Re: Two interesting abstracts on mold growth

[Guest guest]

Ole

1 While mold will not grow well on glass or mineral fibre insulation, it does very well indeed if the insulation has been acting as an air filter before the insulation is wetted. The mold grows on the organic part of the dirt, not the glass or mineral fibre or its adhesives. However, I have noted that really dirty glass fibre insulation that has become wet and got moldy then disintegrates, as if the adhesive had disappeared. Karin Foarde did some fun research on growth of mold on dirty filters that were treated with an anti-microbial. The mold grew just fine on the dirt above the filter, thank you. Maybe it would have grown better if it could have grown down into the filter, but it did quite well enough without that avenue. Food is food, even if in a dangerous neighbourhood.

2 Given the growth regimes of different molds, I would expect that not much growth would occur at lower relative humidities unless the species involved were highly xerophillic. When we did the Wallaceburg study over a decade ago, 'everybody' knew that we would not find Wallemia sebi in house mold samples. But it was there, if a whole cascade of wet-to dry-loving molds were also there. Provide the right conditions and mold will grow. Far from the source of moisture conditions were just fine for the Wallemia sebi, which will continue to grow even at water activities of 0.65, long after it has been too dry for other species with higher water activity requirements.

Jim H. White SSAL

Two interesting abstracts on mold growth

Here are two interesting articles for those who are interrested in mold -growth in buildings.

The first states that glass and rock wool insulation has little succeptibility to mold growth

The second gives 78 % RH / 20 C as the lower level for mold growth on starch-containing materials.

Comments ?

International Biodeterioration & Biodegradation Volume 54, Issue 4 , December 2004, Pages 277-282

Fungal growth on different insulation materials exposed to different moisture regimes

Morten Klamer, , a, beth Morsinga and Thor Husemoenb a Danish Technological Institute, Timber, Gregersensvej, P.O. Box 141, Taastrup DK-2630, Denmarkb Rockwool International A/S, Research and Development, Hovedgaden, Hedehusene DK-2640, Denmark Received 7 December 2003; Revised 1 March 2004; accepted 19 March 2004. Available online 21 May 2004.

Abstract

Commercially available paper, flax, glass wool and rock wool insulation materials were tested for sensitivity to moisture and the ability of fungi to grow on them under different moisture regimes. Three levels of moisture were used, ambient, simulated rain and water holding capacity. After wetting, the materials were inoculated with a mixture of fungi and incubated at 26°C in boxes with high moisture levels for 4 weeks. The greatest degree of fungal growth was observed on paper and flax insulation materials initially conditioned to ambient moisture levels. Paper and flax insulation were strongly affected by moisture, with all treatments showing losses in dry mass of approx. 20%, except for paper subjected to simulated rain treatment in which the loss was 39%. Glass and rock wools were not sensitive to moisture and were resistant to fungal degradation, showing only traces of fungal growth and minimal loss in dry mass over 4 weeks.

Mould growth on building materials under low water activities. Influence of humidity and temperature on fungal growth and secondary metabolism

K. F. Nielsen, , a, b, G. Holma, L. P. Uttrupa, 1 and P. A. Nielsena a Danish Building and Urban Research, Dr Neergaards Vej 15, DK-2970, Hørsholm, Denmarkb Center for Microbial Biotechnology, BioCentrum-DTU, Building 221,Technical University of Denmark, DK-2800 Kgs, Lyngby, Denmark Received 22 March 2004; accepted 12 May 2004. Available online 1 July 2004.

Abstract

The influence of relative humidity (RH) and temperature on growth and metabolism of eight microfungi on 21 different types of building material was investigated. The fungi were applied as a dry mixture to the materials, which were incubated at 5°C, 10°C, 20°C and 25°C at three humidity levels in the range 69–95% RH over 4–7 months. The lower limit for fungal growth on wood, wood composites and starch-containing materials was 78% RH at 20–25°C and increased to 90% RH at 5°C. An RH of 86% was necessary for growth on gypsum board. Ceramic materials supported growth at RH >90%, although 95% RH was needed to yield chemically detectable quantities of biomass. Almost exclusively only Penicillium, Aspergillus and Eurotium (contaminant) species grew on the materials. Production of secondary metabolites and mycotoxins decreased with humidity and the quantities of metabolites were insignificant compared with those produced at high RH (RH >95%), except in the case of Eurotium.

_________________________________________________

Ole Carlson

MYCOTEAM as

Tlf: +47 22 96 56 77

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FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner.

[Guest guest]

So are all those samples that show high mold levels on insulation wrong?

S. Abrams, CIH

ARS Environmental Health, Inc.

Ole Carlson wrote:

Here are two interesting

articles for those who are interrested in mold -growth in buildings.

The first states that glass and

rock wool insulation has little succeptibility to mold growth

The second gives 78 % RH / 20 C

as the lower level for mold growth on starch-containing materials.

