Distribution.pdf
Similar to
Masonry
Cavity Wall
ICF Wall
Cavity Wall
Savings
Cavity Wall
Savings
Cavity Wall
Savings
Table 4 - Annual Cooling Energy Demand (Mbtu /Yr)
CDD=> 2300
1000
4600
1000
5000
1800
Wall
ATL
DNVR
MIA
MINN
PHX
WADC
2
5.68
0.74
32.80
1.32
27.27
3.00
6
7.05
1.70
33.87
1.93
28.76
4.08
-19.4% -56.5% -3.2% -31.6% -5.2% -26.5%
Table 5 - Annual Heating Energy Demand (Mbtu /Yr)
HDD=> 3100
6300
270
7100
1200
3900
Wall
ATL
DNVR
MIA
MINN
PHX
WADC
2
18.88
37.76
0.35
66.75
3.37
33.26
6
19.50
38.91
0.42
67.26
4.73
34.01
-3.2%
-3.0% -16.7% -0.8% -28.8% -2.2%
Table 5 - Annual Heating and Cooling Energy Demand (Mbtu /Yr)
Wall
ATL
DNVR
MIA
MINN
PHX
WADC
2
24.56
38.50
33.15
68.07
30.64
36.26
6
26.55
40.61
34.29
69.19
33.49
38.09
-7.5%
-5.2%
-3.3%
-1.6%
-8.5%
-4.8%
-30%
-21%
-13%
-6%
-34%
-19%
Savings on heat flow through wall only (estimated)
What does this mean?
1. This study shows significant savings for walls
with mass exposed to inside air compared with
mass isolated within insulation.
2. Walls account for only 25% of the heat loss for
these houses.
3. If we divide total savings in heat load by 25%,
we can see that walls with mass exposed to
inside air reduce heat loss through walls by up
to 34% in Phoenix and 30% in Atlanta.
4. DFW savings would be in this 30% range as well.
Limitations on the ORNL study.
1. Significant wall types were not studied:
a. Masonry veneer over steel studs
b. Masonry veneer over wood studs
2. Whole building energy modeling does not show
heat losses in walls directly
NBS 45 Study July 1973
• Computer models
• Full scale testing
• Showed mass benefits
– Stabilized indoor
temperatures
– Reduced heating and
cooling loads
• +/- 0.8° F indoors
• +- 27.5° F outdoors
Proposed Mass House in DFW
Using the adobe effect in DFW, a mass house could greatly reduce
energy consumption by storing several days’ heat flow to take
advantage of outside temperature variations and eliminate
mechanical heating and cooling.
• Walls would be solid masonry or concrete to maximize mass.
• Ground floor would be slab-on-grade with perimeter
insulation to maximize heat storage in the slab and the soil
under it with ground temperature at 68ᵒF.
• Attic floor would be 8” solid concrete.
• Total mass for 1500 sf house would be 600,000 lbm
• At 0.22 sp heat it takes 132,000 btu to raise the temperature
one degree F.
• In 18 hours of 90 deg weather, temperature will rise 3 deg F
2011 Daily High and Low Temperatures, DFW Airport
Daily Highs
Daily Lows
Solar
Heating
Ventilation Only
No Heat or AC
Efficient Air
Conditioning
Dec
Nov
Oct
Sep
Aug
Jul
Jun
May
Apr
Mar
Feb
Jan
Thermostat Set-points
68ᵒF to 75ᵒF
Ventilation Only Solar
No Heat or AC Heating
Proposed Mass House in DFW
• Daily high and low temperatures in the DFW area shows
approximately 6 months when outside temperatures fall
within the comfort zone as defined by thermostat set points.
During these times, outside air could be brought in to either
heat or cool indoor air at appropriate times of the day.
• Light-framed houses will require supplemental heating and
cooling during these times, because they can only store
sufficient heat to maintain temperatures for several hours.
Proposed Mass House in DFW
• Mass houses can store enough heat to maintain comfortable
temperatures for several days. With proper ventilation
programming, mechanical heating will be required for only 2.5
months in winter. This can be easily provided by solar
collectors, which can also supply domestic hot water. So far
we have net zero energy, except for fans, lighting, and plug
loads.
• Cooling will be required for about 3.5 months in summer. But
mass storage allows running cooling system when outside
temperatures are at their lowest.
• This decreases total energy use for cooling by 25% and shifts
energy loads to off-peak hours to allow better use of
alternative energy sources, such as wind power.
Mass House in Any Climate
• Mass houses can store enough heat to maintain comfortable
temperatures for several days.
• Heating and cooling minimized in spring and fall weather
• Long cooling cycles maximize cooling efficiency
• Off-peak heating and cooling
– Better use of alternative energy sources
– Much lower energy costs with electric discounts
Comparing Wall Systems
Summary and Conclusions
• True R values differ widely among wall systems
• Masonry cavity walls can match any level of insulation
• Tilt-up has limited insulation capacity, unless an
insulated cavity and masonry veneer is added.
• ICF has limited insulation capacity that is adequate, but
not better than masonry cavity walls.
• ICF walls are 4”thicker than masonry cavity walls for
the same insulation value.
• Masonry cavity walls cost less than either ICF or tilt-up
walls.
Comparing Wall Systems
Summary and Conclusions
• Steel and wood framed walls have very limited
insulation capacity without added cavity
insulation.
• Steel and wood framed walls often have
moisture damage from corrosion and mold.
• Tilt-up panels with inside insulation have very
limited insulation capacity and also can have
moisture damage from corrosion and mold.
Comparing Wall Systems
Summary and Conclusions
• Masonry cavity walls are by far the most versatile
wall systems:
–
–
–
–
–
–
–
–
–
Widest range of insulation capacities
Strong aesthetic qualities
Moderate cost
8” modules work at a human scale
Speed of construction
No cranes or heavy equipment required
Few site limitations
Disaster resistant – fire, flood, wind, seismic
Carries structural loads with ease
eQUEST & Simergy Energy Modeling
• User-friendly shell for whole building energy
analysis, especially Simergy.
• Complies with IECC energy codes
• ASHRAE 90.1 or IECC compliance paths
• User selects building size, shape, and envelope
and mechanical elements with few limits.
• Change walls, windows, and other envelope
components to compare performance.
• Free! Developed by Lawrence Berkley Labs –
Download at DOE website.
eQUEST & Simergy Energy Modeling
• Demonstrates compliance with IECC where
prescriptive methods fail.
• Single wythe CMU walls comply in Climate
zones 1 – 6.
• Much lower cost buildings to meet or exceed
energy codes.
Enjoy your eQUEST !
And may your life
overflow with Simegy!

John E. Swink, PE, LEED-AP
Acme Brick Company
801 Airport Freeway
Euless, TX 76040
[email protected]
Cell 817-714-9523
http://doe2.com/download/equest/
Kentucky School Energy Study
• The following slides are used by permission
from a PCMA presentation by Dr. W Mark
McGinley, from a recent study directed by him
at University of Louisville.
• Complete report can be obtained from the
author by request.

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