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style="FONT-FAMILY: ; LINE-HEIGHT: 16pt"><FONT face="Times New Roman"><FONT
style="FONT-SIZE: 14pt">It has been noted on this list the problems associated
with night flushing in humid climates such as here in Virginia in the
summer.<SPAN style="mso-spacerun: yes"> </SPAN>I have engaged in this
practice for many years, because it brings down the temperature of the house to
low 70s most nights and keeps the house below 80 most days when outside air temp
is in 90s.<SPAN style="mso-spacerun: yes"> </SPAN>My house has most of a
high standard retrofit continuous foam thermal envelope.<SPAN
style="mso-spacerun: yes"> </SPAN>I have an HRV.<SPAN
style="mso-spacerun: yes"> </SPAN>I choose not to get ERV because I did
not plan to install active dehumidification.<SPAN
style="mso-spacerun: yes"> </SPAN>To do so,<SPAN
style="mso-spacerun: yes"> </SPAN>I tolerate sometimes 80% relative
humidity in mid-summer.<SPAN style="mso-spacerun: yes"> </SPAN>I am not
willing to accept that one must have refrigerant driven dehumidification to
achieve healthy conditions.<SPAN style="mso-spacerun: yes">
</SPAN>However, for my clients that expect a full comfort standard, this is what
I must specify.<SPAN style="mso-spacerun: yes"> </SPAN>The people who
choose to live without air conditioners acclimate to higher amounts of ambient
humidity.<SPAN style="mso-spacerun: yes"> </SPAN>I went to primary school
in Central Florida with no air conditioners.<SPAN
style="mso-spacerun: yes"> </SPAN>None of us complained because ac was not
yet expected in 1960s.</FONT><SPAN style="mso-spacerun: yes"><FONT
style="FONT-SIZE: 14pt"> </FONT></SPAN></FONT></SPAN></P>
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style="FONT-FAMILY: ; LINE-HEIGHT: 16pt"><FONT face="Times New Roman"><FONT
style="FONT-SIZE: 14pt"></FONT></FONT></SPAN> </P>
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style="FONT-FAMILY: ; LINE-HEIGHT: 16pt"><FONT face="Times New Roman"><FONT
style="FONT-SIZE: 14pt">The last few years I have been observing more carefully
relative humidity, where previous years I only observed temperature.<SPAN
style="mso-spacerun: yes"> </SPAN>I have observed that a house as a whole
goes through a cycle of steadily becoming more humid through the summer and peak
in early fall and then go into a drying mode when heating air.<SPAN
style="mso-spacerun: yes"> </SPAN>The drying peaks in early spring (end of
heating season).<SPAN style="mso-spacerun: yes"> </SPAN>It is my
observation that the house as a whole acts somewhat like a desiccant in that it
adsorbs humidity in the early part of summer as the conditions deliver humid air
to the space.<SPAN style="mso-spacerun: yes"> </SPAN>The house's initial
dryness in early spring dampens the air relative humidity in early part of humid
season.<SPAN style="mso-spacerun: yes"> </SPAN>However, steadily, the
house's capacity to adsorb humidity is maxed out and air relative humidity rises
farther.<SPAN style="mso-spacerun: yes"> </SPAN>This creates the slow
drying conditions of contents that cause the problems associated with
humidity.<SPAN style="mso-spacerun: yes"> </SPAN>This past year, I have
added absolute humidity to my observations with the use of a psychometric chart
using temperature and relative humidity.<SPAN style="mso-spacerun: yes">
</SPAN>This also gives dew point.<SPAN style="mso-spacerun: yes">
</SPAN>Absolute humidity and dew point are directly proportional.<SPAN
style="mso-spacerun: yes"> </SPAN>I observed that on a hot fair weather
day (no precipitation), the absolute humidity was the same inside and out.<SPAN
style="mso-spacerun: yes"> </SPAN>If inside was 75F-80%RH and outside
95F-45%RH, the absolute humidity and dew point were approximately the same.<SPAN
style="mso-spacerun: yes"> </SPAN>Although the hotter air would be more
affective at drying and avoiding humidity problems.</FONT><SPAN
style="mso-spacerun: yes"><FONT style="FONT-SIZE: 14pt">
</FONT></SPAN></FONT></SPAN></P>
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style="FONT-FAMILY: ; LINE-HEIGHT: 16pt"><FONT face="Times New Roman"><FONT
style="FONT-SIZE: 14pt"></FONT></FONT></SPAN> </P>
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style="FONT-FAMILY: ; LINE-HEIGHT: 16pt"><FONT face="Times New Roman"><FONT
style="FONT-SIZE: 14pt">This was a particularly humid summer. Early summer was
rainy and cooler than normal.<SPAN style="mso-spacerun: yes"> </SPAN>This
resulted in elevated humidity.<SPAN style="mso-spacerun: yes"> </SPAN>One
day I observed 71F-88%RH in the house.<SPAN style="mso-spacerun: yes">
</SPAN>This was alarming, so I decided to heat the house above comfort in order
to dry it out.<SPAN style="mso-spacerun: yes"> </SPAN>Like a clothes
dryer, I was elevating the temperature to lower the relative humidity and
increase evaporation.<SPAN style="mso-spacerun: yes"> </SPAN>That day was
