Chelelgo et al.
The material included only visible moisture observa-
imply poor air circulation, especially if it occurs between
window glazing, and it can cause deterioration of
wooden window frames.
tions, that is, visible changes or signs on materials with-
out any dismantling of structures. Damage in hidden
locations, for example, due to condensation or leakage
inside structures, may not have been visible. Moreover,
these observations represent only the figures reported by
inspectors and do not take into account those cases where
the damage was repaired. Therefore, this grading system
excludes exposure from previously repaired structural
damage. It also fails to take into account the time factor
of exposure. The subjectivity of the method and the fact
that repairs may or may not have eliminated the expo-
sure mean that the estimates obtained in this study may
be conservative.
Since different people from each of the cities carried
out the investigations, it could be expected that there
would be differences in the way each team judged the
severity of similar damage. Such a difference could even-
tually affect the distribution of homes into grades. Nev-
ertheless, it can be concluded that moisture problems in
homes, when the index homes were taken as problem
indicators, were currently found from both houses and
apartments. This concept is further reinforced by statis-
tical tests [95% confidence interval (CI)] that showed
the spread of index homes throughout the country to
be within a range of 21–32% for apartments and
Even though outdoor air may approach 100% RH
during the cold season, its moisture content is usually
very low. When cold outdoor air replaces indoor air, it
warms up and its RH drops significantly. Condensation
between windowpanes implies that indoor air, contain-
ing higher moisture content than outdoor air, can pen-
etrate into the window compartments and condense on
cold windowpanes. Thus, thermal bridges and the air
exfiltration through other leakage paths in the building
enclosure are more likely to cause both surface and hid-
den condensation on windows, wall cavities, exhaust
ducts, and attic spaces. However, newer dwellings in Fin-
land are often insulated from inside with vapor barriers
along the heated space. Good construction workman-
ship is crucial in avoiding air leakage across the enve-
lope that could result in concealed condensation, a
promoter of hidden mold growth.
The findings of this study indicated that most mois-
ture problems occurred in bathrooms or as leakage through
the envelope in both newer and older buildings. This
emphasizes the importance of good design, maintenance,
and housekeeping as prerequisites for attaining a good
indoor environment. These findings also indicate that
even though moisture preventive measures are generally
incorporated into the building code in Finland, they do
not invariably prevent moisture from entering the build-
ing, regardless of its age. Although RH levels in most
homes were low, there is a need for further research to
establish the major sources of moisture in indoor envi-
ronments and the behavior of heat, air, and moisture in-
doors in response to climatic changes and/or mechanical
systems that regulate the indoor climate. Further investi-
gations are also needed to study moisture condensation
within structural assemblies and in attic spaces where
structural ventilation is important, and to verify the mois-
ture load that structures should be able to tolerate.
3
3–43% for houses.
Findings of Air Moisture and Relative Humidity
This topic was evaluated because the characteristics of
damp housing are often associated with high levels of
1
3
humidity in the indoor environment. According to our
findings, this does not apply in the northern climate of
Finland. Data of current humidity were gathered in all
the dwellings, but without performing any long-term
monitoring. These data were used to calculate the actual
moisture content in both indoor and outdoor environ-
ments, as well as critical values.
Only 12% of the houses had higher than 45% hu-
midity, and in none of the houses did the humidity ex-
ceed 60%. Thirty-three percent of the inspected
apartments had higher than 45% RH, and in only 8%
did it exceed 60%. These findings indicate that it is un-
common to have moist air indoors in Finland. However,
variations might have existed if a long-term measuring
system had been adopted or if special cases like the
amount of moisture generated by the occupants had been
considered.
CONCLUSIONS
The grading system introduced in this study demonstrated
that most homes had been subjected to different levels of
moisture damage, the levels of which varied in severity and
according to the number of places where moisture damage
was observed. Therefore, there is a need to assess how differ-
ent levels of moisture relate to mold exposure and their ef-
fects on occupant health. In this respect, the grading system
can be used (1) to assess the relationships among degree of
damage in a home, exposure, and health of the occupants;
(2) to identify spaces or rooms with high risks of moisture
damage; and (3) as a statistical tool in assessing risks of ex-
posure to moisture-induced problems in buildings.
A total of 25% of the occupants reported surface
condensation on their windows. Windows are gener-
ally the first cold surfaces indoors where condensation
appears when the RH rises or when the surface tem-
perature drops sufficiently. Such condensation may also
76
Journal of the Air & Waste Management Association
Volume 51 January 2001