doi: 10.1111/ina.12176
Online supporting information for the following article published in Indoor Air
DOI: TO BE ADDED BY THE PRODUCTION EDITOR
The effects of building-related factors on classroom relative humidity
among North Carolina schools participating in the “Free to Breathe,
Free to Teach” study
Running Header: Building factor effects on classroom humidity
Authors: K.A. Angelon-Gaetz1; D.B. Richardson1; D.M. Lipton2; S.W. Marshall1; B. Lamb3, T.
LoFrese.4
1
Epidemiology Department, Gillings School of Global Public Health, University of North
Carolina at Chapel Hill, Chapel Hill, NC; 2North Carolina Division of Public Health, Department
of Health and Human Services, Raleigh, NC; 3New Hanover County Schools, Maintenance
Operations Department, Wilmington, NC; 4Chapel Hill-Carrboro City Schools, Support Services,
Chapel Hill, NC.
Corresponding Author: Kim Angelon-Gaetz, Currently working as an ORISE Research Fellow at
the U.S. Environmental Protection Agency, National Exposure Research Laboratory, 109 TW
Alexander Drive, Research Triangle Park, NC 27711.
Tel: 919-541-1512
Email: kangelongaetz@gmail.com
SUPPLEMENTAL MATERIALS: EQUATIONS
Conversion from temperature (oC) to saturation vapor pressure (kPa) (Snyder, 2005)
𝟏𝟕.𝟐𝟕 𝑻
es=0.6108 exp [𝑻+𝟐𝟑𝟕.𝟑], where es is saturation vapor pressure (kPa) and T is temperature (oC).
(Equation S1)
Unit conversion of saturation vapor pressure from kPa to inHg (This step is optional because you will be converting back to kPa in
Equation 5.)
es (inHg)= 0.295300 es (kPa)
(Equation S2)
(http://www.srh.noaa.gov/images/epz/wxcalc/pressureConversion.pdf)
Conversion from saturation vapor pressure values (inHg) to vapor pressure (inHg) (Parish and Putnam, 1977)
𝑼
ev = 𝟏𝟎𝟎 es, where es is saturation vapor pressure (inHg), ev is vapor pressure (inHg), and U is relative humidity (%)
(Equation S3)
Reverse Equation 3 to convert back to kPa.
Conversion from vapor pressure (kPa) to absolute humidity (g/m3) (Snyder, 2005)
𝟐𝟏𝟔𝟓 𝒆
𝒗
χ =𝑻+𝟐𝟕𝟑.𝟏𝟔
, where ev is vapor pressure (kPa), T is temperature (oC), and χ is absolute humidity (g/m3)
(Equation S4)
SUPPLEMENTAL MATERIALS: TABLES
TABLE S1. UNIVARIATE ASSOCIATIONS BETWEEN OTHER BUILDING-RELATED FACTORS AND DAILY AVERAGE
RELATIVE HUMIDITY (N=9044 CLASSROOM-DAYS)
COVARIATE
LEVEL
* UNADJUSTED OR (95% CI)
Low Relative Humidity
High Relative Humidity
>30% vs.
>30% vs.
>50% vs.
>60% vs.
30-50% (ref.)
30-60% (ref.)
30-50% (ref.)
30-60% (ref.)
>40
1.06 (0.55, 2.0)
1.42 (0.72, 2.8)
0.66 (0.44, 0.98)
2.6 (1.4, 4.8)
31-40
4.2 (1.96, 8.8)
7.2 (3.2, 16.3)
0.23 (0.11, 0.51)
1.05 (0.34, 3.3)
11-20
3.5 (1.98, 6.1)
5.9 (3.2, 10.8)
0.23 (0.14, 0.38)
0.70 (0.38, 1.30)
0-10
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
Outdoor relative humidity
10 unit increase
0.62 (0.55, 0.71)
0.56 (0.49, 0.65)
1.49 (1.43, 1.55)
1.73 (1.54, 1.94)
Heating/ cooling season
Cooling
0.52 (0.16, 1.69)
0.41 (0.13, 1.30)
1.82 (1.30, 2.6)
2.4 (1.74, 3.2)
Heating
12.4 (9.3, 16.6)
22.3 (16.5, 30.2)
0.04 (0.03, 0.05)
0.02 (0.01, 0.05)
Transition
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
Yes
0.02 (0.01, 0.04)
0.01 (0.01, 0.02)
3.4 (2.2, 5.1)
0.58 (0.29, 1.16)
No
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
Yes
0.93 (0.40, 2.2)
0.74 (0.30, 1.84)
2.8 (1.77, 4.4)
3.6 (1.4, 9.2)
No
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
Building Age (years)**
Enthalpy wheels for
dehumidification
Thermostat setback
* Generalized logits estimating the bivariate association between other building-related factors used only as confounders in the models presented in Tables 2 and
3. For each factor, two models were run using different relative humidity (RH) cut points as described above and clustered by classroom. Missing n=22
classroom-days. OR=odds ratio, CI=confidence intervals, ref.= referent. ** No schools participating in this study had buildings between the ages of 21-30.
