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Analysis of Moisture Findings in the Interior Spaces of
Finnish Housing Stock
a
a
a
a
a
Joseph Chelelgo , Ulla Haverinen , Mikko Vahteristo , Jari Koivisto , Tuula Husman
,
a
b
Aino Nevalainen & Esa Jääskeläinen
a
Division of Environmental Health , National Public Health Institute , Kuopio , Finland
b
Econs Ltd , Vuorela , Finland
Published online: 27 Dec 2011.
To cite this article: Joseph Chelelgo , Ulla Haverinen , Mikko Vahteristo , Jari Koivisto , Tuula Husman , Aino Nevalainen & Esa
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TECHNICAL PAPER
ISSN 1047-3289 J. Air & Waste Man
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Copyright 2001 Air & Waste Management Association
Analysis of Moisture Findings in the Interior Spaces of Finnish
Housing Stock
Joseph Chelelgo, Ulla Haverinen, Mikko Vahteristo, Jari Koivisto, Tuula Husman, and
Aino Nevalainen
National Public Health Institute, Division of Environmental Health, Kuopio, Finland
Esa Jääskeläinen
Econs Ltd., Vuorela, Finland
ABSTRACT
INTRODUCTION
A grading system was developed to rate the moisture dam-
age profile of dwellings and to study the relationship be-
tween moisture-induced indoor air problems and
occupant health. A total of 630 randomly selected houses
and apartments, built between 1950 and 1989, were visu-
ally inspected. Moisture observations were standardized
into three damage levels. Thus, a system to classify the
homes into three grades was devised. The two grades of
homes associated with the highest levels of damage were
graded as index homes.
Epidemiologic studies have linked exposure to mold in
homes to respiratory illnesses and symptoms of the occu-
1-4
pants living in these houses. Mold growth can develop
when moisture is allowed to accumulate on interior sur-
faces or in construction materials, for example, due to con-
densation or water leaks. The presence of excess moisture
in structures has been used in the epidemiologic literature
5
as a determinant of exposure since it is the primary factor
that leads to growth of microorganisms. In general, mi-
crobes may grow on any surface provided there is enough
moisture and nutrients available. Therefore, such a mois-
ture observation in an indoor environment can be used as
an indicator of a potential microbial problem that may
Overall, 51% of the sample had some kind of moisture
fault in them and one in every three homes (33%) was clas-
sified as an index home. The mean number of damage inci-
dents in the index dwellings varied from 1.4 to 2.6. The
mean number of damage incidents in the reference homes
was 0.28. Prevalence of index dwellings was significantly
higher (p < 0.01) in houses (38%) than in apartments (26%).
There was no major difference in the prevalence of index
buildings in houses built in any particular decade (30–35%).
Moisture was observed in 28% of bathrooms, in 10% of kitch-
ens, and in 17% of other spaces. Indoor relative humidity
6
subsequently lead to exposure to microbial emissions.
In Finland, the climate is cold for most of the year.
Mean temperatures at the height of winter, February, vary
from –6 °C in the south to –14 °C in the mid-interior and
–10 °C in the north. The entire country experiences aver-
age monthly temperatures of 13–17 °C in the summer
7
and less than 650-mm annual precipitation.
In cold climates, transfer of heat, air, and moisture
across a building envelope in response to a difference in
thermal and moisture conditions can lead to accumula-
tion of moisture on building parts, deposition of mois-
ture on cold interior surfaces, and subsequently, may
threaten their durability and functionality. However, the
level of indoor air humidity during cold seasons is gener-
ally low because of the low moisture content in supported
outdoor air. Therefore, problems related to condensation
due to moisture migration across a building enclosure can
be minimized by employing proper insulation with va-
por and moisture barriers.
(RH) levels were low in most homes.
