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Improving the Energy Performance
of Mass Masonry Enclosures
APT DC Symposium
Energy Efficiency of Historic Sites
Chrissie Parker, P.E.
Simpson Gumpertz & Heger
Presentation Outline
• Background
• How Should We Insulate?
– Design Considerations
– Hygrothermal Analysis
– Hygric and Durability Testing
• Case Studies
– Duke Ellington School of the Arts
– St. Elizabeth’s Center Building
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Background
3
Background – How Masonry Walls Perform
• Mass Masonry Walls
– Water: Walls store moisture
and function as a reservoir.
– Vapor: Breathable assembly
allows moisture to dry to
interior and to exterior.
– Air: Generally poor air
barrier; susceptible to air
leakage at transitions (roof-
to-wall) and penetrations
(fenestration).
– Thermal: Brick masonry is
≈R-0.2 /in. (R-2.4 for 12”
wall).
Background - Why Should We Insulate?
• Code Requires Insulation
• Address Enclosure Issues (leakage, deterioration, etc.)
• Change in Use or Interior Conditions
• Improved User Comfort
• Reduce Operating Costs
5
How Should We Insulate?
6
How Should We Insulate?
• Design Considerations
• Hygrothermal Analysis
• Hygric and Durability Testing
How Should We Insulate?
• Design Considerations
• Hygrothermal Analysis
• Hygric and Durability Testing
Design Considerations – Insulating Mass Masonry
Walls
NPS Brief No. 3 – Improving Energy
Efficiency in Historic Buildings”
Design Considerations – Insulating Mass Masonry
Walls
• NPS Brief No. 3 – Improving Energy Efficiency in Historic Buildings”
• “Spray foams are being used for insulation in many masonry buildings. Their ability to be applied over irregular surfaces, provide good air tightness, and continuity at intersections between, walls, ceilings, floors and window perimeters makes them well suited for use in existing buildings. However, the long-term effects of adding either open- or closed-cell foams to insulate historic masonry walls as well as performance of these products have not been adequately documented. Use of foam insulation in buildings with poor quality masonry or uncontrolled rising damp problems should be avoided.”
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Design Considerations – Insulating Mass Masonry
Walls
Considerations for Insulating Masonry Walls
• Loss of usable space or historic fabric with renovation
• Increased freeze-thaw cycling of existing masonry
• Increased brick masonry moisture content due to vapor
impermeable insulation; changes in vapor drive
• Deterioration of wall components due to increased
moisture content (embedded steel or wood)
Soft to hard
brick (left to
right).
Loss of Usable Space and Historic Fabric
Example Insulated Masonry Wall
Example Insulated Masonry Wall
Greater concern if high volumes
of water have or are entering the
wall due to bulk water leakage
(due to windows, roofs, poor
masonry, etc.)
Example Insulated Masonry Wall
Options for Insulating
• Insulation Types
– ccSPF Insulation
– ocSPF Insulation
– Mineral Wool Insulation
Insulation R/inAir
Barrier
Vapor
RetarderCombustible
ccSPF R-6.4/in Yes* Yes Yes
ocSPF R-3.7/in Yes** No Yes
Mineral
WoolR-4.2/in No No No
*Min. 1 in. ccSPF
**Min. 3-1/2 in. ocSPF
How to Insulate
• Design Considerations
• Hygrothermal Analysis
• Hygric and Durability Testing
Moisture Migration in Porous Materials
• Liquid Water Transport– Capillary flow of free water
• Water Vapor Diffusion– Microscopic transfer of vapor through the pore structure of
a material
• Water vapor flows from regions of high vapor pressure to regions of low vapor pressure– Predominately interior to exterior in cold weather climates
– However, summertime moisture drive must also be considered if:
• Spaces are air conditioned
• Moisture sensitive interior finishes
Vapor Migration by Diffusion
Interior: 70°F, 30% RH
Vapor Pressure = 0.109
Exterior: 32°F, 70% RH
Vapor Pressure = 0.062
VAPOR RETARDER(on warm side)
Direction of Vapor Flow
Vapor Migration by Diffusion
Direction of Vapor Flow
Interior: 72°F, 50% RH
Vapor Pressure = 0.194
Exterior: 100°F, 80% RH
Vapor Pressure = 0.760
Absorbed vs. Adsorbed Water?
• A dry brick placed in a container of water will “absorb”
water from the liquid water in the container
• A dry brick placed in a room with 80% relative humidity
will “adsorb” water from the water vapor in the air
WUFI (Wärme und Feuchte Instationär)
• Purpose: Use WUFI Pro to calculate heat and moisture
flow through an assembly to determine the risk of
condensation and moisture accumulation.
