Improving the Energy Performance of Mass Masonry Enclosures

Transcription

1 Improving the Energy Performance of Mass Masonry Enclosures APT DC Symposium Energy Efficiency of Historic Sites Chrissie Parker, P.E. Simpson Gumpertz & Heger

2 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

3 Background 3

4 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 (roofto-wall) and penetrations (fenestration). Thermal: Brick masonry is R-0.2 /in. (R-2.4 for 12 wall).

5 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

6 How Should We Insulate? 6

7 How Should We Insulate? Design Considerations Hygrothermal Analysis Hygric and Durability Testing

8 How Should We Insulate? Design Considerations Hygrothermal Analysis Hygric and Durability Testing

9 Design Considerations Insulating Mass Masonry Walls NPS Brief No. 3 Improving Energy Efficiency in Historic Buildings

10 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 11

12 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).

13 Loss of Usable Space and Historic Fabric

14 Example Insulated Masonry Wall

15 Example Insulated Masonry Wall

16 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.)

17 Options for Insulating Insulation Types ccspf Insulation ocspf Insulation Mineral Wool Insulation Insulation R/in Air Barrier Vapor Retarder Combustible ccspf R-6.4/in Yes* Yes Yes ocspf R-3.7/in Yes** No Yes Mineral Wool R-4.2/in No No No *Min. 1 in. ccspf **Min. 3-1/2 in. ocspf

18 How to Insulate Design Considerations Hygrothermal Analysis Hygric and Durability Testing

19 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

20 Vapor Migration by Diffusion Exterior: 32 F, 70% RH Interior: 70 F, 30% RH Vapor Pressure = Vapor Pressure = VAPOR RETARDER (on warm side) Direction of Vapor Flow

21 Vapor Migration by Diffusion Exterior: 100 F, 80% RH Interior: 72 F, 50% RH Vapor Pressure = Vapor Pressure = Direction of Vapor Flow

22 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

23 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

24 Which are the correct brick properties in WUFI??

25 Brick Testing Variation in Properties 25

26 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?

27 How to Insulate Design Considerations Hygrothermal Analysis Hygric and Durability Testing

28 In-House Hygric Testing Density/Porosity

29 In-House Hygric Testing Equilibrium Moisture Content Testing

30 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

31 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

32 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.

33 Case Studies 33

34 Duke Ellington School of the Arts 34

35 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

36 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 36

37 Duke Ellington School of the Arts Brick Testing 37

38 Duke Ellington School of the Arts Brick Testing 38

39 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

40 Duke Ellington School of the Arts Hygrothermal Modeling Existing Wall Proposed Wall 40

41 Duke Ellington - Construction 41

42 St. Elizabeth s Center Building 42

43 St. Elizabeth s Center Building Initial Assessment Existing brick in serviceable condition Minimal signs of freeze/thaw 43

44 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. 44

45 St. Elizabeth s Center Building Brick Testing 45

46 St. Elizabeth s Center Building Brick Testing 46

47 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 47

48 St. Elizabeth s Center Building Hygrothermal Modeling Existing Wall Proposed Wall - ccspf 48

49 St. Elizabeth s Center Building Hygrothermal Modeling Proposed Wall - ocspf Proposed Wall - ccspf 49

50 St. Elizabeth s Center Building Construction 50

51 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

52 QUESTIONS? Chrissie Parker, P.E. Simpson Gumpertz & Heger Inc