IMPLICATIONS
The grading system developed in this study provides a
method of analyzing moisture findings and their inten-
sity in dwellings. This knowledge is needed both for un-
derstanding the profile of existing moisture damage, par-
ticularly in cold climates, and for assessing how differ-
ent levels of moisture damage relate to mold exposure
and on occupant health. Therefore, the grading system
may be useful both in assessing the condition of a build-
ing as a surrogate of exposure in epidemiologic studies,
and as a decision-making instrument in assessing need
for repair.
However, the absence of high indoor humidity does
not exclude risks of moisture problems in a home. For
instance, water leaks can occur due to defects in roofs,
Volume 51 January 2001
Journal of the Air & Waste Management Association 69

Chelelgo et al.
walls, foundations, balconies, and windows. Frost can also
damage the building enclosure and increase the risk of
leaks. Such defects could lead to moisture being intro-
duced into heated spaces or locations within the enclo-
sure that are difficult to detect, for example, in wall cavities
of an external wall, and this could subsequently result in
not only geographically distinct, but also represent local
variations with respect to the harshness of the winter.
Approximately three-fourths of the residential build-
1
2
ings in Finland were built after the 1950s. Therefore,
houses and apartments were randomly selected from
building permits issued across four decades, from the 1950s
through the 1980s. In each city, 30 houses from each de-
cade were selected. An extra set of 30 houses from the
1970s and only one sample of 30 houses representing the
1950s were drawn from Kuopio. In each town, 20 apart-
ments from 10 block units were randomly selected from
each of the four decades. Each decade not only tells the
age of the building but also represents a construction style,
which in Finland has changed extensively since the 1950s.
8
,9
molds growing in hidden spaces.
Liquid water originating from interior plumbing leaks,
faulty washing machines, and the use of bathrooms and
1
0
kitchens also pose potential moisture problems. Build-
ing materials in spaces where there is a high water usage
may retain high moisture contents even after the sur-
rounding air humidity has returned to normal levels. This
is also a crucial factor favoring microbial growth within
interior materials.
The prevalence of moisture problems in private
houses has been previously reported by Nevalainen et al.
On-Site Inspection
11
The field crew were civil engineers who were all given
similar guidelines on how to seek out and identify signs
of moisture condensation or water damage in locations
within a home such as walls, roofs, floors, windows, ven-
tilation, and plumbing systems. They recorded signs of
water leaks, condensation on cold surfaces, detached in-
terior coverings (e.g., linoleum and tiles), blistered painted
walls, detached interior surfaces or wallboards, and any
other signs that could be interpreted as moisture damage.
No structural components were dismantled. A checklist
was used to standardize the results based on the type and
severity of the damage and to pinpoint the locations on
The paper described both observations of moisture and
moisture repairs. These analyses, however, were based on
dichotomous groupings and did not take into account
the number and severity of the observed moisture faults.
The present paper quantifies these moisture problems in
both private houses and apartments. The material is pre-
dominantly based on information collected during a sur-
vey, that is, only that damage in existence at the time of
the survey was included. The aim of the study was to de-
velop a grading system of dwellings that would provide a
method of analyzing moisture findings in sequence. This
knowledge is needed for understanding the profile of ex-
isting damage and for classifying residences in epidemio-
logic studies.
11
which they were found. Surface moisture recorders were
used to identify moist spots. Temperatures and humidity
levels, both indoors and outdoors, were recorded at the
time of inspection.
METHODS
Homeowners were asked questions about signs of cur-
rent or previous moisture-related damage and repair ac-
tions taken to repair them. They were also asked about
their indoor moisture-producing activities, such as the use
of humidifiers, how they dry their laundry, and the num-
ber of people living in the dwelling. These data were re-
corded according to a checklist in an interview before the
inspection.
Random Sample
Between 1993 and 1996, several surveys were conducted
to assess the extent of moisture-related damage in the
current national housing stock and to investigate the as-
sociation between the presence of moisture and occupant
health. A total of 630 private homes were randomly se-
lected for inspection for signs of current or previous mois-
ture-induced damage in their interior spaces. The selection
comprised 390 houses and 240 apartments, which were
drawn from 120 blocks of flats.