TABLE S2. FULL MODEL FOR ASSOCIATION BETWEEN WATER DAMAGE AND DAILY AVERAGE RELATIVE
HUMIDITY LEVEL (N=9044 CLASSROOM-DAYS)
COVARIATE
* ADJUSTED OR (95% CI)
LEVEL
Low Relative Humidity
High Relative Humidity
>30% vs.
>30% vs.
>50% vs.
>60% vs.
30-50% (ref.)
30-60% (ref.)
30-50% (ref.)
30-60% (ref.)
Yes
0.86 (0.57, 1.30)
0.91 (0.59, 1.42)
0.72 (0.47, 1.09)
0.52 (0.28, 0.96)
No
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
Direct-expansion
(Dx) split system
Heat pump/ refrigerant
2.1 (1.37, 3.1)
2.9 (1.84, 4.5)
0.06 (0.02, 0.16)
0.06 (0.02, 0.19)
1.35 (0.73, 2.5)
1.10 (0.56, 2.2)
1.56 (0.94, 2.6)
0.82 (0.36, 1.84)
Chilled water
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
Outdoor relative
humidity
10 unit increase
0.59 (0.53, 0.67)
0.54 (0.48, 0.62)
1.67 (1.59, 1.75)
1.82 (1.62, 2.0)
Building Age (years)**
>40
0.88 (0.45, 1.71)
1.14 (0.57, 2.3)
0.72 (0.46, 1.13)
3.4 (1.75, 6.5)
31-40
3.2 (1.40, 7.5)
5.8 (2.2, 15.3)
0.19 (0.07, 0.55)
1.44 (0.42, 4.9)
11-20
2.8 (1.42, 5.4)
3.7 (1.76, 7.6)
0.53 (0.35, 0.78)
1.43 (0.81, 2.6)
0-10
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
Visible water damage
Heating/ cooling
mechanism
* *Estimated generalized logits clustered by classroom, using different relative humidity (RH) cut points. Missing n=22 classroom-days. Adjusted OR give the
association between the building-related factor and high RH, using a multivariate model that includes the confounders listed below for each factor. Missing
n=289 classroom-days of observations for water damage. Water damage includes leaks, history of flooding, or visible signs of moisture/ water damage in the
classroom. OR=odds ratio, CI=confidence intervals, ref. = referent. ** No schools participating in this study had buildings between the ages of 21-30.
TABLE S3. FULL MODEL FOR ASSOCIATION BETWEEN HVAC MAINTENANCE AND DAILY AVERAGE RELATIVE
HUMIDITY LEVEL (N=9044 CLASSROOM-DAYS)
COVARIATE
* ADJUSTED OR (95% CI)
LEVEL
Low Relative Humidity
Frequency of HVAC
maintenance
Building Age (years)**
High Relative Humidity
>30% vs.
>30% vs.
>50% vs.
>60% vs.
30-50% (ref.)
30-60% (ref.)
30-50% (ref.)
30-60% (ref.)
Annually
0.47 (0.28, 0.78)
0.32 (0.19, 0.54)
6.6 (4.0, 10.8)
5.8 (2.9, 11.3)
As Needed
1.06 (0.73, 1.53)
0.84 (0.57, 1.25)
4.7 (3.0, 7.4)
4.8 (2.5, 9.2)
Quarterly
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
>40
1.39 (0.67, 2.9)
2.3 (1.07, 5.1)
0.19 (0.11, 0.34)
0.69 (0.32, 1.52)
31-40
4.8 (2.4, 9.6)
9. 6 (4.5, 20.3)
0.07 (0.04, 0.14)
0.31 (0.10, 0.91)
11-20
3.6 (1.97, 6.5)
6.8 (3.6, 12.9)
0.08 (0.05, 0.13)
0.23 (0.11, 0.47)
0-10
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
* *Estimated generalized logits clustered by classroom, using different relative humidity (RH) cut points. Missing n=22 classroom-days. Adjusted OR give the
association between the building-related factor and high RH, using a multivariate model that includes the confounders listed below for each factor. OR=odds
ratio, CI=confidence intervals, ref. = referent. ** No schools participating in this study had buildings between the ages of 21-30.
TABLE S4. FULL MODEL FOR ASSOCIATION BETWEEN PRESENCE OF AN ECONOMIZER AND DAILY AVERAGE
RELATIVE HUMIDITY LEVEL (N=9044 CLASSROOM-DAYS)
COVARIATE
* ADJUSTED OR (95% CI)
LEVEL
Low Relative Humidity
Economizer
Enthalpy wheels for
dehumidification
High Relative Humidity
>30% vs.
