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I am a
building contractor in Utah, and I would like to point out that I have
used cellulose for nine years and have never had any type of mold or
mildew problem. I am under the understanding that of all the reported
mold cases across the country, not a single problem has been reported in
a home insulated with boric acid-treated cellulose. I have seen test
results, surveys, and experiments all showing different results which
allow both cellulose and fiberglass manufacturers to support their own
claims. I want only the best for my homeowners, and obviously do not
want the liability of installing a product that is unsafe and/or
ineffective in what it is supposed to do. I use cellulose because of
the mold-resistant claims and have seen tests and research to support
the claim. I am, however, concerned over the contradictory statements,
claims, and evidence of just the opposite. My one experience has to do
with a client of mine whose tub overflowed and flooded her basement.
Her walls were soaked, and the basement was destroyed by the water. I
truly believed all of the claims that had been made to me and that I had
in turn parlayed to all of my homeowners when the disaster clean-up
company that my homeowner called, said that he had never seen the type
of damage that she had in her basement, without at least a small visible
sign of mold in the wall cavity and on the back side of the drywall. He
was impressed with the condition of the wall, and said that he had never
seen anything like it. He claimed that he was making a substantial
amount of money on mold clean up, and was astounded to not find any in
the wall cavity. I am curious as to what your response is to this, and
if you believe that if WSACI is not the best product, what are the
alternatives.-K , Utah
My experience with wet spray applied
cellulose insulation (WSACI) has mostly involved cases of this material
becoming rewetted as a result of water intrusion or applications
conducted under weather conditions in which WSACI took a long time to
dry.
Though borates (including boric acid)
are good-excellent biocides for mold, they are less than perfect. Some
mold species seem to be somewhat to very tolerant to it, particularly
Penicillium chrysogenum and perhaps Aspergillus versicolor.
In my previous postings on this site, I
provided evidence that infestation of WSACI did occur (as confirmed by
DNA testing) with the greatest degree of infestation in rewetted
material. DNA testing is highly specific for individual mold species,
and results are conclusive. Despite the presence of borates WSACI can
become infested with what is likely to be borate-tolerant species.
As the results of rewetted WSACI
suggest, wetness is a key factor in mold infestation. As such, drying
time is an important variable in initial applications. Unfortunately,
guidelines on adequate drying times based on empirical data (or even
modeled data) are not available (at least to my knowledge). Part of the
reason for this is that it is likely to vary considerably depending on
climatic and day-to-day weather conditions. In the mostly dry
environment of your state, I would expect that the drying time needed
before the closure of wall cavities would be much shorter than those
here in the Midwest during rainy periods and cold winter conditions
Studies on randomly chosen houses are
needed to: (1) determine moisture levels in WSACI after wall closure
(conducted across the country) as well as loss of moisture with time,
(2) determine mold types and concentrations in WSACI using quantitative
PCR several months after application, and (3) determine total airborne
mold levels of target species in WSACI houses using total mold spore
sampling with analyses conducted at 1000X magnification. Such studies
have not been conducted to date. Because of potential economic and
liability issues, it is unlikely that such studies will be conducted by
WSACI manufacturers; and it is not likely that this would be conducted
by independent investigations any time soon.
I have contemplated conducting such
studies. They would, of course, require financial support. The more
difficult part would be to convince homeowners or contractors to
participate. After all, who would want to risk the cost of removing
WSACI if it was shown to be a mold infestation/mold exposure problem?
Most people in my experience don’t go looking for problems that may cost
them a lot of money. As a consequence, one is limited to investigating
buildings associated with complaints.
In the case you report, it is quite
possible that from the naked eye (and even nose) there was no obvious
mold infestation problem. One may not even detect such a problem by
analyzing the material by culture plate techniques. However, the true
test is QPCR (or DNA testing). Such testing is the only valid way of
confirming whether WSACI has become infested during the installation and
curing process or upon rewetting.
I had a new house constructed for me 7
years ago. The contractor planned to install WSACI. I demurred. I
requested that fiberglass batts be installed. Fiberglass itself cannot
grow mold though mold infestation issues related to the bitumen coated
Kraft paper have been raised.
November 21, 2003
Indoor
Environmental Quality (2000), Thad Godish Ph.D., C.I.H
Direct E-mail
00tjgodish@bsu.edu
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