The sample was chosen to represent a cross section
of the current Finnish housing stock. It was drawn from
three large cities in three different regions: Oulu, Kuopio,
and Helsinki. In all, 54% of the houses came from the
Kuopio district (Kuopio and Kiuruvesi), and the remain-
ing sample was drawn in equal proportions (23% each)
from Helsinki and Oulu. All the apartments were drawn
in equal proportions from all three cities: Helsinki, Kuopio,
and Oulu. The regions represent the southern, central,
and northern populated zones, respectively. The zones are
Criteria for Grading Homes
The home spaces were classified into three domains: bath-
rooms, kitchens, and other spaces. All damage was tagged
according to the domain. Furthermore, the damage in each
domain was tagged with the surface on which it was found
or the equipment that had induced the damage (e.g.,
vents). Interior materials were similarly registered with
the type of damage associated with them. Finally, all of
this information was coded and processed using SAS sta-
tistical software.
The degree of damage in a home was estimated by
the severity of each damage incident according to the
70
Journal of the Air & Waste Management Association
Volume 51 January 2001

Chelelgo et al.
1
1
scale of the predesigned checklist, including all signs
of moisture damage. The damage could be located any-
where within the three space domains. Three groups of
damage patterns were created as indicators of the de-
gree of moisture damage within a home. The criteria
were based on the most severe damage in the home,
taking into account other observed damage incidents.
The level of damage in a home was established by orga-
nizing incidents according to one of these three sets of
damage patterns. Samples without any moisture obser-
vation and those with only minor observations were
pooled together and classified as grade I. Samples iden-
tified with notable moisture patterns were classified as
grade II, and those with significant problems were clas-
sified as grade III.
houses). Grade I samples were considered as reference
homes, that is, samples predominately free of moisture
problems.
RESULTS
Prevalence of Moisture Observations
At least one moisture observation was made in 54% of
the houses and 45% of the apartments. Relatively more
houses than apartments had signs of moisture. Table 1
shows the results of houses and apartments divided into
the grades separately.
The overall distribution of homes for index (grades II
and III) and reference (grade I) homes are presented in Fig-
ure 1. These findings indicate that grade II and III homes
made up 33% of the dwellings inspected by our crew, and
that 38% of the houses and 26% of the apartments were
in the index category. A statistically significant difference
(p < 0.01) was observed between the distribution of houses
and apartments into the index and reference groups.
Figure 2 shows the distribution of each grade of houses
and apartments according to which decade they were
built. The results indicate that houses with the most mois-
ture observations were built in the 1960s and 1970s, while
apartments built in the 1950s and 1980s had the most
moisture observations. In general, about one in every two
homes built between 1950 and 1989 had a sign of mois-
ture, and the percentage of index homes among the
samples ranged from 30 to 35%.
A home was classified into grade I if it fulfilled one of
the following conditions during the inspection:
•
•
No visible moisture damage was recorded.
Minor moisture damage, such as colored stains
on interior coverings that were caused by faulty
appliances (e.g., washing and dishwashing ma-
chines) or pipe leaks, was observed, and no fur-
ther consequences would be anticipated.
Only one patch of deteriorated interior finish or
covering, which needed drying, re-gluing, or fix-
ing, was observed.
•
A grade II home met one of the following conditions:
•
A single observation of a damaged interior struc-
tural component that needed opening, drying
and renewal, or minor repair, was recorded.
A single patch of deteriorated interior finishing
or covering (as defined in grade I) was observed,
along with other damage of similar severity. The
other damage could be of the same level of se-
verity or lower, but not worse.