>30% vs.
>50% vs.
>60% vs.
30-50% (ref.)
30-60% (ref.)
30-50% (ref.)
30-60% (ref.)
Yes
0.84 (0.60, 1.17)
0.65 (0.45, 0.94)
3.1 (2.0, 4.6)
2.6 (1.49, 4.5)
No
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
Yes
0.02 (0.01, 0.03)
0.008 (0.004, 0.018)
6.42 (3.9, 10.6)
1.04 (0.49, 2.2)
No
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
* *Estimated generalized logits clustered by classroom, using different relative humidity (RH) cut points. Missing n=22 classroom-days. Adjusted OR give the
association between the building-related factor and high RH, using a multivariate model that includes the confounders listed below for each factor. OR=odds
ratio, CI=confidence intervals, ref.= referent.
TABLE S5. FULL MODEL FOR ASSOCIATION BETWEEN HEATING/ COOLING MECHANISM AND DAILY AVERAGE
RELATIVE HUMIDITY LEVEL (N=9044 CLASSROOM-DAYS)
COVARIATE
* ADJUSTED OR (95% CI)
LEVEL
Low Relative Humidity
Heating/ cooling
mechanism
HVAC Season
Building Age (years)**
High Relative Humidity
>30% vs.
>30% vs.
>50% vs.
>60% vs.
30-50% (ref.)
30-60% (ref.)
30-50% (ref.)
30-60% (ref.)
Direct-expansion
(Dx) split system
2.5 (1.58, 3.8)
2.7 (1.71, 4.4)
0.03 (0.01, 0.12)
0.06 (0.01, 0.23)
Heat pump/ refrigerant
0.97 (0.49, 1.94)
0.93 (0.47, 1.82)
1.35 (0.89, 2.0)
0.85 (0.46, 1.55)
Chilled water
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
Cooling
0.25 (0.08, 0.82)
0.26 (0.08, 0.81)
4.4 (2.9, 6.7)
3.3 (2.4, 4.7)
Heating
14.4 (11.3, 18.3)
20.6 (15.7, 26.9)
0.04 (0.03, 0.05)
0.02 (0.01, 0.05)
Transition
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
>40
0.91 (0.46, 1.79)
0.96 (0.49, 1.86)
0.70 (0.46, 1.08)
3.4 (1.79, 6.4)
31-40
3.3 (1.35, 8.2)
3.8 (1.55, 9.2)
0.33 (0.16, 0.69)
2.1 (0.82, 5.6)
11-20
3.3 (1.98, 5.4)
3.5 (2.1, 5.8)
0.47 (0.30, 0.75)
1.48 (0.82, 2.7)
0-10
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
* *Estimated generalized logits clustered by classroom, using different relative humidity (RH) cut points. Missing n=22 classroom-days. Adjusted OR give the
association between the building-related factor and high RH, using a multivariate model that includes the confounders listed below for each factor. OR=odds
ratio, CI=confidence intervals, ref. = referent. ** No schools participating in this study had buildings between the ages of 21-30.
TABLE S6: JOINT EFFECTS OF VISIBLE CLASSROOM WATER DAMAGE AND DEHUMIDIFIER USE ON DAILY
AVERAGE RELATIVE HUMIDITY (N= 9044 CLASSROOM OBSERVATIONS) *
** Adjusted OR (95% CI)
Water Damage
Dehumidifier Use
Low Relative Humidity
High Relative Humidity
>30% vs.
>30% vs.
>50% vs.
>60% vs.
30-50% (ref.)
30-60% (ref.)
30-50% (ref.)
30-60% (ref.)
Yes
Yes
0.95 (0.49, 1.86)
1.10 (0.54, 2.3)
0.46 (0.21, 1.0)
0.53 (0.19, 1.49)
Yes
No
0.76 (0.48, 1.20)
0.79 (0.50, 1.26)
0.70 (0.44, 1.10)
0.44 (0.25, 0.79)
No
Yes
0.22 (0.04, 1.25)
0.14 (0.02, 1.05)
3.9 (0.73, 20.4)
1.44 (0.15, 13.4)
No
No
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
1.0 (ref.)
* *Estimated generalized logits clustered by classroom, using different RH cut points. Missing n=22 classroom-days. Adjusted OR give the association between
the building-related factor and high RH, using a multivariate model that includes heating/ cooling mechanism, outdoor RH, and building age. Missing n=289
classroom-days of observations for water damage. Water damage includes leaks, history of flooding, or visible signs of moisture/ water damage in the classroom.
OR=odds ratio, CI=confidence intervals, ref. = referent.