ASHRAE Journal - June 2020 - 51
COLUMN HVAC APPLICATIONS
probability of negative health
effects:
* "Moldy, musty, earthy" odors;
* Visible mold;
* Current water damage; and
* History of visible mold or water damage.
The human nose turns out to be
a useful instrument for investigating health-relevant dampness.
Musty odors are the indicator most
strongly associated with buildings
or HVAC systems that have become
damp enough to increase the probability of negative health effects
for some occupants.
The report also suggests four
metrics with quantitative thresholds that indicate abnormal conditions that, if persistent, serve
as early warnings of excessive
dampness. Readers are welcome
to download the report for a full
explanation of the early warning
metrics, the epidemiological studies that support the conclusions
and 16 pages of specific suggestions for building professionals.
One of the report's four early
warning metrics deserves further discussion here, to alert
ventilation system designers to a
significant change to the widely
applied ASHRAE/ANSI Standard
62.1, Ventilation for Acceptable Indoor
Air Quality (Figure 2). As of 2019,
the standard calls for limiting the
absolute humidity to less than a
dew-point temperature of 60°F
(15°C), during both occupied and
unoccupied hours, whenever the
dew point outdoors is above that
level.
Sound logic exists for placing
ASHRAE's upper limit for absolute humidity in the ventilation
design standard. Ventilation air
represents the largest annual
humidity load for nearly all commercial and institutional buildings, in nearly all climates.4
Removing the humidity load
imposed by ventilation air is
important in any building that
is mechanically cooled. Cold
HVAC equipment and distribution systems often condense and
drip moisture, and cooled building surfaces are more likely than
warm surfaces to absorb and
retain moisture. So because ventilation design imposes the largest
humidity load, placing the dewpoint limit in Standard 62.1-2019
is helpful. It alerts the designer
to the issue of humidity control at
an early and therefore influential
stage of design. Later, it may be
more difficult to adjust the system
configurations and equipment
selections to ensure humidity
control at levels low enough to
limit indoor dampness and health
consequences.
The revised limit is a prudent
upper boundary for absolute
humidity to avoid building dampness, rather than a desirable target for comfort. Cooling systems
are typically expected to keep
indoor air at 75°F (24°C) db, 50%
RH, which is a 55°F (12.8°C) dewpoint temperature.4,5 So designing to limit absolute humidity to
less than a 60°F (15°C) dew-point
temperature does not change typical design practice, except in one
important respect: system operation during the unoccupied mode.
This new guidance to keep
buildings dry even when not fully
occupied reflects the fact that
indoor dampness that occurs long
enough for mold to grow is often
FIGURE 1 The new ASHRAE publication is available in
PDF (free) and print formats. Use the QR code below
to download it.
Figure 2 The revised ASHRAE/ANSI Std 62.12019 describes a prudent upper limit for absolute
humidity that is consistent with the findings of the
MTG: Damp Buildings. Use the QR code for more
information.
caused by high humidity when
buildings remain partly active,
but largely unoccupied. Examples
that often appear in the news
include K-12 schools and university dormitories after vacations,
J U N E 2020
ashrae.org
ASHRAE JOURNAL
51
https://www.ashrae.org/
ASHRAE Journal - June 2020
Table of Contents for the Digital Edition of ASHRAE Journal - June 2020
Contents
ASHRAE Journal - June 2020 - Intro
ASHRAE Journal - June 2020 - Cover1
ASHRAE Journal - June 2020 - Cover2
ASHRAE Journal - June 2020 - 1
ASHRAE Journal - June 2020 - Contents
ASHRAE Journal - June 2020 - 3
ASHRAE Journal - June 2020 - 4
ASHRAE Journal - June 2020 - 5
ASHRAE Journal - June 2020 - 6
ASHRAE Journal - June 2020 - 7
ASHRAE Journal - June 2020 - 8
ASHRAE Journal - June 2020 - 9
ASHRAE Journal - June 2020 - 10
ASHRAE Journal - June 2020 - 11
ASHRAE Journal - June 2020 - 12
ASHRAE Journal - June 2020 - 13
ASHRAE Journal - June 2020 - 14
ASHRAE Journal - June 2020 - 15
ASHRAE Journal - June 2020 - 16
ASHRAE Journal - June 2020 - 17
ASHRAE Journal - June 2020 - 18
ASHRAE Journal - June 2020 - 19
ASHRAE Journal - June 2020 - 20
ASHRAE Journal - June 2020 - 21
ASHRAE Journal - June 2020 - 22
ASHRAE Journal - June 2020 - 23
ASHRAE Journal - June 2020 - 24
ASHRAE Journal - June 2020 - 25
ASHRAE Journal - June 2020 - 26
ASHRAE Journal - June 2020 - 27
ASHRAE Journal - June 2020 - 28
ASHRAE Journal - June 2020 - 29
ASHRAE Journal - June 2020 - 30
ASHRAE Journal - June 2020 - 31
ASHRAE Journal - June 2020 - 32
ASHRAE Journal - June 2020 - 33
ASHRAE Journal - June 2020 - 34
ASHRAE Journal - June 2020 - 35
ASHRAE Journal - June 2020 - 36
ASHRAE Journal - June 2020 - 37
ASHRAE Journal - June 2020 - 38
ASHRAE Journal - June 2020 - 39
ASHRAE Journal - June 2020 - 40
ASHRAE Journal - June 2020 - 41
ASHRAE Journal - June 2020 - 42
ASHRAE Journal - June 2020 - 43
ASHRAE Journal - June 2020 - 44
ASHRAE Journal - June 2020 - 45
ASHRAE Journal - June 2020 - 46
ASHRAE Journal - June 2020 - 47
ASHRAE Journal - June 2020 - 48
ASHRAE Journal - June 2020 - 49
ASHRAE Journal - June 2020 - 50
ASHRAE Journal - June 2020 - 51
ASHRAE Journal - June 2020 - 52
ASHRAE Journal - June 2020 - 53
ASHRAE Journal - June 2020 - 54
ASHRAE Journal - June 2020 - 55
ASHRAE Journal - June 2020 - 56
ASHRAE Journal - June 2020 - 57
ASHRAE Journal - June 2020 - 58
ASHRAE Journal - June 2020 - 59
ASHRAE Journal - June 2020 - 60
ASHRAE Journal - June 2020 - 61
ASHRAE Journal - June 2020 - 62
ASHRAE Journal - June 2020 - 63
ASHRAE Journal - June 2020 - 64
ASHRAE Journal - June 2020 - 65
ASHRAE Journal - June 2020 - 66
ASHRAE Journal - June 2020 - 67
ASHRAE Journal - June 2020 - 68
ASHRAE Journal - June 2020 - 69
ASHRAE Journal - June 2020 - 70
ASHRAE Journal - June 2020 - 71
ASHRAE Journal - June 2020 - 72
ASHRAE Journal - June 2020 - 73
ASHRAE Journal - June 2020 - 74
ASHRAE Journal - June 2020 - 75
ASHRAE Journal - June 2020 - 76
ASHRAE Journal - June 2020 - 77
ASHRAE Journal - June 2020 - 78
ASHRAE Journal - June 2020 - 79
ASHRAE Journal - June 2020 - 80
ASHRAE Journal - June 2020 - 81
ASHRAE Journal - June 2020 - 82
ASHRAE Journal - June 2020 - 83
ASHRAE Journal - June 2020 - 84
ASHRAE Journal - June 2020 - 85
ASHRAE Journal - June 2020 - 86
ASHRAE Journal - June 2020 - 87
ASHRAE Journal - June 2020 - 88
ASHRAE Journal - June 2020 - Cover3
ASHRAE Journal - June 2020 - Cover4
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ATMAHK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VHQRAW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XGMDXI
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_YELQLJ
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QJLWMC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_MCDEBX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WNYSQY
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XATVOD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_FJSHSS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_CCBZDS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XDEFVG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2023november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2023november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VHGNBL