Number of Damage Sites in Different
Grades of Homes
•
The mean number of damage sites in graded houses and
apartments is shown in Figure 3. The mean number of dam-
age sites in grade I houses and apartments was 0.28, collec-
tively. The mean number of damage sites in grade II houses
and apartments was 1.4 and 1.7, respectively, whereas in
grade III it was 2.4 and 2.6, respectivly. The mean number
of damage sites in grade II and III homes according to when
they were built is presented in Figure 4. Moisture observa-
tions were spread in relatively equal proportions among
homes built throughout study period, although the 1960s
and 1970s had slightly less than the average values.
A grade III home met one of the following conditions:
•
A damaged interior structural component (as de-
fined in grade II) was observed, together with
other damage. The other damage could be of the
same level of severity or less.
A functional element that needed partial or total
renewal was observed, with or without the pres-
ence of other damage. The severity of damage in
this category had to be more significant than any
damage appearing in grades I and II.
•
Table 1. Distribution of graded houses and apartments and 95% CI for an observa-
tion of grade II or III (index) homes.
This grading system was designed to classify homes
into a spectrum of grades, with grade I representing
homes with no significant moisture problems, grade II
homes with notable moisture problems, and grade III
homes with significant moisture problems. Moisture
findings in grade II and III samples were considered im-
portant, and therefore these homes were collectively re-
ferred to as index homes (index apartments and index
Reference Homes
Grade I
Index Homes
Grade II Grade III
Index Homes
N(%)
N(%)
N(%)
N(%)
95% CI
Houses
Apartments
243 (62)
89 (23)
58 (15)
147 (38)
63 (26)
33–43
21–32
177 (74)
28 (11.5) 35 (14.5)
Volume 51 January 2001
Journal of the Air & Waste Management Association 71

Chelelgo et al.
Figure 1. Percentage of reference and index homes in the Finnish housing stock according to dwelling type.
Figure 2. Distributions of graded (a) houses and (b) apartments into the decades during which they were built.
72
Journal of the Air & Waste Management Association
Volume 51 January 2001

Chelelgo et al.
Figure 3. Mean number of damage sites in each grade of houses and apartments.
Figure 4. Mean number of damage sites in homes in grades II and III according to the decade in which they were constructed.
Distribution of Damage According to Domain
Spaces and Structural Assemblies
the index apartments and in 55% of the index houses.
This figure of index homes with moisture observations in
the bathrooms accounted for 20% of the overall sample
of the apartments and 20% of the houses. Furthermore,
20% of the apartments had an extra bathroom or toilet,
and the proportion of moisture observations was 10%
higher in these homes.
Observations in the bathrooms of apartments were
almost exclusively restricted to damage on the floor and
wall covering. Problems on walls and floors of the overall
apartment sample were seen in 15 and 18% of the apart-
ments, respectively. Plumbing leaks were not common in
the bathrooms. We also checked if the materials used in
The presence of moisture observations in interior spaces
and structural components is presented in Table 2. About
half of the grade III homes showed signs of moisture dam-
age in both the floor and roof structures. Moisture prob-
lems in bathrooms or toilets were prevalent in the homes.
Overall, 28% of the inspected dwellings had some sign of
inappropriate moisture in the bathroom. The grading sys-
tem filtered samples so that the percentage of the homes
with moisture observations in bathrooms in grades I, II,
and III were 12, 51, and 73%, respectively. Moisture-
induced damage in the bathrooms was found in 74% of
Volume 51 January 2001
Journal of the Air & Waste Management Association 73

Chelelgo et al.
Table 2. Distributions of moisture observations into different locations and spaces of the homes.