in mid 80's, so was not an extremely hot day.<SPAN
style="mso-spacerun: yes"> </SPAN>Since I was not going to occupy the
house I turned the HRV off to increase my temperature to avoid delivering new
humid air. I lit the direct air delivered wood stove to a mid-winter full size
fire.<SPAN style="mso-spacerun: yes"> </SPAN>I got the house to 104F.<SPAN
style="mso-spacerun: yes"> </SPAN>I found that the absolute humidity went
way up over what would be expected if no moisture was added to the air.<SPAN
style="mso-spacerun: yes"> </SPAN>This was the moisture being evaporated
from house contents inside thermal envelope.<SPAN
style="mso-spacerun: yes"> </SPAN>Since the house was closed up, I would
assume minimal infiltration.<SPAN style="mso-spacerun: yes"> </SPAN>After
a few hours of this, I opened up the house to vent out the heat and
moisture.<SPAN style="mso-spacerun: yes"> </SPAN>Returning to night
flushing I was able to return house to low 70s and 10% lower RH by
morning.</FONT><SPAN style="mso-spacerun: yes"><FONT
style="FONT-SIZE: 14pt"> This returned my house to an earlier time in the
humid season. </FONT></SPAN></FONT></SPAN></P>
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style="FONT-FAMILY: ; LINE-HEIGHT: 16pt"><FONT face="Times New Roman"><FONT
style="FONT-SIZE: 14pt"></FONT></FONT></SPAN> </P>
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style="FONT-FAMILY: ; LINE-HEIGHT: 16pt"><FONT face="Times New Roman"><FONT
style="FONT-SIZE: 14pt">I would propose that intermittently heating a house that
has humidity build up is a way to manage the humidity.<SPAN
style="mso-spacerun: yes"> </SPAN>The mold is dried and must start all
over. Yes, control humidity at the source where possible.<SPAN
style="mso-spacerun: yes"> </SPAN>However, when the ambient conditions are
humid that strategy is incomplete.<SPAN style="mso-spacerun: yes">
</SPAN><SPAN style="mso-spacerun: yes"> </SPAN>This heating is a is
appropriate where the house has low mass, allowing the temperature to be easily
raised and returned to normal.<SPAN style="mso-spacerun: yes"> </SPAN>I
would also propose that we take steps to build up the desiccant capacity of the
house such that fewer cycles such as this would be needed.<SPAN
style="mso-spacerun: yes"> </SPAN>Because we are taking away the humidity
in the humid seasons, it may result in the house being dryer in the early
heating season.<SPAN style="mso-spacerun: yes"> </SPAN>A strategy of
humidification might be considered.<SPAN style="mso-spacerun: yes">
</SPAN>I am aware that there is risk if air is flowing through the thermal
envelope and cooling to dew point as a result of higher indoor humidity.<SPAN
style="mso-spacerun: yes"> </SPAN>However, if a well designed and built
thermal envelope with a thick layer of foam that is high enough proportion of
the total R value such that humidified air that would penetrate to the warm side
will be above dew point in the expected coldest conditions, this could
work.<SPAN style="mso-spacerun: yes"> </SPAN>With those risk managed,
humidification is much lower energy consumption and environmental risk than the
refrigerant driven dehumidification. </FONT></FONT></SPAN></P>
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style="FONT-FAMILY: ; LINE-HEIGHT: 16pt"><FONT face="Times New Roman"><FONT
style="FONT-SIZE: 14pt"></FONT></FONT></SPAN> </P>
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style="FONT-FAMILY: ; LINE-HEIGHT: 16pt"><FONT face="Times New Roman"><FONT
style="FONT-SIZE: 14pt">Perhaps leaving the windows open during the day and not
pulling cold moist air into the house at night is another way to reduce humidity
risk.<SPAN style="mso-spacerun: yes"> </SPAN>Though the absolute humidity
would be about the same, the higher relative humidity resulting from the higher
temperature would be less vulnerable to humidity problems.<SPAN
style="mso-spacerun: yes"> </SPAN>Although, I contend it is less
comfortable.</FONT><SPAN style="mso-spacerun: yes"><FONT
style="FONT-SIZE: 14pt"> </FONT></SPAN></FONT></SPAN></P>
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style="FONT-FAMILY: ; LINE-HEIGHT: 16pt"><FONT face="Times New Roman"><FONT
style="FONT-SIZE: 14pt"></FONT></FONT></SPAN> </P>
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style="FONT-FAMILY: ; LINE-HEIGHT: 16pt"><FONT face="Times New Roman"><FONT
style="FONT-SIZE: 14pt">Very interesting subject.<SPAN
style="mso-spacerun: yes"> </SPAN>I hope to hear many insightful comments
from the experienced and knowledgeable participants from this list.
</FONT></FONT></SPAN></P>
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style="FONT-FAMILY: ; LINE-HEIGHT: 16pt"><FONT face="Times New Roman"><FONT
style="FONT-SIZE: 14pt">Eli </FONT><SPAN style="mso-spacerun: yes"><FONT
style="FONT-SIZE: 14pt"> </FONT></SPAN></FONT></SPAN></P>
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