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WPKBNJ
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_UUVCDE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RTGDEW
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2023
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LKRFXS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_AZSOFG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ERCDBH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QWDFRV
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JHGVDF
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OPUYHG
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SREIBM
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LRTGLK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OKRFGH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2022november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2022november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TZSERA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_LVRUIX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RPTVYZ
https://www.nxtbook.com/nxtbooks/ashrae/mini_pub_catalog
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XIYTGD
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2022
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RFGDOB
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PABXNU
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_REMKLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PICVBT
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_AOYTVW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JQOPLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_IOYTBC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SGAJJF
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_IGHYER
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_PDRKLS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2021november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2021november_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_XCODFR
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QSLFGO
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ILKVNM
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2021
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OPDJKD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_VJKSRY
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SDHUTC
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JPPKRR
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SDLTTH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_CKLLES
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_SLDOX
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_HJETUK
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_OLUHGE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2020october
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2020october_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ZERDGH
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_QVMNEO
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_RTPOKE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_BBATRE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_STUBMW
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TPEMPE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_JNMKDS
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_FBTTPA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_WQMMNE
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_TVBRYN
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_showguide2020
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_KTUZMA
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_ABEDGD
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201910
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201909
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019septmeber_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2019september
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201908
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201907
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201906
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201905
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201904
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019april
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201903
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2019march
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201902
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201901
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_showguide2019
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018december
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018november
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2018fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_2018october
https://www.nxtbook.com/nxtbooks/ashrae/ashraemexico_2018
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201810
https://www.nxtbook.com/nxtbooks/ashrae/ashraeinsights_201806
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201805
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201804
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201803
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201712
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201711
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201710
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2017fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201709
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201705
https://www.nxtbook.com/nxtbooks/ashrae/ashrae_meetinginsert_201610
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2016fall
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acrexindia
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_amca_2015summer
https://www.nxtbook.com/nxtbooks/amca/2014summer2
https://www.nxtbook.com/nxtbooks/amca/2014summer
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acma_2014summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201311
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201309
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_acmasupp_2013fall
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201305
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201303
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2013winter
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201211
https://www.nxtbook.com/nxtbooks/ashrae/achr_expo_mexico2012
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201209
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v3
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201208_v2
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201205
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201203
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2012winter
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201111_v2
https://www.nxtbook.com/nxtbooks/ashrae/ashraejournal_201109_v2
https://www.nxtbook.com/nxtbooks/ashrae/pubcatalog_2011summer
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201105
https://www.nxtbook.com/nxtbooks/ashrae/meetingplanner_201103
https://www.nxtbookmedia.com