Location:
Floors
Walls
Plum
Roofs
Wind
Vents
Bath
Kitch
Other
a
a
a
a
a
a
a
a
a
Category (N)
%
%
%
%
%
%
%
%
%
Grade I (420)
Grade II (117)
Grade III (93)
Houses (390)
Apartments (240)
5
7
4
11
27
10
7
4
2
11
19
4
1
8
12
51
73
28
29
26
30
26
31
28
2
7
22
48
12
19
28
8
29
53
18
18
11
19
15
24
18
33
42
21
-
22
26
9
26
48
14
21
20
20
13
17
17
16
6
11
3
2
10
14
9
1950s (90)
1960s (150)
1970s (220)
1980s (170)
10
8
8
13
5
12
23
11
15
1
12
18
15
10
7
7
6
8
6
6
10
10
All (630)
9
7
5
Note: N is the sample size; Plum = plumbing, Wind = window frame, Vents = exhaust vents, Bath = bathroom, Kitch = kitchen, and Other = spaces other than kitchens and bathrooms;
a
Homes (%) with moisture fault in this location/facility.
the bathrooms of apartments contributed to the num-
ber of moisture observations, but this was not conclu-
sive because such a high proportion of apartments used
the same kind of covering materials (wall and floor tiles).
However, a small portion of apartments that used plas-
tic wall and floor linoleum usually showed no visible
moisture damage.
Relative Humidity Measurements
and Moisture Content
Figure 5 shows plots of calculated indoor moisture con-
3
tent (g/m ) against outdoor temperatures in 480 homes.
The recordings are based on relative humidity (RH) mea-
surements during the inspection visit. RH recordings in
these homes at the time when outdoor temperatures var-
o
o
The most common wall materials near the water tab
in the bathrooms of the apartments were concrete (61%)
and brick (24%). Unusual moisture was observed in 12%
of the bathrooms with concrete walls, in 9% with brick
walls, and in 20% with building board covering. A few
apartments had bathrooms made of prefabricated me-
tallic sheathings, and they did not appear to have any
problems.
ied from –30 C to +30 C showed that ~85% of the houses
and 60% of the apartments had an RH between 20 and
45%. In all, 20% of the homes had an RH higher than
45%, but only 3% of them showed levels higher than 60%.
Twenty-five percent of homeowners reported frost or
condensation on windowpanes. One-third of the reported
cases occurred between the windowpanes; otherwise, they
were on the inside pane. Occupants of homes in the two
coastal cities, Helsinki and Oulu, reported 10% more con-
densation or frost on windowpanes than those living in
the inland town of Kuopio reported. In grade II and III
homes, condensation was reported 10% more frequently
than it was in grade I homes.
About 10% of the homes were reported to have a
moisture problem in the kitchen. The occurrence of mois-
ture damage in the kitchens was 33% in index apartments,
20% in index houses, and 4% in reference homes. Plumb-
ing leaks caused almost all problems in kitchens. There
was little damage on kitchen walls or windows, or dam-
age that could be attributed to appliances. There was no
damage found on kitchen floors, ceilings, or exhaust ducts
situated in kitchens.
The final domain was made up of spaces such as liv-
ing rooms, bedrooms, closets, porches, and basements.
Damage in this domain was found in 17% of the homes.
Half of grade III homes and one-fourth of grade II homes
were found to have at least one spot of damage in spaces
other than bathrooms or kitchens. Apartments had a
higher percentage of this kind of damage than houses in
each grade of homes had. The overall frequency of mois-
ture observations in this domain was higher than the
observations reported in kitchens, but less than that en-
countered in bathrooms (see Table 2).
DISCUSSION
Analysis of Moisture Observations
Our grading system screened and sorted the sample of
homes according to the number and estimated severity
of moisture damage found. The homes were allocated
into grades I, II, and III, so that grade I contained no or
minimal moisture problems while grade III contained
the most significant accumulation of damage. Even
though 54% of the houses and 45% of the apartments
were found to have some sign of unusual moisture, only
38% of the houses and 26% of the apartments were
graded into the category of index homes with signifi-
cant moisture damage. The grading system in effect classi-
fies the homes so that the risk of moisture damage-induced
74
Journal of the Air & Waste Management Association
Volume 51 January 2001

Chelelgo et al.
is differences in constructional styles taking place with
time. In addition, buildings of different ages are in differ-
ent phases of the renovation cycle.
