Mould growth on building materials - Statens Byggeforskningsinstitut

P. brevicompactum was the most frequently isolated Penicillium, confirming results from the
on-going Danish School study, where P. brevicompactum, P. corylophilum and P. chrysogenum
were the most common penicillia.
These results contradict results from North America, reporting P. aurantiogriseum and P.
viridicatum as the most abundant Penicillium species. This might be due to misidentification
with P. palitans and other species from the aurantiogriseum-complex (J.C. Frisvad, personal
communication), but unfortunately it has not been possible to obtain any of these Penicillium
isolates to verify the identification.
4.2 Fungal <strong>growth</strong> on materials
In papers 2 and 3, material samples were water-damaged (aw ≈ 1) and significantly higher
number of spores were applied to the materials than naturally found in buildings. The moulds
were usually able to cover the materials where they occur "naturally" within 4-10 days, clearly
demonstrating that when water damages occur, action should be taken the same day if materials
should be saved. This also complies with observations by several consultant engineers
(M. Ø. Hansen, personal communication), who report complains from the inhabitants
within 10-30 days after a single water damage, and complaints within 2-4 days in buildings
with a known water damage history.
When using lower aw (papers 10 and 13) the <strong>growth</strong> rate decreased dramatically and with
very few exceptions only the primary and secondary colonisers were observed growing on
the materials. At stationary conditions (paper 10), only Penicillium and Aspergillus species
grew, with P. chrysogenum and A. versicolor being the most common species. However on
wooden materials A. flavus and Eurotium spp. were observed quite frequently and always
with significant biomass. At 5°C only P. chrysogenum and A. versicolor grew, with the latter
producing conidiophores with very few conidia.
Wooden and wallpapered materials supported <strong>growth</strong> down to 78% RH (paper 10), which
was lower than the other materials. It was seen that the planned pinewood was usually not
infested on as much of the surface as the rough materials, but on the areas where <strong>growth</strong>
1
5 cm
Figure 6. Concrete after 4 months at 95% RH
and 10°C, at #1 can A. versicolor conidiophores
be seen and at #2 sterile mycelia.
2
2
occurred there was not significant difference in the
produced biomass. At 5°C this limit was about 90%
RH, whereas the results only indicates a limit between
80 and 90% RH. These results comply perfectly
with the results of Hukka & Viitanen 141 and
Grant et al 55 , when the uncertainties of the RH
measurements of both studies (±2%) are taken into
account.
Interestingly, the gypsum boards did not support
<strong>growth</strong>