Comments ?

International Biodeterioration &

Biodegradation

Volume

54, Issue 4 , December 2004, Pages 277-282

Fungal growth on different insulation materials exposed to

different moisture regimes

Morten Klamer, , a,

beth Morsinga

and Thor Husemoenb

a Danish Technological Institute,

Timber, Gregersensvej, P.O. Box 141, Taastrup DK-2630, Denmark

b Rockwool International A/S, Research

and Development, Hovedgaden, Hedehusene DK-2640, Denmark

Received 7 December 2003; Revised 1 March 2004; accepted 19 March

2004. Available online 21 May 2004.

Abstract

Commercially available paper, flax, glass wool and rock wool

insulation materials were tested for sensitivity to moisture and the

ability of fungi to grow on them under different moisture regimes.

Three levels of moisture were used, ambient, simulated rain and water

holding capacity. After wetting, the materials were inoculated with a

mixture of fungi and incubated at 26°C in boxes with high moisture

levels for 4 weeks. The greatest degree of fungal growth was observed

on paper and flax insulation materials initially conditioned to ambient

moisture levels. Paper and flax insulation were strongly affected by

moisture, with all treatments showing losses in dry mass of approx.

20%, except for paper subjected to simulated rain treatment in which

the loss was 39%. Glass and rock wools were not sensitive to moisture

and were resistant to fungal degradation, showing only traces of fungal

growth and minimal loss in dry mass over 4 weeks.

Mould growth on building materials under low water activities.

Influence of humidity and temperature on fungal growth and secondary

metabolism

K. F. Nielsen, , a,

b,

G. Holma,

L. P. Uttrupa,

1

and P. A. Nielsena

a Danish Building and Urban Research,

Dr Neergaards Vej 15, DK-2970, Hørsholm, Denmark

b Center for Microbial Biotechnology,

BioCentrum-DTU, Building 221,Technical University of Denmark, DK-2800

Kgs, Lyngby, Denmark

Received 22 March 2004; accepted 12 May 2004. Available online 1 July

2004.

Abstract

The influence of relative humidity (RH) and temperature on growth

and metabolism of eight microfungi on 21 different types of building

material was investigated. The fungi were applied as a dry mixture to

the materials, which were incubated at 5°C, 10°C, 20°C and 25°C at

three humidity levels in the range 69–95% RH over 4–7 months. The lower

limit for fungal growth on wood, wood composites and starch-containing

materials was 78% RH at 20–25°C and increased to 90% RH at 5°C. An RH

of 86% was necessary for growth on gypsum board. Ceramic materials

supported growth at RH >90%, although 95% RH was needed to yield

chemically detectable quantities of biomass. Almost exclusively only Penicillium,

Aspergillus and Eurotium (contaminant) species grew on the

materials. Production of secondary metabolites and mycotoxins decreased

with humidity and the quantities of metabolites were insignificant

compared with those produced at high RH (RH >95%), except in the

case of Eurotium.

_________________________________________________

Ole Carlson

MYCOTEAM

as

Tlf: +47 22

96 56 77

Tlf (dir):

+47 22 96 56 79

Tlf (mob):

+47 952 38 931

Faks: +47 22

46 55 52

Forskningsveien

3B

Postboks 5,

Blindern

0313 Oslo

www.mycoteam.no

FAIR USE NOTICE:

This site contains copyrighted material the use of which has not always

been specifically authorized by the copyright owner. We are making such

material available in our efforts to advance understanding of

environmental, political, human rights, economic, democracy,

scientific, and social justice issues, etc. We believe this constitutes

a 'fair use' of any such copyrighted material as provided for in

section 107 of the US Copyright Law. In accordance with Title 17 U.S.C.

Section 107, the material on this site is distributed without profit to

those who have expressed a prior interest in receiving the included

information for research and educational purposes. For more information

go to: http://www.law.cornell.edu/uscode/17/107.shtml.

If you wish to use copyrighted material from this site for purposes of

your own that go beyond 'fair use', you must obtain permission from the

copyright owner.

[Guest guest]

Dear List:

I have some comments on the first of these abstracts. It is no surprise

that fiberglass or rockwool do not support mold growth. Molds need organic

material for a food source. If the material in question is not organic in

nature, one would not expect molds to grow there. What can happen is that

if dust, shed skin cells, or other organic matter accumulate on the surface

of fiberglass, etc., these materials can support the growth of mold.

In the laboratory using "virgin" fiberglass or rockwool, there is not much

if anything for the molds to live on. However, in the real world, molds

can appear to grow on fiberglass or rockwool, although they are really feeding

on the dust, etc. which has accumulated on the surface of the material.

Regards to all,

Dydek Dr. M. Dydek, Ph.D., D.A.B.T., P.E.

