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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

2

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.”

10

11

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

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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?

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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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49

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.

ctparker@sgh.com

202-239-4727

http://www.sgh.com