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A Case Study, Curing Progress in walls of Damp-Apply Cellulose Insulation
by John B. Unger Murphy

Project & Location: Baldwin Block Project, Wells River, Vermont
Project Description:
Historical Building
Renovation for Commercial and Multi-Unit Residential
New Construction walls and roof over residential wing of building
Moisture Test & Related Information
  1. Construction Schedule as it relates to insulation, sheetrock, and moisture testing:
    • Insulation applications:
      • January 8 - 10, 2002: Application completed in residential areas of the building
      • January 24 - 25, 2002: Application completed in commercial areas.
    • Sheetrock applications:
      • Sheetrock was installed on a “rolling” schedule: installed in the areas where insulation was completed while insulation continued in other areas of the building.
    • Moisture Testing:
      • Testing was requested, planned, and implemented during the first week of March.
      • Testing Results were published March 13, 2002.
  2. Application Moisture Content
    • Approximately 43% by weight of mixture was moisture, based on application methods and equipment used at the time.
  3. Moisture Content Test
    • Test locations:
      • 12 test locations were chosen: testing every wall thickness at every compass direction it faced. Wall thickness: ranged from 5-inch new 2x6 construction up to 9+inch renovation “double“ wall construction.
    • Test Method to account for moisture movement during curing:
      • Test 2x6 wall cavities at two depths: close to the inside and outside sheathings.
      • Test larger wall cavities at three depths: close to the inside, middle, and outside.
    • Test readings at each location, and the mean moisture content of each cross-section.
      • See Table 1.

    Table 1.
    Moisture Measurements
    Test Location # Close to Inside Middle Close to Outside Cumulative Total Number of Measuring Depths Mean Moisture Content
    1 8% - 8% 0.16 2 8%
    2 7% 11% 13% 0.31 3 10.3%
    3 8% - 9% 0.17 2 8.5%
    4 9% 10.5% 20.5% 0.40 3 13.3%
    5 8% 14% 23% 0.45 3 15%
    6 8% 20% 24% 0.52 3 17.3%
    7 9% 8.5% 11% 0.29 3 9.5%
    8 9% 10% 15% 0.34 3 11.3%
    9 8% - 8% 0.16 2 8%
    10 9% - 11% 0.20 2 10%
    11 9.5% 10.5% 13% 0.33 3 11%
    12 10% 12.5% 21% 0.44 3 14.5%

  4. Moisture Content as it Relates to Time, and “Static” Moisture Content.
    • Buildings gradually achieve moisture equilibrium by releasing construction moisture during the first and second years after construction, achieving “Static” Moisture Content. Building moisture content will plateau at a relatively steady state of approximately 4% to 8% moisture, (special circumstances excepted). Building moisture content will increase during the humidity of summer, and decreases during the dryness of winter.
    • Table 2 compares moisture content at the time of installation, with the time of testing and with the building’s approximate “static” moisture content. Table 2’s time line gives information as to the speed at which moisture finds its way out of the applied insulation. To put this information into words: Moisture content at the time of application was 35% more than the building’s future “static” moisture content. Curing had occurred for 40 to 60 days prior to the date of testing. The spectrum of moisture content in the cellulose:
      1. Fifty-eight percent (all 2x6 and some thicker wall cavities) had cured from 35% down to within 3% or less of the “static” moisture content.
      2. Seventeen percent had cured from 35% down to between 4% to 5% of the “static” moisture content.
      3. Twenty-five percent had cured down from 35 % to between 7% to 9% of the “static” moisture content.

    Table 2.
    Time Line Day 1 Day 40 to 60 Day 360 to 720
    Test Location # Installed Moisture % Mean Moisture % % Moisture yet to be released to reach Static Static Moisture %
    1 43% 8% 0% 4-8%
    2 43% 10.3% 2.3% 4-8%
    3 43% 8.5% 0.5% 4-8%
    4 43% 13.3% 5.3% 4-8%
    5 43% 15% 7% 4-8%
    6 43% 17.3% 9.3% 4-8%
    7 43% 9.5% 1.5% 4-8%
    8 43% 11.3% 3.3% 4-8%
    9 43% 8% 0% 4-8%
    10 43% 10% 2% 4-8%
    11 43% 11% 3% 4-8%
    12 43% 14.5% 6.5% 4-8%
Conclusion:   The damp spray cellulose does rapidly drop moisture content, even under adverse winter conditions and with interior sheathing installed (gypsum wall board). The remaining moisture will continue to decrease along with the rest of the structure’s building materials until equilibrium (“static” moisture content) is realized.

Cellulose and the installation methods used for this installation are safe and approved as Building Material Compatible. This case study is representative of the hundreds of thousands of structures being similarly insulate through out the USA each year.