6 th Annual North American Passive House Conference. Evaluation of Potential for Moisture in High R- value Walls in Cold Climates

Transcription

1 IMPROVING THE BUILT ENVIRONMENT g 6 th Annual North American Passive House Conference Evaluation of Potential for Moisture in High R- value Walls in Cold Climates October 2011 Lois B. Arena Steven Winter Associates, Inc.

2 Overview of Presentation Project Summary Reasons for research Questions to be answered Modeling Field Testing Analysis

3 Project Summary Evaluate potential for moisture problems in 3 new wall assemblies Modeling this year WUFI THERM Field Monitoring beginning 2012 Brick rehab High- R walls: R- 40 & 60 Code walls: hybrid insulation w/ spray foam & fiberglass

4 Reasons for Research Changes in construction due to: Drastic increase in retrofit activities Programs like PH & NZEH challenges Increased use of hybrid insulation strategies New insulation products Code changes

5 Research Focus Assemblies Brick walls with interior insulation; Super insulated walls at least 12 thick: R- 40 and R- 60; Code built walls using spray foam insulation and fiberglass batts.

6 Research Focus Climate zones 4A, 5A, 6A and 7 experience both cooling and heating seasons considerable humidity during the summer

7 Vapor Pressure Analysis

8 Modeling - WUFI Wall Type Brick Wall Vapor Retarder None, 0.1, 1.0 R- None, 0.1, R- None, 0.1, Evaluated in Climate Zones 4 & 5 2 Evaluated in Climate Zones Table 1. Brick Wall and High-R Walls to be Evaluated in WUFI Cavity Insulation Cavity Insulation Thickness (inches) Spray Foam Thickness 3 (inches) Sheathing Type Sheathing Thickness 4 (inches) Fiberglass n/a n/a Cellulose n/a n/a Fiberglass OSB XPS 2-4 Cellulose OSB XPS 2-4 Fiberglass OSB XPS 4-6 Cellulose OSB XPS 4-6

9 Modeling - THERM WUFI can only analyze continuous components Want to analyze condensation potential due to thermal bridging at framing members - THERM Image from THERM

10 Field Testing Short Term moisture content of components using a hand held moisture meter Adjust values in WUFI if necessary Long Term RH & Temp at critical interfaces Moisture content OSB, brick, studs Climatic conditions

11 Failure Criteria Today s Focus Moisture Content (MC) Total Assembly OSB Condensation Potential Center of Cavity At Stud

12 MC & Condensation Potential Moisture Content (MC) of OSB < 20% Condensation Potential graph interior air dew point temp vs. surface temp WUFI - foam/cavity insulation THERM framing/insulation, foam/cavity insulation Final Water Content of Assembly < Initial

13 EcoVillage Community

14 EcoVillage Co- housing Community Third Phase of the Community 39 Dwelling Units 17 Detached- SF 4 Duplexes 14 Apartments Common House PH Certification Desired

15 EcoVillage Specifications Climate 6 R- 80 Ceiling R- 62 Walls R- 40 Slab (edge & under) Windows: U<0.15 & >0.55 SHGC Solar Thermal DHW Electric Resistance

16 EcoVillage 2 Wall Options 1 st - Architect Larson truss w/ 6 foam + blown/batt cavity insulation

17 EcoVillage Wall Options 2 nd - Builder Modified truss w/ 4 foam + R- 38 batt

18 WUFI

19 Outdoor Conditions Albany, NY (closest profile to Ithaca) Cold Year File Outdoor conditions can be used to generate interior Temp & RH

20 Indoor Conditions - Initial Assumptions 3 bedroom PH Infiltration 0.6 Default moisture generation

21 Case 1: PH ACH, ASHRAE Heat Only, 3 Bedroom

22 Case 7: Sine Curve

23 Case 8:ERV, ASHRAE Heat Only, 1 Bedroom +0.1 perm Vapor Retarder

24 Climate Zone 5 Collected Data

25 Indoor Climate Chosen Sine Curve 65 to to 70% RH Have to chose from predefined list in free version of WUFI

26 Architect s Case Sine Wave Results

27 Architect s Case Sine Wave Results

28 Builder s Case Sine Wave Results

29 Builder s Case Sine Wave Results

30 Builder s Case More Foam

31 THERM

32 Dew Point/Condensation Potential Determine Interior Setpoint Determine Outdoor Temperature to Use in THERM Design? Average of Winter Months? Evaluate Center of Cavity and Near Stud

33 Finding Dewpoint

34 THERM

35 THERM Results At Design Should Condensation Potential be Evaluated at Design for High R- walls?

36 Recommendations

37 Important Factors to Consider Indoor Conditions HRV or ERV # of Occupants Outdoor Climate R- value of Components, not thickness Unusual moisture loads inside home

38 Code Minimum R- values for Class III Vapor Retarder

39 Recommendations for EcoVillage Install enough foam to contribute more than 50% of overall R- value to reduce the potential for condensation Use a vented cladding system

40 Recommendations for Consultants in Cold, Moist Climates Do NOT use code minimums for exterior rigid or spray foam for high R- walls Use WUFI and THERM to evaluate your projects on a case by case basis Evaluate the climate conditions for your project carefully and compare to software assumptions These walls are not forgiving Must prevent interior moisture from getting into the walls investigate smart vapor retarders

41 IMPROVING THE BUILT ENVIRONMENT Thank you. Questions?

42 IMPROVING THE BUILT ENVIRONMENT Thank you. Thank You.