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Mold infestation
of wet spray applied cellulose insulation (WSACI) in the sidewalls of a
brick veneer house. Case History #2
Recently a relatively new brick veneer
house with WSACI in the sidewalls was investigated in response to health
and odor concerns. The house located in an exposed location was subject
to water intrusion through brick veneer on its “weather sides”. Not
uncommonly in brick veneer “pancaked” excess mortar
 on the inside of
brick veneer provides both a reservoir for rainwater and a direct
pathway for water into the sidewalls of houses. In this case rainwater
worked its way into the WSACI on the weather sides of the house.
As the wind came up, mold odor could be
detected emanating from the sidewalls. Removal of gypsumboard and
cellulose insulation in a problem area revealed WSACI samples to be
moist to the touch, greenish stained and to have a strong musty smell.
Again in this case WSACI was observed
to have been subject to rewetting with apparent mold growth(Click on
image).  Samples
were collected and attempts at culturing mold species present were
attempted. A limited number of mold colonies were observed to grow on
hydrophilic and xerophilic culture media.
Subsequently two samples were submitted
to a commercial laboratory for quantitative PCR analyses. One sample
was collected in an area subject to water intrusion or rewetting, the
second (#2) in a wall protected from the weather. The dominant mold
type present in sample #1 was Penicillium chysogenum with 430,000
cells/mg of insulation; P. chysogenum was the dominant mold type
in sample #2 with cells/mg. Measurable infestation by Aspergillus
amstelodami (2 cells/mg) was observed in sample #1 and
Cladosporium cladosporoides (5 cells/mg) and Aspergillus flavus/oryzae(5
cells/mg) in sample #2.
Airborne mold sampling was conducted
using both total mold and culturable-viable techniques. I the latter
case mold levels in all cases were <300 CFUs/M3 on both MEA
and DG-18 a hydrophilic and xerophilic medium respectively. Total mold
spore levels on the other hand were very high with levels varying
from10,000 – 100,000+ S/M3. These counts were conducted very
conservatively in thaty strings of spores were counted as one spore.
These results are quite interesting in
several respects. SACI subject to rewetting was observed to have very
high concentrations of P. chysogenum present; SACI not subject to
rewetting was observed to have considerably less, but a significant
amount in the context of the total mass of WSACI infested material
present in the sidewalls of a house.
In this case history as was the
previous one posted on the Indoor Environment Notebook, an
excessive growth of mold was observed on WSACI as a result of
rewetting. A lesser but likely significant degree of infestation
associated with the installation of the product was observed. This
poses the question whether WSACI represents a mold infestation/potential
human exposure concern only on rewetting or is it a more generic one
that is, because of the nature of the product (cellulosic materials),
its wet application, and subsequent enclosure by building contractors.
If the latter is the case, what are the risks to building occupants as a
result of airborne mold exposures?
Readers in the states of Indiana, Ohio, Michigan, Illinois and Kentucky
who may be experiencing WSACI- related mold problems are welcome to
contact the author of this posting as he is interested in conducting additional
investigations to determine the nature and extent of mold
infestation/exposure problems associated with wet spray applied
cellulose insulation.
September 18, 2003
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