Apartments were drawn from blocks of flats that con-
2
tain a number of small apartments (30–100 m ), while
the sample of houses had bigger dwelling spaces (70–
2
2
00 m ). It should be pointed out that moisture damage
was observed in only 17% of dwellings in locations other
than bathrooms and kitchens, so the effect of room size
seems to be minimal compared with the effect of the
water load. On the other hand, once a material has been
contaminated by microbial growth, the distribution and
extent of the exposure may be influenced by the size of
the facility and other factors, such as the efficiency of
ventilation.
Moisture observations on walls were detected from
both houses and apartments. They were particularly
prevalent in homes built in the 1960s and 1980s. Exter-
nal wall structures in ~85% of apartments were made of
concrete materials, while ~90% of the corresponding
houses consisted of a timber structure. It is possible that
these two types of materials disintegrate over the years
in different ways due to moisture-related stresses, thus
affecting their ability to withstand the elements of ex-
ternal moisture.
Figure 5. Indoor moisture content vs. outdoor saturation temperature
curve based on indoor humidity recorded in 480 homes at the time of
inspection. The curve indicates a border along which moisture would
condense if it came into contact with a cold surface with temperature
equal to the outdoor temperature.
exposure increases with grade. Therefore, grade II and
III homes represent a set of homes with observations of
moisture sufficient to cause concern. These homes were
identified in all types of dwellings drawn from all re-
gions and built in all postwar decades. Thus, they are
representative of current Finnish housing stock, construc-
tion styles, and climate.
The proportion of index houses was significantly
higher than the corresponding proportion of apartments.
However, index apartments had more cases of damage
per home than index houses had. Thus, the lower per-
centage of index homes among apartments did not mean
that apartments were free of moisture problems. It may
indicate that moisture problems were present in both
houses and apartments, but much of the damage in apart-
ments was not considered as serious. In addition, poten-
tial risk locations of moisture problems in buildings’
indoor-outdoor contact areas (e.g., roof, outer walls, and
basement floors) occur more frequently in houses than
in apartments.
Only 12% of the homes in this study had basements;
most of the below-grade moisture problems associated
with basement structures were avoided. Many of the
houses drawn from the 1950s and a few from the 1960s
had basements that were converted into living spaces.
Water could have penetrated through the walls of these
basements from the ground, damaging interior wall fin-
ishes and fasteners, since the basements were originally
not designed as living spaces and, therefore, appropriate
waterproofing and other structures may not have been
incorporated.
The observations associated with external sources
were, in general, serious and identified in all types of
homes, decades, and regions. Equally widespread were
homes with damage caused by occupants’ activities,
plumbing leaks, or faulty equipments. Most of these prob-
lems were observed on floors, particularly in bathrooms.
Construction defects or errors were found on the
building envelope that allowed water to penetrate into
the interior, for example, damage on the roofs, broken-
down gutters, faulty downspouts, poorly constructed roof
overhangs, and poorly shaped ground surfaces that al-
lowed water to pool toward the foundation of the build-
ing. Other problems were due to aging or corrosion of
building materials and lack of maintenance. External leaks
appeared on the inside on sites including ceilings, wall
joints, window frames, and joints to vents extending
through the envelope.
Between 49 and 52% of all the homes in the four
decades had at least one sign of moisture. Our grading
system showed that index homes were rather uniformly
dispersed (30–35%) over these decades and that even
though there were more index observations among houses
from the 1960s and 1970s, the mean numbers of damage
sites in that set of samples were, nevertheless, lower than
in other decades. One factor that could explain this finding
Volume 51 January 2001
Journal of the Air & Waste Management Association 75

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

Chelelgo et al.
1
1. Nevalainen, A.; Partanen, P.; Jääskeläinen, E.; Hyvärinen, A.; Koskinen,
O.; Meklin, T.; Vahteristo, M.; Koivisto, J.; Husman, T. Prevalence of
Moisture Problems in Finnish Houses; Indoor Air 1998, 4, 45-49.
2. Construction and Housing Yearbook 1997; Statistics Finland: Helsinki,
Finland, 1997.