Industrial Toxicologist and Engineer

Dydek Environmental Consulting

Austin, Texas Web Site: www.tox-expert.com

Office Phone:

Office FAX:

Mobile Phone:

Ole Carlson wrote:

Here are two interesting articles

for those who are interrested in mold -growth in buildings.

The first states that glass and rock

wool insulation has little succeptibility to mold growth

The second gives 78 % RH / 20 C as

the lower level for mold growth on starch-containing materials.

Comments ?

International Biodeterioration & Biodegradation

Volume

54, Issue 4 , December 2004, Pages 277-282

Fungal growth on different insulation materials exposed to different

moisture regimes

Morten Klamer

,

, a,

beth Morsinga

and Thor Husemoenb

a Danish Technological Institute, Timber,

Gregersensvej, P.O. Box 141, Taastrup DK-2630, Denmark

b Rockwool International A/S, Research and

Development, Hovedgaden, Hedehusene DK-2640, Denmark

Received 7 December 2003; Revised 1 March 2004; accepted 19 March 2004.

Available online 21 May 2004.

Abstract

Commercially available paper, flax, glass wool and rock wool insulation

materials were tested for sensitivity to moisture and the ability of fungi

to grow on them under different moisture regimes. Three levels of moisture

were used, ambient, simulated rain and water holding capacity. After wetting,

the materials were inoculated with a mixture of fungi and incubated at 26°C

in boxes with high moisture levels for 4 weeks. The greatest degree of fungal

growth was observed on paper and flax insulation materials initially conditioned

to ambient moisture levels. Paper and flax insulation were strongly affected

by moisture, with all treatments showing losses in dry mass of approx. 20%,

except for paper subjected to simulated rain treatment in which the loss

was 39%. Glass and rock wools were not sensitive to moisture and were resistant

to fungal degradation, showing only traces of fungal growth and minimal

loss in dry mass over 4 weeks.

Mould growth on building materials under low water activities. Influence

of humidity and temperature on fungal growth and secondary metabolism

K. F. Nielsen

,

, a,

b,

G. Holma,

L. P. Uttrupa,

1

and P. A. Nielsena

a Danish Building and Urban Research, Dr

Neergaards Vej 15, DK-2970, Hørsholm, Denmark

b Center for Microbial Biotechnology, BioCentrum-DTU,

Building 221,Technical University of Denmark, DK-2800 Kgs, Lyngby, Denmark

Received 22 March 2004; accepted 12 May 2004. Available online 1 July

2004.

Abstract

The influence of relative humidity (RH) and temperature on growth and

metabolism of eight microfungi on 21 different types of building material

was investigated. The fungi were applied as a dry mixture to the materials,

which were incubated at 5°C, 10°C, 20°C and 25°C at three humidity levels

in the range 69–95% RH over 4–7 months. The lower limit for fungal growth

on wood, wood composites and starch-containing materials was 78% RH at 20–25°C

and increased to 90% RH at 5°C. An RH of 86% was necessary for growth on

gypsum board. Ceramic materials supported growth at RH >90%, although

95% RH was needed to yield chemically detectable quantities of biomass.

Almost exclusively only Penicillium, Aspergillus and Eurotium

(contaminant) species grew on the materials. Production of secondary metabolites

and mycotoxins decreased with humidity and the quantities of metabolites

were insignificant compared with those produced at high RH (RH >95%),

except in the case of Eurotium.

_________________________________________________

Ole Carlson

MYCOTEAM

as

Tlf: +47 22 96

56 77

Tlf (dir): +47

22 96 56 79

Tlf (mob): +47 952

38 931

Faks: +47 22 46

55 52

Forskningsveien

3B

Postboks 5, Blindern

0313 Oslo

www.mycoteam.no

FAIR USE NOTICE:

This site contains copyrighted material the use of which has not always

been specifically authorized by the copyright owner. We are making such material

available in our efforts to advance understanding of environmental, political,

human rights, economic, democracy, scientific, and social justice issues,

etc. We believe this constitutes a 'fair use' of any such copyrighted material

as provided for in section 107 of the US Copyright Law. In accordance with

Title 17 U.S.C. Section 107, the material on this site is distributed without

profit to those who have expressed a prior interest in receiving the included

information for research and educational purposes. For more information go

to: http://www.law.cornell.edu/uscode/17/107.shtml.

If you wish to use copyrighted material from this site for purposes of your

own that go beyond 'fair use', you must obtain permission from the copyright

owner.

[Guest guest]

"So are all those samples that show high mold levels on insulation wrong?"

The samplings are not wrong but what is not necessarily made clear by that sampling is what the discovered mold is actually feeding on. Generally speaking, its not the fiberglass or rock wool itself; it’s the organic material that eventually becomes trapped on or within those kinds of insulation materials. Its only newer fiberglass and rock wool products, that have not had sufficient time to gather sufficient nutrients, that have "little susceptibility to mold growth". Give that material a few years in service and those factors will likely change.