• Transient, 1-Dimensional (vs. steady-state which is
snapshot)
• Inputs include:
– Historical hourly weather data (temperature, RH, rain, solar, etc.)
– User defined interior climatic conditions
– Material properties
– Component thicknesses
Which are the “correct” brick properties in
WUFI??
Brick Testing – Variation in Properties
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Brick Properties
• WUFI database reflects immense range of brick
properties
• What causes these variations?
– Brick is made from clay (natural material)
– Firing temperature
– Brick type (exterior “clinker” bricks, interior “salmon” bricks, etc.)
– Different exposures (rain, solar exposure, etc.)
• How do we reconcile the database?
How to Insulate
• Design Considerations
• Hygrothermal Analysis
• Hygric and Durability Testing
In-House Hygric Testing
Density/Porosity
In-House Hygric Testing
Equilibrium Moisture Content Testing
Next Steps…
• Perform hygrothermal analysis with measured brick properties
• Hygrothermal model alone does not predict durability. Outputs include:
– Brick moisture contents (existing wall and proposed wall)
– Freeze-thaw cycles (existing wall and proposed wall)
• The model can help estimate future durability if:
– Insulation does not make the wall significantly wetter and experience significantly more freeze/thaw cycles
– AND the existing masonry does not show evidence of F/T
• Otherwise durability testing is recommended
Durability Testing – Brick and Other Clay Masonry
• National Brick Research
Center at Clemson
University
– Boiling Water Absorption
– Saturation Coefficient
– Mercury porosimetry
(Maage Freeze-Thaw
Resistance Index)
– Thermal Dilatometry (Firing
Temperature)
– Scanning Electron
Microscopy
Will My Brick Be Durable in Future?
• Survey existing masonry for signs of distress,
deterioration as well as freeze-thaw damage.
• Perform hygrothermal analysis using measured brick
properties to determine impact of insulation on heat and
moisture flow.
• Compare hygrothermal outputs with durability testing
results.
Case Studies
33
Duke Ellington School of the Arts
34
Duke Ellington School of the Arts –
Initial Assessment
• Site Survey
– Existing deterioration
– Potential sources of bulk-water leakage
– General quality of masonry
– Does masonry show evidence of distress?
35
Duke Ellington School of the Arts
Material Sampling for Modeling
• 37 bricks removed for testing from four locations
• 10 bricks for hygric testing
• 9 bricks for durability testing
• Tested one brick from each depth at each location:– Interior wythe
– Middle wythe
– Exterior wythe
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Duke Ellington School of the Arts – Brick Testing
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Duke Ellington School of the Arts – Brick Testing
Duke Ellington School of the Arts – Wall Assembly
• Existing Wall Assembly
– Paint Coating
– Brick Masonry
– Air space
– Plaster
• Proposed Wall Assembly
– Paint Coating
– Brick Masonry
– ccSPF
– Batt Insulation
– Gypsum Wallboard
39
Duke Ellington School of the Arts
Hygrothermal Modeling
• Existing Wall • Proposed Wall
40
Duke Ellington - Construction
41
St. Elizabeth’s Center Building
42
St. Elizabeth’s Center Building – Initial Assessment
• Existing brick in serviceable
condition
• Minimal signs of
freeze/thaw
43
St. Elizabeth’s Center Building – Material Sampling
for Modeling
• 14 brick samples
removed for testing from
four test locations.
• All tests sent to NRBC
for durability testing.
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St. Elizabeth’s Center Building – Brick Testing
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St. Elizabeth’s Center Building – Brick Testing
St. Elizabeth’s Center Building – Wall Assembly
• Existing Wall Assembly
– Brick Wall
– Interior lime-based plaster
• Proposed Wall Assembly
– Brick Wall
– ccSPF
– Metal Studs (installed 1 in
inboard)
– Gypsum Wallboard
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St. Elizabeth’s Center Building – Hygrothermal
Modeling
• Existing Wall • Proposed Wall - ccSPF
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St. Elizabeth’s Center Building – Hygrothermal
Modeling
• Proposed Wall - ocSPF • Proposed Wall - ccSPF
St. Elizabeth’s Center Building – Construction
50
Takeaways
• Insulating mass masonry walls may not be appropriate
for all projects
• Review existing conditions for distress
• Perform modeling to assess potential effects on masonry
• Augment hygrothermal models with testing
– Generic material properties will likely overestimate
moisture content (garbage in = garbage out)
– Using measured material properties will increase the
accuracy of models
QUESTIONS?
Chrissie Parker, P.E.
Simpson Gumpertz & Heger Inc.
202-239-4727
http://www.sgh.com