ACKNOWLEDGMENTS
The study was financially supported by the Finnish Min-
istry of Environment and the Finnish Ministry of Social
Affairs and Health.
1
1
3. Strachan, D.P.; Sanders, C.H. Damp Housing and Childhood Asthma;
Respiratory Effects of Indoor Air Temperature and Relative Humid-
ity; J. Epidemiol. Commun. Health 1989, 43, 7-14.
REFERENCES
1
2
3
4
.
.
.
.
Brunekreef, B.; Dockery, D.W.; Speizer, F.E.; Ware, J.H.; Spengler, J.D.;
Ferris, B.G. Home Dampness and Respiratory Morbidity in Children;
Am. Rev. Respir. Dis. 1989, 140, 1363-1367.
Dales, R.E.; Burnett, R.; Zwanenburg, H. Adverse Health Effects among
Adults Exposed to Home Dampness and Molds; Am. Rev. Respir. Dis.
1
991, 143, 505-509.
Spengler, J.; Neas, L.; Nakai, S.; Dockery, D.; Speizer, F.; Ware, J.;
Raizenne, M. Respiratory Symptoms and Housing Characteristics;
Indoor Air 1994, 4, 72-82.
Pirhonen, I.; Nevalainen, A.; Husman, T.; Pekkanen, J. Home Damp-
ness, Moulds and Their Influence on Respiratory Infections and Symp-
toms in Adults in Finland; Eur. Respir. J. 1996, 9, 2618-2622.
Koskinen, O. Moisture, Mold and Health. M.D. Dissertation, Univer-
sity of Kuopio, Kuopio, Finland, February 1999.
Brunekreef, B.; de Rijk, L.; Verhoeff, A.P.; Samson, R. Classifications
of Dampness in Homes. In Proceedings of the 5th Indoor Air Conference;
International Conference on Indoor Air Quality and Climate, Inc.:
Ottawa, Canada, 1990; Vol. 2, pp 15-20.
5
6
.
.
About the Authors
Joseph Chelelgo, M.Sc. (Eng.), Ulla Haverinen, M.Sc. (Eng.),
Mikko Vahteristo, M.Sc., and Jari Koivisto, B.Sc. (Eng.), can
be contacted at National Public Health Institute, Division of
Environmental Health, P.O. Box 95, SF-70701 Kuopio, Fin-
land. Esa Jääskeläinen, M.Sc. (Eng.), can be contacted at
Siilinjärvi Town, P.O. Box 5, SF-71801 Siilinjärvi, Finland. At
the time the study was conducted, Mr. Jääskeläinen was at
Econs Ltd., Tattikuja 1, SF 70910, Vuorela, Finland. Tuula
Husman, MD, and Aino Nevalainen, Ph.D., can be contacted
at National Public Health Institute, Division of Environmental
Health, P.O. Box 95, SF-70701 Kuopio, Finland.
7
8
.
.
Statistical Yearbook of Finland, Karisto, Hämeenlinna; Statistics Finland:
Helsinki, Finland, 1997.
Flannigan, B.; Morey, P.R. Control of Moisture Problems Affecting Bio-
logical Indoor Air Quality; ISAIQ Guideline, Task Force I: Ottawa,
Canada, 1996.
Lawton, M.D.; Dales, R.E.; White, J. The Influence of House Charac-
teristics in a Canadian Community on Microbiological Contamina-
tion; Indoor Air 1998, 8, 2-11.
9
1
.
0. Haverinen, U.; Husman, T.; Toivola, M.; Suonketo, J.; Pentti, M.;
Lindberg, R.; Leinonen, J.; Hyvärinen, A.; Meklin, T.; Nevalainen, A.
An Approach to Management of Critical Indoor Air Problems in School
Buildings; Environ. Health Perspect. 1999, 107 (3), 509-514.
Volume 51 January 2001
Journal of the Air & Waste Management Association 77