Such insulation within wall systems that experience either air infiltration or exfiltration will eventually "filter" out enough organic material from the air passing through to support microbial growth on or within the insulation. The same is true of fiberglass duct liners. All the passage of air eventually deposits dust (some percentage of which will be organic material) on the interior of the duct liner and that is what the mold will seek out when other environmental conditions are favorable for mold development.

While the article about fiberglass and rock wool having little susceptibility to mold growth is all very interesting, its also all very irrelevant unless that information can be taken and used to develop ways of keeping the organic material from building up within those products. While this can often be done by devising better control over the air movement in and around the product, that often ends up creating moisture problems. The added moisture then becomes a bigger problem than just the presence of the deposited nutrients might have otherwise been.

The conventional wisdom in building science therefore currently focused more on maintaining control over the moisture content within a given building product than worrying about its accumulated (or inherent) nutrient content.

Phil S.

Re: Two interesting abstracts on mold growth

So are all those samples that show high mold levels on insulation wrong? S. Abrams, CIHARS Environmental Health, Inc.Ole Carlson wrote:

Here are two interesting articles for those who are interrested in mold -growth in buildings.

The first states that glass and rock wool insulation has little succeptibility to mold growth

The second gives 78 % RH / 20 C as the lower level for mold growth on starch-containing materials.

Comments ?

International Biodeterioration & Biodegradation Volume 54, Issue 4 , December 2004, Pages 277-282

Fungal growth on different insulation materials exposed to different moisture regimes

Morten Klamer, , a, beth Morsinga and Thor Husemoenb a Danish Technological Institute, Timber, Gregersensvej, P.O. Box 141, Taastrup DK-2630, Denmarkb Rockwool International A/S, Research and Development, Hovedgaden, Hedehusene DK-2640, Denmark Received 7 December 2003; Revised 1 March 2004; accepted 19 March 2004. Available online 21 May 2004.

Abstract

Commercially available paper, flax, glass wool and rock wool insulation materials were tested for sensitivity to moisture and the ability of fungi to grow on them under different moisture regimes. Three levels of moisture were used, ambient, simulated rain and water holding capacity. After wetting, the materials were inoculated with a mixture of fungi and incubated at 26°C in boxes with high moisture levels for 4 weeks. The greatest degree of fungal growth was observed on paper and flax insulation materials initially conditioned to ambient moisture levels. Paper and flax insulation were strongly affected by moisture, with all treatments showing losses in dry mass of approx. 20%, except for paper subjected to simulated rain treatment in which the loss was 39%. Glass and rock wools were not sensitive to moisture and were resistant to fungal degradation, showing only traces of fungal growth and minimal loss in dry mass over 4 weeks.

Mould growth on building materials under low water activities. Influence of humidity and temperature on fungal growth and secondary metabolism

K. F. Nielsen, , a, b, G. Holma, L. P. Uttrupa, 1 and P. A. Nielsena a Danish Building and Urban Research, Dr Neergaards Vej 15, DK-2970, Hørsholm, Denmarkb Center for Microbial Biotechnology, BioCentrum-DTU, Building 221,Technical University of Denmark, DK-2800 Kgs, Lyngby, Denmark Received 22 March 2004; accepted 12 May 2004. Available online 1 July 2004.

Abstract

The influence of relative humidity (RH) and temperature on growth and metabolism of eight microfungi on 21 different types of building material was investigated. The fungi were applied as a dry mixture to the materials, which were incubated at 5°C, 10°C, 20°C and 25°C at three humidity levels in the range 69–95% RH over 4–7 months. The lower limit for fungal growth on wood, wood composites and starch-containing materials was 78% RH at 20–25°C and increased to 90% RH at 5°C. An RH of 86% was necessary for growth on gypsum board. Ceramic materials supported growth at RH >90%, although 95% RH was needed to yield chemically detectable quantities of biomass. Almost exclusively only Penicillium, Aspergillus and Eurotium (contaminant) species grew on the materials. Production of secondary metabolites and mycotoxins decreased with humidity and the quantities of metabolites were insignificant compared with those produced at high RH (RH >95%), except in the case of Eurotium.

_________________________________________________

Ole Carlson

MYCOTEAM as

Tlf: +47 22 96 56 77

Tlf (dir): +47 22 96 56 79

Tlf (mob): +47 952 38 931

Faks: +47 22 46 55 52

Forskningsveien 3B

Postboks 5, Blindern

0313 Oslo

www.mycoteam.no

FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. FAIR USE NOTICE:This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available in our efforts to advance understanding of environmental, political, human rights, economic, democracy, scientific, and social justice issues, etc. We believe this constitutes a 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit to those who have expressed a prior interest in receiving the included information for research and educational purposes. For more information go to: http://www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner.